Reactive Polymers - Fundamentals and Applications.pdf

REACTIVE POLYMERS
FUNDAMENTALS AND
APPLICATIONS
A CONCISE GUIDE TO INDUSTRIAL POLYMERS
Johannes Karl Fink
Montanuniversität Leoben
Leoben, Austria

Copyright © 2005 by William Andrew, Inc.
No part of this book may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying, recording, or by any information
storage and retrieval system, without permission in writing from the Publisher.
Cover art © 2005 by Brent Beckley / William Andrew, Inc.
ISBN: 0-8155-1515-4 (William Andrew, Inc.)
Library or Congress Catalog Card Number: 2005007686
Library of Congress Cataloging-in-Publication Data
Fink, Johannes Karl.
Reactive polymers : fundamentals and applications : a concise guide to
industrial polymers / by Johannes Karl Fink.
p. cm. -- (PDL handbook series)
Includes bibliographical references and index.
ISBN 0-8155-1515-4 (acid-free paper)
1. Gums and resins, Synthetic. 2. Gums and resins--Industrial
applications. I. Title. II. Series.
TP1185.R46F56 2005
668'.374--dc22
2005007686
Printed in the United States of America
This book is printed on acid-free paper.
10 9 8 7 6 5 4 3 2 1
Published by:
William Andrew Publishing
13 Eaton Avenue
Norwich, NY 13815
1-800-932-7045
www.williamandrew.com
NOTICE
To the best of our knowledge the information in this publication is accurate; however the
Publisher does not assume any responsibility or liability for the accuracy or completeness
of, or consequences arising from, such information. This book is intended for
informational purposes only. Mention of trade names or commercial products does not
constitute endorsement or recommendation for their use by the Publisher. Final
determination of the suitability of any information or product for any use, and the manner
of that use, is the sole responsibility of the user. Anyone intending to rely upon any
recommendation of materials or procedures mentioned in this publication should be
independently satisfied as to such suitability, and must meet all applicable safety and
health standards.

PDL EDITOR’S PREFACE
The publication of Reactive Polymers Fundamentals and Applications: A
Concise Guide to Industrial Polymers in the PDL (Plastics Design Library)
series gives me a special pleasure. The author, Dr. Johannes Karl Fink,
has brought together an impressive array of information about the reactions
polymers undergo, often resulting in cross-linking. The masterful
interweaving of the applications of these reactions with the discussion of
chemistry has rendered this book easy to read for a variety of scientists and
engineers. The reader learns about the incredible penetration of reactive
plastics into every day life whether in a dentist’s office or an office copier.
On the more cutting edge, the book includes information about carborane
copolymers, which far exceed the temperature resistance of any existing
polymers.
Launched in 1990, the Plastics Design Library (PDL) has established
itself within the materials engineering community as the "go to"
source for information on plastics, elastomers, and adhesives. PDL is a
unique series of reference and data books essential to the daily work of
practicing engineers and scientists in applied industries.
The library encompasses the areas of non-metallic materials with a
special emphasis on plastics, elastomers, coatings, and adhesives. Important
current and future materials, processing technologies, and applications
are emphasized. Future titles are planned in the newer areas of commercial
activity such as nanocomposites, bio-based polymers, recycling and mathematical
modeling. The breadth of the coverage ranges from the nature
and selection of materials to design and fabrication to specification and
performance.
The uniqueness of PDL is in its balance of practical and theoretical
aspects with a clear emphasis of the practical over the theoretical. The
encyclopedic format of the books lends itself to easy reading and referral
while the theoretical sections provide the curious reader with an opportunity
for more in-depth learning. Ample references throughout each book
serve as both bibliography and additional learning.
Our hope is that this book will meet the needs of people who work
with the reactions of polymers for any reason.
Sina Ebnesajjad
2005
i

ii
Sina Ebnesajjad, Editor Plastics Design Library
Dr. Sina Ebnesajjad is a senior technical consultant at the DuPont Company,
where he has been in a variety of technical assignments since 1982.
Sina is the author of three handbooks on the science, technology and applications
of Fluoroplastics, published by William Andrew, Inc.
He is the Series Editor for the Fluorocarbon Handbook Series that includes
six handbooks on fluoroplastics, fluoroelastomers, fluorinated coatings
and fluoroionomers. He has been the Editor of Plastics Design Library
since September 2004.

PREFACE
Most of the synthetic polymers are produced in chemical plants and delivered
to a plastics manufacturer who does the formulating, blending, extruding
or molding in order to fabricate articles. The processes required for the
final product are purely physical that occur essentially without any chemical
reaction of the polymer. Since most of the polymers are immiscible,
there is not much room to modify the polymer properties during the plastics
manufacturing. The properties of the final product are often modified
by the actions of additives.
A minor number of polymers, usually called resins, are delivered as
precursors by the chemical industry to the manufacturer. Here, the manufacturer
gets to the final article by a chemical reaction. There also exists an
in-between state where polymers can be modified by reactive extrusion and
grafting. The modification of polymers is advantageous if comparatively
small changes of certain properties are needed that cannot be achieved in
chemical plants. Since many different precursors of the final resin can be
combined, the variability of, and thus the ability to modify, the final properties
are much more pronounced in comparison to the rest of polymers.
This is the topic with which the present book deals, namely, chemical
reactions that take place during the final stage of part fabrication from
plastics. The text does not deal with the chemical reactions needed to produce
resin precursors and the synthesis of polymers. However, chemical
topics relevant to the part manufacturer are elaborated here. These range
from the manufacture of glass-fiber-reinforced articles such as boats made
by the amateur and in a small scale dockyard to what takes place when a
dentist is filling teeth. Industrial processes for the plastics batch fabrication
are described, in addition to their end uses.
The text describes the basic principles of reactive resins as well as
the most recent developments. Paints, coatings and adhesives that are constituted
from resins are not dealt with here, even when the curing mechanisms
are similar.
The past art is discussed by reference to monographs, whereas the
recent developments are documented by references in the scientific literature
and the patent literature after 2000. In some topics, e.g., urea-formaldehyde
resins, the present research activity is low. In other areas, such
as resins used for nanocomposites, there are many recent papers. Even
those resins, for which the research activity is rather dormant at the moiii

iv
Reactive Polymers Fundamentals and Applications
ment, find widespread use and well established applications. They are not
covered here because they are presented in general reviews cited at the beginning
of the respective chapters. Newer applications of these resins are
discussed in detail.
The text originates from a lecture manuscript developed by the author
that has been expanded into a monograph. The original literature presented
here covers the period until July 2004. The text is at a level that a
chemist with a general eduction in polymer chemistry should understand.
Further, the text is addressed to the advanced student of plastics engineering
and the practicing engineer.
HOW TO USE THIS BOOK
Utmost care has been taken to present reliable data. Because of the vast
variety of material presented here, however, it cannot be complete in all
relevant aspects, and it is recommended that the reader study the original
literature for complete information. Therefore, the author cannot assume
responsibility for the completeness and validity of, nor for the consequences
of, the use of the material presented here. Every attempt was made
to identify trademarked products in this volume; however, there were some
that the author was unable to locate, and we apologize for any inadvertent
omission.
Index
There are three indices: an index of acronyms, an index of chemicals, and
a general index. Unfortunately the acronyms presented in the literature are
not always consistent. This means that in a few cases the same acronym
stands for different terms.
Further, in the literature the acronyms are sometimes expanded in
a different way, in particular for chemical names. The author has not unified
the system of chemical names, even when the same compound appears
with different names, because otherwise back tracing in the original literature
would be difficult. I apologize here for this somewhat unsatisfactory
situation.
In the index of chemicals, compounds that occur extensively, e.g.,
“styrene”, are not included at every occurrence, but rather when they appear
in an important context.

Preface
v
ACKNOWLEDGEMENTS
I am indebted to our local library, Dr. Lieselotte Jontes, Dr. Johann Delanoy,
Franz Jurek, Friedrich Scheer, and Christian Slamenik for support in
literature acquisition. I express my gratitude to all the scientists who have
carefully published their results concerning the topics dealt with here. The
book could not have been compiled otherwise.
I would like to thank Dr. Sina Ebnesajjad, Editor of Plastics Design
Library (PDL) for his review and comments on the manuscript. The
Editorial Staff of William Andrew, Inc. have been most supportive of this
project, especially Ms. Millicent Treloar, Senior Acquisitions Editor, who
has been tireless in her efforts. Thank you Ms. Joan Bally for copy editing
the manuscript.
J. K. F.

Plastics Design Library
PDL Editor: Sina Ebnesajjad
Founding Editor: William A. Woishnis
Fluoroelastomers Applications in Chemical Processing Industries
ISBN: 0-8155-1502-2
Khaladkar, P. R., Ebnesajjad, S., Pub. Date: 2005, 592 Pages
The Effect of Sterilization Methods on Plastics and Elastomers, 2 nd Ed.
ISBN: 0-8155-1505-7
Massey, L. K., Pub. Date: 2005, 408 Pages
Extrusion: The Definitive Processing Guide and Handbook
ISBN: 0-8155-1473-5
Giles, H. F., Jr., Wagner,J. R., Jr., Mount, E. M., III, Pub. Date: 2005, 572 Pages
Film Properties of Plastics and Elastomers, 2 nd Ed.
ISBN 1-884207-94-4
Massey, L. K., Pub. Date: 2004, 250 Pages
Handbook of Molded Part Shrinkage and Warpage
ISBN 1-884207-72-3
Fischer, J., Pub. Date: 2003, 244 Pages
Fluoroplastics, Volume 2: Melt-Processible Fluoroplastics
ISBN 1-884207-96-0
Ebnesajjad, S., Pub. Date: 2002, 448 Pages
Permeability Properties of Plastics and Elastomers, 2 nd Ed.
ISBN 1-884207-97-9
Massey, L. K., Pub. Date: 2002, 550 Pages
Rotational Molding Technology
ISBN 1-884207-85-5
Crawford, R. J., and Throne, J. L. , Pub. Date: 2002, 450 Pages
Specialized Molding Techniques & Application, Design, Materials and Processing
ISBN 1-884207-91-X
Heim, H. P., and Potente, H., Pub. Date: 2002, 350 Pages

Chemical Resistance CD-ROM (3 rd Ed.)
ISBN 1-884207-90-1
Plastics Design Library Staff, Pub. Date: 2001, CD-rom
Plastics Failure Analysis and Prevention
ISBN 1-884207-92-8
Moalli, J., Pub. Date: 2001, 400 Pages
Fluoroplastics, Volume 1: Non-Melt Processible Fluoroplastics
ISBN 1-884207-84-7
Ebnesajjad, S., Pub. Date: 2000, 365 Pages
Coloring Technology for Plastics
ISBN 1-884207-78-2
Harris, R. M., Pub. Date: 1999, 333 Pages
Conductive Polymers and Plastics in Industrial Applications
ISBN 1-884207-77-4
Rupprecht, L. M., Pub. Date: 1999, 302 Pages
Imaging and Image Analysis Applications for Plastics
ISBN 1-884207-81-2
Pourdeyhimi, B., Pub. Date: 1999, 398 Pages
Metallocene Technology in Commercial Applications
ISBN 1-884207-76-6
Benedikt, G. M., Pub. Date: 1999, 325 Pages
Weathering of Plastics
ISBN 1-884207-75-8
Wypych, G., Pub. Date: 1999, 325 Pages
Dynamic Mechanical Analysis for Plastics Engineering
ISBN 1-884207-64-2
Sepe, M.. Pub. Date: 1998, 230 Pages
Medical Plastics: Degradation Resistance and Failure Analysis
ISBN 1-884207-60-X
Portnoy, R. C., Pub. Date: 1998, 215 Pages

Metallocene Catalyzed Polymers
ISBN 1-884207-59-6
Benedikt, G. M., and Goodall, B. L., Pub. Date: 1998, 400 Pages
Polypropylene: The Definitive User’s Guide and Databook
ISBN 1-884207-58-8
Maier, C., and Calafut, T., Pub. Date: 1998, 425 Pages
Handbook of Plastics Joining
ISBN 1-884207-17-0
Plastics Design Library Staff, Pub. Date: 1997, 600 Pages
Fatigue and Tribological Properties of Plastics and Elastomers
ISBN 1-884207-15-4
Plastics Design Library Staff, Pub. Date: 1995, 595 Pages
Chemical Resistance, Volume 1
ISBN 1-884207-12-X
Plastics Design Library Staff, Pub. Date: 1994, 1100 Pages
Chemical Resistance, Volume 2
ISBN 1-884207-13-8
Plastics Design Library Staff, Pub. Date: 1994, 977 Pages
The Effect of UV Light and Weather on Plastics and Elastomers
ISBN 1-884207-11-1
Plastics Design Library Staff, Pub. Date: 1994, 481 Pages
The Effect of Creep and Other Time Related
Factors on Plastics and Elastomers
ISBN 1-884207-03-0
Plastics Design Library Staff, Pub. Date: 1991, 528 Pages
The Effect of Temperature and Other Factors on Plastics
ISBN 1-884207-06-5
Plastics Design Library Staff, Pub. Date: 1991, 420 Pages

Contents
1 Unsaturated Polyester Resins 1
1.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Monomers for the Unsaturated Polyester (UP) . 2
1.2.2 Vinyl Monomers . . . . . . . . . . . . . . . . . 8
1.2.3 Specialities . . . . . . . . . . . . . . . . . . . . 10
1.2.4 Synthesis . . . . . . . . . . . . . . . . . . . . . 13
1.2.5 Manufacture . . . . . . . . . . . . . . . . . . . 15
1.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 17
1.3.1 Inhibitors . . . . . . . . . . . . . . . . . . . . . 17
1.3.2 Thickeners . . . . . . . . . . . . . . . . . . . . 18
1.3.3 Emission Suppressants . . . . . . . . . . . . . . 18
1.3.4 Fillers . . . . . . . . . . . . . . . . . . . . . . . 19
1.3.5 Reinforcing Materials . . . . . . . . . . . . . . 23
1.3.6 Mold Release Agents . . . . . . . . . . . . . . . 25
1.3.7 Low-profile Additives . . . . . . . . . . . . . . 26
1.3.8 Interpenetrating Polymer Networks . . . . . . . 28
1.3.9 Polyurethane Hybrid Networks . . . . . . . . . 30
1.3.10 Flame Retardants . . . . . . . . . . . . . . . . . 31
1.3.11 Production Data . . . . . . . . . . . . . . . . . 34
1.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
1.4.1 Initiator Systems . . . . . . . . . . . . . . . . . 35
1.4.2 Promoters . . . . . . . . . . . . . . . . . . . . . 37
1.4.3 Initiator Promoter Systems . . . . . . . . . . . . 40
1.4.4 Polymerization . . . . . . . . . . . . . . . . . . 40
1.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 44
vii

viii
Reactive Polymers Fundamentals and Applications
1.5.1 Structure Properties Relationships . . . . . . . . 44
1.5.2 Hydrolytic Stability . . . . . . . . . . . . . . . 45
1.5.3 Recycling . . . . . . . . . . . . . . . . . . . . . 45
1.6 Applications and Uses . . . . . . . . . . . . . . . . . . 46
1.6.1 Decorative Specimens . . . . . . . . . . . . . . 47
1.6.2 Polyester Concrete . . . . . . . . . . . . . . . . 47
1.6.3 Reinforced Materials . . . . . . . . . . . . . . . 47
1.6.4 Coatings . . . . . . . . . . . . . . . . . . . . . 48
1.7 Special Formulations . . . . . . . . . . . . . . . . . . . 49
1.7.1 Electrically Conductive Resins . . . . . . . . . . 50
1.7.2 Fluoro Copolymers . . . . . . . . . . . . . . . . 50
1.7.3 Toner Compositions . . . . . . . . . . . . . . . 51
1.7.4 Pour Point Depressants . . . . . . . . . . . . . . 52
1.7.5 Biodegradable Polyesters . . . . . . . . . . . . 52
1.7.6 Bone Cement . . . . . . . . . . . . . . . . . . . 52
1.7.7 Compatibilizers . . . . . . . . . . . . . . . . . . 53
1.7.8 Reactive Melt Modification of Poly(propylene) . 53
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2 Polyurethanes 69
2.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 69
2.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 70
2.2.1 Diisocyanates . . . . . . . . . . . . . . . . . . . 70
2.2.2 Polyols . . . . . . . . . . . . . . . . . . . . . . 84
2.2.3 Other Polyols . . . . . . . . . . . . . . . . . . . 90
2.2.4 Polyamines . . . . . . . . . . . . . . . . . . . . 91
2.2.5 Chain Extenders . . . . . . . . . . . . . . . . . 92
2.2.6 Catalysts . . . . . . . . . . . . . . . . . . . . . 92
2.2.7 Blowing . . . . . . . . . . . . . . . . . . . . . 94
2.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 109
2.3.1 Fillers . . . . . . . . . . . . . . . . . . . . . . . 109
2.3.2 Reinforcing Materials . . . . . . . . . . . . . . 110
2.3.3 Flame Retardants . . . . . . . . . . . . . . . . . 111
2.3.4 Production Data . . . . . . . . . . . . . . . . . 113
2.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
2.4.1 Recycling . . . . . . . . . . . . . . . . . . . . . 114
2.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 115
2.5.1 Mechanical Properties . . . . . . . . . . . . . . 115

Contents
ix
2.5.2 Thermal Properties . . . . . . . . . . . . . . . . 116
2.5.3 Weathering Resistance . . . . . . . . . . . . . . 116
2.6 Applications and Uses . . . . . . . . . . . . . . . . . . 116
2.6.1 Casting . . . . . . . . . . . . . . . . . . . . . . 116
2.7 Special Formulations . . . . . . . . . . . . . . . . . . . 117
2.7.1 Interpenetrating Networks . . . . . . . . . . . . 117
2.7.2 Grafting with Isocyanates . . . . . . . . . . . . 118
2.7.3 Medical Applications . . . . . . . . . . . . . . . 118
2.7.4 Waterborne Polyurethanes . . . . . . . . . . . . 120
2.7.5 Ceramic Foams . . . . . . . . . . . . . . . . . . 122
2.7.6 Adhesion Modification . . . . . . . . . . . . . . 122
2.7.7 Electrolytes . . . . . . . . . . . . . . . . . . . . 122
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3 Epoxy Resins 139
3.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 139
3.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 139
3.2.1 Epoxides . . . . . . . . . . . . . . . . . . . . . 139
3.2.2 Phenols . . . . . . . . . . . . . . . . . . . . . . 140
3.2.3 Specialities . . . . . . . . . . . . . . . . . . . . 144
3.2.4 Manufacture . . . . . . . . . . . . . . . . . . . 146
3.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 151
3.3.1 Toughening Agents . . . . . . . . . . . . . . . . 151
3.3.2 Antiplasticizers . . . . . . . . . . . . . . . . . . 159
3.3.3 Lubricants . . . . . . . . . . . . . . . . . . . . 160
3.3.4 Adhesion Improvers . . . . . . . . . . . . . . . 160
3.3.5 Conductivity Modifiers . . . . . . . . . . . . . . 161
3.3.6 Reinforcing Materials . . . . . . . . . . . . . . 161
3.3.7 Interpenetrating Polymer Networks . . . . . . . 164
3.3.8 Organic and Inorganic Hybrids . . . . . . . . . 167
3.3.9 Flame Retardants . . . . . . . . . . . . . . . . . 168
3.3.10 Production Data . . . . . . . . . . . . . . . . . 173
3.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
3.4.1 Initiator Systems . . . . . . . . . . . . . . . . . 173
3.4.2 Compounds with Activated Hydrogen . . . . . . 174
3.4.3 Coordination Catalysts . . . . . . . . . . . . . . 182
3.4.4 Ionic Curing . . . . . . . . . . . . . . . . . . . 183
3.4.5 Photoinitiators . . . . . . . . . . . . . . . . . . 186

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Reactive Polymers Fundamentals and Applications
3.4.6 Derivatives of Michler’s Ketone . . . . . . . . . 189
3.4.7 Epoxy Systems with Vinyl Groups . . . . . . . . 193
3.4.8 Curing Kinetics . . . . . . . . . . . . . . . . . . 193
3.4.9 Thermal Curing . . . . . . . . . . . . . . . . . 197
3.4.10 Microwave Curing . . . . . . . . . . . . . . . . 197
3.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 198
3.5.1 Hybrid Polymers and Mixed Polymers . . . . . 199
3.5.2 Recycling . . . . . . . . . . . . . . . . . . . . . 200
3.6 Applications and Uses . . . . . . . . . . . . . . . . . . 203
3.6.1 Coatings . . . . . . . . . . . . . . . . . . . . . 203
3.6.2 Foams . . . . . . . . . . . . . . . . . . . . . . 203
3.6.3 Adhesives . . . . . . . . . . . . . . . . . . . . . 203
3.6.4 Molding Techniques . . . . . . . . . . . . . . . 203
3.6.5 Stabilizers for Polyvinyl Chloride . . . . . . . . 204
3.7 Special Formulations . . . . . . . . . . . . . . . . . . . 204
3.7.1 Development of Formulations . . . . . . . . . . 204
3.7.2 Restoration Materials . . . . . . . . . . . . . . . 205
3.7.3 Biodegradable Epoxy-polyester Resins . . . . . 205
3.7.4 Swellable Epoxies . . . . . . . . . . . . . . . . 205
3.7.5 Reactive Membrane Materials . . . . . . . . . . 206
3.7.6 Controlled-release Formulations for Agriculture 206
3.7.7 Electronic Packaging Application . . . . . . . . 206
3.7.8 Solid Polymer Electrolytes . . . . . . . . . . . . 207
3.7.9 Optical Resins . . . . . . . . . . . . . . . . . . 207
3.7.10 Reactive Solvents . . . . . . . . . . . . . . . . . 210
3.7.11 Encapsulated Systems . . . . . . . . . . . . . . 211
3.7.12 Functionalized Polymers . . . . . . . . . . . . . 212
3.7.13 Epoxy Resins as Compatibilizers . . . . . . . . 212
3.7.14 Surface Metallization . . . . . . . . . . . . . . . 215
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
4 Phenol/formaldehyde Resins 241
4.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 242
4.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 243
4.2.1 Phenol . . . . . . . . . . . . . . . . . . . . . . 244
4.2.2 o-Cresol . . . . . . . . . . . . . . . . . . . . . 244
4.2.3 Formaldehyde . . . . . . . . . . . . . . . . . . 245
4.2.4 Multihydroxymethylketones . . . . . . . . . . . 246

Contents
xi
4.2.5 Production Data of Important Monomers . . . . 246
4.2.6 Basic Resin Types . . . . . . . . . . . . . . . . 247
4.2.7 Specialities . . . . . . . . . . . . . . . . . . . . 247
4.2.8 Synthesis . . . . . . . . . . . . . . . . . . . . . 249
4.2.9 Catalysts . . . . . . . . . . . . . . . . . . . . . 251
4.2.10 Manufacture . . . . . . . . . . . . . . . . . . . 254
4.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 255
4.3.1 Low Emission Types . . . . . . . . . . . . . . . 255
4.3.2 Boric Acid-modified Types . . . . . . . . . . . 257
4.3.3 Fillers . . . . . . . . . . . . . . . . . . . . . . . 259
4.3.4 Flame Retardants . . . . . . . . . . . . . . . . . 259
4.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
4.4.1 Model Studies . . . . . . . . . . . . . . . . . . 260
4.4.2 Experimental Design . . . . . . . . . . . . . . . 261
4.4.3 Water Content . . . . . . . . . . . . . . . . . . 262
4.4.4 Influence of Pressure . . . . . . . . . . . . . . . 262
4.4.5 Wood . . . . . . . . . . . . . . . . . . . . . . . 262
4.4.6 Novolak Curing Agents . . . . . . . . . . . . . 262
4.4.7 Resol Resin Hardeners . . . . . . . . . . . . . . 263
4.4.8 Ester-type Accelerators . . . . . . . . . . . . . . 264
4.4.9 Ashless Resol Resins . . . . . . . . . . . . . . . 264
4.4.10 Recycling . . . . . . . . . . . . . . . . . . . . . 265
4.5 Applications and Uses . . . . . . . . . . . . . . . . . . 266
4.5.1 Binders for Glass Fibers . . . . . . . . . . . . . 266
4.5.2 Molding . . . . . . . . . . . . . . . . . . . . . 268
4.5.3 Novolak Photoresists . . . . . . . . . . . . . . . 268
4.5.4 High Temperature Adhesives . . . . . . . . . . 269
4.5.5 Urethane-modified Types . . . . . . . . . . . . 269
4.5.6 Carbon Products . . . . . . . . . . . . . . . . . 270
4.6 Special Formulations . . . . . . . . . . . . . . . . . . . 272
4.6.1 Chemical Resistant Types . . . . . . . . . . . . 272
4.6.2 Ion Exchange Resins . . . . . . . . . . . . . . . 272
4.6.3 Brakes . . . . . . . . . . . . . . . . . . . . . . 273
4.6.4 Waterborne Types . . . . . . . . . . . . . . . . 273
4.6.5 High Viscosity Novolak . . . . . . . . . . . . . 273
4.6.6 Foams . . . . . . . . . . . . . . . . . . . . . . 273
4.6.7 Visbreaking of Petroleum . . . . . . . . . . . . 274
4.7 Testing Methods . . . . . . . . . . . . . . . . . . . . . . 274

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4.7.1 Water Tolerance . . . . . . . . . . . . . . . . . 274
4.7.2 Salt Tolerance . . . . . . . . . . . . . . . . . . 274
4.7.3 Free Phenol Content . . . . . . . . . . . . . . . 275
4.7.4 Free Formaldehyde . . . . . . . . . . . . . . . . 275
4.7.5 pH . . . . . . . . . . . . . . . . . . . . . . . . 275
4.7.6 Solids Content . . . . . . . . . . . . . . . . . . 275
4.7.7 o-Cresol Contact Allergy . . . . . . . . . . . . . 275
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
5 Urea/formaldehyde Resins 283
5.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 283
5.2 Synthesis of Resin . . . . . . . . . . . . . . . . . . . . . 283
5.2.1 Formaldehyde . . . . . . . . . . . . . . . . . . 283
5.2.2 Urea . . . . . . . . . . . . . . . . . . . . . . . 284
5.2.3 Ammonia . . . . . . . . . . . . . . . . . . . . . 284
5.2.4 Diketones . . . . . . . . . . . . . . . . . . . . . 284
5.2.5 Specialities . . . . . . . . . . . . . . . . . . . . 284
5.2.6 Polymerization . . . . . . . . . . . . . . . . . . 286
5.2.7 Manufacture . . . . . . . . . . . . . . . . . . . 290
5.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 290
5.3.1 Modifiers . . . . . . . . . . . . . . . . . . . . . 290
5.3.2 Flame Retardants . . . . . . . . . . . . . . . . . 291
5.3.3 Production Data of Important Monomers . . . . 291
5.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
5.5 Measurement of Curing . . . . . . . . . . . . . . . . . . 292
5.6 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 293
5.6.1 Formaldehyde Release . . . . . . . . . . . . . . 293
5.6.2 Storage . . . . . . . . . . . . . . . . . . . . . . 293
5.7 Applications and Uses . . . . . . . . . . . . . . . . . . 294
5.7.1 Glue Resins . . . . . . . . . . . . . . . . . . . . 294
5.7.2 Binders . . . . . . . . . . . . . . . . . . . . . . 294
5.7.3 Foundry Sands . . . . . . . . . . . . . . . . . . 294
5.8 Special Formulations . . . . . . . . . . . . . . . . . . . 294
5.8.1 Ready-use Powders . . . . . . . . . . . . . . . . 294
5.8.2 Cyclic Urea Prepolymer in PF Laminating Resins 295
5.8.3 Liquid Fertilizer . . . . . . . . . . . . . . . . . 295
5.8.4 Soil Amendment . . . . . . . . . . . . . . . . . 295
5.8.5 Microencapsulation . . . . . . . . . . . . . . . 296

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
6 Melamine Resins 299
6.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 299
6.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 299
6.2.1 Melamine . . . . . . . . . . . . . . . . . . . . . 299
6.2.2 Other Modifiers . . . . . . . . . . . . . . . . . 300
6.2.3 Synthesis . . . . . . . . . . . . . . . . . . . . . 300
6.2.4 Manufacture . . . . . . . . . . . . . . . . . . . 302
6.3 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 302
6.4 Applications and Uses . . . . . . . . . . . . . . . . . . 303
6.4.1 Wood Impregnation . . . . . . . . . . . . . . . 303
6.5 Special Formulations . . . . . . . . . . . . . . . . . . . 304
6.5.1 Resins with Increased Elasticity . . . . . . . . . 304
6.5.2 Microspheres . . . . . . . . . . . . . . . . . . . 304
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
7 Furan Resins 307
7.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 307
7.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 307
7.2.1 Furfural . . . . . . . . . . . . . . . . . . . . . . 308
7.2.2 Furfuryl Alcohol . . . . . . . . . . . . . . . . . 309
7.2.3 Specialities . . . . . . . . . . . . . . . . . . . . 309
7.2.4 Synthesis . . . . . . . . . . . . . . . . . . . . . 309
7.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 310
7.3.1 Reinforcing Materials . . . . . . . . . . . . . . 310
7.3.2 Production Data of Important Monomers . . . . 311
7.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
7.4.1 Acidic Curing . . . . . . . . . . . . . . . . . . 312
7.4.2 Oxidative Curing . . . . . . . . . . . . . . . . . 312
7.4.3 Ultrasonic Curing . . . . . . . . . . . . . . . . 312
7.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 313
7.5.1 Recycling . . . . . . . . . . . . . . . . . . . . . 313
7.6 Applications and Uses . . . . . . . . . . . . . . . . . . 313
7.6.1 Carbons . . . . . . . . . . . . . . . . . . . . . . 313
7.6.2 Chromatography Support . . . . . . . . . . . . 314
7.6.3 Composite Carbon Fiber Materials . . . . . . . 315
7.6.4 Foundry Binders . . . . . . . . . . . . . . . . . 316
7.6.5 Glass Fiber Binders . . . . . . . . . . . . . . . 316

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7.6.6 Oil Field Applications . . . . . . . . . . . . . . 317
7.6.7 Plant Growth Substrates . . . . . . . . . . . . . 317
7.6.8 Photosensitive Polymer Electrolytes . . . . . . . 317
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
8 Silicones 321
8.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 321
8.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 322
8.2.1 Chlorosilanes . . . . . . . . . . . . . . . . . . . 322
8.2.2 Silsesquioxanes . . . . . . . . . . . . . . . . . . 322
8.2.3 Hydrogen Silsesquioxanes . . . . . . . . . . . . 322
8.2.4 Alkoxy Siloxanes . . . . . . . . . . . . . . . . . 324
8.2.5 Epoxy-modified Siloxanes . . . . . . . . . . . . 325
8.2.6 Silaferrocenophanes . . . . . . . . . . . . . . . 325
8.2.7 Synthesis . . . . . . . . . . . . . . . . . . . . . 327
8.2.8 Manufacture . . . . . . . . . . . . . . . . . . . 330
8.3 Modified Types . . . . . . . . . . . . . . . . . . . . . . 331
8.3.1 Chemical Modifications . . . . . . . . . . . . . 331
8.3.2 Fillers . . . . . . . . . . . . . . . . . . . . . . . 331
8.3.3 Reinforcing Materials . . . . . . . . . . . . . . 332
8.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
8.4.1 Curing by Condensation . . . . . . . . . . . . . 332
8.5 Crosslinking . . . . . . . . . . . . . . . . . . . . . . . . 334
8.5.1 Condensation Crosslinking . . . . . . . . . . . . 334
8.5.2 Peroxides . . . . . . . . . . . . . . . . . . . . . 335
8.5.3 Hydrosilylation Crosslinking . . . . . . . . . . . 335
8.6 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 336
8.6.1 Silicone Rubber . . . . . . . . . . . . . . . . . 336
8.6.2 Thermal Properties . . . . . . . . . . . . . . . . 336
8.6.3 Electrical Properties . . . . . . . . . . . . . . . 338
8.6.4 Surface Tension Properties . . . . . . . . . . . . 338
8.6.5 Antioxidants . . . . . . . . . . . . . . . . . . . 338
8.6.6 Gas Permeability . . . . . . . . . . . . . . . . . 338
8.6.7 Weathering . . . . . . . . . . . . . . . . . . . . 340
8.7 Applications and Uses . . . . . . . . . . . . . . . . . . 340
8.7.1 Antifoaming Agents . . . . . . . . . . . . . . . 340
8.7.2 Release Agents . . . . . . . . . . . . . . . . . . 340
8.7.3 Sealing and Jointing Materials . . . . . . . . . . 341

Contents
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8.7.4 Electrical Industry . . . . . . . . . . . . . . . . 341
8.7.5 Medical Applications . . . . . . . . . . . . . . . 341
8.8 Special Formulations . . . . . . . . . . . . . . . . . . . 342
8.8.1 Polyimide Resins . . . . . . . . . . . . . . . . . 342
8.8.2 Thermal Transfer Ribbons . . . . . . . . . . . . 342
8.8.3 Self-Assembly Systems . . . . . . . . . . . . . 343
8.8.4 Plasma Grafting . . . . . . . . . . . . . . . . . 343
8.8.5 Antifouling Compositions . . . . . . . . . . . . 344
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
9 Acrylic Resins 349
9.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 349
9.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 350
9.2.1 Specialities . . . . . . . . . . . . . . . . . . . . 350
9.2.2 Synthesis . . . . . . . . . . . . . . . . . . . . . 352
9.2.3 Manufacture . . . . . . . . . . . . . . . . . . . 353
9.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 356
9.3.1 Ultraviolet Absorbers . . . . . . . . . . . . . . 356
9.3.2 Flame Retardants . . . . . . . . . . . . . . . . . 356
9.3.3 Production Data of Important Monomers . . . . 358
9.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
9.4.1 Initiator Systems . . . . . . . . . . . . . . . . . 358
9.4.2 Promoters . . . . . . . . . . . . . . . . . . . . . 360
9.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 360
9.5.1 Electrical Properties . . . . . . . . . . . . . . . 360
9.5.2 Hydrolytic and Photochemical Stability . . . . . 361
9.5.3 Recycling . . . . . . . . . . . . . . . . . . . . . 361
9.6 Applications and Uses . . . . . . . . . . . . . . . . . . 361
9.6.1 Acrylic Premixes . . . . . . . . . . . . . . . . . 361
9.6.2 Protective Coatings in Electronic Devices . . . . 362
9.6.3 High-performance Biocomposite . . . . . . . . 363
9.6.4 Solid Polymer Electrolytes . . . . . . . . . . . . 363
9.7 Special Formulations . . . . . . . . . . . . . . . . . . . 365
9.7.1 Silane and Siloxane Acrylate Resins . . . . . . . 365
9.7.2 Marble Conservation . . . . . . . . . . . . . . . 365
9.7.3 Tackifier Resins . . . . . . . . . . . . . . . . . 366
9.7.4 Drug Release Membranes . . . . . . . . . . . . 366
9.7.5 Support Materials for Catalysts . . . . . . . . . 367

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9.7.6 Electron Microscopy . . . . . . . . . . . . . . . 367
9.7.7 Stereolithography . . . . . . . . . . . . . . . . 367
9.7.8 Laminated Films . . . . . . . . . . . . . . . . . 367
9.7.9 Ink-jet Printing Media . . . . . . . . . . . . . . 368
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
10 Cyanate Ester Resins 373
10.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 373
10.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 373
10.2.1 Specialities . . . . . . . . . . . . . . . . . . . . 373
10.2.2 Synthesis . . . . . . . . . . . . . . . . . . . . . 375
10.3 Special Additives . . . . . . . . . . . . . . . . . . . . . 377
10.3.1 Fillers . . . . . . . . . . . . . . . . . . . . . . . 377
10.3.2 Flame Retardants . . . . . . . . . . . . . . . . . 378
10.4 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
10.4.1 Thermal Curing . . . . . . . . . . . . . . . . . 379
10.4.2 Curing with Epoxy Groups . . . . . . . . . . . . 381
10.4.3 Curing with Unsaturated Compounds . . . . . . 382
10.4.4 Initiator Systems . . . . . . . . . . . . . . . . . 384
10.5 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 385
10.5.1 Modelling . . . . . . . . . . . . . . . . . . . . 385
10.6 Applications and Uses . . . . . . . . . . . . . . . . . . 385
10.6.1 Composites . . . . . . . . . . . . . . . . . . . . 385
10.6.2 Electronic Industry . . . . . . . . . . . . . . . . 385
10.6.3 Spacecraft . . . . . . . . . . . . . . . . . . . . 386
10.7 Special Formulations . . . . . . . . . . . . . . . . . . . 386
10.7.1 PT Resins . . . . . . . . . . . . . . . . . . . . . 386
10.7.2 Blends with Epoxies . . . . . . . . . . . . . . . 386
10.7.3 Bismaleimide Triazine Resins . . . . . . . . . . 387
10.7.4 Siloxane Crosslinked Resins . . . . . . . . . . . 388
10.7.5 Alloys with Thermoplastics . . . . . . . . . . . 389
10.7.6 Coupling Agents for Cyanate Ester Resins . . . 391
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391
11 Bismaleimide Resins 397
11.1 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 397
11.1.1 4,4 ′ -Bis(maleimido)diphenylmethane . . . . . . 397
11.1.2 2,2 ′ -Diallyl bisphenol A . . . . . . . . . . . . . 397
11.1.3 Poly(ethylene glycol) End-capped with Maleimide 400

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11.1.4 Bismaleimide Bisimides . . . . . . . . . . . . . 400
11.1.5 Maleimide Epoxy Monomers . . . . . . . . . . 402
11.1.6 Phosphorous-containing Monomers . . . . . . . 402
11.1.7 Multiring Monomers with Pendant Chains . . . 405
11.1.8 Reactions of Maleimides . . . . . . . . . . . . . 405
11.1.9 Specialities . . . . . . . . . . . . . . . . . . . . 412
11.2 Special Additives . . . . . . . . . . . . . . . . . . . . . 417
11.2.1 Tougheners and Modifiers . . . . . . . . . . . . 417
11.2.2 Fillers . . . . . . . . . . . . . . . . . . . . . . . 421
11.2.3 Titanium dioxide . . . . . . . . . . . . . . . . . 421
11.2.4 Reinforcing Materials . . . . . . . . . . . . . . 422
11.2.5 Flame Retardants . . . . . . . . . . . . . . . . . 422
11.3 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
11.3.1 Monitoring Curing Reactions . . . . . . . . . . 423
11.3.2 Polymerization . . . . . . . . . . . . . . . . . . 423
11.3.3 Interpenetrating Networks . . . . . . . . . . . . 429
11.4 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 431
11.4.1 Thermal Properties . . . . . . . . . . . . . . . . 431
11.4.2 Water Sorption . . . . . . . . . . . . . . . . . . 431
11.4.3 Recycling . . . . . . . . . . . . . . . . . . . . . 433
11.5 Applications and Uses . . . . . . . . . . . . . . . . . . 433
11.5.1 Biochemical Reagents . . . . . . . . . . . . . . 433
11.6 Special Formulations . . . . . . . . . . . . . . . . . . . 433
11.6.1 Adhesives . . . . . . . . . . . . . . . . . . . . . 433
11.6.2 Phosphazene-triazine Polymers . . . . . . . . . 435
11.6.3 Phosphazene-triazine Polymers . . . . . . . . . 435
11.6.4 Porous Networks . . . . . . . . . . . . . . . . . 435
11.6.5 Nonlinear Optical Systems . . . . . . . . . . . . 435
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 438
12 Terpene Resins 447
12.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 447
12.2 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 447
12.2.1 Resin . . . . . . . . . . . . . . . . . . . . . . . 448
12.2.2 Turpentine . . . . . . . . . . . . . . . . . . . . 450
12.2.3 Rosin . . . . . . . . . . . . . . . . . . . . . . . 450
12.2.4 Production Data of Important Monomers . . . . 450
12.3 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 451

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12.3.1 Homopolymers . . . . . . . . . . . . . . . . . . 451
12.3.2 Copolymers . . . . . . . . . . . . . . . . . . . . 452
12.3.3 Terpene Phenolic Resins . . . . . . . . . . . . . 452
12.3.4 Terpene Maleimide Resins . . . . . . . . . . . . 454
12.4 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 455
12.4.1 Solubility . . . . . . . . . . . . . . . . . . . . . 455
12.4.2 Adhesive Properties . . . . . . . . . . . . . . . 456
12.4.3 Characterization . . . . . . . . . . . . . . . . . 458
12.4.4 Recycling . . . . . . . . . . . . . . . . . . . . . 459
12.5 Applications and Uses . . . . . . . . . . . . . . . . . . 459
12.5.1 Sealants . . . . . . . . . . . . . . . . . . . . . . 460
12.5.2 Pressure-sensitive Adhesives . . . . . . . . . . . 460
12.5.3 Polyacrylate Hot-melt Pressure-sensitive Adhesives 461
12.5.4 Hot-Melt Adhesives . . . . . . . . . . . . . . . 462
12.5.5 Coatings . . . . . . . . . . . . . . . . . . . . . 463
12.5.6 Sizing Agents . . . . . . . . . . . . . . . . . . . 463
12.5.7 Toner Compositions . . . . . . . . . . . . . . . 465
12.5.8 Chewing Gums . . . . . . . . . . . . . . . . . . 465
12.6 Special Formulations . . . . . . . . . . . . . . . . . . . 466
12.6.1 Toughener for Novolaks . . . . . . . . . . . . . 466
12.6.2 Fluoro Copolymers . . . . . . . . . . . . . . . . 467
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 467
13 Cyanoacrylates 471
13.1 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 471
13.1.1 Synthesis . . . . . . . . . . . . . . . . . . . . . 471
13.1.2 Crosslinkers . . . . . . . . . . . . . . . . . . . 472
13.1.3 Commercial Products . . . . . . . . . . . . . . 473
13.2 Special Additives . . . . . . . . . . . . . . . . . . . . . 475
13.2.1 Plasticizers . . . . . . . . . . . . . . . . . . . . 475
13.2.2 Accelerators . . . . . . . . . . . . . . . . . . . 477
13.2.3 Thickeners . . . . . . . . . . . . . . . . . . . . 480
13.2.4 Stabilizers . . . . . . . . . . . . . . . . . . . . 480
13.2.5 Primers . . . . . . . . . . . . . . . . . . . . . . 482
13.2.6 Diazabicyclo and Triazabicyclo Primers . . . . . 483
13.2.7 Polyamine Dendrimers . . . . . . . . . . . . . . 484
13.3 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . 485
13.3.1 Photo Curing . . . . . . . . . . . . . . . . . . . 485

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13.4 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 486
13.5 Applications and Uses . . . . . . . . . . . . . . . . . . 486
13.5.1 Manicure Composition . . . . . . . . . . . . . . 486
13.5.2 Tissue Adhesives . . . . . . . . . . . . . . . . . 487
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 489
14 Benzocyclobutene Resins 493
14.1 Modified Polymers . . . . . . . . . . . . . . . . . . . . 498
14.1.1 Thermotropic Copolymers . . . . . . . . . . . . 498
14.1.2 BCB-modified Aromatic Polyamides . . . . . . 498
14.1.3 BCB End-capped Polyimides . . . . . . . . . . 498
14.1.4 Flame Resistant Formulations . . . . . . . . . . 501
14.2 Crosslinkers . . . . . . . . . . . . . . . . . . . . . . . . 501
14.2.1 Modified Poly(ethylene terephthalate) . . . . . . 501
14.3 Applications and Uses . . . . . . . . . . . . . . . . . . 501
14.3.1 Applications in Microelectronics . . . . . . . . 502
14.3.2 Optical Applications . . . . . . . . . . . . . . . 504
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 504
15 Reactive Extrusion 507
15.1 Extruder . . . . . . . . . . . . . . . . . . . . . . . . . . 508
15.1.1 Heat of Polymerization . . . . . . . . . . . . . . 510
15.1.2 Ceiling Temperature . . . . . . . . . . . . . . . 510
15.1.3 Strategy of Reactive Extrusion . . . . . . . . . . 511
15.2 Compositions of Industrial Polymers . . . . . . . . . . . 512
15.2.1 Poly(styrene) . . . . . . . . . . . . . . . . . . . 513
15.2.2 Poly(tetramethylene ether) and Poly(caprolactam) 513
15.2.3 Polyamide 12 . . . . . . . . . . . . . . . . . . . 513
15.2.4 Poly(butyl methacrylate) . . . . . . . . . . . . . 514
15.2.5 Poly(carbonate) . . . . . . . . . . . . . . . . . . 514
15.3 Biodegradable Compositions . . . . . . . . . . . . . . . 517
15.3.1 Poly(lactide)s . . . . . . . . . . . . . . . . . . . 519
15.3.2 Biodegradable Fibers . . . . . . . . . . . . . . . 521
15.3.3 Poly(ε-caprolactone) . . . . . . . . . . . . . . . 521
15.3.4 Cationically Modified Starch . . . . . . . . . . . 523
15.3.5 Blends of Starch and Poly(acrylamide) . . . . . 523
15.3.6 Blends of Protein and Polyester . . . . . . . . . 523
15.4 Chain Extenders . . . . . . . . . . . . . . . . . . . . . . 524
15.4.1 Recycling of Poly(ethylene-terephthalate) . . . . 524

xx
Reactive Polymers Fundamentals and Applications
15.4.2 Modified Poly(ethylene terephthalate) . . . . . . 524
15.4.3 Poly(butylene terephthalate) . . . . . . . . . . . 525
15.5 Related Applications . . . . . . . . . . . . . . . . . . . 525
15.5.1 Transesterification . . . . . . . . . . . . . . . . 525
15.5.2 Hydrolysis and Alcoholysis . . . . . . . . . . . 526
15.5.3 Flame Retardant Master Batch . . . . . . . . . . 526
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 526
16 Compatibilization 531
16.1 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . 532
16.2 Basic Terms . . . . . . . . . . . . . . . . . . . . . . . . 532
16.2.1 Thermodynamic Compatibility . . . . . . . . . 532
16.2.2 Thermodynamic Models . . . . . . . . . . . . . 533
16.2.3 Particle Size . . . . . . . . . . . . . . . . . . . 533
16.2.4 Interfacial Slip . . . . . . . . . . . . . . . . . . 534
16.2.5 Interpolymer Radical Coupling . . . . . . . . . 534
16.2.6 Technological Compatibility . . . . . . . . . . . 534
16.3 Compatibilization by Additives . . . . . . . . . . . . . . 538
16.3.1 Poly(ethylene) Blended with Inorganic Fillers . . 538
16.3.2 Filler Materials without Chemical Compatibilizers 538
16.3.3 Modified Inorganic Fillers . . . . . . . . . . . . 539
16.3.4 Clay Nanocomposites . . . . . . . . . . . . . . 540
16.3.5 Thermoplastic Elastomers . . . . . . . . . . . . 540
16.3.6 Polyamide 6,6 and Poly(butylene terephthalate) . 541
16.3.7 Poly(ethylene)/Wood Flour Composites . . . . . 541
16.3.8 Recycled Polyolefins . . . . . . . . . . . . . . . 542
16.3.9 Block Copolymers . . . . . . . . . . . . . . . . 542
16.3.10 Impact Modification of Waste PET . . . . . . . 544
16.3.11 Starch . . . . . . . . . . . . . . . . . . . . . . . 544
16.3.12 Blends of Cellulose and Chitosan . . . . . . . . 545
16.4 Reactive Compatibilization . . . . . . . . . . . . . . . . 545
16.4.1 Coupling Agents for Compatibilization . . . . . 548
16.4.2 Vector Fluids . . . . . . . . . . . . . . . . . . . 549
16.4.3 Poly(ethylene) and Polyamide 6 . . . . . . . . . 549
16.4.4 PEO and PBT . . . . . . . . . . . . . . . . . . 551
16.4.5 Poly(ethylene-octene) and Polyamide 6 . . . . . 552
16.4.6 Ethylene Acrylic Acid Copolymers and Polyamide
6 . . . . . . . . . . . . . . . . . . . . . . . 552

Contents
xxi
16.4.7 Sisal Fibers . . . . . . . . . . . . . . . . . . . . 552
16.4.8 Thermotropic Liquid Crystalline Polyesters . . . 553
16.4.9 Ionomers and Ionomeric Compatibilizers . . . . 554
16.4.10 Poly(styrene) . . . . . . . . . . . . . . . . . . . 556
16.4.11 Polyolefins/Poly(ethylene oxide) . . . . . . . . . 558
16.4.12 Poly(phenylene sulfide)/Liquid Crystalline Polymers
. . . . . . . . . . . . . . . . . . . . . . . 559
16.4.13 LDPE/Thermoplastic Starch . . . . . . . . . . . 559
16.4.14 PE and EVA . . . . . . . . . . . . . . . . . . . 559
16.4.15 SBR and EVA . . . . . . . . . . . . . . . . . . 560
16.4.16 NBR and EPDM . . . . . . . . . . . . . . . . . 560
16.4.17 NBR and PA6 . . . . . . . . . . . . . . . . . . 561
16.4.18 Poly(carbonate)–Poly(vinylidene fluoride) Blends 561
16.4.19 Bisphenol A-poly(carbonate) and ABS Copolymers 561
16.4.20 Kevlar . . . . . . . . . . . . . . . . . . . . . 563
16.4.21 Polyamides . . . . . . . . . . . . . . . . . . . . 563
16.4.22 Polyethers . . . . . . . . . . . . . . . . . . . . 564
16.4.23 Polyurethane and Poly(ethylene terephthalate) . 566
16.5 Functionalization of End Groups . . . . . . . . . . . . . 566
16.5.1 Mechanisms . . . . . . . . . . . . . . . . . . . 566
16.5.2 Amino-terminated Nitrile Rubber . . . . . . . . 569
16.5.3 Functionalization of Olefinic End Groups of Poly-
(propylene) . . . . . . . . . . . . . . . . . . . . 569
16.5.4 Muconic Acid Grafted Polyolefin Compatibilizers 573
16.5.5 Polyfunctional Polymers and Modified Polyolefin 573
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 574
17 Rheology Control 587
17.1 Melt Flow Rate . . . . . . . . . . . . . . . . . . . . . . 587
17.2 Rheology Control Techniques . . . . . . . . . . . . . . 587
17.2.1 Pelletizing . . . . . . . . . . . . . . . . . . . . 589
17.3 Peroxides for Rheology Control . . . . . . . . . . . . . 590
17.3.1 Hydroperoxides . . . . . . . . . . . . . . . . . 590
17.3.2 Peroxides . . . . . . . . . . . . . . . . . . . . . 591
17.3.3 Diacyl Peroxides . . . . . . . . . . . . . . . . . 593
17.3.4 Ketone Peroxides . . . . . . . . . . . . . . . . . 593
17.3.5 Masterbatches of Peroxides . . . . . . . . . . . 595
17.3.6 Peresters . . . . . . . . . . . . . . . . . . . . . 595

xxii
Reactive Polymers Fundamentals and Applications
17.3.7 Properties of Peroxides . . . . . . . . . . . . . . 595
17.3.8 Azo Compounds . . . . . . . . . . . . . . . . . 600
17.4 Scavengers . . . . . . . . . . . . . . . . . . . . . . . . 601
17.4.1 Stable Nitroxyl Radicals . . . . . . . . . . . . . 601
17.5 Mechanism of Degradation . . . . . . . . . . . . . . . . 601
17.6 Ultra High Melt Flow Poly(propylene) . . . . . . . . . . 605
17.7 Irregular Flow Improvement . . . . . . . . . . . . . . . 605
17.8 Heterophasic Copolymers . . . . . . . . . . . . . . . . . 606
17.9 Poly(propylene) . . . . . . . . . . . . . . . . . . . . . . 608
17.9.1 Long Chain Branched Poly(propylene) . . . . . 608
17.9.2 Effect of MFR on Temperature and Residence Time 608
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 609
18 Grafting 611
18.1 The Techniques in Grafting . . . . . . . . . . . . . . . . 611
18.1.1 Parameters that Influence Grafting . . . . . . . . 611
18.1.2 Free Radical Induced Grafting . . . . . . . . . . 614
18.1.3 Grafting Using Stable Radicals . . . . . . . . . 614
18.2 Polyolefins . . . . . . . . . . . . . . . . . . . . . . . . 616
18.2.1 Monomers for Grafting onto Polyolefins . . . . 616
18.2.2 Mechanism of Melt Grafting . . . . . . . . . . . 617
18.2.3 Side Reactions . . . . . . . . . . . . . . . . . . 618
18.2.4 Viscosity . . . . . . . . . . . . . . . . . . . . . 618
18.2.5 Ceiling Temperature . . . . . . . . . . . . . . . 620
18.2.6 Effect of Initiator Solubility . . . . . . . . . . . 620
18.2.7 Distribution of the Grafted Groups . . . . . . . . 622
18.2.8 Effect of Stabilizers on Grafting . . . . . . . . . 622
18.2.9 Radical Grafting of Polyolefins with Diethyl
Maleate . . . . . . . . . . . . . . . . . . . . . . 622
18.2.10 Inhibitors for the Homopolymerization of Maleic
anhydride . . . . . . . . . . . . . . . . . . . . . 623
18.2.11 Inhibitors for Crosslinking . . . . . . . . . . . . 623
18.2.12 Special Initiators . . . . . . . . . . . . . . . . . 624
18.2.13 Maleic anhydride . . . . . . . . . . . . . . . . . 629
18.2.14 Polyolefins Grafted with Itaconic Acid Derivatives 629
18.2.15 Imidized Maleic Groups . . . . . . . . . . . . . 630
18.2.16 Oxazoline-modified Polyolefins . . . . . . . . . 630
18.2.17 Modification of Polyolefins with Vinylsilanes . . 631

Contents
xxiii
18.2.18 Ethyl Diazoacetate-modified Polyolefins . . . . 631
18.2.19 Grafting Antioxidants . . . . . . . . . . . . . . 632
18.2.20 Comonomer Assisted Free Radical Grafting . . . 633
18.2.21 Radiation Induced Grafting in Solution . . . . . 636
18.2.22 Characterization of Polyolefin Graft Copolymers 636
18.2.23 PVC/LDPE Melt Blends . . . . . . . . . . . . . 637
18.3 Other Polymers . . . . . . . . . . . . . . . . . . . . . . 637
18.3.1 Poly(styrene) Functionalized with Maleic anhydride
. . . . . . . . . . . . . . . . . . . . . . . 637
18.3.2 Multifunctional Monomers for PP/PS Blends . . 637
18.3.3 Poly(ethylene-co-methyl acrylate) . . . . . . . . 638
18.3.4 n-Butyl methacrylate Grafted onto PVC . . . . . 638
18.3.5 Starch Esterification . . . . . . . . . . . . . . . 639
18.3.6 Starch Grafted Acrylics . . . . . . . . . . . . . 639
18.3.7 Thermoplastic Phenol/Formaldehyde Polymers . 640
18.3.8 Polyesters and Polyurethanes . . . . . . . . . . 640
18.3.9 Polyacrylic Hot-melt Pressure-sensitive Adhesive 642
18.4 Terminal Functionalization . . . . . . . . . . . . . . . . 642
18.4.1 Ene Reaction with Poly(propylene) . . . . . . . 642
18.4.2 Styrene-butadiene Rubber . . . . . . . . . . . . 643
18.4.3 Diels-Alder Reaction . . . . . . . . . . . . . . . 643
18.5 Grafting onto Surfaces . . . . . . . . . . . . . . . . . . 644
18.5.1 Grafting onto Poly(ethylene) . . . . . . . . . . . 644
18.5.2 Grafting onto Poly(tetrafluoroethylene) . . . . . 647
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649
19 Acrylic Dental Fillers 657
19.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . 658
19.2 Polymeric Composite Filling Materials . . . . . . . . . . 658
19.3 Monomers . . . . . . . . . . . . . . . . . . . . . . . . . 659
19.3.1 Acrylics and Methacrylics . . . . . . . . . . . . 659
19.3.2 Cyclic Monomers . . . . . . . . . . . . . . . . 665
19.3.3 Epoxy Monomers . . . . . . . . . . . . . . . . 666
19.3.4 Highly Loaded Composite . . . . . . . . . . . . 668
19.4 Radical Polymerization . . . . . . . . . . . . . . . . . . 668
19.4.1 Chemical Curing Systems . . . . . . . . . . . . 668
19.4.2 Photo Curing . . . . . . . . . . . . . . . . . . . 673
19.4.3 Curing Techniques . . . . . . . . . . . . . . . . 676

xxiv
Reactive Polymers Fundamentals and Applications
19.4.4 Dual Initiator Systems . . . . . . . . . . . . . . 676
19.5 Inhibitors . . . . . . . . . . . . . . . . . . . . . . . . . 677
19.6 Additives . . . . . . . . . . . . . . . . . . . . . . . . . 677
19.6.1 Fillers and Reinforcing Materials . . . . . . . . 677
19.6.2 Pigments . . . . . . . . . . . . . . . . . . . . . 681
19.6.3 Photostabilizers . . . . . . . . . . . . . . . . . . 681
19.6.4 Caries Inhibiting Agents . . . . . . . . . . . . . 682
19.6.5 Coloring or Tint Agents . . . . . . . . . . . . . 682
19.6.6 Adhesion Promoter . . . . . . . . . . . . . . . . 682
19.6.7 Thermochromic Dye . . . . . . . . . . . . . . . 686
19.7 Properties . . . . . . . . . . . . . . . . . . . . . . . . . 686
19.7.1 Water Sorption . . . . . . . . . . . . . . . . . . 686
19.7.2 Cytotoxicity . . . . . . . . . . . . . . . . . . . 687
19.8 Applications . . . . . . . . . . . . . . . . . . . . . . . . 687
19.8.1 Filling Techniques . . . . . . . . . . . . . . . . 687
19.8.2 Primer Emulsions . . . . . . . . . . . . . . . . 688
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 688
20 Toners 693
20.1 Toner Components . . . . . . . . . . . . . . . . . . . . 694
20.2 Toner Resins . . . . . . . . . . . . . . . . . . . . . . . 695
20.3 Manufacture of Toner Resins . . . . . . . . . . . . . . . 696
20.3.1 Suspension Polymerization . . . . . . . . . . . 696
20.3.2 Terephthalic Ester Resins . . . . . . . . . . . . 697
20.3.3 Unsaturated Ester Resins . . . . . . . . . . . . . 697
20.3.4 Toner Resins with Low Fix Temperature . . . . 698
20.3.5 Toners for Textile Printing . . . . . . . . . . . . 700
20.4 Characterization of Toners . . . . . . . . . . . . . . . . 701
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 701
Index 703
Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 703
Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 724
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 757

1
Unsaturated Polyester Resins
Unsaturated polyester resins consist of two polymers, i.e., a short chain
polyester containing polymerizable double bonds and a vinyl monomer.
The curing reaction consists of a copolymerization of the vinyl monomer
with the double bonds of the polyester. In the course of curing, a three-dimensional
network is formed. Unsaturated polyester resins belong to the
group of so-called thermosets. There are several monographs and reviews
on unsaturated polyesters and unsaturated polyester resins. 1–7
We will differentiate between unsaturated polyesters and unsaturated
polyester resins. Unsaturated polyesters are the polyesters as they
emerge from the condensation vessel. They are rarely sold as such, because
they are brittle at room temperature and difficult to handle. Instead,
whenever a polyester is freshly synthesized in a plant, it is mixed with the
vinyl monomer in the molten state. Thus materials that are viscous at room
temperature, with a styrene content of ca. 60% are sold. Such a mixture
of an unsaturated polyester with the vinyl polymer is referred to here as an
unsaturated polyester resin.
1.1 HISTORY
It was realized long ago that some natural oils as well as alkyde resins can
be dried by certain additives and used as coatings. This drying results from
a polymerization of the unsaturated moieties in the ester molecules. Next
it was discovered that the addition of styrene would accelerate the drying.
1

2 Reactive Polymers Fundamentals and Applications
CH 3
HO
CH 2 CH 2
OH
HO
CH CH 2
OH
Ethylene glycol
Propylene glycol
CH 3
HO
CH 2
C CH 2
CH 3
OH
Neopentyl glycol
H 3 C
CH 2 OH
CH 2 C CH 2 OH
CH 2 OH
CH 2 CH CH 2
OH
OH OH
Trimethylol propane
Glycerol
Figure 1.1: Diols and Triols Used for Unsaturated Polyester Resins
The invention of unsaturated polyester resins is ascribed to Carleton Ellis
(1876–1941). The first patents with regard to polyester resins emerged in
the 1930’s. 8–10 Commercial production started in 1941 already reinforced
with glass fibers for radar domes, also referred to as radomes.
1.2 MONOMERS
According to the composition of an unsaturated polyester resin, the monomers
can be grouped in two main classes, i.e., components for the polyester
and components for the vinyl monomer.
1.2.1 Monomers for the Unsaturated Polyester (UP)
Monomers used for unsaturated polyesters are shown in Table 1.1 and in
Figures 1.1 and 1.2. Unsaturated diols are only rarely used.

Unsaturated Polyester Resins 3
Saturated alcohols
1,2-Propylene glycol
Ethylene glycol
Diethylene glycol
Neopentyl glycol
Glycerol
Table 1.1: Monomers for Unsaturated Polyesters
Tetrabromobisphenol A (TBBPA)
Trimethylolpropane
Trimethylolpropane mono allyl ether
(TMPAE)
Undecanol
Saturated acids and anhydrides
Remarks
Most common glycol
Less compatible with styrene than
Propylene glycol
Good drying properties
Good hydrolysis resistance
Trifunctional alcohol, for branched
polyesters. Danger of crosslinking
during condensation
Flame retardant
Trifunctional alcohol, cheaper than
glycerol
Weather resistant for coatings11, 12
Used as chain stopper
Remarks
Phthalic anhydride
Most common anhydride
Isophthalic acid
Good hydrolysis resistance
Terephthalic acid
Superior hydrolysis resistance
HET acid
Flame retardant systems. In fact, even
when addressed as HET acid, the
HET anhydride is used
Tetrabromophthalic anhydride Flame retardant systems
Adipic acid
Soft resins
Sebacic acid
Soft resins
o-Carboxy phthalanilic acid
13
Unsaturated acids and anhydrides
Maleic anhydride
Fumaric acid
Itaconic acid
Remarks
Most common
Copolymerizes better with styrene
than maleic anhydride

4 Reactive Polymers Fundamentals and Applications
O
COOH
O
O
Phthalic anhydride
COOH
Isophthalic acid
COOH
Cl
Cl
Cl
Cl
O
Cl
Cl
O
COOH
Terephthalic acid
O
HET-anhydride
H
O
H
O
O
CH
HOOC
COOH
CH
Maleic anhydride
Fumaric acid
Figure 1.2: Acids and Anhydrides Used for Unsaturated Polyester Resins

Unsaturated Polyester Resins 5
1.2.1.1 Alcohol Components
The most common alcohol components are 1,2-propylene glycol and ethylene
glycol. Ether containing alcohols exhibit better air drying properties
and are used in topcoats. Polyesters based on unsaturated diols can be prepared
by the transesterification of diethyl adipate with unsaturated diols,
e.g., cis-2-butene-1,4-diol, and 2-butyne-1,4-diol. The transesterification
method is a suitable procedure for the preparation of unsaturated polyesters
in comparison to the direct polycondensation. 14 cis-2-Butene-1,4-diol, the
most available aliphatic unsaturated diol, has been used to produce some
valuable polymers such as graftable unsaturated segmented polyurethanes
and crosslinkable polyesters for medical purposes.
1.2.1.2 Acid and Anhydride Components
A general purpose industrial unsaturated polyester is made from 1,2-propylene
glycol, phthalic anhydride, and maleic anhydride. The most commonly
used vinyl monomer is styrene. Maleic anhydride without phthalic
anhydride would yield a polyester with a high density of double bonds
along the polyester chain. This would result in a high crosslinking density
of the cured product, thus in a brittle product. Therefore, the unsaturated
acid component is always diluted with an acid with non-polymerizable
double bonds. Note that aromatic double bonds also will not polymerize
with vinyl components. The double bond in HET acid will not polymerize.
Fumaric acid copolymerizes well with styrene, but fumaric acid is more
costly than maleic anhydride. Therefore, maleic anhydride is the preferred
unsaturated acid component. Another aspect is that during the condensation
of fumaric acid, 2 mol of water must be removed from the reaction
mixtures, whereas in the case of maleic anhydride only 1 mol of water
must be removed. Anhydrides are preferred over the corresponding acids
because of the higher reactivity.
Isophthalic acid and terephthalic acid cannot form an anhydride.
These compounds do not condense as fast as phthalic anhydride. On the
other hand, the polyesters from isophthalic acid and terephthalic acid are
more stable than those made from phthalic anhydride. That is why these
polyesters with neopentyl glycol are used in aggressive environments and
also as gel coats and top coats. A gel coat is the first layer of a multi layer
material; the top coat is the layer on the opposite side. For instance, if a
polyester boat is built, the gel coat is first painted into the model. Then

6 Reactive Polymers Fundamentals and Applications
a series of glass fiber reinforced laminates are applied, and finally the top
coat is painted.
Isomerization. During the synthesis of the polyester, maleic anhydride
partly isomerizes to fumaric acid. The isomerization follows a secondorder
kinetics because of the catalysis by maleic acid. The activation energy
of the isomerization is ca. 63.2 kJ/mol. 15
2-Methyl-1,3-propanediol offers significant process advantages to
resin producers because it is an easily handled liquid, it has a high boiling
point, and it has two primary hydroxyl groups for rapid condensations.
Polyester resins produced from 2-methyl-1,3-propanediol using conventional
condensation polymerization, however, have relatively low fumarate
contents (60 to 70%), and simply increasing the reaction temperature to
promote isomerization causes color problems.
The two-step process helps increase the degree of isomerization for
such systems. First, the aromatic dicarboxylic acid is allowed to react with
2-methyl-1,3-propanediol at a temperature of up to 225°C to produce an
ester diol intermediate. In the second step, the intermediate reacts with
maleic anhydride and with 1,2-propylene glycol. The resulting unsaturated
polyester resin has a fumarate content greater than about 85%. 16 The high
fumarate content helps the resins to cure quickly and thoroughly with vinyl
monomers, giving the resulting thermosets excellent water resistance.
1.2.1.3 Amine Modifiers
The adducts of ethylene oxide or propylene oxide with N,N ′ -diphenylethane-1,2-diamine
or N,N-dimethyl-p-phenylene diamine and ethylene oxide
with N,N ′ -diphenylhexane-1,6-diamine can be used as modifiers. When
used in amounts up to 2%, the amines substantially reduce the gelation
time of these modified unsaturated polyesters. However, as the reactivity
of the resins increases, their stability decreases.
17, 18
1.2.1.4 Dicyclopentadiene
Dicyclopentadiene is used in a wide variety of applications, including elastomers,
flame retardants, pesticides, and resins for adhesives, coatings and
rubber tackifiers. Approximately 30% of the production is used for unsaturated
polyester resins because of its valuable properties. 19

Unsaturated Polyester Resins 7
O
O
OH
OH
+
O
O
OH
H
O
Figure 1.3: Ene Reaction between Maleic acid and Dicyclopentadiene
O
O
O
O
+
O
O
O
O
Figure 1.4: Retro Diels-Alder Reaction of Dicyclopentadiene and Diels-Alder
Reaction between Maleic acid units and Cyclopentadiene
Dicyclopentadiene polyester resins are synthesized from dicyclopentadiene,
maleic anhydride, and a glycol. The reaction is performed
in the presence of water to generate maleic acid from the maleic anhydride
to form dicyclopentadiene maleate. The ene reaction is shown in
Figure 1.3.
The maleate is esterified with the glycol to form the unsaturated
polyester resin. 20, 21 The ene adduct serves to form end-capped polyesters.
At higher temperatures dicyclopentadiene undergoes a retro Diels-Alder
reaction and can add to the unsaturations of fumaric acid and maleic acid
(as pointed out in Figure 1.4), to form nadic acid units When the dicyclopentadiene-modified
unsaturated polyester is used for a molding material,
the polyester is usually mixed with a radically polymerizable monomer and
a polymerization initiator. This allows the viscosity or curing time of the
molding material to be suitable for the molding operation.

8 Reactive Polymers Fundamentals and Applications
Monomer
Table 1.2: Vinyl Monomers for Unsaturated Polyester Resins
Styrene
p-Vinyltoluene
α-Methylstyrene
Methyl acrylate
Methyl methacrylate
Diallyl phthalate
Triallyl cyanurate
Remarks
Most common, but carcinogenic
Not really a substitute for styrene
Slower curing reaction to avoid thermal stress
Good optical properties
Dicyclopentadiene-modified unsaturated polyesters yield molded articles
with excellent performance. The function of dicyclopentadiene is to
impart air drying characteristics, low-profile properties, high heat distortion,
excellent weathering performance, and increased filler dispersibility
in the resulting polymer. 22
1.2.2 Vinyl Monomers
The vinyl monomer serves as solvent for the polyester and reduces its viscosity.
Further, it is the agent of copolymerization in the course of curing.
Vinyl monomers for unsaturated polyester resins are shown in Table 1.2
and in Figure 1.5.
1.2.2.1 Styrenes
Styrene is the most widely used vinyl monomer for unsaturated polyesters.
However, styrene has a carcinogenic potential: therefore,replacing styrene
by some other vinyl monomer has been discussed for years.
With larger amounts of styrene the rigidity of the material can be
increased. α-Methylstyrene forms less reactive radicals, and thus slows
down the curing reaction. Therefore, α-methylstyrene is suitable for decreasing
the peak temperature during curing.
Polar vinyl monomers, such as vinylpyridine, improve the adhesion
of the polyester to glass fibers, which is useful in preventing delamination.
1.2.2.2 Acrylates and Methacrylates
Acrylates improve outdoor stability. Methyl methacrylate, in particular,
enhances the optical properties. The refractive index can be varied with

Unsaturated Polyester Resins 9
CH CH 2
CH CH 2
CH 3
Styrene
p-Vinyltoluene
CH 3
C CH 2
CH 2
C
O
O
CH 2 CH 2
CH 3
α-Methylstyrene
Methyl methacrylate
O
C
C
O
O
CH 2
CH
CH 2
CH
CH 2
CH 2
O
Diallyl phthalate
Figure 1.5: Vinyl Monomers for Unsaturated Polyester Resins

10 Reactive Polymers Fundamentals and Applications
CH 2 CH 2 O CH 2 CH 2 O CH 2 CH 2
O
CH
O
CH
CH 2 CH 2
Triethylene glycol divinyl ether
Figure 1.6: Vinyl ethers
mixtures of styrene and methyl methacrylate close to that of glass, so that
fairly transparent materials could be produced.
1.2.2.3 Vinyl Ethers
Various vinyl and divinyl ethers have been used as substitutes for styrene.
Divinyl ethers with unsaturated polyesters are used preferably in radiation
curable compositions and coatings. However, special formulations containing
no styrene but triethylene glycol divinyl ether (c.f. Figure 1.6) are
available that can be used for gel coats. 23
Propenyl ethers are generally easier to prepare than their corresponding
vinyl ethers. The propenyl ethers are simply prepared by isomerization
of the corresponding allyl ethers. Due to the steric effect of the methyl
groups in the propenyl ether molecules, they are expected to be much less
reactive than their vinyl ether analogs. 24 Examples for propenyl ethers are
ethoxylated hexanediol dipropenyl ether and, 1,1,1-trimethylolpropane dipropenyl
ether.
1.2.2.4 Other Vinyl Monomers
Triallyl cyanurate enhances the thermal stability of the final products. Since
the compound is trifunctional, it enhances the crosslinking density.
1.2.3 Specialities
1.2.3.1 Monomers for Waterborne Unsaturated Polyesters
Waterborne unsaturated polyesters are used for wood coatings. They have
UV-sensitive initiator systems. The basic constituents are selected from

Unsaturated Polyester Resins 11
ethylene glycol, 1,2-propylene glycol, diethylene glycol, and tetrahydrophthalic
anhydride, terephthalic acid, and trimellitic anhydride. 25 The vinyl
monomer is trimethylolpropane diallyl ether. The UV-sensitive compound
is 2-hydroxy-2-methylphenylpropane-1-one. When diluted with water, the
resins exhibit a proper viscosity in the range of 2,500 cps. The cured products
show good tensile properties and weatherability.
Another method used to make unsaturated polyesters water soluble
is to introduce polar hydrophilic groups such as carboxylic and sulfonic
groups into the resin molecule, which ensures a good dispersibility in water.
An example of such a compound is sodium 5-sulfonatoisophthalic
acid. Instead of styrene, glycerol monoethers of allyl alcohol and unsaturated
fatty alcohols are used as vinyl monomer. 26
Unsaturated polyester resins diluted in water are used for particleboards
and fiberboards. They are modified with acrylonitrile and also used
as mixtures with urea/formaldehyde (UF) resins. A mixture of a UP resin
and a UF resin allows the production of boards which have considerably
higher mechanical properties than those bonded exclusively with UF resins.
27
1.2.3.2 Low Emission Modifiers
Several methods have been proposed for reducing volatile organic compounds
(VOCs) emissions:
• Adding skin forming materials,
• Replacement of the volatile monomer with a less volatile monomer,
• Reduction in the amount of the monomer in the compositions, and
• Increasing the vinyl monomers by attaching them onto the polyester
chain.
Low Volatile Monomers. Styrene can be partly substituted for by low
volatile monomers, such as bivalent metal salts of acrylic acid or methacrylic
acid. Examples include zinc diacrylate, zinc dimethacrylate, calcium
diacrylate, and calcium dimethacrylate. 28
The metal salt monomer is typically a solid, and therefore has much
lower vapor pressure than, e.g., styrene. The acrylate functionality copolymerizes
readily with styrene. Due to the bivalent metal ions, the acrylates

12 Reactive Polymers Fundamentals and Applications
act as crosslinkers of the ionomer type. Therefore, an additional crosslinking
occurs in comparison to pure styrene.
Acrylate-modified Unsaturated Polyesters. Acrylate-modified unsaturated
polyesters may be used for low-viscosity resins and resins with
low emission of volatile monomers. In commercially available unsaturated
polyester resin applications, up to 50% of styrene or other vinyl monomers
are used. During curing some of the organic monomer is usually lost to
the atmosphere, which causes occupational safety hazards and an environmental
problem.
Tailoring the polyester by synthesizing branched structures and incorporating
additional vinyl unsaturations has been proposed. The diol
alcohols used for condensation may be partly replaced by glycidyl compounds
in order to obtain low molecular weight methacrylate or acrylatemodified
or terminated polyesters. 29 Suitable glycidyl compounds include
glycidyl methacrylate and glycidyl acrylate. Not more than 60 mol-% of
the alcohols can be replaced by glycidyl compounds.
23, 30
These polyesters have low viscosities because of the branched structures.
In addition to the maleic or fumaric units, they bear additional unsaturations
resulting from the pending reactive acrylate or methacrylate
moieties. For this reason these types need less vinyl monomer (styrene)
to increase the crosslinking density of the cured product. The increased
unsaturation results in a higher reactivity, which in turn leads to an increase
in heat distortion temperature and better corrosion resistance, good
pigmentability and excellent mechanical and physical properties. 31 Such
resins are therefore suitable as basic resins in gel coats.
1.2.3.3 Epoxide-based Unsaturated Polyesters
Epoxide-based unsaturated polyesters are obtained from the reaction of
half esters of maleic anhydride of fumaric acid with epoxy groups from
epoxide resins. For example, n-hexanol reacts easily with maleic anhydride
to form acidic hexyl maleate. This half ester is then used for the addition
reaction with the epoxy resin. 32
Allyl alcohol in the unsaturated resins enhances their properties. The
glass-transition temperatures of the epoxy fumarate resins exceed 100°C.
The glass-transition temperatures epoxy maleates are higher than 70°C.
The resins have good chemical resistance. 33

Unsaturated Polyester Resins 13
HO
C
O
O
O
OH
C
NH
C
Figure 1.7: o-Carboxy phthalanilic acid 13
1.2.3.4 Isocyanates
Isocyanates, such as toluene diisocyanate can be added to a formulated
resin, such as polyester plus vinyl monomer. The gelation times increase
with the concentration of toluene diisocyanate.
Also the viscosity increases strongly. Resins with only 3% of toluene
diisocyanate are thixotropic. 34 An increase in the viscosity is highly
undesirable.
1.2.3.5 o-Carboxy phthalanilic acid
A new acid monomer, o-carboxy phthalanilic acid, c.f., Figure 1.7, has
been synthesized from o-aminobenzoic acid with phthalic anhydride. This
monomer was condensed with different acids and glycols to prepare unsaturated
polyesters. These polyesters were admixed with styrene and cured.
The final materials were extensively characterized.
13, 35
It was found that the styrene/poly(1,2-propylene-maleate-o-carboxy
phthalanilate) polyester resin has the highest compressive strength value
and the best chemical resistance and physical properties among the materials
under investigation.
1.2.4 Synthesis
The synthesis of unsaturated polyesters occurs either by a bulk condensation
or by azeotropic condensation. General purpose polyesters can be condensed
by bulk condensation, whereas more sensitive components need the
azeotropic condensation technique, which can be performed at lower temperatures.
The synthesis in the laboratory scale does not differ significantly
from the commercial procedure.

14 Reactive Polymers Fundamentals and Applications
1.2.4.1 Kinetics of Polyesterification
The kinetics of polyesterification have been modelled. In the models,
the asymmetry of 1,2-propylene glycol was taken into account, because
it bears a primary and secondary hydroxyl group. The reactivities of these
hydroxyl groups differ by a factor of 2.6. The relative reactivity of maleic
and phthalic anhydride towards 1,2-propylene glycol, after the ring opening
of both anhydrides is complete, increases from ca. 1.7 to 2.3 when the
temperature is increased from 160 to 220°C. 36
The rate constants and Arrhenius parameters are estimated by fitting
the calculated conversion of the acid with time to the experimental
data over the entire range of conversion. For the copolyesterification reactions
involving two acids, a cross-catalysis model is used. 37 The agreement
between model predictions and experimental data has been proved
to be satisfactory. For example, the energy of activation for the condensation
reaction of 2-methyl-1,3-propanediol (MPD) with maleic anhydride
was obtained to 65 kJ/mol, and with phthalic anhydride 82 kJ/mol was
obtained.
1.2.4.2 Sequence Distribution of Double Bonds
The polycondensate formed by the melt condensation process of maleic
anhydride, phthalic anhydride, and 1,2-propylene glycol in the absence of
a transesterification catalyst has a non-random structure with a tendency towards
blockiness. On the other hand, the distribution of unsaturated units
in the unsaturated polyester influences the curing kinetics with the styrene
monomer. Segments containing double bonds close together appear
to lower the reactivity of the resin due to steric hindrance. This is suggested
by the fact that the rate of cure and the final degree of conversion
increase as the average sequence length of the maleic units decreases. Due
to the influence of the sequence length distribution on the reactivity, the
reactivity of unsaturated polyester resins may be tailored by sophisticated
condensation methods.
Methods to calculate the distributions have been worked out.
38, 39
Monte Carlo methods can be used to investigate the effects of the various
rate constants and stoichiometry of the reactants. Also, structural asymmetry
of the diol component and the influence of the dynamics of the ring
opening of the anhydride is considered.

Unsaturated Polyester Resins 15
O
CH 3
O + CH CH 2
OH OH
O
O
OH
O CH CH 2
O CH 3
OH
Figure 1.8: Reaction of Maleic anhydride with 1,2-Propanediol
1.2.5 Manufacture
Unsaturated polyesters are still produced in batch. Continuous processes
have been invented, but are not widespread. Most common is a cylindrical
batch reactor equipped with stirrer, condenser, and a jacket heater. Thus
the synthesis in laboratory and in industry is very similar. The typical size
of such reactors is between 2 and 10 m 3 .
We now illustrate a typical synthesis of an unsaturated polyester.
The reactor is filled at the room temperature with the glycol, in slight excess
to compensate the losses during the condensation. Losses occur because
of the volatility of the glycol, but also due to side reactions. The glycol
may eliminate water at elevated temperatures. Then maleic anhydride
and phthalic anhydride are charged to the reactor. Typical for a general
purpose unsaturated polyester resin is a ratio of 1 mol maleic anhydride, 1
mol phthalic anhydride, and 1.1 mol 1,2-propylene glycol. Further, other
components, such as adhesion promoters, can be added.
The reactor is sparged with nitrogen and slowly heated. At ca. 90°C
the anhydrides react with the glycol in an exothermic reaction. This is the
initial step of the polyreaction, shown in Figure 1.8. At the end of the
exothermic reaction a condensation catalyst may be added.
Catalysts such as lead dioxide, p-toluenesulfonic acid, and zinc acetate
40 affect the final color of the polyester and the kinetics of curing.
Temperature is raised carefully up to 200°C, so that the temperature
of the distillate never exceeds ca. 102 to 105°C. Otherwise the glycol
distills out. The reaction continues under nitrogen or carbon dioxide atmosphere.
The sparging is helpful for removing the water. Traces of oxygen
could cause coloration. The coloration emerges due to multiple conjugated
double bonds. Maleic anhydride is helpful in preventing coloration,
because the series of conjugated double bonds are interrupted by a Diels-
Alder reaction. In the case of sensitive components, e.g., diethylene glycol,

16 Reactive Polymers Fundamentals and Applications
even small amounts of oxygen can cause gelling during the condensation
reaction.
There are certain variations of water removal. Simply sparging with
inert gas is referred to as the melt condensation technique. In the case of
thermal sensitive polyesters, the water may be removed by the azeotrope
technique. Toluene or xylene is added to the reaction mixture. Both compounds
form an azeotrope with water. During reflux, water separates from
the aromatic solvent and can be collected. In the final stage, the aromatic
solvent must be removed either by enhanced sparging or under vacuum.
The azeotrope technique is in general preferred, because condensation proceeds
faster than in the case of melt condensation.
Vacuum also can be used to remove the water, although this technique
is used only rarely for unsaturated polyesters because of the risk of
removal of the glycol.
At early stages, the progress of the condensation reaction can be
controlled via the amount of water removed. In the final stage, this method
is not sufficiently accurate and the progress is monitored via the acid number.
Samples are withdrawn from the reactor and are titrated with alcoholic
potassium hydroxide (KOH) solution. The acid number is expressed in
milligrams KOH per gram of resin. Even though other methods for the determination
of the molecular weight are common in other fields, the control
of the acid number is the quickest method to follow the reaction.
The kinetics of self-catalyzed polyesterification reactions follows a
third-order kinetic law. Acid catalyzed esterification reactions follow a
second-order kinetics. In the final stage of the reaction, the reciprocal of
the acid number is linear with time.
General purpose unsaturated polyester resins are condensed down
to an acid number of around 50 mgKOH/g resin. This corresponds to a
molecular weight of approximately 1000 Dalton. After this acid number
has been reached, some additives are added, in particular polymerization
inhibitors, e.g., hydroquinone, and the polyester is cooled down, to initiate
the mixing with styrene. The polyester should be cooled down to the lowest
possible temperature. In any case the temperature of the polyester should
be below the boiling point of the vinyl monomer. There are two limiting
issues:
1. If the polyester is too hot, after mixing with the vinyl monomer a
preliminary curing may take place. In the worst case the resin may
gel.

Unsaturated Polyester Resins 17
Table 1.3: Inhibitors and Retarders for Unsaturated Polyester Resins
Inhibitor
Hydroquinone
1,4-Naphthoquinone
p-Benzoquinone
Chloranil
Catechol
Picric acid
Retarder
2,4-Pentanedione
2. If the polyester is too cold, its viscosity becomes too high, which
jeopardizes the mixing process.
Mixing can occur in several ways: either the polyester is poured into
styrene under vigorous stirring, or under continuous mixing, or the styrene
is poured into the polyester. The last method is preferred in the laboratory.
After mixing, the polyester resin is then cooled down to room temperature
as quickly as possible. Finally some special additives are added, such as
promoter for preaccelerated resin composition. An unsaturated polyester
resin is not miscible in all ratios with styrene. If an excess of styrene is
added, a two-phase system will emerge.
The resins have a slightly yellow color, mainly due to the inhibitor.
The final product is filtered, if necessary, and poured into vats or cans.
1.3 SPECIAL ADDITIVES
1.3.1 Inhibitors
There is a difference between inhibitors and retarders. Inhibitors stop the
polymerization completely, whereas retarders slow down the polymerization
rate. Inhibitors influence the polymerization characteristics. They act
in two ways:
1. Increasing the storage time
2. Decreasing the exothermic peak during curing
Common inhibitors are listed in Table 1.3. Inhibitors are used to increase
the storage time, and also to increase the pot life time. Sometimes a combination
of two or more inhibitors is used, since some types of inhibitors act
more specifically on the storage time and others influence the pot life time.

18 Reactive Polymers Fundamentals and Applications
The storage time of an unsaturated polyester resin increases with
the amount of inhibitor. Storage at high temperatures decreases the possible
shelf life. On the other hand, high doses of inhibitor detrimentally
influence the curing of the resin. Higher amounts of radical initiators are
required in the presence of high doses of inhibitors. The exothermic peak
during curing is reduced. This influences the degree of monomer conversion.
A high degree of conversion is needed to have optimal properties.
1.3.2 Thickeners
1.3.2.1 Multivalent Salts
For sheet molding compounds and bulk molding compounds, the resins are
thickened. This can be achieved particularly with MgO, at a concentration
of about 5%.
It is believed that it first interacts with the carboxylic acid group on
chains. Then a complex is formed with the salt formed and the carboxylic
acid groups of other chains, leading to an increase in viscosity. The maximum
hardness is achieved at 2% MgO with an increase from 190 MPa to
340 MPa for the specimen cured at room temperature. High temperature
curing decreases hardness.
1.3.2.2 Thixotropic Additives
For gel coat applications, fumed silica, precipitated silica or an inorganic
clay can be used. Hectorite and other clays can be modified by alkyl quaternary
ammonium salts such as di(hydrogenated tallow) ammonium chloride.
These organoclays are used in thixotropic unsaturated polyester resin
systems. 41
1.3.3 Emission Suppressants
If a polyester is exposed to open air during curing, the vinyl monomer can
easily evaporate. This leads to a change in the composition and thus to
a change in the glass transition temperature of the final product. 42 Still
more undesirable is the emission of potentially toxic compounds. There
are several approaches to achieving products with low emission rates.
The earliest approach has been the use of a suppressant which reduces
the loss of volatile organic compounds. The suppressants are often

Unsaturated Polyester Resins 19
waxes. The wax-based products are of a limited comparability with the
polyester resin. The wax-based suppressants separate from the system during
polymerization or curing, forming a surface layer which serves as a
barrier to volatile emissions.
For example, a paraffin wax having a melting point of about 60°C
significantly improves the styrene emission results. Waxes with a different
melting point from this temperature will not perform adequately at the low
concentrations necessary to maintain good bonding and physical properties
while inhibiting the styrene emissions. 43 The waxy surface layer must be
removed before the next layer can be applied, because waxes are likely to
cause a reduction in the interlaminar adhesion bond strength of laminating
layers.
Suppressants selected from polyethers, polyether block copolymers,
alkoxylated alcohols, alkoxylated fatty acids or polysiloxanes show a suppression
of the emission as well and better bonding properties. 44–46 Unsaturated
polyesters that contain α,β-unsaturated dicarboxylic acid residues
and allyl ether or polyalkylene glycol residues (so-called gloss polyesters)
require no paraffin for curing the surface of a coating, because the ether
groups initiate an autoxidative drying process. 47
1.3.4 Fillers
Examples for fillers include calcium carbonate powder, clay, alumina powder,
silica sand powder, talc, barium sulfate, silica powder, glass powder,
glass beads, mica, aluminum hydroxide, cellulose yarn, silica sand, river
sand, white marble, marble scrap, and crushed stone. In the case of glass
powder, aluminum hydroxide, and barium sulfate the translucency is imparted
on curing. 48 Common fillers are listed in Table 1.4. Fillers reduce
the cost and change certain mechanical properties of the cured materials.
1.3.4.1 Inorganic Fillers
Bentonite. Ca-bentonite is used in the formulation of unsaturated polyester-based
composite materials. Increasing the filler content, at a constant
styrene/polyester ratio, improves the properties of composites. Maximum
values of compressive strength, hardness, and thermal conductivity of composites
are observed at about 22.7% of styrene, whereas the water absorption
capacity was a minimum at a styrene content of 32.8%. 49

20 Reactive Polymers Fundamentals and Applications
Table 1.4: Fillers for Unsaturated Polyester Resins
Filler
Reference
Bentonite
49
Calcium carbonate
50
Clay
51
Glass beads
Flyash
52
Woodflour
53
Rubber particles
54
Nanocomposites
55–57
Montmorillonite. Sodium montmorillonite and organically modified
montmorillonite (MMT) were tested as reinforcing agents. Montmorillonite
increases the glass transition temperatures. At 3-5% modified montmorillonite
content, the tensile modulus, tensile strength, flexural modulus and
flexural strength values showed a maximum, whereas the impact strength
exhibited a minimum. Adding only 3% of organically modified montmorillonite
improved the flexural modulus of an unsaturated polyester by 35%.
The tensile modulus of unsaturated polyester was also improved by 17%
at 5% of montmorillonite. 51
Instead of styrene, 2-hydroxypropyl acrylate (HPA) as a reactive diluent
has been examined in preparing an unsaturated polyester/montmorillonite
nanocomposite. 58 The functionalization of MMT can be achieved
with polymerizable cationic surfactants, e.g., with vinylbenzyldodecyldimethyl
ammonium chloride (VDAC) or vinylbenzyloctadecyldimethyl ammonium
chloride (VOAC). Polymerizable organophilic clays have been
prepared by exchanging the sodium ions of MMT with these polymerizable
cationic surfactants. 59 With an unsaturated polyester, nanocomposites
consisting of UP and clay were prepared. The dispersion of organoclays
in UP caused gel formation. In the UP/VDAC/MMT system, intercalated
nanocomposites were found, while in the UP/VOAC/MMT system partially
exfoliated nanocomposites were observed.
When the content of organophilic montmorillonite is between 25%
and 5%, the mechanical properties, such as the tensile strength, the impact
strength, the heat resistance, and the swelling resistance of the hybrid
are enhanced. The properties are better than those of composites prepared
with pristine or non-polymerizable quaternary ammonium-modified montmorillonite.
60

Unsaturated Polyester Resins 21
Flyash. Flyash is an inexpensive material that can reduce the overall
cost of the composite if used as filler for unsaturated polyester resin. A
flyash-filled resin was found to have a higher flexural modulus than those
of a calcium carbonate-filled polyester resin and an unfilled resin. Flyash
was found to have poor chemical resistances but good saltwater, alkali,
weathering, and freeze-thaw resistances. 52
An enhancement of the tensile strength, flexural strength, and impact
strength is observed when the flyash is surface-treated with silane coupling
agents. 61
1.3.4.2 Wood flour
Plant-based fillers like sawdust, wood flour and others are utilized because
of their low density, and their relatively good mechanical properties and
reactive surface. The main disadvantage is the hygroscopicity 62 and the
difficulties in achieving acceptable dispersion in a polymeric matrix.
Surface modification of these materials can help reduce these problems.
Wood flour can be chemically modified with maleic anhydride to
improve the dispersion properties and adhesion to the matrix resin. This
treatment decreases the hygroscopicity, but excessive esterification has to
be avoided, because it leads to the deterioration of the wood flour, adversely
affecting its mechanical properties. 53
The incorporation of wood flour into the resin increases the compression
modulus and the yield stress but decreases the ultimate deformation
and toughness in all cases.
Thermogravimetric analysis of wood flour indicates changes in the
wood structure occur as a consequence of chemical modifications. Alkaline
treatment reduces the thermal stability of the wood flour and produces
a large char yield. In composites a thermal interaction between fillers and
matrix is observed. Thermal degradation of the composites begins at higher
temperature than the neat wood flours. 63
1.3.4.3 Rubber
Rubber particles toughen the materials.
54, 64
They act also as low-profile
additives. A low-profile additive, in general, diminishes shrinking in the
course of curing.

22 Reactive Polymers Fundamentals and Applications
Toughening. Rubbers with functional groups have been tested in blends
of unsaturated polyesters with respect to improving the mechanical properties.
In particular, functional rubbers such as hydroxy terminated poly-
(butadiene), epoxidized natural rubber, hydroxy-terminated natural rubber,
and maleated nitrile rubber were tested. The performance of a maleic anhydride-grafted-nitrile
rubber is superior to all other rubbers studied. The improvement
in toughness, impact resistance, and tensile strength is achieved
without jeopardizing other properties. 65
Rubber as Low-profile Additive. A low-profile additive consisting of
a styrene-butadiene rubber solution is prepared by heating styrene with
hydroquinone up to 50°C. Into this liquid a styrene-butadiene rubber is
dissolved to obtain a resin solution having a solid content of 35%. This
solution is taken as a low-profile additive. 66
1.3.4.4 Nanocomposites
Only a few nanocomposite materials are commercially available and these
materials are very expensive. In order to make a successful nanocomposite,
it is very important to be able to disperse the filler material thoroughly
throughout the matrix to maximize the interaction between the intermixed
phases.
Titanium dioxide. Titanium dioxide nanoparticles with 36 nm average
diameter have been investigated. The nanoparticles have to be dispersed
by direct ultrasonification. 55 The presence of the nanoparticles has
a significant effect on the quasi-static fracture toughness. Even at small
volume fractions an increase in toughness is observed. The changes in
quasi-static material properties in tension and compression with increasing
volume fraction of the nanoparticles are small due to the weak interfacial
bonding between the matrix and the filler. The dynamic fracture toughness
is higher than quasi-static fracture toughness. Quite similar experimental
results have been presented by another group. 67 Titanium dioxide nanoparticles
can also be bound by chemical reaction to the polyester itself. 68
Aluminum Oxide. It was observed that the addition of untreated, Al 2 O 3
particles does not result in an enhanced fracture toughness. Instead, the
fracture toughness decreases. 56, 57 However, adding an appropriate amount

Unsaturated Polyester Resins 23
Table 1.5: Reinforcing Materials for Unsaturated Polyesters
Fiber
Reference
Glass fibers
Jute
69
Sisal
70
Hemp
71
Wollastonite
70
Barium titanate
72
of (3-methacryloxypropyl)trimethoxysilane to the liquid polyester resin
during particle dispersion process leads to a significant enhancement of the
fracture toughness due to the crack trapping mechanism being promoted by
strong particle-matrix adhesion.
For example, the addition of 4.5% volume fraction of treated Al 2 O 3
particles results in a nearly 100% increase in the fracture toughness of the
unsaturated polyester.
1.3.5 Reinforcing Materials
Suitable reinforcing materials are shown in Table 1.5. The application of
reinforcement fibers is strongly governed by the relation of the price of
matrix resin and fiber. Therefore, expensive fibers, such as carbon fiber,
are usually used with epoxide resins, not with unsaturated polyester resins.
If the fiber is expensive and has superior properties, then the matrix resin
should have superior properties.
1.3.5.1 Glass Fibers
The most common “fillers” are reinforcing materials, like glass fibers. Because
of the unavoidable shrinking during curing, interfacial stresses between
resin and glass fiber arise that lower the adhesion forces.
To enhance the adhesion, glass fibers are surface-modified. Silane
coupling agents such as (3-methacryloxypropyl)trimethoxysilane and
(3-aminopropyl)triethoxysilane are preferably used.
In the case of (3-methacryloxypropyl)trimethoxysilane the pendent
double bonds may take part in the curing reaction; thus chemical linkages
between resin and glass surface are established.

24 Reactive Polymers Fundamentals and Applications
The surface free energy and the mechanical interfacial properties
especially showed the maximum value for 0.4% silane coupling agent.
73, 74
In an E-glass/vinylester composite it was observed that the fibers
significantly inhibit the final conversion. 75
1.3.5.2 Wollastonite
A suitable coupling agent for wollastonite is (3-methacryloxypropyl)trimethoxysilane.
In such a treated wollastonite-unsaturated polyester composite,
the tensile and flexural strength increase initially with the wollastonite
content and then decrease. The flexural strength reaches an optimum
value at 30% wollastonite content, whereas the tensile strength reaches an
optimum point at 50% wollastonite content. 70
1.3.5.3 Carbon Fibers
Reports on carbon fiber reinforced polyester are rare. 76 Carbon fibers have
mainly been used in aerospace with epoxide resins or high temperature
thermoplastics, whereas polyesters have found application in large-volume
and low-cost applications with primarily glass fibers as reinforcement. The
combination of carbon fibers and polyester matrix is becoming more attractive
as the cost of carbon fibers decreases. In comparison to epoxide
resins, unsaturated polyester exhibits a relatively low viscosity. This property
makes them well suited for the manufacture of large structures. 77
The interfacial shear strength with untreated carbon fibers increases
with increasing degree of unsaturation of the polyester. The unsaturation is
adjusted by the amount of maleic anhydride in the feed. This is explained
by a contribution of chemical bonding of the double bonds in the polymer
to the functional groups of the carbon fiber surface. 77
1.3.5.4 Natural Fibers
Agrowastes and biomass materials, e.g., sawdust, wood fibers, sisal, bagasse,
etc. are slowly penetrating the reinforced plastics market, presently
dominated by glass fibers and other mineral reinforcements. These fillers
have very good mechanical properties and low density, and are loaded into
polymeric resin matrices to make useful structural composite materials. 62

Unsaturated Polyester Resins 25
Jute. Jute as reinforcing fiber is particularly significant from an economic
point of view. On a weight and cost basis, bleached jute fibers are claimed
to have better reinforcement properties than other fibers. 69
Sisal. Sisal fiber is a vegetable fiber having specific strength and stiffness
that compare well with those of glass fiber. Most synthetic resins are,
however, more expensive than the sisal fiber, making these composites less
attractive for low-technology applications. Therefore, for sisal fibers naturally
occurring resol-type resins, cashew nut shell liquid is an attractive
alternative. 78
For unsaturated polyester composites the surface treatment of sisal
fibers is done with neopentyl(diallyl)oxy tri(dioctyl)pyrophosphatotitanate
as the coupling agent.
70, 79
In a sisal/wollastonite reinforcing system for
unsaturated polyester resins, the tensile strength and the flexural strength
drop with increasing sisal content.
Sisal composites with unsaturated polyesters can be formulated to
be flame retarded using decabromodiphenyloxide and antimony trioxide to
reach a satisfactory high state of flame retardancy. 80
1.3.6 Mold Release Agents
Mold release agents are needed for the molding processes, i.e., for the
manufacture of bulk molding compounds and sheet molding compounds.
There are two classes of mold release agents:
1. External mold release agents,
2. Internal mold release agents.
External mold release agents are applied directly to the mold. This
procedure increases the manufacturing time and must be repeated every
one to five parts. In addition, the mold release agent builds up on the mold,
so the mold must be cleaned periodically with a solvent or washing agent.
This is costly and time consuming.
Internal mold release agents are added directly into the molding
compound. Since they do not have to be continuously reapplied to the
mold, internal mold release agents increase productivity and reduce cost.
There are mostly internal mold release agents, e.g., metal soaps, amine
carboxylates, amides, etc. Zinc stearate acts by exuding to the surface

26 Reactive Polymers Fundamentals and Applications
of the molding compound, thereby contacting the mold and providing lubrication
at the mold surface to permit release. Liquid mold release agents
are liquid zinc salts and phosphate esters and higher fatty acid amines. 81
The amine salts are obtained simply by neutralizing the acids with appropriate
amines.
1.3.7 Low-profile Additives
Low-profile additives (LPA) reduce the shrinking of the cured products.
Shrinking causes internal voids and reduced surface quality. Thermoplastic
resins are added to reduce shrinking, e.g., poly(vinyl acetate). This
additive absorbs some styrene in the early stages of curing. When the temperature
is increased in the course of curing, the styrene eventually evaporates
and consequently a counter pressure is formed which counterbalances
the shrinking.
The successful performance of low-profile additives depends essentially
on the phase separation phenomena in the course of curing, c.f. Section
1.4.4.2.
The effects of poly(vinyl acetate), poly(vinyl chloride-co-vinyl acetate),
and poly(vinyl chloride-co-vinyl acetate-co-maleic anhydride), have
been studied. 82, 83 The curing rate decreases with an increase of the molecular
weight of the low-profile additive which causes the chain entanglement
effect. The plasticizing effect is reduced with an increase in the molecular
weight of the low-profile additive. 84
Low-profile additives with higher molecular weight and lower content
of additive seem to work better under low-temperature curing conditions.
85 Polymers from the acrylic group have been tested as low-profile additives.
In particular, binary copolymers from methyl methacrylate and n-
butyl acrylate, and ternary copolymers from methyl methacrylate, n-butyl
acrylate, and maleic anhydride have been studied. 86, 87 The volume fraction
of microvoids generated during the curing process is governed by the
stiffness of the UP resin, the compatibility of the uncured ST/UP/LPA systems,
and the glass-transition temperature of the low-profile additive. A
good volume shrinkage control can be achieved by raising the curing temperature
slowly to allow sufficient time for phase separation, and going to
a high final temperature to allow the formation of microvoids. 88
Dilatometric studies in the course of curing of a low-profile resin

Unsaturated Polyester Resins 27
containing poly(vinyl acetate) 89 have revealed that there are two transition
points in both volume and morphological changes in the course of curing.
The thermoplastics start to be effective on shrinkage control at the
first transition point when the low-profile additive-rich phase and the unsaturated
polyester resin-rich phase become co-continuous. At the second
transition point when the fusion among the particulate structures is severe,
the shrinkage control effect vanishes.
The relative rate of polymerization in the two phases plays an important
role in shrinkage control. Instead of poly(vinyl acetate) a copolymer
with acrylic acid or itaconic acid should have better properties as a
low-profile additive. This is based on the assumption that the presence of
acid groups on the copolymer chain changes the selectivity of the cobalt
promoter, and therefore, the relative reaction rate in the thermoplastic-rich
and the unsaturated polyester resin-rich phases during polymerization.
Itaconic acid is about twice as acidic as acrylic acid and more reactive
than maleic acid or fumaric acid. The two carboxyl groups allow the
introduction of larger amounts of acidity into the copolymer even at rather
low comonomer concentrations in comparison to acrylic acid. The monoester
of 2-hydroxyethyl acrylate and tetrachlorophthalic anhydride also has
been proposed as a comonomer. The acidity of tetrachlorophthalic anhydride
is much stronger than that of itaconic acid because of the four chloro
substituents in its structure.
Samples with an acid-modified low-profile additive showed an earlier
volume expansion during curing, as a result of faster reaction in the
low-profile additive-rich phase. 90
The relative reaction rate in the two phases can be controlled in
addition to the selectivity control by the low-profile additive in a reverse
manner, i.e., by the addition of secondary vinylic comonomers and special
promoters. Secondary monomers, such as divinylbenzene and trimethylolpropane
trimethacrylate, were added to the formulation. 2,4-Pentandione
was chosen as co-promoter. 91 In fact, the combination of trimethylolpropane
trimethacrylate and 2,4-pentandione increased the reaction rate in the
low-profile rich-phase.
Methyl methacrylate was tested as a secondary monomer. 92 At a low
ratio of methyl methacrylate to styrene, the amount of residual styrene decreases
and the volume shrinkage of the resin system remains unchanged.
However, at a high ratio of methyl methacrylate to styrene, the amount of
residual styrene can be substantially reduced. This advantageous behav-

28 Reactive Polymers Fundamentals and Applications
ior occurs because of the monomer reactivity ratios. However, the study
of shrinkage shows that methyl methacrylate has a negative effect on the
shrinkage control.
Styrene has a polymerization shrinkage of 15% and methyl methacrylate
has a shrinkage of 20%. Therefore, the addition of methyl methacrylate
contributes to a larger volume shrinkage. The performance of a
low-profile additive becomes less effective when the molar ratio of methyl
methacrylate to styrene exceeds 0.1.
A dual initiator system, i.e., methylethylketone peroxide/tert-butylperoxybenzoate,
was used in combination with cobalt octoate as a promoter.
tert-Butylperoxybenzoate cannot be considered a low temperature
initiator because the reaction temperature needs to reach almost 90°C
to ensure the proper progress of the reaction. On the other hand, tertbutylperoxybenzoate
is more active compared to methylethylketone peroxide
at high temperatures, because the latter completely decomposes.
tert-Butylperoxybenzoate is therefore a good initiator to finish the reaction.
Volume shrinkage measurements of the resin system initiated with
dual initiators revealed that a good performance of the low-profile additive
was achieved at low temperatures (e.g., 35°C) and high temperatures
(100°C) but not at intermediate temperatures. 93
It was found that in bulk molding compounds calcium stearate, which
is primarily used as an internal mold release agent, is active as a low-profile
additive. 94 Even when added in small quantities, some internal mold
release agents may provoke the formation of a polyester-rich phase in the
form of spherical globules ca. 60 µm.
1.3.8 Interpenetrating Polymer Networks
An interpenetrating polymer network is a mixture of two or more polymers
that are not necessarily independently crosslinked. If another polymer that
is capable of crosslinking separately is added to an unsaturated polyester
resin, the physical properties can be enhanced dramatically. Other special
types of such systems are also addressed as hybrid systems.
1.3.8.1 Polyurethanes
For example, besides the unsaturated polyester resin, compounds that simultaneously
form a crosslinkable polyurethane are added, such as poly-

Unsaturated Polyester Resins 29
glycols and diisocyanates. 95
The rate of reaction of one component might be expected to be reduced
due to the dilutional effects by the other components. 96 However,
during free radical polymerization, the reaction may become diffusion
controlled and a Trommsdorff effect emerges. The Trommsdorff effect
consists of a self-acceleration of the overall rate of polymerization. When
the polymerizing bulk becomes more viscous as the concentration of polymer
increases, the mutual deactivation of the growing radicals is hindered,
whereas the other elementary reaction rates, such as initiation and propagation,
remain constant.
For an unsaturated polyester resin – polyurethane system, the rate of
the curing process increased substantially in comparison to the pure homopolymers.
Collateral reactions between the polyurethane isocyanate groups
and the terminal unsaturated polyester carboxyl groups were suggested that
may lead to the formation of amines, c.f. Eq. 1.1.
R−N=C=O+R ′ COOH → R−NHCO−O−CO−R ′
→ R−NHCO − R ′ + CO 2
(1.1)
These amines may act as promoters of the curing process. Moisture,
which does not influence the curing reaction of the unsaturated polyester
resin, would also lead to the formation of amines by the reaction of water
with the isocyanate groups. 97
A tricomponent interpenetrating network system consisting of castor
oil-based polyurethane components, acrylonitrile, and an unsaturated
polyester resin (the main component) was synthesized in order to toughen
the unsaturated polyester resin. By incorporating the urethane and acrylonitrile
structures, the tensile strength of the matrix (unsaturated polyester
resin) decreased and flexural and impact strengths were increased. 98
1.3.8.2 Epoxides
Mixtures of unsaturated polyester resin systems and epoxy resins also form
interpenetrating polymer networks. Since a single glass transition temperature
for each interpenetrating polymer network is observed, it is suggested
that both materials are compatible. On the other hand, an interlock between
the two growing networks was suggested, because in the course of
curing, a retarded viscosity increase was observed. 99 A network interlock

30 Reactive Polymers Fundamentals and Applications
is indicated by a lower total exothermic reaction during simultaneous polymerization
in comparison to the reaction of the homopolymers. 100
In bismaleimide-modified unsaturated polyester–epoxy resins, the
reaction between unsaturated polyester and epoxy resin could be confirmed
by IR spectral studies. 101 The incorporation of bismaleimide into epoxy
resin improved both mechanical strength and thermal behavior of the epoxy
resin.
1.3.8.3 Vinylester Resins
Unsaturated polyesters modified with up to 30% of vinylester oligomer
are tougheners for the unsaturated polyester matrix. The introduction of
vinylester oligomer and bismaleimide into an unsaturated polyester resin
improves thermomechanical properties. 102
1.3.8.4 Phenolic Resins
An interpenetrating network consisting of an unsaturated polyester resin
and a resol-type of phenolic resin improves heat resistance but also helps
to suppress the smoke, toxic gas, and heat release during combustion in
comparison to a pure unsaturated polyester resin. 103
1.3.8.5 Organic-inorganic Hybrids
Organic-inorganic polymer hybrid materials can be prepared using an unsaturated
polyester and silica gel. First an unsaturated polyester is prepared.
To this polyester the silica gel precursor is added, i.e., tetramethoxysilane,
methyltrimethoxysilane, or phenyltrimethoxysilane.
Gelling of the alkoxysilanes was achieved at 60°C using HCl catalyst
in the presence of the unsaturated polyester resin. It was confirmed by
nuclear magnetic resonance spectroscopy that the polyester did hydrolyze
during the acid treatment. Finally, the interpenetrating network was formed
by photopolymerization of the unsaturated polyester resin. 104 It is assumed
that between the phenyltrimethoxysilane and the aromatic groups in the unsaturated
polyester resin π-interactions arise.
1.3.9 Polyurethane Hybrid Networks
The mechanical properties of the unsaturated polyester resin can be greatly
improved by incorporating a polyurethane linkage into the polymer net-

Unsaturated Polyester Resins 31
work. The mechanical properties also can be altered by the techniques used
in segmented polyurethanes. The basic concept is to use soft segments and
hard segments.
The polyester is prepared with an excess of diol and dilute with styrene
as usual. Additional diols as chain extenders are blended into the resin
solution. 4,4 ′ -Diphenylmethane diisocyanate dissolved in styrene is added
to form the hybrid linkages. Suitable peroxides are added to initiate the
radical curing.
The curing starts with the reaction between the isocyanates and the
hydroxyl groups, thus forming the polyurethane linkage. Then the crosslinking
reaction takes place. 105
The mechanical properties of the hybrid networks were generally
improved by the incorporation of a chain extender at room temperature.
Hexanediol increased the flexibility of the polymer chains, resulting in a
higher deformation and impact resistance of the hybrid networks. Hybrid
networks with ethylene glycol as the chain extender are stiffer.
1.3.10 Flame Retardants
Flame retardant compositions can be achieved by flame retardant additives,
by flame retardant polyester components, and by flame retardant vinyl
monomers. Halogenated compounds are still common, but there is a trend
towards substituting these compounds with halogen free compositions. In
halogenated systems, bromine atoms mostly are responsible for the activity
of the retardant. On the other hand, a disposal problem arises when a
pyrolytic recycling method is intended at the end of the service times of
such articles. Flame retardants are summarized in Table 1.6.
In general, bromine compounds are more effective than chlorine
compounds. Suitable additives are chlorinated alkanes, brominated bisphenols
and diphenyls. Antimony trioxide is synergistic to halogenated
flame retardants. It acts also as a smoke suppressant in various systems. 106
1.3.10.1 Flame Retardant Additives
Decabromodiphenyloxide. Decabromodiphenyloxide with 2% of antimony
trioxide increases the oxygen index values linearly with the bromine
content. Some improvement of the mechanical properties can be achieved
by adding acrylonitrile to the polyester. 107 Decabromodiphenyloxide with

32 Reactive Polymers Fundamentals and Applications
Table 1.6: Flame Retardants for Unsaturated Polyester Resins
Flame Retardant
Remarks Reference
Aluminum hydroxide
Melamine diphosphate
Melamine cyanurate
108
Ammonium polyphosphate
109
Antimony trioxide
Synergist
Zinc hydroxystannate
110–112
2-Methyl-2,5-dioxo-1-oxa-2-phospholane Reactive
113
Decabromodiphenyloxide
114
HET acid
Reactive
2,6,2 ′ ,6 ′ -Tetrabromobisphenol A (TBBPA) Reactive
115
Tetrachlorophthalic anhydride
Reactive
Tetrabromophthalic anhydride
Reactive
antimony trioxide increases the activation energy of the decomposition of
the unsaturated polyester. 114
Aluminum Hydroxide. Fillers, such as aluminum hydroxide, yield crystallization
water at higher temperatures, thus achieving a certain flame retardancy.
At high degrees of filling in the range of 150 to 200 parts of aluminum
hydroxide per 100 parts of unsaturated polyester resin, it is possible
to achieve self-extinguishing and a low smoke density. A disadvantage of
such systems is that the entire material has a high density. The density can
be reduced, if hollow filler is used for reinforcement. 116
Lower amounts of aluminum hydroxide are sufficient, if red phosphorus
and melamine or melamine cyanurate is admixed. 108 Magnesium
hydroxide acts in a similar way to aluminum hydroxide.
Ammonium polyphosphate. Ammonium polyphosphate is a halogenfree
flame retardant for unsaturated polyester resin composites. 109 Commonly
used are ammonium polyphosphates having the general formula
(NH 4 ) n+2 P n O 3n+1 .
A significant reduction of the flame spread index is achieved by
a combination of a polyhydroxy compound, a polyphosphate, melamine,
cyanuric acid, melamine salts, e.g., melamine cyanurate, and a polyacrylate
monomer. 117
The fire retardant polyacrylate component should be distinguished

Unsaturated Polyester Resins 33
O
H 3 C P CH 2
O CH 2
C
O
O
O
P CH 2 CH 2 C O
CH 3
Figure 1.9: Ring opening of 2-Methyl-2,5-dioxo-1-oxa-2-phospholane 113
from the unsaturated monomers that may be included as crosslinkers in the
resin systems. It cannot be ruled out that the polyacrylate may become involved
in the crosslinking reactions of such systems. However, it has been
observed that the fire retardant effect of the polyacrylates is also effective
in those resin systems that do not involve curing by way of unsaturated
groups. Preferred polyacrylates are those having backbones of a type that
is known to contribute to char formation, for example, those having alkylene
or oxyalkylene backbones. 118
Reactive Phosphor Compound. Oxaphospholanes are heterocyclic compounds.
Certain derivatives are reactive to alcohols and can be incorporated
in a polyester backbone. Due to their phosphor content they also act
as flame retardants, with the advantage that they are chemically bound to
the backbone. 113 The ring opening reaction of 2-methyl-2,5-dioxo-1-oxa-
2-phospholane is shown in Figure 1.9. As a side effect, phosphoric compounds
increase the adhesion of the final products, without toughening too
much.
Expandable Graphite. The flammability of crosslinked unsaturated polyester
resins is reduced by the addition of expandable graphite even at levels
as low as 7 phr. Expandable graphite is particularly useful when used in
combination with ammonium polyphosphate or with a halogenated flame
retardant. 119
1.3.10.2 Flame Retardant Polyester Components
The flame retardant can be also built in the polymer backbone. Examples
are HET acid, tetrachlorophthalic anhydride, and tetrabromophthalic anhydride.
The mechanical properties decrease with increasing halogen content

34 Reactive Polymers Fundamentals and Applications
in the backbone. 120 HET acid is used for fireproof applications, e.g., for
panels in subways, etc.
1.3.10.3 Flame Retardant Vinyl Monomers
Dibromostyrene is a suitable brominated vinyl monomer. 121 However, it
is not commonly used. Dibromoneopentylglycol and diallyl ether of bromobutenediol
have been used as curing agents for unsaturated polyester
resins in paint coatings. Both monomers act effectively against inhibition
by oxygen. The bromine content decreases the flammability of the final
products. The monomers can be obtained in a direct allylation by the use
of allyl bromide. The resins can be photocured in a system consisting of
mono- or diazide and hydroxyalkylphenone. 122
Flame-retardant polyester resin polymers wherein the ability of the
polyester resin to transmit light is not significantly affected can be formulated
using, instead of antimony trioxide, organic antimony compounds
together with halogen flame retardants. Antimony ethylene glycoxide (i.e.,
ethylene glycol antimonite) can be incorporated in the polyester backbone.
Antimony tri-alloxide and antimony methacrylate are vinyl monomers. 123
The antimony alkoxides can be prepared by dissolving antimony trichloride
in a slight excess of the corresponding alcohol in an inert solvent, e.g.,
carbon tetrachloride or toluene and sparging with anhydrous ammonia.
The antimony acylates are prepared by mixing the stoichiometric amounts
of saturated or unsaturated acid and antimony alkoxide.
In addition to good light transmission, polyester resins may contain
a smaller proportion of combined antimony than those produced using antimony
trioxide and still retain their self-extinguishing properties. Moreover,
a smaller proportion of chlorine, than for formulations using antimony trioxide,
is sufficient to retain the self-extinguishing properties.
1.3.11 Production Data
Global production data of the most important monomers used for unsaturated
polyester resins are shown in Table 1.7.
1.4 CURING
Curing is achieved in general with a radical initiator and a promoter. A
promoter assists the decomposition of the initiator delivering radicals, even

Unsaturated Polyester Resins 35
Table 1.7: Global Production/Consumption Data of Important Monomers
and Polymers 124
Monomer Mill. Metric tons Year Reference
Methyl methacrylate 2 2002
125
Styrene 21 2001
126
Phthalic anhydride 3.2 2000
127
Isophthalic acid 0.270 2002
128
Dimethyl terephthalate (DMT)
and terephthalic acid (TPA) 75 2004
129
Adipic Acid 2 2001
130
Bisphenol A 2 1999
131
Maleic anhydride 1.3 2001
132
1,4-Butanediol 1 2003
133
Dicyclopentadiene 0.290 2002
134
Unsaturated Polyester Resins 1.6 2001
135
at low temperatures at which the initiator alone does not decompose at a
sufficient rate. Promoters are also addressed as accelerators.
1.4.1 Initiator Systems
Even when a wide variety of initiators are available, common peroxides
are used for cold curing and hot curing. Coatings of unsaturated polyester
resins are cured with light sensitive materials.
Peroxide initiators include ketone peroxides, hydroperoxides, diacyl
peroxides, dialkyl peroxides, alkyl peresters, and percarbonates. Azo compounds,
such as 2,2 ′ -azobis(isobutyronitrile) and 2,2 ′ -azobis(2-methylbutyronitrile)
are also suitable. These curing agents can be used alone, or two
or more can be used in combination. Some peroxide initiators are shown
in Table 1.8.
1.4.1.1 In-Situ Generated Peroxides
Allyl alcohol propoxylate can generate a peroxide in-situ in the presence
of metal salt promoter. This peroxide cures the unsaturated polyester resin.
The curing proceeds with a very low exothermic reaction and low product
shrinkage. 136

36 Reactive Polymers Fundamentals and Applications
Peroxide Type
Ketone Peroxides
Hydroperoxides
Diacyl peroxides
Dialkyl peroxides
Alkyl peresters
Percarbonates
Table 1.8: Peroxide Initiators
Example
Methylethylketone peroxide
Acetylacetone peroxide
Cumene hydroperoxide
Dibenzoyl peroxide
Dicumyl peroxide
tert-Butylcumyl peroxide
tert-Butylperoxy-2-ethylhexanoate
tert-Butylperoxybenzoate
tert-Amylperoxybenzoate
tert-Hexylperoxybenzoate
bis(4-tert-Butylcyclohexyl)peroxydicarbonate
1.4.1.2 Functional Peroxides
Peroxides can be functionalized. Functional peroxides based on pyromellitic
dianhydride, poly(ethylene glycol)s and tert-butyl hydroperoxide contain
two types of functional groups:
1. Carboxylic groups that can participate in ionic reactions,
2. Peroxide groups that can initiate certain radical reactions.
The oligoesters are able to form three-dimensional networks when
heated to 130 °C. 137
1.4.1.3 Photoinitiators
Photoinitiators are mostly used for coating applications. Some common
photoinitiators are listed in Table 1.9. A common problem is yellowing
during curing. α-Aminoacetophenones and thioxanthone derivatives impart
yellowness. Such derivatives are used in thin layers.
Although suitable initiators for clear systems have become available
only in the last few years, photoinitiators for pigmented systems have been
developed for some time. Problems with regard to the absorbtion of ultraviolet
light, needed for curing, arise when the coating is pigmented or
when it is UV stabilized for outdoor applications. Ultraviolet stabilizers
consist of ultraviolet absorbers or hindered amine light stabilizers. The
curing performance depends on the pigment absorption and particle size.

Photoinitiator
Unsaturated Polyester Resins 37
Table 1.9: Common Photoinitiators
Reference
Benzoin methyl ether
138
2,2-Dimethoxy-2-phenylacetophenone
2-Hydroxy-2-methylphenylpropane-1-one
α-Hydroxy-acetophenone
139
Bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide
140
2-Hydroxy-2-methyl-1-phenyl-propan-1-one
2,4,6-Trimethylbenzoyldiphenylphosphine oxide
Bis(2,6-dichlorobenzoyl)-(4-propylphenyl)phosphine oxide
The adsorption of bisacylphosphine oxides is in the near UV-visible
range, and thus at much lower energy than other common photoinitiators.
Those photoinitiators therefore allow the curing of thick pigmented layers.
Acylphosphine oxides were originally used in dental applications.
Acylphosphine oxides and bisacylphosphine oxides are prone to solvolysis
attack; that is why the carbon phosphor bond is shielded by bulky
groups.
Earlier investigations on acylphosphine oxides, in particular 2,4,6-trimethylbenzoyldiphenylphosphine
oxide, did not show any advantage over
2,2-dimethoxy-2-phenylacetophenone. It was even concluded that acylphosphonates
cannot be considered useful photoinitiators.
141, 142
A mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine
oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one is suitable for
curing thick pigmented furniture coatings. 140 The structures of these compounds
are shown in Figure 1.10. Further, a combination of a bis-acylphosphineoxide
and an α-hydroxy-acetophenone photoinitiator overcomes the
limitations imposed by filtering of UV radiation by the pigments and provides
a balanced cure. 139
The chloro compounds, e.g., bis(2,6-dichlorobenzoyl)-(4-propylphenyl)phosphine
oxide are less satisfactory, c.f. Figure1.11.
1.4.2 Promoters
There is a difference between hydroperoxides such as methylethylketone
peroxide and peroxides, such as dibenzoyl peroxide. Redox promoters,
e.g., cobalt naphthenate, can stimulate the decomposition of hydroperoxides
catalytically, whereas they cannot stimulate the decomposition of di-

38 Reactive Polymers Fundamentals and Applications
OCH 3
O
CH 3 O
O
C P C
OCH 3
CH3 O
H 3 C
CH 3
C CH 2
CH 3
CH 2
CH CH 3
Bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine
O
C
CH 3
C OH
CH 3
2-Hydroxy-2-methyl-1-phenyl-propan-1-one
Figure 1.10: Bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine and
2-Hydroxy-2-methyl-1-phenyl-propan-1-one
peroxides. Therefore, for hydroperoxides only catalytic amounts of metal
salts are necessary, whereas the salts do not act readily on diperoxides. The
mechanism of catalytic action of metal salts is shown in Eq. 1.2.
ROOH+Co 2+ → RO ·+OH − + Co 3+
ROOH+Co 3+ → ROO ·+H + + Co 2+ (1.2)
The cobalt ion is either oxidized or reduced by the peroxides depending
on its value. If too much promoter is added, then the exotherm
can be very high. Since the thermal conductivity of polymers is small, the
heat of reaction cannot be transported out of the resin. The material would
overheat and gas bubbles would form.
Promoters can be metal soaps, e.g., cobalt octoate or manganese octoate,
or further metal chelates such as cobalt acetylacetonate and vanadium
acetylacetonate. These promoters are redox promoters and amine
compounds such as N,N-dimethylaniline. These accelerators can be used
alone, or two or more kinds of them can be used in combination.
Examples of promoters are shown in Table 1.10. The auxiliary accelerator
is used for enhancing the potency of the accelerator and includes, for

Unsaturated Polyester Resins 39
Cl
O
C
P
Cl
O
C
Cl
Cl
H 3 C
CH 2
CH 2
Bis(2,6-dichlorobenzoyl)-(4-propylphenyl)phosphine oxide
H 3 C
CH 3
O
CH 3
C
O
P
2,4,6-Trimethylbenzoyl-diphenylphosphine oxide
Figure 1.11: 2,4,6-Trimethylbenzoyldiphenylphosphine oxide and Bis(2,6-dichlorobenzoyl)-(4-propylphenyl)phosphine
oxide
Table 1.10: Promoters
Promoter Type Example
Metal soaps Cobalt octoate
Manganese octoate
Metal chelates Cobalt acetylacetonate
Vanadium acetylacetonate
Amine compounds N,N-Dimethylaniline

40 Reactive Polymers Fundamentals and Applications
Table 1.11: Initiator Promoter Systems
Initiator Promoter Temperature °C
Methylethylketone peroxide Cobalt naphthenate 20
Dibenzoyl peroxide N,N-Dimethylaniline 60
Di-tert-butyl peroxide 130
tert-Butylperoxybenzoate 130
example, acetylacetone, ethyl acetoacetate and anilide acetoacetate. These
auxiliary accelerators can be used alone, or two or more of them can be
combined.
1.4.3 Initiator Promoter Systems
Some common initiator promoter systems are shown in Table 1.11. Methylpropylketone
peroxide offers some advantage over methylethylketone
peroxide, as the curing times are shorter. 143
Diperoxyketal initiators are used for high-temperature molding processes.
Dichloroacetic acid is a suitable promoter. It does not negatively
influence the pot life and the cure cycle. 144
1.4.4 Polymerization
The initiators together with the accelerator initiate a crosslinking copolymerization.
The monomer reactivity ratios for the system styrene/fumarate
indicate an alternating system, i.e., a styrene radical reacts with a fumarate
unit, and vice versa. On the other hand, the system styrene/maleate will
tend to form blocks. Therefore, the fumarate system yields final products
with better properties. Fortunately the maleate unit isomerizes during the
condensation reaction.
If a nonazeotropic composition is used, then the ratio of styrene to
polymerizable double bonds in the polyester varies in the course of curing.
Such systems show a decrease in network density in the course of
conversion. 145
1.4.4.1 Kinetics of Curing
The kinetics of curing can be conveniently investigated by differential scanning
calorimetry and infrared spectroscopy. Both methods have been com-

Unsaturated Polyester Resins 41
pared. 146 The overall conversion measured by differential scanning calorimetry
is in-between the styrene consumption and the consumption of the
pending double bonds in the polyester obtained by infrared spectroscopy.
The curing of laminates containing 50 to 70% glass fiber mat can
be monitored by Raman spectroscopy. 147 Also, white and lightly colored
gel coats can easily be monitored by Raman spectroscopy, but fluorescent
problems are encountered with heavily colored pigments.
Using differential scanning calorimetry, both isothermal runs and
temperature programmed runs can be used. Usually a complete conversion
is not achieved during ordinary curing.
There are two portions of reaction enthalpy that can be investigated
under laboratory conditions,
1. The enthalpy characterizing the styrene homopolymerization and
copolymerization during curing,
2. A residual enthalpy that can be determined by heating up to near
the degradation point of the resin.
At isothermal curing experiments, it was found that the sum of enthalpy
of polymerization and residual enthalpy depends on the curing (isothermal)
temperature. 148
An unsaturated polyester resin initiated with a curing system of methylethylketone
peroxide and a cobalt salt as promoter was studied by dynamic
scans from −100°C to 250°C at heating rates from 2°C/min to
25°C/min. The amount of heat generated by a curing reaction decreases
with increasing heating rate. The energy of activation of the overall reaction
is around 90 kJ/mol. The traces can be fitted by either an empiric
model or a model based on the theory of free-radical polymerization. 149
The rate of curing depends on the amount of initiator added to the
mixture. A universal isoconversional relationship of the type
t = d − bln[I] 0 + E a
RT
(1.3)
was established that expresses the dependency of the curing time t on the
temperature, T, and the initial concentration of the initiator [I] 0 and the
energy of activation E a . 150
Gel Point. At a certain conversion the reacting mixture rather suddenly
changes its appearance: it gels. The gel point is an important parameter for

42 Reactive Polymers Fundamentals and Applications
the pot life time. The gel point can be determined most simply by stirring
from time to time, although there are other more sophisticated methods
available.
A well-known phenomenon in radical polymerization is the acceleration
at moderate conversion which is addressed as the Trommsdorff effect.
This effect can also be observed in crosslinking polymerization. The
increase in rate causes a temperature rise in the bulk material. It was found
that the gel time corresponds closely to the initial rise of the temperature. 151
The same is true when inhibitors are added or when the curing system
is changed. For example, the addition of a tert-butyl catechol inhibitor
increases the gel time in a linear fashion and the exothermic reaction is
similarly delayed. An increase in the concentrations of initiator (either
methylethylketone peroxide or acetyl acetone peroxide) or cobalt octoate
promoter decreases the gel time.
The gel point has been extrapolated by thermal mechanical analysis,
as the point at which the shrinkage rate drops to zero and the dimensions
of the material show no appreciable change. 152
The curing characteristics can also be measured by the change of
ultrasonic properties in the course of curing. 153 The sound velocity is constant
until the gel point is reached. Afterwards the sound velocity increases
to a plateau. Reaching the plateau indicates the end of the chemical reaction.
The attenuation reaches a maximum which is attributed to the vitrification.
The transition into the vitreous state causes a strong change of the
acoustic properties.
The glass transition temperature increases continuously with conversion.
When the glass transition temperature reaches the polymerization
temperature, then vitrification occurs. Vitrification strongly hinders the
mobility of the reactive groups. For this reason, the polymerization reaction
slows down or stops before complete conversion is reached.
The increase of the longitudinal sound velocity with curing time can
be associated with the increase of longitudinal modulus L ′ , while the irreversible
viscous losses are responsible for the increase of sound attenuation.
Kinetic Model. To describe the curing behavior of sheet molding compounds,
a kinetic model based on radical polymerization mechanisms was
developed. 154 In the model, three radical reaction steps are involved:

Unsaturated Polyester Resins 43
Initiation : I 0 → 2R·
Propagation : R ·n +M → R·n+1
Inhibition : R· → Products
(1.4)
Here I 0 is the (initial) initiator concentration, R·n a growing radical with
chain length n, and M a monomer unit. R· refers to the total concentration
of growing radicals. The kinetic constants were experimentally obtained
by differential scanning calorimetry (DSC) measurements in model unsaturated
polyester resins.
Another kinetic model has been presented that is based on the irreversible
thermodynamic fluctuation theory. Because the glass transition
temperature is related to molecular relaxation processes, the chemical kinetics
also can be explained in terms of fluctuation theory. 155
The physical or mechanical properties of polymers during curing can
be expressed by Eq. 1.5
P(∞) − P(t)
(
P(∞) − P(0) = exp −(t/τ) β) . (1.5)
P(t), P(∞), and P(0) is some property at times t,∞, and 0, β is a constant,
and τ is the curing relaxation time, τ ∝ exp(H/RT), where H is the activation
energy of the curing reaction. If the property P is addressed as the
monomer concentration, then the left hand term in Eq. 1.5 is the fraction
of unreacted monomer 1 − α. Thus the conversion α is a function of the
curing relaxation time, reaction time, and the reaction temperature.
155, 156
1.4.4.2 Phase Separation
A phase separation may occur in the course of curing, when styrene is in
excess. In this case a crosslinked phase and a poly(styrene) rich phase
appear.
In the case of unsaturated polyester systems, the phase separation
occurs mainly by chemical changes of the system, in contrast to the more
common thermally induced phase separation. The phase separation is
therefore addressed as a chemically induced phase separation. Thermodynamic
models have been established to understand this phenomenon. 157
The final morphology of the resin is primarily determined by the
phase separation process and the gelation resulting from the polymerization.
158 The cured polymer of a single phase resin shows a flake-like structure,
while spherical particles form in the two-phase system. 159

44 Reactive Polymers Fundamentals and Applications
The phase behavior can be observed by measuring the glass transition
temperatures where shoulders are observed in the presence of a twophase
system. The shoulders become more evident utilizing dynamic mechanical
analysis by plotting logtanδ vs. temperature. 160
Phase separation is an important feature in low-profile resin systems.
Here the system separates in a thermoplastic-rich phase and in an unsaturated
polyester-rich phase. This two-phase structure provides a weak interface
where microcracking can initiate and microvoids can form to compensate
the shrinkage. 90
In such systems an optical microscope equipped with a heating chamber
is employed to observe the phase separation process during curing. At
the same time, conversion is monitored by infrared spectroscopy. The results
show that the copolymerization routes locate between the azeotropic
and the alternating copolymerization line, and shift gradually toward the
azeotropic line.
1.5 PROPERTIES
1.5.1 Structure Properties Relationships
The properties can be widely influenced by the choice of the components,
since there is a wide variety of compounds. Some aspects are briefly indicated
in Table 1.1.
Aliphatic chains, both in the acid moiety and in the diol moiety,
will result in comparatively soft materials. Therefore, 1,2-butanediol and
diethylene glycol and adipic acid will make the resin softer than phthalic
anhydride. The rigidity decreases in the following order: 1,2-propanediol,
2,3-butanediol, 1,4-butanediol, dipropylene glycol, diethylene glycol. For
acids the rigidity decreases in the order orthophthalic acid, isophthalic acid,
succinic acid, adipic acid, glutaric acid, isosebacic acid, and pimelic acid. 1
More rigid materials do not absorb water as much as flexible materials.
Therefore, because there is less water available, the rigid materials
show better resistance to hydrolysis. Bisphenol A and neopentyl glycol-containing
resins shield the access of small molecules to the ester group
and therefore they exhibit a better chemical resistance.
The crosslink density grows with the amount of maleic anhydride
feed. The rigidity can be controlled with the content of maleic anhydride
in the polyester. The glass transition temperature also increases with increasing
crosslinking density.

Unsaturated Polyester Resins 45
The resistance against hydrolysis increases, as the ester linkages are
more stable. Bulky alcohol molecules, like neopentyl glycol, cyclohexanediol,
or hydrogenated bisphenol A, are used for hydrolytic resistant materials.
The alcohols are used in combination with isophthalic acid and
terephthalic acid.
1.5.2 Hydrolytic Stability
The ester group is a weak link with regards to hydrolysis. Hydrolysis occurs
in aqueous media and is enhanced at elevated temperatures and in
particular in alkaline media.
The long-term behavior of glass fiber-reinforced plastic pipes was
tested in an aqueous environment at 20°C. The strength of the wet pipes
after a 1000 hour loading reduced to about 60% of the dry strength in
short-term loading. 161
1.5.3 Recycling
1.5.3.1 Poly(ethylene terephthalate) Waste Products
Oligomers obtained from depolymerization of poly(ethylene terephthalate)
waste products can be reused. The glycolysis products can be used for the
synthesis of polyester polyols for rigid polyurethane foams and also for
the synthesis of unsaturated maleic or fumaric polyester resins. Bis(2-hydroxyethyl)terephthalate
(BHET) is the main product from the glycolysis
of poly(ethylene terephthalate). A mixture of maleic anhydride and sebacic
acid is added and a condensation is performed. 162
The glycolysis reaction is conducted by heating poly(ethylene terephthalate)
and the glycol in a nitrogen atmosphere at a temperature preferably
within a range from 200°C to 260°C to obtain a terephthalate oligomer
48 containing two to three terephthalate units. Zinc acetate is a suitable
transesterification catalyst. 163
Unsaturated polyesters based on the glycolyzed poly(ethylene terephthalate)with
propylene glycol or diethylene glycol and mixtures of both
glycols show a broad bimodal molecular weight distribution. Larger molecular
weight oligomers were obtained with increasing diethylene glycol
contents in the glycol mixtures. The tensile modulus decreased and the
toughness of cured products increased with increasing diethylene glycol
content. 164

46 Reactive Polymers Fundamentals and Applications
A study of the glycolysis of waste bottles made from poly(ethyleneterephthalate)
and back condensation with maleic anhydride indicated that
the type of glycol used in glycolysis had a significant effect on the characteristics
of the uncured and cured resins. 165
On the other hand, it was also found that no separation of the type of
bottles was needed before glycolysis, since the resins prepared from either
water bottles, soft drink bottles, or a mixture of both bottles showed all
the same characteristics. The properties of materials recycled in this way
have been presented in detail. 166 Similarly, residues from the manufacture
of dimethyl terephthalate has been tried as feedstock for the aromatic
acid component and condensed with maleic anhydride. 167 The complete
process of how to come from a poly(ethylene terephthalate) to a suitable
unsaturated polyester resin composition is described in detail in the literature.
168 The glycolysis products can be directly incorporated in an unsaturated
polyester resin composition. However, toluene diisocyanate as an
intermediating agent must be added. The isocyanate accelerates the curing
significantly. 169 It is proposed that at the beginning of the curing, the
isocyanate reacts with the oligo glycols to form chain-extended products.
The glycolysis product acts as a modifier that improves the mechanical
properties of the resulting composites. The procedure allows an effective
utilization of the waste products. It is reasonable to use only partly
glycolyzed products, when the molecular mass of the degradation products
is still higher.
1.5.3.2 Cured Unsaturated Polyester Resin Waste
Cured unsaturated polyester resin waste can be decomposed with a decomposition
component such as a dicarboxylic acid or a diamine to obtain resin
raw material. The unsaturated polyester resin is re-synthesized with this resin
raw material. 170 It is also possible to synthesize polyurethane resin by
reacting the glycolic raw material with a diisocyanate compound. 171
1.6 APPLICATIONS AND USES
The properties can be adjusted in a wide range, since a wide variety of
basic materials can be used. Consequently, unsaturated polyesters have a
very wide area of application. They can be used either as pure resin or with

Unsaturated Polyester Resins 47
fillers, or reinforced, respectively.
One of the early uses of unsaturated polyesters was to produce cast
items such as knife and umbrella handles, encapsulation of decorative articles,
and electronic assemblies.
1.6.1 Decorative Specimens
Pure resins can be used for embedding of decorative specimens. Together
with a photosensitive curing formulation, furniture coatings are on the market.
The most important casting application is the manufacture of buttons.
1.6.2 Polyester Concrete
Polymer concrete is usually composed of silica sand and a binder consisting
of a thermoset resin, such as unsaturated polyester. Polyester concrete
is more resistant to chemicals than conventional concrete. An unsaturated
polyester concrete is developed by adding the methyl methacrylate monomer
to the resin to improve the early-age strength and the workability of
the UP polymer concrete. 172 The study revealed that the workability is remarkably
improved as the methyl methacrylate content is increased. The
ratio of filler to binder is an important parameter for the workability.
1.6.3 Reinforced Materials
Bulk and sheet molding compounds are used in a wide variety of areas
such as transportation, electrical applications, building, and construction.
Reinforced unsaturated polyester resins are used for the manufacture
of articles for sanitary furniture, panels, pipes, boats, etc.
There are several techniques for manufacturing the final products,
i.e.,
• Hand lay-up process
• Fiber spray-up process
• Cold press molding, hot press molding
• Sheet molding, bulk molding
• Wet-mat molding
• Pultrusion
In the hand lay-up process, parts in an open, glass reinforced, mold
are produced. First the mold surface is treated with release wax and then

48 Reactive Polymers Fundamentals and Applications
coated with a special polyester resin, the so-called gel coat. Then glass
fibers are placed into the mold and impregnated with the formulated resin
which cures after a short time. This procedure is repeated several times,
until the desired thickness is reached. Finally a top coat is placed. In this
way, for example, glass fiber reinforced boats can be fabricated.
The fiber spray-up process is an improvement of the hand lay-up
process. A spray system is used to apply both chopped glass strands and
the polyester resin. The spray system places simultaneously resin, catalyst,
and glass strands by means of air pressure. The fiber spray-up process is
much faster than hand lay-up process and can be automated.
In cold press molding and hot press molding, a preimpregnated fiber
is placed in presses and cured there.
In sheet molding and bulk molding, the resin is mixed with the reinforcing
material, either in bulk form or as mats or sheets. To the resin
a thickener is added. The articles are formed in presses. The situation is
similar in wet-mat molding.
In pultrusion, the reinforcement fiber is wheeled off a spool, dipped
into a resin mixture, and pulled through a heated die to cure the compound.
1.6.4 Coatings
Unsaturated polyester resins are used for a wide variety of coatings. The
formulations are usually thixotropic. Curing is mostly achieved by UVsensitive
initiators.
1.6.4.1 Powder Coatings
Thermosetting powder coatings have gained considerable popularity over
liquid coatings for a number of reasons. Powder coatings are virtually free
of harmful fugitive organic solvents normally present in liquid coatings.
They give off little, if any, volatiles to the environment when cured. This
eliminates solvent emission problems and exposure risk of workers employed
in the coating operations.
Powder coatings also improve working hygiene, since they are in
dry solid form with no messy liquids associated with them to adhere to the
clothes of the workers and the coating equipment. Furthermore, they are
easily swept up in the event of a spill without requiring special cleaning
and spill containment supplies.

Unsaturated Polyester Resins 49
Table 1.12: Special Applications of Polyester Resins
Application
Reference
Polyester concrete
173
Bone cement
174
Coatings
Road paints
175
Electronic and microwave industries
121
Electrically conductive resins
176
Toner material
177
Compatibilizers
178
Pour point depressants
179
Reactive melt modifier
180
Another advantage is that they are 100% recyclable. Over sprayed
powders are normally recycled during the coating operation and recombined
with the original powder feed. This leads to very high coating efficiencies
and minimal waste generation.
However, in spite of the many advantages, powder coatings traditionally
have not been suitable for heat sensitive substrates, such as wood
and plastic articles, due to the high temperatures demanded to fuse and
cure the powders.
Unsaturated polyester powder coatings are available that undergo
rapid polymerization at low temperatures, making them particularly attractive
for coating of heat sensitive substrates.
Low temperature curable unsaturated polyester powder coatings contain
polyols with active hydrogens. Allylic, benzylic, cyclohexyl, and tertiary
alkyl hydrogen atoms are readily abstracted during free radical induced
curing to form the corresponding stable allylic, benzylic, cyclohexyl,
and tertiary alkyl free radicals, all of which promote curing at the surface
of the coating film in an open air atmosphere. A suitable polyol is
1,4-cyclohexanedimethanol. 181
1.7 SPECIAL FORMULATIONS
Unsaturated polyester resins have a broad field of application. Unsaturated
polyester resins for special purposes are summarized in Table 1.12.

50 Reactive Polymers Fundamentals and Applications
1.7.1 Electrically Conductive Resins
Electrically conductive resins can be formulated by the addition of carbon
black particles. The particles have a strong tendency to agglomerate in
a low-viscosity resin. The agglomeration process generates electrically
conductive paths already in the uncured state.
The fully cured resins containing carbon black above percolation
concentration have a constant, temperature-independent conductivity, over
a wide temperature range. 176
1.7.2 Poly(ε-caprolactone)-perfluoropolyether Copolymers
Basically, fluorinated materials are attractive modifying agents because of
their unique properties such as chemical inertness, solvent and high temperature
resistance, barrier properties, low friction coefficient and low surface
tension. These properties can be imparted to other polymeric materials
by blending or copolymerization.
This type of modification has been usually achieved by the use of
fluorine-containing comonomers of low molecular weight which usually
lead to homogeneous UP resin and therefore have to be added in significant
amounts to achieve an appreciable performance improvement. Furthermore,
the high cost of fluorinated monomers leads to very expensive
polymeric materials.
Unsaturated polyester resins can be modified by hydroxy-terminated
telechelic ∗ perfluoropolyethers as comonomers during the synthesis of the
polyester. 182 A disadvantage of this approach is the reactivity of these
materials. A fraction of perfluoropolyether does not react.
Another method of introducing fluorine into the unsaturated polyester
resins is simply blending fluorinated materials. A problem arises,
however, because fluorinated polymers are usually immiscible with nonfluorinated
polymers. They segregate in a separate phase with poor adhesion
to the non-fluorinated matrix, leading to poor mechanical properties.
However, separate block or graft copolymers containing fluorinated segments
can be prepared that are compatible with the unsaturated polyester
resin.
Poly(ε-caprolactone)-perfluoropolyether block copolymers are prepared
by ring opening polymerization of ε-caprolactone with fluorinated
∗ from τέλoς: end and χηλή: claw of a crab, an oligomer or polymer with well defined
end groups, often star branched, whereas τ ˜ηλη means far, therefore better telochelic

Unsaturated Polyester Resins 51
hydroxy ethers of the formula 1.6. Titanium tetrabutoxide is used as catalyst.
183 H−(OC 2 H 4 ) n −OCH 2 CF 2 O−(C 2 F 4 O) p ×
(CF 2 O) q −CF 2 CH 2 O−(C 2 H 4 O) n −H
(1.6)
This polymer can be added to an ordinary unsaturated polyester resin and
cured with conventional initiator systems.
Applications of fluorine-modified unsaturated polyester resins include
thermosetting resins for gel coating with excellent resistance to corrosion,
water and atmospheric agents, formulations for resins and foams,
etc.
1.7.3 Toner Compositions
Toner resins, and consequently toners are propoxylated bisphenol A fumarate
resins that are crosslinked in a reactive extrusion process in the presence
of the liquid 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane as
initiator. 177
1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane has advantages
in comparison to the conventionally used dibenzoyl peroxide. Dibenzoyl
peroxide generates benzoic acid as a by-product, which is undesirable.
Benzoic acid is difficult to remove from the crosslinked resin in that it
condenses in a vacuum system, rapidly clogging the system and requiring
frequent apparatus shutdowns for cleaning. As a result of the difficulty
in the removal of the benzoic acid by-product, the crosslinked toner resin
contains a significant amount of acids. Such acidity has been found to negatively
affect the charging, the humidity sensitivity of the charging, and the
background density properties of the toners.
Crosslinked resins are used in making toner. The resins can be subsequently
melt blended or otherwise mixed with a colorant, charge carrier
additives, surfactants, emulsifiers, pigment dispersants, flow additives, etc.
The resultant product can then be pulverized to form toner particles.
UV curable resins for incorporation in toner particles are powders
based on unsaturated polyesters and polyurethaneacrylates with bis-ethoxylated
2,2-bis(4-hydroxyphenyl)propane or bis-propoxylated 2,2-bis(4-hydroxyphenyl)propane.
184
The toner particles can be prepared by melt kneading the toner ingredients,
i.e., toner resin composition, charge control agent, pigment, etc.

52 Reactive Polymers Fundamentals and Applications
After the melt kneading the mixture is cooled and the solidified mass is
pulverized.
1.7.4 Pour Point Depressants
Copolymers of dialkyl fumarates and dialkyl maleates with vinyl acetate
and vinylpyrrolidone are effective as flow improvers and pour point depressants,
respectively. Among a series of similar polymers, copolymers
based on didodecyl fumarate vinyl acetate are the most effective pour point
depressants. 179 These polymers are suitable additives for improving the
flow properties and viscosity index of lubricating oils.
1.7.5 Biodegradable Polyesters
Aliphatic polyesters are almost the only promising structural materials for
biodegradable plastics. In fact, aliphatic unsaturated polyesters, succinic
fumaric units, and 1,4-butanediol are biodegradable as such.
However, the condensation of aliphatic polyesters derived from diacids
and diols failed to obtain high-molecular weight polyesters. Effective
transesterification catalysts, high vacuum technique and chain extenders
enable the synthesis of high-molecular weight polyesters with improved
mechanical properties. 185
1.7.6 Bone Cement
An unsaturated polyester, made from propylene glycol and fumaric acid, is
suitable as resorbable bone cement. Depending on the molecular weight,
poly(propylene) fumarate is a viscous liquid. A filler of calcium gluconate/hydroxyapatite
is used. An injectable form of a resorbable bone
cement can be crosslinked in-situ. The material cures to a hard cement
degradable by hydrolysis. 186 Bis(2,4,6-trimethylbenzoyl)phenylphosphine
oxide has been found useful as photoinitiator for poly(propylene) fumarate,
for the treatment of large bone defects. 187
Citric acid and sodium bicarbonate as the foaming agent develop
porosity in the material by generating carbon dioxide during the effervescence
reaction. 174

Unsaturated Polyester Resins 53
1.7.7 Compatibilizers
An unsaturated polyester is a suitable compatibilizer for styrene-butadiene
and acrylonitrile-butadiene (NBR) rubber blends. By the addition of 10
parts unsaturated polyester per hundred parts of rubber, the degree of compatibility
was greatly enhanced. The rheological and mechanical properties
of the blends were also improved. 178
1.7.8 Reactive Melt Modification of Poly(propylene)
Melt blending of poly(propylene) with a low molecular weight unsaturated
polyester in the presence of peroxide in a batch mixer and a twin-screw
extruder improves the morphology. Under these conditions competitive
degradation and crosslinking reactions take place. These reactions result
in a significant change in the viscosity ratio.
Rheological studies show that depending on the process conditions
some reacted PP/UP blends have a pronounced suspension behavior due
to the presence of the dispersed polyester gel particles in a low molecular
weight poly(propylene) matrix.
Infrared studies of the blends suggest the presence of block or graft
structures that promote the compatibility in the treated blends. Such blends
are suitable as compatibilizers for blends of poly(propylene) with high
molecular weight thermoplastic polyester blends. 180
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66 Reactive Polymers Fundamentals and Applications
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68 Reactive Polymers Fundamentals and Applications

2
Polyurethanes
Polyurethanes consist basically of two components, an isocyanate component
and a diol component. The diol component can be a polyether endcapped
diol or a polyester end-capped diol. The urethane structure may be
identified as the esters of carbamic acid or ester amides of a carbonic acid.
The urethane formation is achieved by the addition of a tertiary amine and
an organometallic compound.
There are many monographs on the topic, 1–11 the most recent of
W. Dias Vilar 12 and Klempner. 13 Polyurethanes also find use in medical
applications.
14, 15
They are used to a large extent as adhesives 16 and as
coatings.
2.1 HISTORY
Polyurethane was first described by Bayer ∗ in 1937. 17 The first polyurea
was composed from hexane-1,6-diamine and hexane-1,6-diisocyanate.
Two diisocyanates used at that time, diphenylmethane-4,4 ′ -diisocyanate
and naphthalene-1,5-diisocyanate, are still key products in polyurethane
chemistry. Besides O. Bayer, H. Rinke, A. Hoechtlen, P. Hoppe and
E. Meinbrenner contributed significantly to the development of polyurethanes.
In 1940, toluene diisocyanate was introduced. From the beginning
polyurethanes were utilized as foams, coatings, and cast elastomers.
∗ Otto Bayer, born in Frankfurt/Main 1902, died 1982
69

70 Reactive Polymers Fundamentals and Applications
Cl
R NH 2
+ C
Cl
O R N C O
Figure 2.1: Synthesis of Isocyanates
2.2 MONOMERS
Monomers for the synthesis of polyurethanes consist of two types, i.e.,
diisocyanates and polyols.
2.2.1 Diisocyanates
The basic synthesis of isocyanates is shown in Figure 2.1. The synthesis
starts with an amine, aliphatic or aromatic and phosgene. The isocyanate
is formed by the elimination of two molecules of HCl.
Phosgene Route. The synthesis route via phosgene was invented in 1884
by Hentschel, although isocyanates had been discovered in 1848 by Wurtz.
The synthesis runs via two basic steps, i.e.
1. Formation of the carbamic chloride,
2. Elimination of hydrochloric acid.
The industrial synthesis has to minimize the various side reactions
that may occur, as shown in Figure 2.2.
Phosgene-free Route. There is also a phosgene-free synthesis route,
because of the hazards of handling phosgene. The route is shown in Figure
2.3. The synthesis starts with nitrobenzene; from that the ethyl urethane
is directly formed with carbon monoxide and ethanol. The urethane is
dimerized by a carbonylation reaction. Finally, by heating the urethane is
decomposed into the isocyanate and the alcohol.
Typical diisocyanates are shown in Table 2.1. Aromatic diisocyanates
are shown in Figure 2.4. The highly volatile isocyanates are very toxic.
During curing there is also an emission of the unreacted isocyanate.
The emission also depends on the reactivity of the particular isocyanate, as

Polyurethanes 71
R NH 2 + HCl R NH 3 Cl
R N C O
+
H
N R
H
H
H
R
N
C
N
R
O
R NH 2
R NH 2
+
Cl
Cl
C
R
H N
O C O
H N
R
Figure 2.2: Side Reactions in Isocyanate Synthesis: Salt Formation with HCl
generated, Formation of Urea from Amine and Isocyanate, Formation of Urea
from Amine and Phosgene
CO +
NO 2
CH 3
CH 2 OH
NH C
O CH 2
CH 3
O
CHO
CH 3
CH 3
CH 2
CH 2
O
O
C HN
CH2
NH C
O
O
OCN
CH 2
NCO
Figure 2.3: Phosgene-free Synthesis of Diisocyanates

72 Reactive Polymers Fundamentals and Applications
CH 3
NCO
OCN
CH 3
NCO
NCO
Toluene 2,4-diisocyanate
Toluene 2,6-diisocyanate
OCN
CH 2
NCO
4,4'-Diphenyl methane diisocyanate
NCO
CH 2
NCO
2,4'-Diphenyl methane diisocyanate
NCO
OCN
Naphthalene 1,5-diisocyanate
Figure 2.4: Aromatic Diisocyanates

Isocyanate
Table 2.1: Isocyanates for Polyurethanes
Hexamethylene diisocyanate
Isophorone diisocyanate
Dicyclohexylmethane-4,4 ′ -diisocyanate
4,4 ′ -Diisocyanato dicyclo hexylmethane
2,4-Toluene diisocyanate
Remarks
Color-free
Color-free
Polyurethanes 73
A mixture of 65% 2,4 isomer and
35% 2,6 isomer is most common
2,6-Toluene diisocyanate
1,5-Naphthalene diisocyanate
4,4 ′ -Methylene diphenyl diisocyanate Lower volatile then TDI
4,4-Methylene biscyclohexyl diisocyanate
(HMDI)
1,2-Bis(isocyanate)ethoxyethane
(TEGDI)
Extremely soft 18
Macromonomers See Ref. 19
Lysine-diisocyanate Biodegradable formulations 20
detected in a mixture of 2,4 ′ -methylene diphenyl diisocyanate (2,4 ′ -MDI)
and 4,4 ′ -methylene diphenyl diisocyanate (4,4 ′ -MDI). Because of the high
reactivity with moisture, the analysis requires special techniques; less than
5 ng/m 3 can be detected. 21
2.2.1.1 Toluene diisocyanate
In technical applications, toluene diisocyanate (TDI) is used either as pure
2,4-isomer or as a blend of the 2,4- and 2,6-isomers. Two blend qualities
are available, TDI-80/20 and TDI-65/35, which means 80% 2,4-isomer
with 20% 2,6-isomer, and 65% 2,4-isomer with 35% 2,6-isomer, respectively.
The two isocyanate groups have unequal reactivity; the isocyanate
group at the p-position is more reactive.
Toluene diisocyanate is synthesized from toluene via dinitrotoluene,
reduction of the nitro group with hydrogen (c.f. Figure 2.5) and phosgenation
as shown in Figure 2.1.
The nitration of toluene is achieved in a two-step procedure. In the
first step a mixture of the ortho, para, and meta isomers (63% o-isomer,
33% p-isomer, 4% m-isomer) is obtained. The isomers can be separated
by distillation. When p-nitrotoluene is used in the second nitration step, a

74 Reactive Polymers Fundamentals and Applications
CH 3 CH 3
HNO 3 /H 2 SO 4 O 2 N NO 2
H 2
O
CH 3
NH 2
H 2 N
Cl
C
Cl
OCN
CH 3
NCO
Figure 2.5: First Steps of the Synthesis of Toluene diisocyanate
100% 2,4-dinitrotoluene is obtained. The nitration of o-nitrotoluene finally
yields the TDI-65/35 quality. If the blend obtained from the first step is
directly reacted, the TDI-80/20 quality will be obtained.
2.2.1.2 Diphenylmethane diisocyanate
Diphenylmethane diisocyanate (MDI) has a lower vapor pressure and is
therefore less toxic than TDI. The synthesis of MDI starts with the condensation
of aniline with formaldehyde as shown in Figure 2.6 for the ortho
adducts. In fact, 2,2 ′ - and 2,4 ′ - and 4,4 ′ -isomers are formed, the yield of
the dimer of 4,4 ′ -diphenylmethane diamine being in an amount of ca. 50%.
The isocyanates are obtained then in the usual way by phosgenation. The
crude mixture can be directly used. However, the mixture can be separated
or otherwise modified in order to obtain products with more convenient
properties.
4,4 ′ -MDI has a melting point around 38°C. It forms insoluble dimers
when stored above the melting point. Further, it tends to crystalize. A
mixture of 2,4 ′ -MDI and 4,4 ′ -MDI shows a lowering of the melting point
with a minimum of 15°C at 50% p-isomer.
2.2.1.3 Aliphatic Diisocyanates
A disadvantage of aromatic diisocyanates is that they become yellow to
dark brown when they are cured. This limits the fields of applications.

Polyurethanes 75
NH 2
CH 2 NH 2
+
CH 2
O
H 2 N
NH 2 NH 2 NH 2
CH 2 CH 2 CH 2
Figure 2.6: Condensation of Aniline with Formaldehyde
Aliphatic diisocyanates are colorless, but have other disadvantages. In particular,
the mechanical properties of the final products, such as such as
elongation, tensile strength and flexibility, are inferior. However, aliphatic
isocyanates find important applications in coating formulations. Aliphatic
diisocyanates include 1,6-hexane diisocyanate (HDI), isophorone diisocyanate
(IPDI), dicyclohexylmethane-4,4 ′ -diisocyanate, i.e., hydrogenated
MDI, c.f. Figure 2.7.
In general, aliphatic are less reactive than aromatic isocyanates. Due
to steric hinderance, the affinity of m-tetramethylxylene diisocyanate to
water is so small that it can be dispersed in water without reacting.
2.2.1.4 Modified Diisocyanates
The isocyanates can be modified in several ways, i.e. by dimerization,
oligomerization with diols, or capping the isocyanate group.
Dimerization. Diisocyanates can be dimerized, by splitting off carbon
dioxide, to the respective carbodiimides. The carbodiimide can react further
with an excess of isocyanate to a uretonimine, c.f. Figure 2.8. Such

76 Reactive Polymers Fundamentals and Applications
OCN
CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2
NCO
Hexamethylene diisocyanate
NCO
CH 2
NCO
H 3 C
C CH 3
H 3 C
CH 3
NCO
CH 3
C
NCO
H 3 C
Isophorone diisocyanate
m-Tetramethylxylene diisocyanate
Figure 2.7: Aliphatic Diisocyanates: 1,6-Hexane diisocyanate, Isophorone diisocyanate,
m-Tetramethylxylene diisocyanate
compounds have now three isocyanate groups in the molecule, i.e., they
have a functionality of three.
The properties of MDI can be varied in wide ranges, and consequently
can be used for different applications. The crude MDI is used for
rigid foams. Pure 4,4 ′ -MDI is used, among other applications, for shoe
soles and also for thermoplastic polyurethanes.
Biuret Reaction. Water hydrolyzes the isocyanate group very quickly.
Therefore it is essential to store the isocyanate material moisture-free. On
the other hand, the action of water can be purposefully used to modify
isocyanates. A biuret is formed by the reaction of a substituted urea with
isocyanate, as shown in Figure 2.9. The substituted urea itself can be obtained
by the reaction of water with isocyanate. An amine is formed in the
course of hydrolysis that condenses immediately with water to the substituted
urea. The substituted urea is the reagent for the biuret reaction as
explained above.
Prepolymers. If a glycol or a glycol ether is reacted with an excess
of a diisocyanate, then a prepolymer is formed. In this reaction one diol
couples two molecules of diisocyanate, as schematically shown in Figure
2.10. Also, branched alcohols, like 1,1,1-trimethylolpropane, can be used.

Polyurethanes 77
NCO
NCO
NCO
NCO
CH 2
CH 2
CH 2
CH 2
NCO
N
N
NCO
C
N
C
N
N
C
O
CH 2
CH 2
CH 2
NCO
NCO
NCO
Figure 2.8: Formation of Uretonimine
R N C O
H
N C O
R
N R’
H
R N C O
N C O
R
N R’
Figure 2.9: Biuret Formation of Isocyanates

78 Reactive Polymers Fundamentals and Applications
OCN
CH 2
NCO
HO
+
CH 2 CH 2 O CH 2 CH 2 OH
H
O
OCN
CH 2
N
C
O
CH 2
CH 2
O
CH 2
CH 2
O
OCN
CH 2
N
C
H
O
Figure 2.10: Formation of Prepolymers

Polyurethanes 79
In this case ideally a trifunctional isocyanate is formed.
When the stoichiometric ratio of isocyanate groups to alcohol groups
is more then two, appreciable amounts of unreacted diisocyanate is left behind,
which causes an increased toxicity. If the diisocyanate is sufficiently
volatile, the unreacted residual diisocyanate can be removed by distillation
under vacuum. Such mixtures are liquids at room temperature. Because of
larger structure the prepolymers are less volatile and therefore less toxic.
Toluene diisocyanate and isophorone diisocyanate possess two isocyanate
groups with different reactivities. When forming the prepolymer,
the more reactive group is reacted. The less reactive group is left unreacted.
The properties of the final product can be adjusted by the selection
of the components and the amounts making the prepolymer. For example,
prepolymers based on poly(ethylene oxide) or poly(propylene oxide) will
be used for hydrophilic gels, whereas hydrophobic polyols will result in
hydrophobic polyurethanes. For hydrophobic polyurethanes, polyols with
very nonpolar backbones, e.g., hydroxyl functional poly(butadiene), can
be used to introduce the hydrophobicity. 22
By choosing the stoichiometric ratio of NCO to OH groups, the content
of free isocyanate groups can be adjusted from 2% to 20%.
Viscosity is an important parameter for the processability of the raw
materials. The viscosity increases with molecular weight and decreases
with the content of unreacted isocyanate. The viscosity also increases with
increasing allophanate formed, because this is a crosslinking reaction. The
allophanate formation is favored at temperatures above 60 to 80°C and catalyzed
by alkaline residues in polyether polyols, if any is present. Therefore,
to increase the storage time of the prepolymer, acid stabilizers such as
benzoyl chloride, acetyl chloride, or p-toluenesulfonic acid can be added.
End-capped Diisocyanates. The reaction of the isocyanate group with
alcohols to form the urethane functionality is thermoreversible. At elevated
temperatures the urethane decomposes into the isocyanate. This reaction
is utilized at the phosgene-free route of synthesis of isocyanates. On the
other hand, the reversibility can be used in the preparation of end-capped,
or blocked diisocyanates.
The isocyanate group is allowed to react with compounds containing
acidic hydrogen atoms. In this way the isocyanate group is masked and not
accessible for other reactants. At elevated temperatures the retro reaction
takes place, the isocyanate group is set free, and in presence of amines the

80 Reactive Polymers Fundamentals and Applications
urethane can be formed. A necessary condition for the concept to work
properly is that the unblocking reaction takes places at lower temperatures
than the thermal decomposition of the urethane group.
The temperatures for the retro reaction of unblocking are between 90
and 160°C. Aromatic isocyanates are less stable than aliphatic isocyanates.
The temperature of unblocking decreases in the following order for the
types of blocking agents: alcohols > lactams > ketoximes > active methylene
groups containing compounds. Suitable blocking agents are phenol,
ethyl acetoacetate, ε-caprolactam, methylethylketoxime, diethyl malonate,
and 3,5-dimethylpyrazole.
N,N ′ -Carbonylbiscaprolactam (CBC), c.f. Figure 2.11, offers an isocyanate-free
route to new families of thermosets and reactive resins with
caprolactam-blocked isocyanates. CBC reacts with primary amines into
blocked isocyanates at 100 to 150°C. The reaction is also suitable for
highly functional amine dendrimers and polymers.
With polyols, a ring-opening of the caprolactam occurs. Catalysts
include zirconium alcoholates, magnesium bromide or dibutyltin dilaurate
(DBTDL). N-carbamoyl caprolactam end groups are formed by a nucleophilic
attack of the hydroxy group at one of the CBC caprolactam rings and
subsequent ring opening. Thus, the corresponding blocked ester-functional
isocyanates are formed.
The CBC derivatives are attractive crosslinking agents and interfacial
coupling agents for adhesives and coatings. Further, due to the
non-toxic CBC-intermediates and polyesterurethanes, they are also suitable
for medical applications. 23, 24 When the ring opening reaction is done
with poly(propylene oxide)-based triols, then crosslinked polyurethanes
are obtained. 25 Thus, 1,2-bis-[2(2-hydroxy-5-methylphenyl)-5-benzotriazolyl]-ethane
(BHMBE) reacts with the phenolic hydroxyl groups and is
thus a reactive UV-absorber. 26 The synthesis starts from 4,4 ′ -diaminodibenzyl
in several steps. The structure is shown in Figure 2.12.
Isocyanurate. The formation of an isocyanurate is in fact a trimerization
of an isocyanate (Figure 2.13). Trimers from toluene diisocyanate and
hexamethylene diisocyanate are available. Such isocyanate isocyanurate
structures are trifunctional, i.e., they have three isocyanate groups pending.
They can be modified to become more hydrophilic, if one isocyanate
group is allowed to be coupled with a polyglycol, e.g., poly(ethylene oxide)
or poly(propylene oxide).

Polyurethanes 81
O
R X C N +
O
O
N
H
O
N
C
N
+ RXH
O
O
R
X
H
N
C
N
O
O
O
Figure 2.11: Reaction of N,N ′ -Carbonylbiscaprolactam with a Nucleophile RXH.
Top: ring elimination with formation of caprolactam. Bottom: ring opening reaction.
23 CH 2 CH 2
OH
N
N
N
N
N
N
HO
H 3 C CH 3
Figure 2.12: 1,2-Bis-[2(2-hydroxy-5-methylphenyl)-5-benzotriazolyl]-ethane 26

82 Reactive Polymers Fundamentals and Applications
O
3 R NCO
R
N
N
R
O
N
O
R
Figure 2.13: Trimerization: Formation of an Isocyanurate Structure
Macromonomers. A macromonomer is a polymer that contains reactive
groups, here isocyanate groups. A macromonomer from 2-(dimethylamino)ethyl
methacrylate that bears a 1-(isopropenylphenyl)-1,1-dimethylmethyl
isocyanate group has been synthesized. However, 2-(dimethylamino)ethyl
methacrylate (DMAEMA) reacts with 2-mercaptoethanol
preferably in an addition reaction that acts as chain transfer agent in radical
telomerization. In this way, an adduct of the methacrylate and the mercapto
compound is formed. The structure of the adduct and the product
of functionalization are shown in Figure 2.14. The oligomers can be then
functionalized with 1-(isopropenylphenyl)-1,1-dimethylmethyl isocyanate
(TMI), resulting in macromonomers. 19
α,α ′ -Dihydroxyl-poly(butyl acrylate) prepared by atom transfer radical
polymerization (ATRP) has been used as a macromonomer with two
hydroxyl groups at one end. This macromonomer was used for chain extension
of diphenyl-methane-4,4-diisocyanate to obtain comb-like oligo
isocyanates, as shown in Figure 2.15. These materials have potential interest
as pressure-sensitive adhesives (PSA). 27
In a completely different way rodlike macromonomers were obtained.
In a first step, the N=C bond n-hexyl isocyanate was polymerized
by titanium catalysts in a living polymerization. The living chain end was
deactivated by methacryloyl chloride to result in a methacrylic-terminated
poly(n-hexyl isocyanate. 28
Block copolymers from n-hexyl isocyanate and isoprene have been
obtained by a living polymerization technique. 29 The living anionic polymerization
proceeds very fast and therefore low temperatures −98°C, are
required to control the selectivity. 3,5-Bis(4-aminophenoxy)benzoic acid,
c.f. Figure 2.16, is a monomer from the type AB 2 . It can be polycondensed
to form dendritic polymers. These polymers contain pendant amino groups
that can be crosslinked with diisocyanates. 30

Polyurethanes 83
O
O
S
CH 2
H
CH 2
CH C
CH 3
O
CH 2
CH 2 CH 2
S
CH 3
C
O
CH 2
CH 2
CH 2
CH 2
CH 2
OH
N
H 3 C CH 3
CH 2
OH
N
H 3 C CH 3
H 2 CH
CH 3
C
CH 3
O
S
CH 2
CH 2 CH 2
CH 3
O
C
O
CH 2
C
NH
C
O
CH 2
CH 2
CH 3
N
H 3 C CH 3
Figure 2.14: Adduct from 2-(dimethylamino)ethyl methacrylate and 1-(isopropenylphenyl)-1,1-dimethylmethyl
isocyanate 19
CH 3
N
H
O
C
CH 2 O
O CH 2 C CH 2 O C N CH 2 NCO
CH 2 H
O
O CH 2 CH 2 CH 2 CH 3
O C
C O
H 3 C C CH 2 CH CH 2 CH
CH 3 C O
O CH 2 CH 2 CH 2 CH 3
Figure 2.15: Comb-like Oligo Isocyanates 27

84 Reactive Polymers Fundamentals and Applications
H 2 N
H 2 N
O
O
O
C
OH
Figure 2.16: 3,5-Bis(4-aminophenoxy)benzoic acid
2.2.1.5 Enzymatic Synthesis of Polyurethanes
Polyurethanes have been synthesized using the enzyme Candida antarctica
lipase B. The use of enzymatic methods offers the possibility to reverse the
conventional process by creating the urethane first and then using a low
temperature enzymatic polyester synthesis to build the polymer. A novel
series of biscarbamate esters and polyesters also could be obtained. 31
2.2.1.6 Synthesis of Urethanes via Carbonate Esters
The synthesis of urethanes avoiding handling of isocyanates is also possible
by the reaction of amines or diamines with ethylene carbonate. The
scheme is shown in Figure 2.17. Urethane dimethacrylates suitable for
dental fillers have been synthesized in this way. For example, ethylene
carbonate in two-fold excess was reacted with 1,6-hexane diamine to obtain
a urdiol. This was reacted with methacrylic anhydride. 32
2.2.2 Polyols
Polyols are the second basic component beside diisocyanates. There are
two types of polyols,
1. Polyether polyols,
2. Polyester polyols.
2.2.2.1 Polyether Polyols
Most widely used are polyether polyols. Monomers commonly used for
polyether polyols are listed in Table 2.2.

Polyurethanes 85
O
O
O
HO(CH 2 ) 2 O
H 2 N
NH 2
O
CH 2
H 2 C
O
CH 2
H 2 C
O
O
C HN NH C O(CH 2 ) 2 OH
O
Figure 2.17: Reaction of Ethylene Carbonate with 1,6-Hexane diamine
Table 2.2: Monomers for Polyether Polyols
Monomer
Propylene oxide
Ethylene oxide
Butylene oxide
Tetrahydrofuran
Remarks
As copolymer with propylene oxide
In fibers and elastomers

86 Reactive Polymers Fundamentals and Applications
R OH + B R O
O
R O + CH 2 CH 2
CH 3
R
O
CH 2
CH 2 O
CH 3
Figure 2.18: Initial Steps of the Formation of Polyether polyols
Anionic Ring Opening. Polyols with a molecular weight between 1,000
and 6,000 Dalton and a functionality between 1.8 and 3.0 are used in flexible
foams and elastomers. Polyols with a molecular weight below 1,000
Dalton and high functionalities result in high crosslinked rigid chains and
are used in rigid foams and high performance coatings.
The polymerization is initiated with an alcohol and a strong base.
The base is usually potassium hydroxide that forms initially the monomeric
alcoholate. The alcoholate anion is subjected to a series of ring opening reactions
of the epoxide or the cyclic ether. The basic mechanism is sketched
in Figure 2.18.
In the case of nonsymmetric epoxides the alcoholate anion attacks
the less hindered carbon atom of the epoxide, as shown in Figure 2.18.
Therefore, polyols composed exclusively from propylene oxide bear
secondary hydroxyl groups as end groups. Secondary hydroxyl groups are
less reactive than primary hydroxyl groups.
To get polyols with the more reactive primary hydroxyl groups, the
polymerization is started with propylene oxide, and in the final stage ethylene
oxide is added. Ethylene oxide improves the water solubility of the
polyol.
Due to the mechanism of polymerization without termination in preparing
polyether polyols, the molecular weight distribution of the polyols
exhibits a Poisson distribution. This is narrower than the distribution of
polyester polyols. Instead of alcohols, amines can also be used. Typical
initiator alcohols are propylene glycol, glycerol, trimethylolpropane, triethanolamine,
pentaerythritol, sorbitol, or sucrose.
Sucrose results in highly branched polyols suitable for rigid foams,
whereas the alcohols with a lower functionality are used for flexible materials.
Amines include ethylene diamine, toluene diamine, 4 ′ ,4 ′ -diphenyl-

Polyurethanes 87
methane diamine, and diethylenetriamine. The resulting polyols exhibit a
higher basicity than the polyols with an alcohol as initiator and are therefore
more reactive with isocyanates.
A side reaction of the base in polymerization is the isomerization
reaction. For example, propylene oxide isomerizes to allyl alcohol. As a
consequence, vinyl-terminated monofunctional polyols are formed. Such
monofunctional polyols are addressed as monols. Such compounds have
negative influence on the mechanical properties of the final products.
The formation of monols can be suppressed by using special catalysts,
e.g., zinc hexacyanocobaltate. This type of catalyst is referred to as
double metal cyanide catalyst.
Grafted Polyols. Copolymer polyols are obtained by grafting styrene
or acrylonitrile to poly(propylene oxide). The radicals attack the tertiary
hydrogen sites (−CH 2 CH tert (−CH 3 )−O) in the poly(propylene oxide) as
a transfer reaction to the poly(propylene oxide). Originally pure acrylonitrile
was used for grafting, but the so formed copolymer polyols cause
discoloration problems in slabstock flexible foams. For this reason styrene/acrylonitrile
copolymer polyols were developed.
Vinyl Functionalized Polyols. Another method is to functionalize the
polyols with a vinyl moiety. This is achieved by reaction of the polyols
with maleic anhydride, or methacryloyl chloride. Of course the functionality
of the polyols must be greater than two with respect to the hydroxyl
group, because hydroxyl groups are lost. If to the vinyl functionalized
polyol a polymerizing vinyl monomer mixture is added, the pendent vinyl
group polyols take part in the polymerization reaction. With respect to the
vinyl polymer a comb-like structure is formed, the teeth of the “comb” being
the polyol moieties. The styrene is hydrophobic, and at higher conversion
the backbone of the comb may collapse to yield a spherical structure.
The polyol chains are at the surface of the sphere.
Polyurea-modified Polyols. Urea urethane polyols and polyurea-modified
polyols are another type of polyols. They are synthesized in a twostage
reaction.
1. In the first stage a diamine or an amino alcohol is allowed to react
with an excess of diisocyanate. The amine groups react with

88 Reactive Polymers Fundamentals and Applications
the isocyanate group to form urea groups, whereas the hydroxy
groups react with the isocyanate group to form urethane groups.
The excess of isocyanate causes the formation of an isocyanate
end-capped prepolymer. In the case of a diamine, isocyanates are
formed that contain exclusively urea groups in their backbone. In
the case of amino alcohols isocyanates containing urea and urethane
in the backbone are formed. Suitable diamines are hydrazine,
ethylene diamine, etc.
2. In the second stage a diol or a polyol in molar excess with respect
to the unreacted isocyanate groups is added. The pending isocyanate
groups react with the hydroxy groups to form chain-extended
polymeric polyols. The reaction of diamines with isocyanates proceeds
fast in comparison to the reaction of polyols with isocyanates.
Autocatalytic Polyols. The alkylamine group can be introduced in a
polyol chain by using N-alkylaziridine or N,N-dialkyl glycidylamine as
a comonomer with ethylene oxide or propylene oxide. Since the amine
groups in the chain catalyze the reaction of the hydroxyl groups with the
isocyanate, this type of polyol is called autocatalytic. 33
Autocatalytic polyols require less capping with primary hydroxyls,
that is, less ethylene oxide capping to obtain the same performance in flexible
molded foam than conventional polyols when used under the same
conditions. Moreover, low emission polyurethane polymers can be made
with autocatalytic polyols.
2.2.2.2 Polyester Polyols
Typical monomer combinations for polyester polyols are shown in Table
2.3.
Polyesters from Acid and Alcohols. The polyesters are produced by preheating
the diol to ca. 90°C and adding the acid into it. The reaction temperature
is raised gently up to 200°C to completion. Inert gas or vacuum
is used to remove the water. The condensation is an equilibrium reaction,
and a Schulz-Flory distribution of the molecular weight is obtained.
The condensation is catalyzed by acids, bases, and transition metal
compounds. However, catalysts should be used with care, because they

Polyurethanes 89
Table 2.3: Monomers for Polyester Polyols
Acid Alcohol Components
Uses
Adipic acid, diethylene glycol, 1,1,1-trimethylolpropane
Flexible foam
Adipic acid, phthalic acid, 1,2-propylene glycol, glycerol
Semi-rigid foam
Adipic acid, phthalic acid, oleic acid, 1,1,1-trimethylolpropane
Rigid foam
Adipic acid, ethylene glycol, diethylene glycol Shoe soles
Adipic acid, ethylene glycol, 1,4-butanediol Elastomers
ε-caprolactone, various diols
Ring opening condsation
Castor oil, glycerol, trimethylolpropane
Transesterification
could have undesirable effects on the subsequent curing reaction. Condensation
catalysts based on tin and other transition metals added only in
the ppm range did not show negative effects on the later procedures and
properties.
The hydroxyl numbers increase from flexible foams to rigid foams
from 60 mgKOH/g up to 400 mgKOH/g. Acids for soft foams are aliphatic
acids, such as adipic acid, whereas phthalic anhydride increases the
rigidity.
Terephthalic acid or isophthalic acid are used in high performance
hard coatings and adhesives. Such foams are improved to be flame resistant.
Foams based on aromatic polyester polyols show charring upon
exposure to flame.
Polyesters based on terephthalic acid are manufactured by transesterification
of dimethyl terephthalate. Also poly(ethylene terephthalate)
waste materials, such as polyester fibers or soft drink bottles, can be recycled
by glycolysis to obtain suitable polyols.
Triols, such as glycerol and 1,1,1-trimethylolpropane, will result
in branched polyesters. Alcohols for flexible foams are ethylene glycol,
diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, etc.
Longer chains result in a greater hydrolytic stability, simply because there
are fewer ester groups in the structure.
Polyesters from a single acid component and a single alcohol component
are crystalline. The crystallinity can be reduced by using mixtures
of diols or mixtures of different polyesters.

90 Reactive Polymers Fundamentals and Applications
Mixed polyesters from waste acids of the production of nylon contain
adipic acid, glutaric acid, and succinic acid. The acids can be also
hydrogenated to obtain the respective diols that can be used in the condensation.
The ester group in polyester polyols is sensitive to hydrolysis attack.
The hydrolysis stability can be improved with additives that react
with carboxylic and alcoholic groups, which are formed during the hydrolysis.
These additives include oxazolines, epoxy compounds, and carbodiimide
structures. In particular, polyester polyols can be stabilized by the
addition of 1 to 2% of hindered aromatic carbodiimides. These compounds
are scavengers for the acid generated by ester hydrolysis. The acid would
catalyze further hydrolysis.
Polyester polyols can contain 10 to 20% of vinyl polymers. The
vinyl polymers improve the hydrolysis stability, hardness and the form stability.
ε-Caprolactone based polyesters. Another synthesis route for aliphatic
polyester polyols is the ring opening polymerization of ε-caprolactone with
various glycols.
These include diethylene glycol, 1,4 butanediol, neopentyl glycol, or
1,6-hexanediol. Branched products are obtained by adding 1,1,1-trimethylolpropane
or glycerol to a bifunctional alcohol. Higher branched polyesters
utilize pentaerythritol. The poly(ε-caprolactone)-containing polyesters
exhibit a greater hydrolysis resistance and lower viscosity than comparable
polyadipate glycols.
2.2.3 Other Polyols
2.2.3.1 Hydrocarbon Polyols
Hydrocarbon polyols can be obtained by living anionic polymerization of
butadiene initiated by sodium naphthalene, which is the common route to
polymerize butadiene. However, the living chains are finally terminated by
adding ethylene oxide or propylene oxide. By adding water a poly(butadiene)
with primary and secondary hydroxyl groups is obtained.
Hydroxy-terminated poly(butadiene) is also accessible by free-radical
polymerization of butadiene, initiated by hydrogen peroxide. The major
advantage of hydrocarbon polyols is the high chemical resistance. The
low glass transition temperature keeps its elastomeric properties down to

Polyurethanes 91
extremely low temperatures. The double bonds in the chain or pendent
double bonds open the possibility of further reactions, like vulcanization
and other chemical reactions. The functionality of these diols is two, therefore
they can be used for thermoplastic polyurethanes.
2.2.3.2 Polythioether Polyols
Polythioether polyols include products obtained by condensing thiodiglycol
either alone or with other glycols, alkylene oxides, dicarboxylic acids,
formaldehyde, amino-alcohols, or aminocarboxylic acids.
2.2.3.3 Polyacetal Polyols
Polyacetal polyols are prepared by reacting glycols such as diethylene glycol,
triethylene glycol, or hexanediol with formaldehyde. Suitable polyacetals
may also be prepared by polymerizing cyclic acetals.
2.2.3.4 Acrylic Polyols
Acrylic polyols are obtained by copolymerization of acrylic monomers,
such as ethyl acrylate, n-butyl acrylate, acrylic acid, methyl methacrylate,
or styrene with minor amounts of 2-hydroxyethyl acrylate or 4-hydroxybutyl
acrylate. Styrene, if added, makes the acrylic polyol more hydrophobic.
Acrylic polyols are used in two-component coating systems. They
exhibit good chemical resistance and weatherability.
2.2.3.5 Liquefied Wood
Liquefied wood can be obtained by the liquefaction of benzylated wood
wastes using dibasic esters as solvent with hydrochloric acid as catalyst.
The reaction is completed at 80°C after 3 hours. Liquefied wood acts as
a diol component for, e.g., TDI, IPDI, and HDI. Polyurethane resins from
liquefied wood have a higher thermal stability than the traditional polyurethane
resins. 34
2.2.4 Polyamines
The amine functionality reacts with the isocyanate group to a urea moiety.
In this way an amine group corresponds to a hydroxy group that reacts with
the isocyanate group to a urethane moiety.

92 Reactive Polymers Fundamentals and Applications
Hydroxyl end groups in polyether polyols can be converted into amine
end groups by reductive amination. This type of compound is called an
amine-terminated polyether, or simply polyetheramine. Polyetheramines
are suitable for soft segments of polyurea resins.
2.2.5 Chain Extenders
Chain extenders, curing agents, and crosslinkers are low molecular compounds
for improving properties of the final products. Examples are shown
in Table 2.4. Chain extenders are difunctional compounds. Glycols are
used in polyurethanes. Diamines or hydroxylamines are used in polyureas
and mixed polyurethane ureas. Low-molecular weight polyamines react
with the isocyanate group very fast, and can be used in reactive injection
molding, where short cycles are essential.
2,2 ′ -Pyromellitdiimidodisuccinic anhydride (DA) can act as a chain
extender for isocyanates in the presence of polyols. In a first stage, the
polyol is allowed to react with the isocyanate compound to get isocyanateterminated
oligomers. In the second stage, the 2,2 ′ -pyromellitdiimidodisuccinic
anhydride reacts with the oligomer, splitting off carbon dioxide to
result in a poly(urethane-imide-imide). This class of polyurethane has a
higher thermal stability than conventional polyurethanes. 35
Chain extenders with the triazene structure are photosensitive compounds.
36 They are used together with another extender as a coextender.
Because the resulting triazene polyurethanes become crosslinked by exposure
to UV irradiation, they have a potential use as negative-resist polymers.
2.2.6 Catalysts
Catalysts are necessary to obtain the desired end products. The final properties
depend strongly on the content of urethane, urea, allophanate, biuret,
and isocyanurate bonds. Therefore, catalysts govern the final properties of
the materials. The nature of the catalysts also greatly influences the reaction
time and the properties of the final product. The catalysts can be
classified into three main categories:
1. Catalysts for blowing,
2. Catalysts for gelling, and
3. Catalysts for crosslinking.

Polyurethanes 93
Compound
Ethylene glycol
Diethylene glycol
Propylene glycol
Dipropylene glycol
1,4 Butanediol
2-Methyl-1,3-propylene diol
N,N ′ -bis(2-hydroxypropylaniline)
Water
1,4-Di(2-hydroxyethyl)hydroquinone
Diethanolamine
Triethanolamine
1,1,1-Trimethylolpropane
Glycerol
Dimethylol butanoic acid (DMBA)
Table 2.4: Chain Extenders
Hydrazine
Ethylene diamine (EDA)
1,4-Cyclohexane diamine
Isophorone diamine
4,4 ′ -bis(sec-Butylamine)dicyclohexylmethane
4,4 ′ -bis(sec-Butylamine)diphenylmethane
Diethyltoluene diamine
4,4 ′ -Methylene bis(2-chloroaniline)
4-Chloro-3,5-diamino-benzoic acid isobutylester
3,5-Dimethylthio-toluene diamine
Trimethylene glycol-di-p-aminobenzoate
4,4 ′ -Methylene bis(3-chloro-2,6-diethylaniline)
1-(α-Naphthyl)-3,3-di(2-hydroxyethyl)-
triazene-1 (NT-D)
1-Phenyl-3,3-di(2-hydroxyethyl)-
triazene-1 (PT-D)
Remarks
Waterborne chain extender
37
Both isomers
Both isomers
Photosensitive 36
Photosensitive 36

94 Reactive Polymers Fundamentals and Applications
Table 2.5: Catalysts Classified According to the Reaction
Reaction
Catalyst Type
Trimerization Strong bases, quaternary ammonium salts, phosphines
Dimerization Phosphorous compounds
Polymerization Alkaline metal hydroxides
Addition to alcohols Tertiary amines, organometals, metal salts
Reaction with water Tertiary amines
Addition to urethane Metal salts
Addition to amines Tin and zinc salts
From the chemical view, catalysts for producing polyurethanes can be divided
into two general types: tertiary amines and organo-tin compounds.
Organometallic tin catalysts predominantly favor the gelling reaction,
while amine catalysts exhibit a more varied range of blow/gel balance.
A lot of catalysts have been described and reviewed. 6, 38 The choice
of the catalyst depends on which reaction and which structure is to be favored.
Table 2.5 lists types of catalysts that are suitable for the individual
reactions.
It is important to tune the kinetics of the individual reactions properly.
For example, if the blowing reactions take place significantly before
the sufficient progress of gelling (crosslinking), the viscosity of the reacting
material is low, causing the carbon dioxide to escape, and will not yield
a foam.
On the other hand, if the gelling (or crosslinking reaction) occurs too
fast, the blowing gas cannot expand the material. Thus, it is necessary to
balance the individual reactions. This balance can be readily controlled by
the nature and quantity of the catalyst used.
2.2.7 Blowing
Chemical blowing is effected by the reaction of isocyanate and water. The
rate of blowing increases with the catalyst and water content. 39 As an
intermediate, carbamic acid is formed. The carbamic acid is not stable; it
decomposes into an amine and carbon dioxide. Carbon dioxide expands
the polyurethane into a foam.
There are also physical blowing agents available. In this case the
foam is generated by the evaporation of the blowing agent supported by

Polyurethanes 95
external heating but also by the temperature rise due to the formation of the
polyurethane from the diisocyanate and the polyol. Suitable reagents for
physical blowing were previously fluorocarbons and chlorofluorocarbons.
The latter class of substance has been removed because of its ozone depletion
potential. Pentane is a substitute for chlorofluorocarbons. The release
of the physical blowing agents occurs in three ways when a foamed material
is recycled or shredded: 40
1. The instantaneous release from cells split or damaged by the shredding,
2. The short-term release from cells adjacent to the cut surface , and
3. The long-term release by normal diffusion processes.
Formic acid has been proposed as a chemical blowing agent.
41, 42
Formic acid can behave either as an acid or an aldehyde. In contrast to
water that yields exclusively carbon dioxide, formic acid upon contact with
an isocyanate group reacts to initially liberate carbon monoxide and further
decomposes to form an amine with a release of carbon dioxide, according
to the following reaction:
2Φ−NCO+HCOOH → CO+CO 2 + Φ−NH−CO−NH−Φ (2.1)
Aside from its zero ozone depletion potential, a further advantage of using
formic acid is that 2 mol of gas are released for every mole of formic acid
present, whereas a water-isocyanate reaction results in the release of only
1 mol of gas per mol of water. In both the water-isocyanate and the formic
acid-isocyanate reactions, the isocyanate is consumed and one must add a
proportionate excess of isocyanate to compensate for the loss. However,
since formic acid is a more efficient blowing agent than water, the number
of moles of formic acid necessary to produce the same number of moles of
gas as a water-isocyanate reaction is greatly reduced, thereby reducing the
amount of excess isocyanate and leading to a substantial economic advantage.
43 It is believed that liberation of carbon monoxide and subsequently
carbon dioxide in the reaction Eq. 2.1 proceeds at a slower rate than the
release of carbon dioxide in a water-isocyanate reaction for two reasons:
1. The anhydride is more stable than the carbamic acid formed in
a water-isocyanate reaction and, therefore, requires more thermal
energy to decompose, and

96 Reactive Polymers Fundamentals and Applications
2. The reaction is a two-step reaction rather than the one-step reaction
present in a water-isocyanate reaction.
The exothermic reaction in a polyol composition containing formic acid
proceeds in a more controlled manner than in an all water blown reaction.
Formic acid in combination with hydrochlorofluorocarbons improves
the mechanical and thermal properties. It exhibits a delayed action and
thus a prolonged gel time. Rigid foams produced with formic acid possess
excellent dimensional stability at low densities. 43 However, the generation
of carbon monoxide during the curing and corrosion problems are evident
drawbacks.
2.2.7.1 Gelling and Crosslinking
Gelling reactions are discussed as curing reactions that do not blow, but
yield linear urethanes. These reactions are similar to crosslinking reactions,
from the chemical view. The technical term “curing” is not common
in polyurethanes, except for unsaturated polyester technology, epoxies,
etc., because the resulting final products are often not hard, e.g., flexible
foams.
The basic reactions in the course of polyurethane formation are shown
in Figure 2.19. These include the reaction of isocyanate with a polyol
to yield a polyurethane, the formation of urea from an isocyanate and an
amine, and the blowing reaction. Other reactions are the formation of a
biuret, c.f. Figure 2.9 and the trimerization, c.f. Figure 2.13.
The action of a catalyst can be studied conveniently with model compounds.
Suitable experimental techniques are liquid chromatography,infrared
spectroscopy, and nuclear magnetic resonance spectroscopy. Infrared
spectroscopy conveniently monitors the disappearance of the isocyanate
group.
Raman spectroscopy is advantageous in two ways. Since the Raman
effect is a scattering process, samples of any shape or size can be examined.
Moreover, Raman spectroscopy measurements can be conducted remotely
using inexpensive, communications grade, fused-silica optical fibers. 44
Nuclear magnetic resonance spectroscopy suffers from the disadvantage
that the spectroscopic shifts of the urethane, urea, allophanate, and
biuret linkages are very similar.
Rheological techniques are also suitable for monitoring the progress
of curing. 45–47 The dynamic viscosity has been measured as a function of

Polyurethanes 97
R N C O
H O R’
R N C O
H O R’
R N C O
H N R’
R N C O
H N R’
R N C O
H O H
R N C O
H O H
R
H
N
H
CO 2
R N C O
H
N C O
R
O R’
H
R N C O
N C O
R
O R’
Figure 2.19: Basic Reactions in Polyurethane Formation: Reaction of Isocyanate
with a Polyol; Formation of Urea from Isocyanate and Amine; Chemical Blowing
with Water; Allophanate formation

98 Reactive Polymers Fundamentals and Applications
time and found to be independent of the shear rate. 47 A simple technique of
this kind is to drop metal ball bearings consecutively into a growing foam.
The position of the ball bearings in the final foam reflects the viscosity
profile. The simultaneous measurement of the height of the foam gives
information of the degree of expansion.
The gel times can be used to evaluate the activity of catalysts. In particular,
it was found that the activity of catalysts, among them organometallic
catalysts, decreases in the order Bi > Pb > Sn > triethylamine > .... 46
The rheological properties determined by dynamic mechanical techniques
can be sensitive to the rate of mechanical deformation. The rate of
expansion or possibly the rate of foam rise can be used characterizing the
activity of certain catalysts.
A combined measurement of the expansion and the weight loss permits
characterizing the mass of CO 2 trapped within a foam, the mass of
CO 2 lost, and the total mass of CO 2 generated during curing.
There are three major classes of catalysts: tertiary amines, organic
salts, and organometallics. Often the chemical nature of the catalysts is
not disclosed in the patent literature. However, a compilation of chemical
structures of commercially available catalysts useful in the manufacture of
flexible foams is available. 48 Nevertheless, it is often difficult to establish
structure-property relationships because of the unavailability of information.
2.2.7.2 Tertiary Amine Catalysts
Commercially used amines are summarized in Table 2.6 and shown in Figure
2.20. Amine catalysts are often delivered as a solution in dipropylene
glycol. This makes the dosage of small quantities easier.
Tertiary amines are used most commonly to catalyze the urethane
formation. They catalyze both gelling and blowing reactions but not the
formation of isocyanurate. Tertiary amines are often formulated with organotin
compounds.
As the basicity increases, the crosslinking is favored. A known problem
is volatility that causes odor. Further, the migration of amine catalysts
can cause a discoloration when the final polyurethane is used with poly-
(vinyl chloride) (PVC). This problem emerges in the automotive industry
and is addressed as “vinyl staining”.
The discoloration of poly(vinyl chloride) bound to polyurethane has

Polyurethanes 99
Amine
Table 2.6: Tertiary Amine Catalysts
1,4-Diazabicyclo[2.2.2]octane (DABCO)
Bis(2-dimethylaminoethyl)ether (BDMAEE)
N-Ethylmorpholine
N-Methylmorpholine
N ′ ,N ′ -dimethylpiperazine
Triethylamine
N,N-dimethylethylamine
Substituted pyridines
2-Azabicyclo[2.2.1]heptane
N-(3-Dimethylaminopropyl)-2-ethylhexanoic acid
amide
N,N,N ′ ,N ′ ,N ′′ -pentamethyldiethylene triamine
Remarks
Widely employed
High-resiliency
foams, heavy blowing
catalyst
Polyester slabstock
foam
Polyester slabstock
foam
High vapor pressure,
improves skin formation
in molded foam
Highly volatile cure
catalyst
Low odor
Uretdiones
Heavy blowing
catalyst
N,N-dimethylcyclohexylamine
Odorous liquid
N,N-dimethylbenzylamine
Polyester flexible
foams
N,N-Dimethylethanolamine
Polyether flexible
foams
3-Hydroxy-1-azabicyclo[2.2.2]octane
Reactive catalyst
2-(2-N,N-Diethylaminoethoxy)ethanol
Reactive catalyst
5-Dimethylamino-3-methyl-1-pentanol
Reactive catalyst, low
odor 50
1-(2-hydroxypropyl)imidazole
Reactive catalyst
1-(3 ′ -Aminopropyl)imidazole Reactive catalyst 51
1-(3 ′ -(Imidazolinyl)propyl)urea
51
Bis(3-(N,N-dimethylamino)propyl)amine,
chain-extended with polyol and polyisocyanate
49
52

100 Reactive Polymers Fundamentals and Applications
O
N
CH 2 CH 2
CH 2 CH 2
CH 2 CH 2
N
N
CH 2 CH 3
1,4-Diazabicyclo[2.2.2]octane
N-Ethylmorpholine
H 3 C
H 3 C
N
CH 3
CH 2 CH 2 O CH 2 CH 2 N
CH 3
Bis(2-dimethylaminoethyl)ether
CH 2
N
CH3
H 3 C
H 3 C
N
CH 2 CH 2 OH
2-Methyl-2-azabicyclo[2.2.1]heptane
N,N-Dimethylethanolamine
Figure 2.20: Tertiary Amine Catalysts: 1,4-Diazabicyclo[2.2.2]octane, N-Ethylmorpholine,
Bis(2-dimethylaminoethyl)ether, 2-Azabicyclo[2.2.1]heptane, N,N-
Dimethylethanolamine

Polyurethanes 101
been attributed to the catalyzed dehydrochlorination of the PVC by the
residual amine catalyst. 53 Amine-free catalyst systems based on carboxylates
are helpful to avoid this phenomenon.
54, 55
The activity of amines increases with increasing basicity. However,
the activity is negatively influenced by steric hindrance. The urethane
formed by the reaction catalyzes further formation of urethane. Amines of
the general structure RR ′ N(CH 2 ) n OR ′′ are effective blowing catalysts at
n = 2, but good gelling catalysts at n = 3.
Triethylene diamine is a synonym for 1,4-diazabicyclo[2.2.2]octane,
which is both an excellent gelling and blowing catalyst. It is the most used
tertiary amine in the production of polyurethanes. The unusual high activity
of 1,4-diazabicyclo[2.2.2]octane emerges from a lack of steric hindrance
in spite of its moderate basicity. Its complex with boric acid exhibits
a reduced odor.
Bis(2-dimethylaminoethyl)ether is used to produce high-resiliency
foam, because it promotes the reaction of the isocyanate with water. It
is often used together with triethylene diamine. N-ethylmorpholine and N-
methylmorpholine have lower activity and are therefore used in the production
of polyester slabstock foam, where only catalysts with lower activity
are needed. N-Methylmorpholine, N-ethylmorpholine and triethylamine
belong to the group of skin cure catalysts. These are tertiary amines with
high vapor pressure. They volatilize from the developing foam to the foam
mold surface, thus promoting an additional reactivity there.
Substituted hexahydro-s-triazines, like 1,3,5-tris(3-dimethylaminopropyl)-s-hexahydrotriazine
and hexamethylenetetramine 56 and alkylated
imidazoles, like 1-methylimidazole or 1,2-dimethylimidazole 57–60 (Figure
2.21) are also used in both high resiliency and rigid foams. An amidine
contains a chemical structure as presented in Eq. 2.2.
C N N
(2.2)
Certain bicyclic amidines (Fig. 2.22) exhibit a high gelling activity coupled
with low volatility. However, these materials are sensitive to heat,
light, and oxygen. 1,8-Diazobicyclo[5.4.0]undec-7-ene or 1,5-diazobicyclo[4.3.0]non-5-ene
in combination with primary amines can catalyze the
reaction of phenol blocked isocyanates. 61 The bicyclic catalyst is capa-

102 Reactive Polymers Fundamentals and Applications
H 3 C
N
H 3 C
H 2 C
H 2 C
H 2 C
N
N CH 2
CH 3
CH 2 CH 2 N
CH 3
N
CH 2 CH 2 CH 2
CH 3
N
CH 3
1,3,5-Tris(3-dimethylaminopropyl)-s-hexahydrotriazine
N
H 2 C CH 2
N N
CH 2
N
H 2 C CH2
N
N
CH 3
Hexamethylenetetramine
1-Methylimidazole
Figure 2.21: 1,3,5-tris(3-dimethylaminopropyl)-s-hexahydrotriazine, hexamethylenetetramine,
1-methylimidazole
ble of unblocking phenol blocked isocyanate groups, and can effect curing
within an hour at ambient temperature. Among the amidines the bicyclic
amidines have greater activity than the monocyclic amidines. 62 Alkylamino
amides, i.e. secondary amides with a pendent tertiary amine with the
basic structure [(CH 3 ) 2 N(CH 2 ) 3 ] 2 NCOR are odorless and have a high resistance
to hydrolysis. 63 For example, formaldehyde can be condensed
with N,N-bis(3-dimethylamino-n-propyl)amine. Ammonia is evolved to
yield N,N-bis[3-(dimethylamino)propyl]formamide.
N
N
N
N
1,8-Diazobicyclo [5.4.0]
undecene-7
1,5-Diazobicyclo [4.3.0]
non-5-ene
Figure 2.22: 1,8-Diazobicyclo[5.4.0]undec-7-ene, 1,5-Diazobicyclo[4.3.0]non-
5-ene

Polyurethanes 103
These types of compounds are strong gelling catalysts. Combination
of the latter compound with a weak blowing catalyst, such as methoxyethylmorpholine
has been described. 64
Formamide-type catalysis can be used to replace the highly volatile
dimethylpiperazine. The use of N,N-Bis[3-(dimethylamino)propyl]formamide
as the sole catalyst produces a tight foam. Blends with methoxyethylmorpholine
or optionally with 2,2 ′ -oxybis(N,N-dimethylethanamine) are
strong blowing catalysts. They improve flow, skin cure, and de-mold times
in flexible molded polyether foams. 64
Still less volatile catalysts can be prepared using bifunctional oxalic
esters instead of formic acid derivatives. 65 This class is addressed as alkylamino
oxamides. An aqueous catalyst mixture is obtained to form the salts
by, e.g., salicylic acid. Alternative catalysts have cyclic structures, e.g.,
bis[N-(3-imidazolidinylpropyl)]oxamide, or bis[N-(3-morpholinopropyl)]-
oxamide. Headspace gas chromatography was applied to measure the fugitivity.
The oxalic acid amide adducts were not volatile under the conditions
of analysis.
To combine good in-mold flowability and fast curing, delayed-action
catalysts were developed. Reduced reactivity in reactive injection molding
is sometimes desirable so that large molds could be filled completely before
cure. The activity of an amine catalyst can be delayed by adding acids, such
as formic acid, 2-ethylhexanoic acid, or amino acids. 66 The amine salt is
less active then the free amine. As the curing proceeds the temperature
rises. At elevated temperatures the amine salt dissociates to the free amine
and acid.
Zwitterionic salts from triethylene diamine and tetra-n-butylammonium
chloroacetate also delay the reaction. The effect of controlled catalysis
may be realized in improved reactivity profiles, for instance, delayed initiation
or accelerated cure.
67, 68
A disadvantage in the usage of amine salts is the possibility of corrosion,
a negative influence on the long-term properties of the final product.
Half esters of diethylene glycol with maleic anhydride or phthalic
anhydride can be used to neutralize, or block amines, such as bis(2-dimethylaminoethyl)ether
(BDMAEE). Such types of blocked amines are
noncorrosive, delayed-action catalysts for flexible foams. 69 The reaction
can be performed in one stroke, allowing phthalic anhydride to react with
BDMAEE in diethylene glycol.
Acid-blocked amine catalysts have an unpleasant odor associated

104 Reactive Polymers Fundamentals and Applications
with their use, especially when the polyurethane mixtures are cured in
an oven at temperatures above 120°C. This unpleasant odor also remains
in the final product, making these catalysts unsuitable for some applications.
70 The incorporation of active hydrogens, such as primary and secondary
hydroxyl groups and amino groups, into the catalyst structure is
suitable to reduce odors and emissions.
2.2.7.3 Mechanisms of Tertiary Amine Catalysts
Two basic mechanisms for tertiary amine-catalyzed formation of urethane
are under discussion. The first mechanism deals with the formation of
an isocyanate-amine complex followed by reaction with an alcohol. This
mechanism suggests that the nucleophilicity of the amine is the dominant
factor. The second mechanism postulates an amine-alcohol complex that
reacts with the isocyanate. According to this mechanism, the amine basicity
is the dominant factor.
The mechanism based on an isocyanate-amine complex seems to be
more generally accepted. It is suggested that Lewis bases are activating the
alcohols. 71
2.2.7.4 Reactive Catalysts
If the catalysts are modified with a group that reacts with isocyanates, then
the catalysts can be incorporated into the polyurethane material. For example,
triethanolamine has three hydroxy functions and is at the same time a
tertiary amine. Other compounds include an adduct of glycidyl diethylamine
with 2(di-methylamino)ethanol.
72, 73
A hydroxy functional tertiary amine can be produced by a Michael
type reaction followed by reductive amination of the cyano group, as exemplified
with 1-(3-dimethylaminopropoxy)-2-butanol in Figure 2.23. Since
the butanol can attack the acrylonitrile either with the primary hydroxyl
group or with the secondary hydroxyl group, in fact an isomeric mixture
will be obtained. 74 In the same way an adduct with 1-methylpiperazine can
be obtained.
Reactive catalysts typically show a high activity in the initial stage
of polymerization and then a reduced activity when they are included in
the growing polymer.

Polyurethanes 105
H 2 C CH C N
O H
CH 2 CH CH 2 CH 3
OH
H 2 C CH C N
O H
CH 2 CH CH 2
OH
CH 3
CH 3
H 2 C CH CH 2 N
CH
O H
3
CH 2 CH CH 2 CH 3
OH
CH 3 N CH 3
+ H 2 - NH 3
1-(3-Dimethylaminopropoxy)-2-butanol
Figure 2.23: Synthesis of a Hydroxy Functional Tertiary Amine: 1-(3-Dimethylaminopropoxy)-2-butanol
2-Dimethylaminoethyl urea or N,N ′ -Bis(3-dimethylaminopropyl)
urea contains the ureido group which enables the catalysts to react into
the polyurethane matrix. These reactive catalysts can be used as gelling
catalysts or blowing catalysts with complementary blowing or gelling cocatalysts,
respectively, which may or may not contain reactive functional
groups to produce polyurethane foam materials. The reactive catalysts produce
polyurethane foams which have no amine emissions. 75
Examples for reactive catalysts include 3-quinuclidinol (3-hydroxy-
1-azabicyclo[2.2.2]octane), 76, 77 propoxylated 3-quinuclidinol, 3-hydroxymethyl
quinuclidine, 78 and 2-(2-N,N-diethylaminoethoxy)ethanol.
Propoxylated 3-quinuclidinol is a liquid, which is soluble in dipropylene
glycol, whereas 3-quinuclidinol is a high melting solid. 3-Methyl-3-hydroxymethyl
quinuclidine may be prepared by reacting ethylpyridine
with formaldehyde to afford 2-methyl-2-(4-pyridyl)-1,3-propanediol
which is hydrogenated to 2-methyl-2-(4-piperidyl)-1,3-propanediol which
in turn is cyclized to the quinuclidine product. 78 2-(2-N,N-diethylaminoethoxy)ethanol
is superior with regard to vinyl staining.
Combinations of a nonreactive catalyst and a reactive catalyst, e.g.,
N,N-bis(3-dimethylaminopropyl)formamide and dimethylaminopropylurea,
have been proposed for foams for interior components of automo-

106 Reactive Polymers Fundamentals and Applications
biles. 79 Such low-volatility catalysts do not emit vapors over time or under
the effects of heat which would otherwise cause nuisance fogging of windshields,
and also reduce the chemical content of the air inside vehicles to
which a driver and passengers are otherwise exposed.
2.2.7.5 Anionic Catalysts
Anionic catalysts favor the isocyanurate formation. Isocyanurate units are
built by trimerizing an isocyanate. The isocyanurate group improves properties
such as thermal resistance, flame retardancy, and chemical resistance.
In quaternary ammonium carboxylates, alkali metal carboxylates
and substituted phenols such as 2,4,6-tris(dimethylaminomethyl)phenol,
the active species is the anion. This is different from amine salt catalysts
where the active species is the free amine.
Examples for quaternary ammonium carboxylates are benzylammonium
carboxylate, 80 tetramethylammonium pivalate, and methyldioctyldecylammonium
pivalate (C 8 H 17 ) 2 (C 10 H 21 )(CH 3 )N +− O 2 CC(CH 3 ). 81
Tetraalkylammonium fluorides and cesium fluoride are extremely
selective catalysts for the formation of isocyanurate. 82
The trimerization of diisocyanates produces not only the trimer, i.e.,
monoisocyanurate, but also higher oligomers. The viscosity of the demonomerized
polyisocyanate increases as the oligomer content increases.
The deactivation of the catalyst is necessary in order to terminate the
trimerization and to ensure the storage stability of the polyisocyanate. The
degree of trimerization can be controlled by the addition of a catalyst inhibitor.
After adding the catalyst inhibitor, the trimerization stops. 83 Suitable
catalyst inhibitors are compounds which enter into chemical reactions
with quaternary ammonium fluorides. Examples include calcium chloride
or alkyl chlorosilanes such as ethyl chlorosilane, or substances which adsorptively
bind quaternary ammonium fluorides, such as silica gel. Further
organic acids or acid chlorides deactivate the catalysts.
Potassium octoate and tertiary phosphines are other catalysts useful
for the dimerization and trimerization of isocyanates. Carboxylic acids
favor the formation of urea bond compounds. 84, 85 Potassium acetate is a
general purpose catalyst.
2.2.7.6 Organometallic Catalysts
Commonly used organometallic catalysts are shown in Table 2.7.
It is

Compound
Table 2.7: Organometallic Catalysts
Dibutyltin dilaurate (DBTDL)
Stannous octoate
Dibutyltin diacetate
Dibutyltin dimercaptide
Lead naphthenate
Lead octoate
Dibutyltin bis(4-hydroxyphenylacetate)
Dibutyltin bis(2,3-dihydroxypropylmercaptide)
Ferric acetylacetonate
Remarks
Polyurethanes 107
Standard Compound
Polyether-based slabstock foams
Hydrolytically stable
Elastomers
believed that the catalytic action occurs by a ternary complex of the isocyanate,
hydroxyl, and the organometallic compound. A Lewis acid-isocyanate
complex is formed followed by complexation with the alcohol. 71
For gelling reactions, organometallic catalysts are more selective
than tertiary amines. Some organotin compounds lose their activity in the
presence of water or at high temperatures. As in the case of amine catalysts,
the activity decreases in sterically hindered compounds. Also, solvent
effects are observed. The solvent effect is relevant for solvent-based
coating formulations. Dialkyltin dimercaptides, such as dibutyltin dilauryl
mercaptide, exhibit good storage times when admixed with other catalyst
components. 86
Dibutyltin dilaurate catalyzes the formation of urethane suppressing
the formation of allophanates and isocyanurates. 87 With high resiliency
foams (HR), where more reactive polyols are generally employed, very
few tin catalysts can be used because the foam cell walls are less prone
to rupture than with conventional foams, and this can result in shrinkage
problems. 56 Bis(2-acyloxyalkyl)diorganotins exhibit only a small activity
at room temperature. However they decompose at elevated temperatures
into diorganotin dicarboxylates, which are the active species and olefins.
For this reason they are also referred to as latent catalysts. This effect can
be used to tailor catalysts. One advantage of the latent catalysts of the formula
like Figure 2.24 is, therefore, to be able to mix the starting materials
with the latent catalyst without catalysis of the reaction taking place and
to initiate the catalysis of the reaction by heating the mixture to the decomposition
temperature of the latent catalyst. 2-Acetoxyethyl-dibutyltin

108 Reactive Polymers Fundamentals and Applications
Bu
Bu
Sn
Cl
CH 3
C O
O
H
CH
CH 2
hν
∆
Bu
Bu
Sn
Cl
CH 3
C O
O
CH 2 CH 2
Bu = CH 3
CH 2
CH 2
CH 2
Figure 2.24: Synthesis of 2-Acetoxyethyl-dibutyltin chloride from Chlorodibutyltin
hydride and Vinyl acetate
chloride is prepared from chlorodibutyltin hydride and vinyl acetate, c.f.
Figure 2.24, and it is decomposed by heat at 90°C within one hour.
88, 89
Another latent tin catalyst consists of the adduct of a tin carboxylate
or other tin compound with a sulfonylisocyanate, such as dibutyltin dilaurate
or dibutyltin methoxide and tosyl isocyanate. 90 Tin alkoxides or tin
hydroxides have a far higher catalytic activity than the tin carboxylates.
These additional compounds are extremely sensitive to hydrolysis, alcoholysis
and are decomposed by the presence of water.
Moisture can be supplied by the substrate, the atmosphere or by
compounds containing reactive groups toward isocyanate, in particular hydroxyl
groups, with release of the catalysts. Before hydrolytic or alcoholytic
decomposition of the addition compounds takes place, these compounds
are completely inert towards isocyanate groups. They give rise to
no side reactions which would impair the storage stability of organic polyisocyanates.
Combinations of organotin catalysts and hydrogen chloride
extend the pot-life time in coating compositions without changing the cure
time. 91 Bismuth neodecanoate and combinations of bismuth and zirconium
carboxylic acid salts also exhibit longer pot-life times combined with
rapid curing. 92 However, catalysts based on bismuth are water sensitive
and deactivate in the presence of moisture.
Polymeric metal catalysts are less prone to migrate. They can be
synthesized by reacting a diorganotin dichloride or dibutyltin oxide with
a hydroxymercaptan, such as 3-mercapto-1,2-propanediol with water removal.
A viscous polymeric material is obtained. 93
Dibutyltin bis(4-hydroxyphenylacetate) and dibutyltin bis(2,3-dihydroxypropylmercaptide)
are hydrolytically particularly stable. The hy-

Polyurethanes 109
droxy functionality allows an incorporation in the polyurethane chain. 94
A low odor and migration resistant organotin catalyst consists of
the reaction products of dibutyltin oxide and aromatic aminocarboxylic
acids, e.g., 3,5-diaminobenzoic acid to result in tin-di-n-butyl-di-3,5-amino
benzoate. 95
2.3 SPECIAL ADDITIVES
Chemical formulations of polyurethane foams are based on the following
ingredients:
1. Polyol,
2. Isocyanate,
3. Catalysts,
4. Water,
5. Blowing agent,
6. Surfactant,
7. Pigment,
8. Additives.
2.3.1 Fillers
2.3.1.1 Rectorite Nanocomposites
Rectorite (REC) is a clay mineral with a 1:1 regular interstratification of
a dioctahedral mica and a dioctahedral smectite. Rectorite has been used
to yield intercalated or exfoliated thermoplastic polyurethane rubber nanocomposites
by melt processing intercalation.
X-ray diffraction and transmission electron microscopy clarified that
the composites with lower amounts of clay are intercalation or part exfoliation
nanocomposites. The mechanical properties of the composites are
substantially enhanced. 96
2.3.1.2 Zeolite
Zeolite has been used for modifying the structure of polyurethane membranes
and to improve their properties. Membranes with zeolite content
between 10 and 70%, have been prepared. The preparation method induces
an anisotropy in the membranes. The membranes have therefore an

110 Reactive Polymers Fundamentals and Applications
asymmetric structure consisting of the top skin, i.e., the active layer, the
substructure, and the bottom skin. 97
2.3.1.3 Iron Particles
The sound absorption characteristic within a certain frequency bandwidth
of a flexible polyurethane foam can be changed, when 2 to 5 µm carbonyl
iron particles are incorporated, when constant intensity magnetic fields are
applied. 98
2.3.2 Reinforcing Materials
2.3.2.1 Nanosilica Particles
Polyurethane ionomers in an aqueous emulsion were reinforced with hydrophobic
nanosilica to give composites. The aqueous emulsion was stable
and the particle size increased as the content of hydrophobic nanosilica was
increased. The reinforcing effects of nanosilica on the mechanical properties
were examined in various tests. The composites showed an enhanced
thermal and water resistance. 99
Nanosized SiO 2 particles can be prepared via the sol-gel process.
In a sol-gel process, the inorganic mineral is formed and deposited in-situ
in the organic polymer matrix, for example, aqueous emulsions of cationic
polyurethane ionomers, mixed with tetraethoxysilane, hydrolyze by the action
of acid. In this way, silica nanocomposites, based on poly(ε-caprolactone
glycol) as soft segment, and isophorone diisocyanate as hard segment,
and 3-dimethylamino-1,2-propanediol as chain extender were prepared. 100
Mechanical properties are improved by the incorporation of the particles.
The particles do not essentially affect the low temperature-resistant
properties, but improve the heat-resistance of the resin. 101 The dispersion
of the particles can be enhanced by a surface modification with (3-aminopropyl)triethoxysilane.
102
Polyurethane/filler composites also can be prepared by mixing the
polyol with a solution of the silica in methylethylketone, then stripping
the methylethylketone. This solution is then reacted with a diisocyanate,
and then chain-extended with 1,4-butanediol. Atomic force microscopy
revealed that the filler particles were evenly distributed in the hard and soft
phases. 103

Table 2.8: Flame Retardants for Polyurethanes
Compound
Expandable graphite
105
Triethyl phosphate
106
Ammonium polyphosphate
107
Melamine cyanurate
107
Poly(epichlorohydrin) (PECH)
108
3-Chloro-1,2-propanediol, reactive
109
Polyurethanes 111
Reference
2.3.2.2 Layered Silicate Nanocomposites
High performance nanocomposites that consist of a polyurethane elastomer
(PUE) and an organically modified layered silicate have been described. 104
The polyurethane is based on poly(propylene glycol), 4,4 ′ -methylene bis-
(cyclohexyl isocyanate) and 1,4-butanediol. The tensile strength and strain
at break for these PUE nanocomposites increases more than 150%. An
isocyanate index of 1.10 results in the best improvement in stress and elongation
at break.
Polyurethane/organophilic montmorillonite (PU/OMT) nanocomposites
have an enhanced tensile strength and improved thermal properties, in
comparison to unmodified polyurethane. 110 An amphiphilic urethane precursor
with hydrophilic poly(ethylene oxide) (PEO) was used to prepare
nanocomposites containing Na + -montmorillonite. 111
2.3.2.3 Nanoclays
Waterborne polyurethane/poly(methyl methacrylate) hybrid materials were
reinforced with exfoliated organoclay. The size of the particles in the emulsion
increased when the contents of PMMA or organoclay was increased.
X-ray measurements showed an effective exfoliation of the silicate layer in
the polymer matrix. 112
2.3.3 Flame Retardants
Flame retardants, recently described, are summarized in Table 2.8.

112 Reactive Polymers Fundamentals and Applications
2.3.3.1 Poly(epichlorohydrin)
Poly(epichlorohydrin) (PECH) was phosphorylated by the reaction the P-H
bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)
with the pendent chloromethyl groups of PECH. A phosphorus-containing
PECH with hydroxyl terminal groups is thus obtained. 108 From this compound
a phosphorous-containing polyurethane is obtained by the reaction
with 2,4-toluene diisocyanate. The polymers are useful as multifunctional
modifiers for epoxy resins and for improving the toughness and flame retardancy.
2.3.3.2 Expandable Graphite
The protective shield in a polyurethane expandable graphite (EG) system
consists of expanded worms of graphite embedded in the tarry degraded
matrix of polyurethane. 105
The expansion of EG is due to a redox process between H 2 SO 4 ,
intercalated between graphite layers, and the graphite itself that originates
the blowing gases according to the reaction:
C+2H 2 SO 4 → CO 2 + 2H 2 O+2SO 2 (2.3)
Expandable graphite can be used in poly(isocyanurate) polyurethane
foams in order to improve fire behavior of such foams. In order to
obtain a completely halogen-free material, water blown foams must be
prepared thus avoiding the use of hydrochlorofluorocarbons or hydrofluorocarbons.
The limiting oxygen index of the material without expandable
graphite is at 24% and reaches 30.5% in presence of 25% of expandable
graphite. 113 Triethyl phosphate shows a synergistic effect with expandable
graphite. 106 Further expandable graphite or triethyl phosphate do not
worsen the mechanical properties. Ammonium polyphosphate, melamine
cyanurate, and expandable graphite were tested in a comparative study.
Expandable graphite showed the best results. 107
2.3.3.3 Charring Agents
In the case of ammonium polyphosphate, the blowing effect is less important
105 than in expandable graphite. Ammonium polyphosphate, melamine
cyanurate and expandable graphite are compounds that form char layers
that provide a thermal isolation.

Polyurethanes 113
Table 2.9: Global Production/Consumption Data of Important Monomers
and Polymers 115
Monomer Mill. Metric tons Year Reference
Phosgene 5 2002
116
Toluene diisocyanate 1.3 2000
117
p,p ′ -Methylene diphenyl diisocyanate (MDI) 2.4 2000
117
Ethyleneamines 0.248 2002
118
Phthalic anhydride 3.2 2000
119
Maleic anhydride 1.3 2001
120
1,4-Butanediol 1 2003
121
Polyurethane foams (flexible and semi-rigid) 2.3 2001
122
Polyurethane foams (rigid) 1.6 2001
122
Polyurethane elastomers 0.581 2001
123
Urethane surface coatings 1.5 1999
124
However, the action takes place in different ways. Ammonium polyphosphate
leads to the formation of a char layer through a series of processes
consisting of initial peroxide formation, decomposition to alcohols
and aldehydes, formation of alkyl-phosphate esters, dehydration and subsequent
char formation. 114 Thermogravimetric studies showed that the addition
of ammonium polyphosphate accelerates the decomposition of the
matrix but leads to an increase in the amount of high-temperature residue,
under an oxidative or inert atmosphere.
This stabilized residue acts as a protective thermal barrier during
the intumescence fire retardancy process. The resulting char consists of
an aromatic carbonaceous structure which condenses and oxidizes at high
temperature. In the presence of ammonium polyphosphate, a reaction between
the additive and the polymer occurs, which leads to the formation of
a phosphocarbonaceous polyaromatic structure. 125
Melamine cyanurate acts in an endothermic decomposition and gives
off ammonia. Still nitrogen-containing polymers form then a char layer. 107
2.3.4 Production Data
Global Production Data of the most important monomers used for unsaturated
polyurethane resins are shown in Table 2.9.

114 Reactive Polymers Fundamentals and Applications
2.4 CURING
The isocyanurate formation and isocyanate degree of conversion can be
measured simultaneously by means of FT-IR spectroscopy. 126
The curing behavior of polyurethanes based on modified methylene
diphenyl diisocyanate and poly(propylene oxide) polyols has been studied
using isothermal Fourier-transform infrared (FTIR) spectroscopy , differential
scanning calorimetry (DSC) and adiabatic exothermic experiments.
Increasing the concentration of the catalyst, i.e., dibutyltin dilaurate
(DBTDL) or decreasing the molecular weight of the polyol raises the
rate of reaction and shifts the DSC exothermic peak temperature to lower
temperatures.
However, the heat of reaction remains constant. A marked increase
in reaction rate is observed when an ethylene oxide end-capped polyol
is used instead of a standard propylene oxide end-capped polyol. The
conversion of isocyanate for several concentrations of dibutyltin dilaurate
(DBTDL) fits a second-order kinetics. The activation energy of curing is
independent of the molecular weight of the hydroxy compound. 127 However,
the activation energy depends on the extent of conversion. 47
With isocyanate reactive hot-melt adhesives an autocatalytic effect
was observed. The autocatalysis is not dependent on the structure of diols
but on the isocyanates. 128
2.4.1 Recycling
2.4.1.1 Solvolysis
In recycling, catalysts can effect a reduction of the time required to recycle
polyurethanes via hydrolysis and glycolysis. The products of polyurethane
recycling are a complex mixture of alcohols and amines. Useful catalysts
for recycling include titanium tetrabutoxide, potassium acetate, sodium hydroxide
or lithium hydroxide. uncatalyzed polyurethane recycling is also
possible.
The recovery and purification of the polyol-containing liquid products
can be achieved by the distillation of the glycolysis products. The
amount of recoverable products by distillation reaches a maximum of 45%,
when a process temperature of 245 to 260°C is applied. 129

Polyurethanes 115
2.4.1.2 Ultrasonic Reactor
High resiliency polyurethane foam has been recycled by the application of
high-power ultrasound in a continuous ultrasonic reactor. The foam has
been decrosslinked at various screw speeds and various ultrasound amplitudes,
then blended at different ratios with the virgin polyurethane rubber
and then cured. In comparison to the ground recycled samples, the blends
of the decrosslinked samples are easier to mix and exhibit enhanced properties.
130
2.4.1.3 Polyacetal-modified Polyurethanes
Polyacetals are thermally stable but undergo a degradation by treatment
with aqueous acid even at room temperature. Therefore, polyacetals are
candidates for degradable polymers for chemical recycling. Polyurethane
elastomers with degradable polyacetal soft segments have been synthesized.
131 The polyurethanes were synthesized from polyacetal glycol and
4,4-diphenylmethane diisocyanate. 1,4-Butanediol was used as a chain
extender. For comparison, samples containing a polyether glycol instead
of the polyacetal glycol were prepared. Acid treatment indicated that the
degradation took place.
2.4.1.4 Production Wastes
Waste residue from the production of toluene diisocyanate was used as a
modifier in making improved waterproofing bitumen. The degree of improvement
of the softening point could be correlated with the blend morphology.
132
2.5 PROPERTIES
2.5.1 Mechanical Properties
Copolymers of propylene oxide and ethylene oxide are used for softer
foams in comparison with polyols obtained exclusively from propylene
oxide.
In comparison with polyether polyurethanes, polyester polyurethanes
are more resistant to oil, grease, solvents, and oxidation. They exhibit
better mechanical properties. On the other hand, polyester polyurethanes
are less chemically stable and are also sensitive to microbiological attack.

116 Reactive Polymers Fundamentals and Applications
2.5.2 Thermal Properties
Additives, in particular nanocomposites, have a positive effect on the thermal
properties. On heating up to degradation, the urethane structure undergoes
a retro reaction into isocyanates. Therefore, highly poisonous products
can be formed. The isocyanates yield depends greatly on the specific
combustion conditions selected, such as temperature, ventilation, and fuel
load.
The mechanism of thermal degradation has been sketched. 133 Polyurethane
undergoes a depolycondensation. Volatile diisocyanate and isocyanate-terminated
fragments are formed. 134
In laboratory combustion experiments, isocyanates could be detected
in the gaseous effluent. They were analyzed using impinger flasks containing
1-(2-methoxyphenyl)piperazine (MOPIP) as derivatizing reagent. The
derivatives were analyzed by high performance liquid chromatography and
tandem mass spectrometry. Isocyanic acid, aliphatic isocyanates, alkenyl
isocyanates, and other derivatives were found. 135
Heavy metals influence the thermal degradation. Manganese, cobalt,
and iron ions favor the polyurethane degradation. Chromium and copper
ions reduce the initial thermal stability of the polyurethane and have a
catalytic effect on the second stage of its decomposition, but enhance the
thermal stability of its intermediate decomposition products. By the modification
of polyurethanes with these transition metal ions, changes in the
decomposition mechanism of the polyurethane are induced. 136
2.5.3 Weathering Resistance
In aliphatic polyurethane-acrylate (PUA) resins, usually used for coatings,
the urethane linkage is the most sensitive bond type with respect to photodegradation.
The materials exhibit good weathering properties. 137
2.6 APPLICATIONS AND USES
2.6.1 Casting
Cold casting and hot casting systems are available. A polyurethane/poly-
(styrene-co-divinylbenzene) system can be cured at room temperature, in
a one-step process. 138

Table 2.10: Interpenetrating Polymer Networks
Polyurethanes 117
Polyurethane Further Component Reference
Castor oil-based
polyurethane
Poly(acrylonitrile),
unsaturated polyester resin
Polyurethane– Poly(acrylonitrile)
140
poly(ethylene oxide)
Polyurethane Vinylester resin
141
Polyurethane Poly(styrene)
142
Polyurethane ionomer Poly(vinyl chloride)
143
Polyurethane Poly(acrylate) latex
144, 145
Polyurethane Poly(methacrylate)
146–148
Polyurethane Poly(butyl methacrylate)
149
Polyurethane Poly(acrylamide)
150
Polyurethane Nitrokonjac glucomannan
151
Polyurethane Epoxy resin
152, 153
Polyurethane Poly(vinylpyrrolidone)
154
Polyurethane Poly(benzoxazine)
155
Polyurethane Poly(allyl diglycol carbonate)
156
139
2.7 SPECIAL FORMULATIONS
2.7.1 Interpenetrating Networks
Several types of interpenetrating networks with polyurethanes have been
prepared and characterized. These types are summarized in Table 2.10.
In a tricomponent interpenetrating polymer network composed of
castor oil, toluene diisocyanate, acrylonitrile, ethylene glycol diacrylate,
and an unsaturated polyester resin, it was found that the tensile strength of
the unsaturated polyester (UP) matrix was decreased and flexural and impact
strengths were increased upon incorporating polyurethane/polyacrylonitrile
(PU/PAN) networks. 139
Poly(methyl methacrylate-co-2-methacryloyloxyethyl isocyanate) can
be crosslinked with various diols that result in polyurethane structures. The
crosslinking kinetics of diols, such as ethylene glycol (EG), 1,6-hexanediol,
and 1,10-decanediol (DD) has been investigated, and second-order
kinetics was observed. The rate constants decreased from EG to DD. 146
The addition of nanosized silicon dioxide can improve compatibility,
damping and phase structure of interpenetrating networks. 152

118 Reactive Polymers Fundamentals and Applications
CH 2 OH
CH 2 OH
O
O
OH
O
OH
O
NH 2
n
H 3 C CH 2 N C O
CH 3
H 3 C
NH
C O
NH
CH 2
CH 3
n
O
C
N
CH 3
O
C
N
CH 3
Figure 2.25: Reaction of Chitosan with Isophorone
2.7.2 Grafting with Isocyanates
2.7.2.1 Chitosan
Chitosan is a linear polysaccharide obtained from the N-deacetylation of
chitin. The amino group in chitosan can be reacted with an isocyanate,
as shown in Figure 2.25, exemplified with isophorone diisocyanate. If in
addition a polyol is present, then the second isocyanate group in isophorone
can react with the polyol and longer pendent polyurethane chains can be
formed. 157
2.7.3 Medical Applications
2.7.3.1 Siloxane-based Polyurethanes
Polyurethane elastomers are used for medical implants. Deficiencies of
conventional polyurethanes include deterioration of mechanical properties
and degradation by hydrolysis reactions. Polyurethanes with improved
long-term biostability are based on polyethers, hydrocarbons, poly(carbonate)s,
and siloxane macrodiols. These components are intended to replace
the conventional polyesters and polyethers. Siloxane-based polyurethanes
show excellent biostability. 158

Polyurethanes 119
2.7.3.2 Blood Compatibility
Polyurethanes are widely used as blood-contacting biomaterials because
they exhibit good biocompatibility and further due to their mechanical
properties. However, the blood compatibility is not adequate for certain
applications. Modification of the surface is an effective way to improve
the blood compatibility.
Sulfonic and carboxyl groups can effectively improve the blood compatibility
of polyurethane. Films of polyurethane containing acrylic acid
were exposed to a sulfur dioxide plasma to graft sulfonic acid group on its
surfaces. During the preparation of the films by dissolution, acrylic acid
polymerizes to some extent. 159
Carboxybetaine has been grafted onto polyurethane. A three-step
procedure was used. First, the film surfaces were treated with hexamethylene
diisocyanate in presence of DBTDL. Then, N,N-dimethylethylethanolamine
(DMEA) or 4-dimethylamino-1-butanol (DMBA), respectively,
was allowed to react in toluene with the pendent isocyanate groups. Finally,
carboxybetaines were formed in the surface by ring opening involving
the tertiary amine of DMEA or DMBA and β-propiolactone (PL). 160
Similarly, sulfobetaines can be formed on the surface by the reaction of
1,3-propanesulfone (PS) instead of PL.
161, 162
A polyurethane containing a phosphorylcholine structure has improved
blood compatibility. The phosphorylcholine moiety consists of
(6-hydroxy)hexyl-2-(trimethylaminonio)ethyl phosphate (HTEP). A segmented
polyurethane (SPU) containing the phosphorylcholine structure
was synthesized from diphenylmethane diisocyanate, soft segment polytetramethylene
glycol (PTMG), and HTEP, with 1,4-butanediol (BD) as a
chain extender. 163 The phosphorylcholine structure on the surface of the
SPU was proven by attenuated total reflectance Fourier transform infrared
spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and
water contact angle measurements.
2.7.3.3 Degradable Polyurethanes
Longitudinal lesions in the meniscus are frequent orthopedic problems of
the knee. The repair by simple techniques is limited to the vascular part
of the meniscus. For the repair of the avascular part of the meniscus, a
scaffold consisting of polyurethane foam has been developed. The scaffold
is intended to assist the body in the formation of new meniscus cell tissue.

120 Reactive Polymers Fundamentals and Applications
A segmented polyurethane with poly(ε-caprolactone) as the soft segment
and 1,4-butanediisocyanate and 1,4-butanediol as uniform hard segments
was chosen. 164 The material has a micro phase separated morphology
and excellent mechanical properties. Foams were prepared for a porous
scaffold. The scaffold was tested by implantation in the knees of beagles.
It was found that meniscus-like tissue had been formed in the scaffold.
Another biodegradable, sponge-like polyurethane scaffold consists
of lysine-diisocyanate (LDI) and glycerol. Ascorbic acid (AA) was copolymerized
with LDI-glycerol. 20
The cytocompatibility of polyurethane porous scaffolds is improved
by photo grafting of methacrylic acid or poly(2-hydroxyethyl acrylate)
onto the surface.
165, 166
Polyurethanes can be degraded by esterase. This may contribute
to the failure of medical implants. A strong dependence on the enzyme
concentration for polyurethanes with different hard segment chemistry was
established. 167
2.7.3.4 Prevention of Polyurethane Heart Valve Cusp Calcification
The calcification of polyurethane prosthetic heart valve leaflets is highly
undesirable. Polyurethane valves modified with covalently linked bisphosphonate
groups are resistant to calcification, but the highly polar bisphosphonate
groups on the polyurethane surface attract sodium counter ion,
therefore, water absorption is increased. However, attaching diethylamino
groups to the bisphosphonate-modified polyurethane will reduce water
absorption. 168
2.7.4 Waterborne Polyurethanes
Waterborne polyurethanes are used mainly for coatings, but also for composites
and nanocomposites. They are covered briefly, with special attention
to their chemistry. Water dispersable paints can be produced from
polyester polyol, isophorone diisocyanate and hydrophilic monomers such
as dimethylol propionic acid (DMPA) and tartaric acid (TA). 169 Phosphorus-containing
flame retardant water-dispersed polyurethane coatings
were also synthesized by incorporating a phosphorus compound into the
polyurethane main chain. 170

Polyurethanes 121
Table 2.11: Composites Made From Waterborne Polyurethane Materials
Second Compound
Reference
Starch
174
Carboxymethyl konjac glucomannan (CMKGM)
175
Casein
176
Carboxymethyl chitin
177, 178
Soy flour
179
Bis(4-aminophenyl)phenylphosphine oxide (BAPPO) was obtained
from bis(4-nitrophenyl)phenylphosphine oxide by the reduction of the nitro
groups. 171
The stability of waterborne dispersions can be improved by using a
continuous process of preparation. 172 Acetone addition has a large effect
on the particle diameter. 173
Waterborne anionomeric polyurethane-ureas can be made from dimethylol
terminated perfluoropolyethers, isophorone diisocyanate, dimethylol
propionic acid, and ethylene diamine. The materials are obtained as
stable aqueous dispersions.
Surface properties and chemical resistance were estimated by the
measurement of contact angles and spot tests with different solvents. The
surface hydrophobicity was not affected by the composition. Water-sorption
behavior is however sensitive to the content of carboxyl groups in the
polymer. 180
Another type of waterborne polyurethane-urea anionomers consists
of isophorone diisocyanate, poly(tetramethylene ether) glycol, dimethylol
butanoic acid (DMBA), and hydrazine monohydrate (HD). Ethylene diamine
(EDA), 1,4-butane diamine (BDA) are chain extenders. The pendent
carboxylic groups are neutralized by ammonia/copper hydroxyde or
triethylamine (TEA). 181
Table 2.11 summarizes composites made from waterborne polyurethane
materials. Composite materials were prepared by blending carboxymethyl
konjac glucomannan (CMKGM) and a waterborne polyurethane
(WPU). A blend sheet with 80% CMKGM exhibited good miscibility and
higher tensile strength (89.1 MPa) than that of both of the individual materials,
i.e. waterborne polyurethane sheets (3.2 MPa) and CMKGM (56.4
MPa) sheets. With an increase of CMKGM content, the tensile strength,
Young’s modulus, and thermal stability increased significantly, attributed

122 Reactive Polymers Fundamentals and Applications
to intermolecular hydrogen-bonding between CMKGM and WPU. 175
Waterborne polyurethane and casein have been prepared by blending
at 90°C for 30 min, and then crosslinking with ethanedial. Water resistance
of the materials proved to be quite good. 176
2.7.5 Ceramic Foams
Organic polymers can be used in the manufacture of ceramic components.
The organic polymers are admixed with the inorganic ceramic components,
either to ceramic powder or to an inorganic monomer, as processing aids.
Such a mixture can be processed in injection molding machines or by other
techniques. The organic polymer supports the process of shaping a green
part. Subsequently it is volatilized by pyrolysis or oxidation during heating.
Ceramic foams can be produced with polyurethane and ceramic powder
mixtures. 182
2.7.6 Adhesion Modification
In order to increase the compatibility between polyamide 6 and thermoplastic
polyurethane, the polyurethane was reactively modified. 183
2.7.7 Electrolytes
Polymer electrolytes are used as solid electrolyte materials in rechargeable
lithium batteries and electrochromic devices.
Solid polymer electrolytes (SPE) have been introduced since the discovery
of poly(ethylene oxide)electrolytes. 184–186
In polyethers, the dissociation of alkali-metal salts occurs by the formation
of transient crosslinks between the ether oxygen groups in the host
polymer and alkali-metal cations. The anion is usually not solvated. The
main deficiency of polyether-type electrolytes is the high degree of crystallization
of the polyether.
Thermoplastic polyether polyurethanes (TPU), doped with various
alkali metal salts, have also been studied as polymer electrolytes. TPU
exhibits good mechanical properties, a tough crystallinity of the polyether
segments is reduced.
Polyurethanes can be modified with chelate groups in order to enhance
the electrical properties. ((3-(4-(1-(4-(3-(Bis-carboxymethylamino)
2-hydroxy-propoxy) phenyl)-1-methyl-ethyl) phenoxy) 2-hydroxypropyl)

Polyurethanes 123
HO
CH 3
CH 2 O
C
O CH 2
CH
CH 3
CH
OH
CH 2 CH 2
N
N
H 2 C CH 2
H 2 C CH 2
O C C O
O C C O
HO
OH
Figure 2.26: ((3-(4-(1-(4-(3-(Bis-carboxymethylamino) 2-hydroxy-propoxy)
phenyl)-1-methyl-ethyl) phenoxy) 2-hydroxypropyl) carboxy methylamino) acetic
acid
HO
OH
carboxy methylamino) acetic acid (EPIDA), c.f. Figure 2.26, is such a
chelate. The molecule bears hydroxyl functions, which are basically reactive
with isocyanate groups. Therefore, it can be built into a polyurethane
chain. 187 These electrolytes, due to the chelating groups, exhibit a significant
interaction of the Li + ions. A change in polymer morphology is
also observed. An increase in the glass transition temperature of the soft
segment occurs.
Porous polymers, based on polyurethane/polyacrylate, can be prepared
by emulsion polymerization. During the production, no organic solvent
is used. The synthesis proceeds in four steps, listed here. 188
1. A prepolymer is prepared from 2,4-toluene diisocyanate and poly-
(propylene glycol). 2,4-toluene diisocyanate is in a two-fold excess.
2. 2-Hydroxyethyl methacrylate (HEMA) is added to the prepolymer.
The hydroxyl groups react with the residual isocyanate groups.
3. Again poly(ethylene glycol) is added in order to react with the remaining
isocyanate groups. A macromonomer with pendant double
bonds is obtained.
4. The macromonomer is emulsified and polymerized by the addition
of 2,2 ′ -azobis(isobutyronitrile).
The ionic conductivity is about 10 −3 Scm −1 at room temperature.
This conductivity is useful for many practical electrochemical applications.
A light-emitting electrochemical cell (LEC) is composed of a blend

124 Reactive Polymers Fundamentals and Applications
of semiconducting polymer and polymer electrolyte mixture.
An electrochemical cell was built from poly(p-phenylene vinylene)
(PPV), as light-emitting material and lithium ion conducting waterborne
polyurethane ionomer as solid electrolyte. 189 The polyurethane was prepared
from a poly(ethylene glycol), α,α ′ -dimethylol propionic acid and
isophorone diisocyanate.
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Polyurethanes 137
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176. N. G. Wang, L. Zhang, Y. S. Lu, and Y. M. Du. Properties of crosslinked
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138 Reactive Polymers Fundamentals and Applications
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3
Epoxy Resins
Epoxy resins are formed from an oligomer containing at least two epoxide
groups and a curing agent, usually either an amine compound or a diacid
compound. A great variety of such resins is on the market. There are many
monographs on epoxy resins available. 1, 2
3.1 HISTORY
N. Prileschajew discovered in 1909 that olefins can react with peroxybenzoic
acid to epoxides. 3 Schlack claimed in 1939 a polymeric material based
on amines and multi functional epoxides. 4 Castan ∗ , in the course of searching
for dental materials claimed the preparation of bisphenol A diglycidyl
ether (DGEBA). 5, 6 A similar material, but higher in molecular weight,
was invented by S. O. Greenlee. 7 Epoxy resins came on the market around
1947. The first major intended application was as coating material.
3.2 MONOMERS
3.2.1 Epoxides
Epichlorohydrin is the monomer used for the synthesis of glycidyl ethers
and glycidyl esters. Epichlorohydrin (1-chloro-2,3-epoxypropane) is synthesized
from propene via allyl chloride. A number of epoxides are shown
∗ Pierre Castan, born in Bern 1899, died in Geneva 1985
139

140 Reactive Polymers Fundamentals and Applications
O
O
CH 2 O C
CH 3 H 3 C
O
O
O
O
O
O
O
O
Figure 3.1: Cycloaliphatic Epoxides
in Table 3.1. Reactive diluents, i.e. monofunctional epoxide compounds
are shown in Table 3.2. The curing of cycloaliphatic epoxides proceeds
easily with anhydrides, but is too slow with amines. Synthetic procedures
for including styrenic, cinnamoyl, or maleimide functionalities, into cycloaliphatic
epoxy compounds, have been described. 8
3.2.1.1 Epoxide Equivalent Weight
The equivalent weight of the epoxide used is an important parameter for
the amount of curing agent needed. The common method to determine the
equivalent weight is the titration procedure with HBr in glacial acetic acid.
However, a method for the determination of the epoxide equivalent weight
in liquid epoxy resins using proton nuclear magnetic resonance ( 1 H-NMR)
spectroscopy has been described. 9
3.2.2 Phenols
Bisphenol A is the most important ingredient in standard epoxy resins. It is
prepared by the condensation of acetone with phenol. The latter two compounds
can be prepared in the Hock process by the oxidation of cumene.
Phenolic products are shown among others in Table 3.3 and Figure
3.2. The hydroxyl and amino functions are epoxidized with epichlorohydrin.

Epoxide
Epichlorohydrin
Butadiene diepoxide
1,4-butanediol diglycidyl ether
(1,4-BDE)
Glycerol diglycidyl ether
1,3-Didodecyloxy-2-glycidylglycerol
Table 3.1: Epoxides
Remark/Reference
Epoxy Resins 141
Used for the formation of glycidyl
ethers and esters
10
Amphiphilic polymers, for potential
use as emulsifiers and solubilizing
agents 11
Poly(butadiene) epoxides
Flexible
Vinylcyclohexene epoxide
Both with vinyl and epoxy function
Styrene oxide ( = ethenylphenyloxirane)
Both with vinyl and epoxy function 12
Glycidyl methacrylate (GMA) Both with vinyl and epoxy function
Epoxidized linseed oil
13
Epoxy methyl soyate
14
Epoxy allyl soyate
14
Vernonia oil
Naturally epoxidized,
E-12,13-epoxyoctadeca-E-9-enoic
acid esters 15–17
Triglycidyl isocyanurate
Triglycidyloxy phenyl silane Flame retardant 18
2-(6-Oxid-6H-dibenz[c,e][1,2]oxaphoshorin-6-yl)-1,4-benzenediol
Flame retardant 19
3,4-Epoxycyclohexyl-methyl- Coatings
3,4-epoxycyclohexane carboxylate
2,3,8,9-Di(tetramethylene)-
Dental applications 20
1,5,7,11-tetraoxaspiro[5.5]undecane
Bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate
Dental applications 20
Epoxidized cyclololefins Multifunctional, c.f. Figure 3.1
Fluoro-epoxides
21
Biphenyl-based epoxies Liquid crystalline, c.f. Figure 3.3
Terephthaloylbis(4-oxybenzoic) acid Liquid crystalline 22
DGEBA adduct
Bis[3-(2,3-epoxypropyl thio)phenyl]- Optical applications 23
sulfone
4,4 ′ -Dihydroxychalcone-epoxy Optical applications 24
oligomer

142 Reactive Polymers Fundamentals and Applications
Reactive Diluent
Table 3.2: Reactive Diluents
Phenyl glycidyl ether (PGE)
Styrene oxide
Allyl glycidyl ether
Tetraethyl orthosilicate caprolactone
diol adducts
2-Hydroxy-4(2,3-epoxypropoxy)-
benzophenone
exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalimidocaproic
acid
exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalic
anhydride
Remark/Reference
Cationic curable coatings 25
Reactive photostabilizer for wood 26
Polymers show anticarcinogenic activity
27
Polymers show anticarcinogenic activity28,
29
Table 3.3: Compounds for Glycidyl Functionalization for Epoxide Resins
Compound a
Bisphenol A
Bisphenol F
Phenol novolak
Naphthyl or limonene-modified Bisphenol
A formaldehyde novolak
Cresol novolak
Tetrakis(4-hydroxyphenyl)ethane
p-Aminophenol b
Aminopropoxylate
31
4,4 ′ -Diaminodiphenylmethane b
Hexahydrophthalic acid c
1,3-Bis(3-aminopropyl)tetramethyl-
32
disiloxane
Tetrabromobisphenol A
Bishydantoin
Isocyanurate
Cresol
1,4-Butanediol
Remark/Reference
Standard resins
Improved mechanical properties, reduced
water absorption 30
Increases crosslinking density
Higher reactivity at amine curing
For flame retardant formulations
Powder coatings
Reactive diluent
Reactive diluent
a : Compounds are epoxidized at the hydroxyl function with epichlorohydrin
b : Compounds epoxidized at the amino function with epichlorohydrin
c : Compounds epoxidized at the carboxyl function with epichlorohydrin

Epoxy Resins 143
HO
CH 2
OH
HO NH 2
Bisphenol-F
p-Aminophenol
HO
OH
CH 3
HO
C
OH
CH 3
CH
CH
Bisphenol-A
HO
OH
H 2 N
CH 2 NH 2
Tetrakis(4-hydroxyphenyl)ethane
4,4’-Diaminodiphenylmethane
OH OH OH
CH 2 CH 2 CH 2
Novolac
Figure 3.2: Compounds for Epoxide Resins

144 Reactive Polymers Fundamentals and Applications
3.2.3 Specialities
3.2.3.1 Hyperbranched Polymers
Hyperbranched polymers are highly branched macromolecules that are prepared
through a single-step polymerization process. 33 Many polymers of
this type are also known as dendrimers, because their structure resembles
the branches of a tree. Also, star-like and comb-like polymers belong to the
class of hyperbranched polymers. However, hyperbranched polymers are
built up from dendritic, linear, and terminal units. They can be synthesized
via three routes:
1. Step-growth polycondensation of AB x monomers,
2. Self-condensing vinyl polymerization of AB∗ monomers,
3. Multibranching ring-opening polymerization of latent AB x monomers.
The methods of synthesis available allow a wide variety of different
polymer types. Further special properties can be imparted by suitable end
capping reactions. This type of polymer has unique properties that are
characteristic for dendritic macromolecules, such as low viscosity, good
solubility, and a high functionality.
Dendrimers are used in medical fields, as carriers of organic compounds.
Hyperbranched polymers are easier to synthesize in large quantities
and are used as tougheners, plasticizers, antiplasticizers and curing
agents.
34, 35
Hyperbranched polymers (HBP) with hydroxyl terminal
groups can initiate curing by a proton donor-acceptor complex. In curing
a tetrafunctional epoxy resin, the activation energy is lower than in an
epoxy system with linear polymers. 36 Hyperbranched polymers strongly
enhance the curing rate due to the catalytic effect of hydroxy groups. 37
The gel time increases with increasing functionality from diglycidyl ether
of bisphenol A (DGEBA) to tetraglycidyl-4,4 ′ -diaminodiphenylmethane
(TGDDM). 38 A hydroxyl-functionalized HBP reduced the gel time of the
blends because of the accelerating effect of -OH groups to the epoxy curing
reaction.
Star-like epoxy polymers can be rooted from polyhydroxy fullerene
with a cycloaliphatic epoxy monomer. 39 Around 8 to 10 epoxy units can
be attached to the fullerene core.
The addition of small amounts of hyperbranched polymer to an epoxy
system enhances dramatically its toughness. The critical strain energy

Epoxy Resins 145
release rate DGEBF resin can be increased by a factor of 6 by the addition
of only 5% of hyperbranched polymer. 40 At higher concentrations, a phase
separation is indicated by two glass transition temperatures. 41
In composite materials, resins modified by hyperbranched polymers
allow higher volume fractions of fibers for producing void-free laminates
in comparison to unmodified resins. 42
3.2.3.2 Liquid Crystalline Epoxide Resins
Initially a few technical terms concerning liquid crystals are recalled. There
are textbooks on liquid crystals, e.g., that of Collings and Hird. 43
Liquid Crystal. Liquid crystals were discovered by the Austrian chemist
and botanist Friedrich Reinitzer, who found that cholesterol benzoate did
not melt into a clear liquid, but remained turbid. On further heating the
turbid liquid turned suddenly clear. This transition point is now called
the clearing point. For this reason, in addition to the common states of
aggregation, the liquid crystalline state was established. The term liquid
crystal goes back to the German physicist Otto Lehmann.
Liquid crystals are formed mostly by rod-like molecules. They are
sometimes addressed as mesomorphic phases. Materials that can form such
phases are called mesogens. An ordinary fluid is called isotropic, i.e., its
properties are independent of direction. A liquid crystal is orientated, or
likewise an anisotropic liquid. This means that the molecules are oriented
preferably in a certain direction. Such an anisotropic fluid is a nematic liquid
crystal. A liquid crystal more similar to a solid is a smectic phase. Here
the molecules are arranged in layers, but within the layers the molecules
have no fixed positions.
Polymers. Liquid crystalline polymers exhibit a number of improved
properties in comparison with traditional plastics, in particular increased
elastic moduli at high temperatures, reduced coefficients of thermal expansion,
increased decomposition onset temperatures, and reduced solvent
absorption.
Suitable epoxide monomers are based on biphenyl moieties. 44 Monomers
for liquid crystalline epoxide resins are shown in Figure 3.3. It is
believed that micro-Brownian motion in the polymer chain is increasingly
suppressed as the mesogen concentration increases. This effect causes an

146 Reactive Polymers Fundamentals and Applications
O
CH 2 C
H
O
CH 2 O O CH 2 C CH 2
H
O
CH 2 C
H
H 3 C
CH 3
O
CH 2 O O CH 2 C CH 2
H 3 C
CH 3
H
O
CH 2 C
H
O
(CH 2 )n CH 2
O
CH 2
(CH 2 )n
O
C CH 2
H
Figure 3.3: Monomers for Liquid Crystalline Epoxide Resins
increase in the thermal decomposition onset temperatures, a decrease of
the coefficient of thermal expansion, and a decrease in water absorption.
When the diglycidyl ether of bisphenol A is cured with sulfanilamide,
a crosslinked network with liquid crystalline properties is obtained. 45
Sulfanilamide has two different amine functions of unequal reactivity. This
causes the formation of a smectic phase when it is used as a curing agent.
Polarized optical microscopy indicates that the epoxy monomer does not
show a liquid cristalline (LC) phase. Also a mixture of sulfanilamide and
diglycidyl ether of bisphenol A does not show LC properties. An isotropic
liquid is formed above the melting point. However, when the reaction between
epoxy and amine proceeds, an LC texture is developed, which is
locked in the crosslinked network by the nematic arrangement.
3.2.4 Manufacture
3.2.4.1 Epoxides
Epoxides can be manufactured by the epoxidation reaction, in particular
1. By direct oxidation,
2. Via peroxyacids,
3. In-situ epoxidation,

Epoxy Resins 147
4. By hypochlorite reaction, and
5. By reaction with fluoro complexes.
Direct Oxidation. Olefins can epoxidized by oxidizing them in the vapor
phase in the presence of a silver catalyst. The catalyst is activated by
adding small amounts of dichloroethane to the reaction mixture. The direct
oxidation with oxygen is less important for the synthesis of epoxies used
for epoxy resins, in favor of peroxyacids.
Certain Schiff bases that are attached on polymers allow the direct
oxidation of olefins. A polymer bound Schiff base ligand is prepared from
poly(styrene) bound salicylaldehyde and glutamic acid. With complexes of
these catalysts, cyclohexene, 1-octene, 1-decene, 1-dodecene and 1-tetradecene
can be oxidized by molecular oxygen. 46
Peroxyacids. Also, organic peroxides can serve as an oxygen source.
Unsaturated fatty acids and their esters are epoxidized with peroxyacetic
acid. Originally peroxybenzoic acid was used, which is highly selective.
However, this reagent is comparatively expensive. Several other peroxyacids
have been investigated; they are in general less efficient. The reaction
of olefins with peroxyacids is a single-step reaction.
Hydrogen peroxide itself is a rather poor epoxidation oxidant, however,
it is used to generate the peroxyacids that are much more active. The
peroxyacids are prepared by reacting hydrogen peroxide with the corresponding
acid. The reaction is an equilibrium reaction. Highly concentrated
peroxyacids can be obtained by adding anhydrides, or removing
the water by azeotropic distillation. Another route to prepare peroxyacids
starts from the anhydride and sodium peroxide, in presence of an acid as
catalyst. There should not be even traces of heavy metals present that cause
a loss in activity of the hydrogen peroxide.
For technical synthesis, peroxyacetic acid is used most frequently,
because it has a high equivalent weight, a high efficiency for epoxidation,
and a sufficient stability.
In-Situ Epoxidation. The peroxyacids can be regenerated during the
epoxidation reaction with hydrogen peroxide. In this way all the hazards
in preparation and handling of the peroxyacids as such are avoided. The
reaction is heterogeneous and the peroxyacid has to be regenerated under
conditions that would result in ring opening of the epoxide. Therefore, only

148 Reactive Polymers Fundamentals and Applications
fast epoxidation reactions can be conducted utilizing the in-situ technique.
For this reason, the most reactive peroxyacids are also selected. These are
in particular the 3-nitroperoxybenzoic acid and 4-nitroperoxybenzoic acid.
Less reactive olefins must still be epoxidized with the peroxyacids
formed in a previous step. The ring opening of the epoxide with the acid
formed from the peroxyacid can be minimized, allowing the phases utmost
separation. This means there should be only small agitation. On the other
hand, with certain solvent combinations the epoxide and the acid are mutually
insoluble.
Hypochlorite. Partially fluorinated epoxides can be prepared by the oxidation
of the corresponding olefins by NaOCl or NaOBr with phase transfer
catalysts, e.g., methyltricaprylylammonium chloride. 47 For example,
hexafluoroisobutene reacts with the solution of sodium hypochlorite in water
at 0 to 10°C giving the corresponding epoxide in a yield of 65 to 70%.
Fluoro Complex. By reacting diluted fluorine with aqueous acetonitrile,
a complex HOF × CH 3 CN is formed. This complex is a very efficient
oxygen transfer agent. It was shown to be useful to obtain various types
of epoxides that are otherwise difficult to synthesize. The products can be
obtained in a single-step reaction with high yield. 48
3.2.4.2 Glycidyl Ethers
In the simplest case a glycidyl ether for an epoxy resin is prepared by the
reaction of bisphenol A (and epichlorohydrin), as pointed out in Figure
3.4. In the first step DGEBA is formed, however, the condensation can
proceed further. The reaction proceeds in two steps. First the epoxide ring
is opened and then the ring is formed again, as shown in Figure 3.5.
Hydrogen chloride is evolved during the condensation and captured
with caustic soda. The ring opening occurs such that the primary carbon
atom is attacked and thus a 1,2-chlorohydrin (ΦCH 2 CH(OH)CH 2 Cl) is
formed, as shown in Figure 3.5.
However in a side reaction the secondary carbon atom is also attacked
and thus a 1,3-chlorohydrin (HOCH 2 CH(Φ)CH 2 Cl) is formed. If
the degree of dehydrochloration is not complete, then 1,2-chlorohydrin end
groups also may be present.

Epoxy Resins 149
O
CH 3
CH 2
CH
CH 2 Cl +
HO
C
OH
CH 3
O
CH 3
CH 2
CH
CH 2
O
C
O
O
CH 3
CH 3
CH 2
CH OH
CH 2
n
CH 2
CH
CH 2 O
C
O
CH 3
Figure 3.4: Synthesis of an Epoxide Oligomer
O
OH + CH 2 CH CH 2 Cl
OH
O
CH 2
CH
CH 2
Cl
-HCl
O
O CH 2 CH CH 2
Figure 3.5: Formation of the Glycidyl Ether

150 Reactive Polymers Fundamentals and Applications
Concerning the nomenclature, the situation is confusing. There are
many synonyms for the glycidyl ethers. The Chemical Abstracts name for
diglycidyl ether of bisphenol A (DGEBA) is 2,2 ′ -[(1-Methylethylidene)-
bis(4,1-phenyleneoxymethylene)]bis(oxirane), and there are some 12 other
synonyms of chemical names in use, besides the trade names.
We focus back to the main reaction. The newly formed epoxide
groups from the second step of the reaction may again undergo a reaction
with the phenolic group, and in the case of a bifunctional phenol, such as
bisphenol A, the molecule grows. The degree of oligomerization (n − 1 in
Figure 3.4) can vary from 1 to approximately 25. The oligomer is liquid at
room temperature when n is smaller than one and becomes solid when n is
larger than two.
The degree of polymerization that can be achieved depends on the
ratio of bisphenol A to epichlorohydrin. If epichlorohydrin is in excess,
then the diglycidyl ether will be the main product. Impurities such as water
can substantially decrease the degree of polymerization by side reactions.
Water reacts with epichlorohydrin to form a glycol.
3.2.4.3 Fluorinated Epoxides
The incorporation of fluorine enhances the chemical and the thermal stability,
the weathering resistance. Further the surface tension is lowered and
thus the hydrophobicity is enhanced. Fluorinated epoxy monomers have
been synthesized from fluorinated diols, such as 2,2,3,3,4,4,5,5-octafluoro-hexane-1,6-diol
or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluoro-decane-1,10-diol
by etherification with allyl chloride and subsequent oxidation
of the allyl group. 21 In UV curing, the monomers showed a higher
reactivity than hexanediol diglycidyl ether.
The adduct of 2-chlorobenzotrifluoride and glycerol diglycidyl ether
(DGEBTF) has been co-reacted with DGEBA using 4,4 ′ -diaminodiphenylmethane
as hardener. 49 The introduction of the trifluoromethyl group
into the chain of the epoxy resin results in an improvement of the dielectric
and mechanical properties. Further the glass transition temperature is
lowered. The glass transition temperature of a pure DGEBA resin is 193°C
whereas the glass transition temperature of the DGEBTF resin is 105 °C.
This indicates that the introduction of fluorine enhances the mobility of the
network.

Compound Class
Table 3.4: Toughening Agents for Epoxy Resins
Epoxy Resins 151
Reference
Poly(ethylene) phthalates
50
Poly(ethylene phthalate-co-ethylene terephthalate)
51
Hyperbranched aliphatic polyester
52, 53
Hyperbranched block copolyethers
54
Epoxidized soyabean oil
14, 55, 56
Copolymers of 2-ethylhexyl acrylate and acrylic acid
57
Methacrylic microgels
58
Terpolymers of N-phenylmaleimide, styrene and p-hydroxystyrene
59
Triblock copolymer poly(styrene-b-ethylene-co-buteneb-styrene)
60
Poly(benzimidazole)
61
Poly(phenylene oxide
62
Silicon-modified polyurethane oligomers
63
Poly(dimethylsiloxane) polymers
Epoxy-aminopropyltriethoxysilane
64
Poly(ether ether ketones)
65
Polyetherimides
66–68
Carboxylated polymers
69
Phenolic hydroxy-terminated polysulfones
70, 71
Liquid rubbers
72
Liquid rubbers carboxyl-terminated with poly(2-ethylhexyl
73–75
acrylate)
Poly(vinyl acetate)
76
Rubbery epoxy based particles
77
Glass beads
78, 79
3.3 SPECIAL ADDITIVES
3.3.1 Toughening Agents
Highly crosslinked epoxy resins are brittle. For various applications they
need to be toughened. Toughening agents are summarized in Table 3.4. Extensive
literature on toughening of polymers is available. 80–83 The toughening
mechanisms of elastomer-modified epoxy systems are different from
flexibilized epoxy systems.
• Flexibilized epoxy systems reduce mechanical damage through
lowering modulus or plasticization; this allows stress to be relieved

152 Reactive Polymers Fundamentals and Applications
through distortion of the material. 84
• Elastomer-toughened epoxy systems in general maintain a large
percentage of the modulus and temperature resistance of the unmodified
resin system. Stress is absorbed by cavitation of the
elastomer particles and shear banding in the cavitated zone. Elastomer-toughened
epoxy systems can tolerate a certain degree of
damage by preventing growth of a crack. In this way the damaged
region remains local. 85
When using thermoplastic-modified thermosets, compromises between
toughness and thermal stability associated with the rubber toughening
of thermosets can be avoided. Another advantage of using the reaction
induced phase separation procedure is that by the adequate selection
of cure cycles and initial formulations, a variety of morphologies can be
generated.
However, the fracture toughness is significantly improved with a
nonreactive thermoplastic, only, when bicontinuous or inverted phase structures
are formed. On the other hand, when the phase separation produces
thermoplastic-rich particles that are dispersed in a continuous thermosetrich
matrix, little or no improvement of the fracture properties is obtained.
This is mainly due to the poor adhesion between the phases. 60
Basically, functionalized thermoplastics are capable of forming a
chemical linkage between the phases. This interphase bonding could improve
the adhesion properties. However, the reactivity of the modifier can
also complicate the behavior and the control of the phase separation process.
3.3.1.1 Polyvinylic Compounds
Many polyvinylic compounds increase the flexibility and are used as toughening
agents.
Poly(styrene). Blends of poly(styrene) (PS) with an epoxy monomer
(DGEBA) and a tertiary amine, benzyldimethylamine (BDMA), are initially
miscible at 120°C. However, at very low conversions a phase separation
occurs. Here, at the cloud point, a sharp decrease of the light transmittance
is observed. There is a significant difference between the refractive
indices of poly(styrene) and the DGEBA/BDMA solution. The refractive
index of the epoxy network increases in the course of polymerization. Due

Epoxy Resins 153
to the continuous increase of the refractive index of the epoxy phase during
curing, finally the refractive indices of both phases match, so that the final
materials at complete conversion appear transparent. 86
Copolymers of Styrene and Acrylonitrile. In an epoxy system containing
tetraglycidyl-4,4 ′ -diaminodiphenylmethane (TGDDM) and a 4,4 ′ -diaminodiphenylsulfone
(DDS) hardener, blends with poly(styrene-co-acrylonitrile)
(SAN) up to 40 phr show complete miscibility over the entire
range. 87 The glass transition temperature and the curing characteristics
can be modelled with various theories. 88 In several systems autocatalytic
curing kinetics is observed. 89–93
Copolymers of Phenylmaleimide, Benzyl methacrylate, and Styrene.
The vinylic compounds can be polymerized in-situ during the curing of the
epoxy system. 94 A suitable monomer system consists of three monomers:
phenylmaleimide, benzyl methacrylate, and styrene. An advantage is that
by the admixing of the monomers the viscosity of the uncured resins drops
significantly.
Graft Polymers of Ethylene/vinyl acetate to Methyl methacrylate. A
graft polymer synthesized by grafting ethylene/vinyl acetate (EVA) onto
poly(methyl methacrylate) thus resulting in a poly(ethylene-co-vinyl acetate)graft-poly(methyl
methacrylate) exhibits a special performance. The
EVA moieties are initially immiscible in the uncured epoxide formulation.
The PMMA moieties are initially miscible, however they separate during
curing. Therefore, EVA-g-PMMA as modifier yields stable dispersions of
EVA blocks, favored by the initial solubility of PMMA blocks. So the
PMMA acts initially as a compatibilizer for the epoxy moieties. 95
Blends of Poly(methyl methacrylate) and Poly(ethylene oxide). Blends
of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA)
form a single phase in the melt. In solid mixtures of these polymers, phase
separation is often observed. In blends of an epoxy resin with PMMA,
PEO acts as a compatibilizer. The morphology of the resulting polymer
mixture may be changed dramatically by only small amounts of PEO. The
stiffness is controlled by the corresponding matrix of the ternary mixture,
but both strength and fracture toughness are a function of the resulting
morphology. 96

154 Reactive Polymers Fundamentals and Applications
Poly(benzimidazole). The incorporation of poly(benzimidazole) into a
difunctional epoxy resin matrix enhances both the glass transition temperature
of the matrix and its toughness. 61
Multilayer Particles. Multilayer particles of PMMA can be manufactured
formed by emulsion polymerization. They consist of alternate glassy
and rubbery layers. The outer layer bears glycidyl groups to allow a chemical
bonding of the particles onto the cured resin. This type of toughening
particles is more effective than acrylic toughening particles or a liquid
carboxyl-terminated butadiene-acrylonitrile rubber. 97
3.3.1.2 Polycondensates
Aromatic polyesters that are prepared from aromatic dicarboxylic acids
and 1,2-ethanediol are improving the toughness of bisphenol A diglycidyl
ether epoxy resins. In particular, phthalic anhydride, isophthalic acid, terephthalic
acid and 2,6-naphthalene dicarboxylic acid, and mixtures of these
compounds are used. The aromatic polyesters are soluble in the epoxy resin
without solvents and are effective modifiers for toughening the epoxy
resins. 50 The inclusion of 20% poly(ethylene phthalate) increases the fracture
toughness of a cured resin by 130% with no loss of mechanical and
thermal properties. 51
Instead of 1,2-ethanediol, 1,4-cyclohexanedimethanol can be used to
obtain poly(1,4-cyclohexylenedimethylene phthalate). 98 Other flexibility
enhancers are polyamide, polyetherimides, 66, 67 carboxylated polymers, 69
phenolic hydroxy-terminated polysulfones, 70 and fatty diamines.
Polyetherimide. In blends of an epoxy system of diglycidyl ether of bisphenol
A and nadic methyl anhydride, a phase separation occurs by the
addition of polyetherimide in the course of curing. The phase separation is
not observed without polyetherimide. By increasing the amount of polyetherimide
in the blends, the final conversion is decreased. This indicates
that polyetherimide hinders the cure reaction between the epoxy and the
curing agent. 99 Homogeneous structures are formed at low polyetherimide
concentration (5 phr). 100
Poly(ether ether ketone). Poly(ether ether ketone) (PEEK) is a tough,
semi-crystalline high performance thermoplastic polymer with good ther-

Epoxy Resins 155
O
O
C
O
C
O
C
O
PEEK-C
H 3 C
CH 3
C
CH3
O
O O C
PEEK-T
Figure 3.6: Poly(ether ether ketone)s
mal and mechanical properties. Because of its semi-crystalline nature, it is
difficult to blend this material with epoxy resins.
Phenolphthalein poly(ether ether ketone) (PEEK-C) is miscible with
TGDDM. Several methods, including dynamic mechanical analysis, Fourier-transform
infrared spectroscopy, and scanning electron microscopy indicate
that the cured blends are homogeneous. With increasing PEEK-C
content, the tensile properties of the blends decrease slightly. The fracture
toughness factor also decreases. This happens presumably due to the reduced
crosslink density of the epoxy network. Inspection of the fracture
surfaces of fracture toughness test specimens by scanning electron microscopy
shows the brittle nature of the fracture for the pure epoxy resins and
its blends with PEEK-C. 101 A lower curing temperature favored the homogeneous
morphology in amine cured DGEBA+PEEK-C blends. 102
In general, the processing of blends with PEEK should be easier, by
using PEEK with terminal functional groups and bulky pendant groups.
However, poly(ether ether ketone) based on tertiary butyl hydroquinone
(PEEK-T) showed a decreasing rate of reaction with increasing PEEK-T
content. The rate of reaction also decreased with the isothermal curing
temperature. This can be explained by the phase separation. As the curing
reaction proceeds, the thermoplastic component undergoes a phase sepa-

156 Reactive Polymers Fundamentals and Applications
ration. The separated thermoplastic could retard the curing reaction. The
dispersed particle size increases with the lowering of curing temperature
and with an increase in the thermoplastic material added. 65 Poly(ether
ether ketone)s are shown in Figure 3.6.
Chain-extended Ureas. The synthesis of chain-extended ureas runs via
a two-stage process. In the first stage, a prepolymer with isocyanate end
groups is synthesized by the reaction of poly(propylene) glycol and toluene
diisocyanate. In the second step, the prepolymer is end-capped with dimethylamine
or imidazole, to result in an amine-terminated chain-extended
urea (ATU) or an imidazole-terminated chain-extended urea, respectively,
with flexible spacers. 103 This type of toughening agent accelerates the curing
of the epoxide groups significantly because of the amino functions in
the molecule.
3.3.1.3 Liquid rubbers
The addition of elastomers to epoxy adhesives can improve peel strength,
fracture resistance, adhesion to oily surfaces and ductility. Liquid rubbers,
like carboxyl, amine, or epoxy-terminated butadiene/acrylonitrile rubbers,
are used as toughening agents. 72, 104 Liquid rubber modifiers are initially
miscible with the epoxy resin. However, in the course of curing a phase
separation takes place.
Carboxy-terminated butadiene/acrylonitrile copolymers (CTBN) are
particularly suitable because of their miscibility in many epoxy resins. The
carboxyl group can react easily with an epoxy group. If a CTBN is not
prereacted with an epoxy resin, the carboxylic acid groups can react during
curing.
Solid acrylonitrile-butadiene rubbers (NBR), in particular with high
content of acrylonitrile are also suitable tougheners. 105 A high content of
acrylonitrile in the rubber imparts better compatibility between NBR and
the epoxy resin.
3.3.1.4 Silicone Elastomers
CTBN and amine-terminated butadiene-acrylonitrile elastomers (ATBN)
lose the desired mechanical properties in the high temperature region and
in the low temperature region. Silicone rubbers are superior in this aspect.
However, silicone rubbers are completely immiscible with epoxy resins

Epoxy Resins 157
and cannot be used for this reason. The addition of a silicone grafted poly-
(methyl methacrylate) is effective to stabilize the interface of the silicone
rubber and the epoxy resin and helps to disperse the silicone rubber in the
epoxide matrix in this way. The molecular weight of the silicone segment
strongly affects the effectiveness of the compatibilizer. With increasing
particle diameter of the silicone the fracture toughness decreases and drops
eventually below the unmodified resin. 106
For a carboxyl-terminated dimethyl siloxane oligomer used as a rubber
modifier, aramid/silicone block copolymers were used as compatibilizers.
107 The aramid-type blocks have phenolic groups on the aromatic rings.
These groups can react with the epoxy resin to cause the compatibilization.
3.3.1.5 Rubbery Epoxy Compounds
Instead of liquid rubber, rubbery epoxy based particles obtained from an
aliphatic epoxy resin can be blended with another epoxy resin to act as
toughening agents themselves. 77 One of the limitations of epoxy-CTBN
adducts is their high viscosity; however, there are also low-viscosity types
available.
3.3.1.6 Phase Separation
During curing of polymer resin blends, a phase separation occurs. The
phase separation can be characterized by
1. Small angle X-ray scattering,
2. Light transmission,
3. Light scattering,
4. Transmission electron microscopy, and
5. Atomic force microscopy.
The viscosity at the cloud point can have a strong effect on the final
morphology and mechanical properties of the resin. The phase separation
mechanisms are dependent on the initial modifier concentration and on the
ratio of the phase separation rate to the curing rate. The curing temperature
has a strong effect on the extent of phase separation. Annealing allows the
phase separation process to proceed further. 67
The extent of phase separation depends on the cure cycle, as shown
in blends of a standard epoxy resin and poly(methyl methacrylate). The

158 Reactive Polymers Fundamentals and Applications
extent of phase separation can be diminished or suppressed by longer precuring
times at lower temperatures, before the main curing is started. 108
In addition, the phase separation can be controlled by the choice of
the curing agents. In the case of poly(methyl methacrylate) as modifier, in
an epoxy system, based on DGEBA some hardeners effect a phase separation
before gelation and others do not. For example, 4,4 ′ -diaminodiphenylsulfone
(DDS) and 4,4 ′ -methylenedianiline (MDA) result in a phase separation,
but for 4,4 ′ -methylene bis(3-chloro-2,6-diethylaniline) (MCDEA)
no phase separation is observed. 109
3.3.1.7 Preformed Particles
Preformed particles do not require phase separation and remain in that
shape in which they were added to the neat resin or composite. Therefore,
these particles may be synthesized prior to the resin formulation and
then added to the thermosetting resin or formed in-situ, i.e., during the
formulation of the resin, before the resin is cured. 110
Prereacted urethane microspheres can be formed by dynamic vulcanization
method in liquid diglycidyl ether of bisphenol A. The prereacted
particles are then added to an uncured epoxy resin system and cured. The
mechanical and adhesion properties do not depend on any curing condition
of epoxy resin because the particles are stable, in contrast to a process
where a phase separation occurs during curing. 111
3.3.1.8 Inorganic Particles
In contrary to rubber, the toughening of inorganic particles is rather modest.
However, the toughening by inorganic particles has an advantage insofar
as it can also improve the modulus. Rubber toughens such that the
increase in toughness is accompanied at the expense of a decrease in the
modulus.
The toughening of inorganic particles is explained by the crack front
bowing mechanism. 112–114 A crack front increases its length by changing
its shape when it interacts with two or more inhomogeneities in a brittle
material. The inorganic particles inside the polymer matrix can resist a
crack propagation.
When a crack propagates in a rigid particle filled composite, the rigid
particles try to resist. Because of this resistance, the primary crack front has
to change its direction between the rigid particles (bowing), thus forming

Epoxy Resins 159
a secondary crack front. The bowed secondary crack front now has more
elastic energy stored than the straight unbowed crack front. A crack front
starts to bow out between particles, when it meets the particles.
Microcracking with debonding has been proposed as one of the
toughening mechanisms of glass bead-filled epoxies. Three types of micro-mechanical
deformations can be distinguished: 78
1. Step formation
2. Debonding of glass beads and diffuse matrix shear yielding
3. Micro-shear banding
Among the micro-mechanical deformations, micro-shear banding is
considered the major toughening mechanism for glass bead-filled epoxies.
Step formation and combined debonding and diffuse matrix yielding are
secondary toughening mechanisms. 79
3.3.2 Antiplasticizers
Antiplasticizers are additives for increasing the strength and modulus of
the respective material. They act via strong interactions with the epoxide
matrix. Epoxides with antiplasticizers characteristically 115
1. Have a sufficiently high value of the glass transition temperature
as needed for the applications,
2. Exhibit a higher modulus and higher toughness around room temperature,
3. Exhibit a lower water uptake at equilibrium.
Antiplasticizers for epoxide resins are shown in Table 3.7. The addition
of the reaction product of 4-hydroxyacetanilide and 1,2-epoxy-3-phenoxypropane
(EPPHAA) to an epoxide resin increases the tensile strength
and the shear modulus of the cured system. 116 The mechanism of antiplasticization
can be formulated in terms of hindrance of the short-scale cooperative
motions in the glassy state as a dynamic coupling between the
epoxy polymer and the antiplasticizer molecule. 117
In systems where the antiplasticizers have a poor affinity to the resin,
a phase separation during curing occurs. The mobility of the constituting
groups can be characterized by nuclear magnetic resonance techniques. 118

160 Reactive Polymers Fundamentals and Applications
OH
O
O CH 2 CH CH 2 O NH C
CH 3
EPPHAA
OH
O CH 2 CH CH 2 O CH 3
AM
CH 3
AO
O
O CH 2 CH CH 2 O
CH 3
Figure 3.7: Antiplasticizers for Epoxide Resins
3.3.3 Lubricants
In automotive, aviation and the related industries, there is a tendency to use
metallic materials with polymeric materials. For many parts in such applications,
good tribological properties are required. 119 Fluorinated polymers
are known as low friction materials. This property arises due to their low
surface energies.
Fluorinated poly(aryl ether ketone) (12F-PEK) can be added to epoxy
resins to improve the tribological properties. At low concentrations
of 12F-PEK, homogeneous systems are obtained after curing. Above 10%
12F-PEK, a phase separation is observed. At still higher concentrations,
an inversion of the morphology is observed. With fluoropolymer concentrations
of 10% 12F-PEK, a friction reduction of 30% can be obtained. 120
3.3.4 Adhesion Improvers
Epoxy polyurethane hybrid resins are used in high strength adhesives. Elastomer-modified
resins are used for adhesive formulations that cure under
water.

Material
Table 3.5: Reinforcing Materials for Epoxides
Remark/Reference
Epoxy Resins 161
Glass fibers
121–123
Hollow glass fibers
124
Carbon fibers
125–127
Carbon nanotubes
128–131
Graphite
132–138
Aluminum
139, 140
Boron
Aluminum borate whiskers
141
Paper
Poly(ethylene) fibers
Polyaramid Fabric Low density and extremely high strength
Cotton
Flax
142
3.3.5 Conductivity Modifiers
To modify the thermal and electrical properties, thermally and electrically
conductive materials are added.
3.3.6 Reinforcing Materials
3.3.6.1 Composites and Laminates
Composites and laminates are made by reinforcing the polymers with continuous
fibers. About 1/4 of the epoxy resins are reinforced materials. Reinforcing
materials are shown in Table 3.5. Traditional composite structures
are usually made of glass, carbon, or aramid fibers. The advances
in the development of natural fibers in genetic engineering and in composite
science offer significant opportunities for improved materials from
renewable resources with enhanced support for sustainable applications.
Biodegradable composites from biofibers and biodegradable polymers will
serve to solve environmental problems. 143
Often the surface of the fiber is chemically modified to increase the
adhesion properties to the resin matrix. For example, glass fibers are coated
with a silane coupling agent. The interfacial bonding between carbon fiber
and epoxy resin can be improved by modification with poly(pyrrole). Poly-
(pyrrole) (PPy) can be deposited on carbon fibers via the oxidation-polymerization
of pyrrole (Py) with ferric ions. 144

162 Reactive Polymers Fundamentals and Applications
Laminates are used for insulations. Impregnated sheets of woven
glass, paper, and polyaramid fabric or cotton are laminated in large presses.
These sheets are used for printed circuit boards in the electronics industry.
3.3.6.2 Nanocomposites
Polymer nanocomposites, in particular polymer-layered silicate nanocomposites,
are a radical alternative to macroscopically filled polymers. The
preparation of epoxy resin-based nanocomposites was first described by
Messersmith and Giannelis. 145 Extensive work on epoxy based nanocomposites
has been done and is reviewed among other polymers in the literature.
146, 147
Organoclays. Organoclays are used as precursors for nanocomposites in
many polymer systems. Usually montmorillonite is used for organoclays.
Montmorillonite belongs to the 2:1 layered silicates. Its crystal structure
consists of layers of two silica and a layer of either aluminum hydroxide
or magnesium hydroxide. Water and other polar molecules can enter between
the unit layers because of the comparatively weak forces between
the layers. Substitution of the ions originally in the layers by such ions
with different charges generates charged interlayers. The stacked array of
clay sheets separated by a regular spacing is addressed as gallery.
For true nanocomposites, the clay nanolayers must be uniformly dispersed
in the polymer matrix, to avoid larger aggregations. Small aggregations
are still addressed as nanocomposites, as intercalated nanocomposites,
ordered exfoliated nanocomposites, and disordered exfoliated nanocomposites.
148 Originally, intercalation was the insertion of an extra day
into a calendar year. Exfoliation refers to the peeling of rocky materials
into sheets due to weathering.
Clay nanolayers in elastomeric epoxy matrices dramatically improve
both the toughness and the tensile properties. 145, 149 The dimensional stability,
the thermal stability and the chemical resistance can also be improved
with clay nanolayers. 150
Exfoliated clays are formed when the clay layers are well separated
from one another and individually dispersed in the continuous polymer matrix.
Since exfoliated nanocomposites exhibit a higher phase homogeneity
than the intercalated clays, exfoliated clays are more effective in improving
the properties of the nanocomposites.

Epoxy Resins 163
Successful nanocomposite synthesis depends not only on the cure
kinetics of the epoxy system but also on the rate of diffusion of the curing
agent into the galleries, because it affects the intragallery cure kinetics.
The nature of the curing agent influences these two phenomena substantially
and therefore the resulting structure of the nanocomposite. The curing
temperature controls the balance between the extragallery reaction rate
of the epoxy system and the diffusion rate of the curing agent into the galleries.
151 It was found that the activity energy decreases with the addition
of organic montmorillonite. 152 Hexahydrophthalic anhydride (HHPA) is
usually used for hot curing of epoxy resins. With an alkoxysilane, it also
acts as a condensation agent. 153 Hot curing of montmorillonite-layered
silicates has been described with methyltetrahydrophthalic anhydride. 154
An exfoliated epoxy-clay nanocomposite structure can be synthesized
by loading the clay gallery with hydrophobic onium ions and then
allowing diffusion in the epoxide and a curing agent. The degree of exfoliation
increases with decreasing curing agent. 155 Clays exert catalytic
effects on the curing of epoxy resins. 156
An organically modified montmorillonite, prepared by a cation exchange
reaction between the sodium cation in montmorillonite and dimethyl
benzyl hydrogenated tallow ammonium chloride is suitable for high
degrees of filling for epoxy resins. 157 Nanocomposites exhibit a significant
increase in thermal stability in comparison to the original epoxy resin. 158
Quaternary ammonium ions both catalyze the epoxy curing reactions
and plasticize the epoxy material. This causes a large reduction in
glass transition temperature and lowers the storage modulus. Plasticization
is small for aromatic epoxy resins, but large for aliphatic resins. Therefore,
aromatic epoxy-clay systems may result in a complete exfoliation
of the clay galleries, whereas mixtures of aliphatic and aromatic epoxy
may produce intercalated systems. 159 Poly(oxypropylene)amine intercalated
montmorillonite is highly organophilic and compatible with epoxy
materials. 160
Star branched functionalized poly(propylene oxide-block-ethylene
oxide) was used with an organophilic modified synthetic fluorohectorite as
compatibilizer for nanocomposites. The polarity of the polyol could be tailored
by the type of functionalization. A mixture of two epoxy resins, tetraglycidyl
4,4 ′ -diaminodiphenylmethane and bisphenol A diglycidyl ether,
cured with 4,4 ′ -diaminodiphenylsulfone, was used as matrix material. 161
The hybrid nanocomposites were composed of intercalated clay particles

164 Reactive Polymers Fundamentals and Applications
Table 3.6: Interpenetrating Polymer Networks
Epoxide Further Component Reference
Diglycidyl ether of
bisphenol A
Aliphatic epoxide resin
Unsaturated polyesters
162
Vinylester resin (Bisphenol A
glycidylmethacrylate adduct in
styrene with layered
silicate nanoparticles)
Bisphenol A diacrylate
163
Diglycidyl ether of
bisphenol A
Epoxide bismaleimide resin Cyanate ester
164
Epoxide-amine network Silica
165
Diglycidyl ether of Hexakis(methoxymethyl)melamine
166
bisphenol A
Novolak epoxy resin 2,2 ′ -Diallyl bisphenol A (DBA)
167
Epoxy resin Polyaniline
168
10
as well as separated PPO spheres in the epoxy matrix. Phenolic alkylimidazolineamides
were also used to exchange the interlayer sodium cations of
the layered silicates. 169
Electric capacitors based on epoxy clay nanocomposites can be integrated
into electronic devices. 170
3.3.7 Interpenetrating Polymer Networks
Interpenetrating polymer networks are ideally compositions of two or more
chemically distinct polymer networks held together exclusively by their
permanent mutual entanglements. 171 In practice, interactions of both networks
beyond entanglement may occur, for instance, intercrosslinking.
In a simultaneous interpenetrating polymer network, the two network
components are polymerized concomitantly. In a sequential interpenetrating
polymer network, the first network is formed and then swollen
with a second crosslinking system, which is subsequently polymerized.
Interpenetrating polymer networks are known to remarkably suppress
creep phenomena in polymers. The motion of the segments in interpenetrating
polymer networks is diminished by the entanglement between
the networks.
Interpenetrating polymer networks including epoxide resins as one
of the components are summarized in Table 3.6.

Epoxy Resins 165
3.3.7.1 Curing Kinetics
If a thermosetting system is cured at a temperature below its maximally attainable
glass transition temperature, vitrification occurs during cure. The
vitrification slows down the reaction. The reaction may freeze before
reaching full conversion.
In contrast, in an interpenetrating network, if one component (I) reacts
more slowly than the other component (II), the former component (I)
may act as a plasticizer of the polymeric component (II). This allows a
faster reaction of the second component (II) and a more thorough cure
without vitrification. 172
In the simultaneous curing of a vinylester resin (VER) and an epoxy
resin a reduction in reaction rate due to the dilution of each reacting system
by the other resin components is observed.
The radical polymerization of an acrylate monomer is hardly affected
by the oxygen inhibition effect, while the cationic polymerization
of an epoxy monomer is enhanced by the atmosphere humidity. 173
The decomposition of peroxides is known to be accelerated by amines.
In fact, if for the radical curing of the vinylester component peroxides
are used instead of azo compounds, a strong redox interaction between the
peroxide and the amine used for curing the epoxide component is observed.
In such systems the peroxide decomposes too quickly to develop its full
power for curing the vinylester system.
Further, there is an interaction between the vinyl groups of the vinylester
system and the amine via a Michael addition. The curing performance
of the epoxide resin is less affected by the radical initiator. 174
3.3.7.2 Unsaturated Polyesters
In mixtures of epoxy based on diglycidyl ether of bisphenol A and unsaturated
polyesters, the curing monitored with differential scanning calorimetry
indicated a higher rate constant than the pure epoxide resin. It
is believed that the hydroxyl end group of the unsaturated polyester in the
blend provides a favorable catalytic environment for the epoxide curing. 162
The interpretation of the viscosity development suggests that an interlock
between the two growing networks exists that causes a retarded
increase of the viscosity. 175 The introduction of unsaturated polyester into
epoxy resin improves toughness but reduces the glass transition temperature.
176

166 Reactive Polymers Fundamentals and Applications
Functional Peroxides. Peroxy ester oligomers can be obtained by condensation
of anhydrides with poly(ethylene glycol)s and tert-butyl hydroperoxide.
Suitable anhydrides are pyromellitic dianhydride and the tetrachloroanhydride
of pyromellitic anhydride. The resulting esters contain
carboxylic groups and peroxy groups. These compounds can be used as
curing agents for unsaturated polyesters as such and for hybrid resins consisting
of an epoxy resin and an unsaturated polyester resin. 177
3.3.7.3 Acrylics
For interpenetrating polymer networks consisting of diglycidyl ether of
bisphenol A (DGEBA) and bisphenol A diacrylate as radically polymerizable
component, 4,4 ′ -methylenedianiline and dibenzoyl peroxide are suitable
curing agents. The curing can be achieved between 65°C and 80°C.
The kinetics of curing of the epoxide takes place as a combination of an uncatalyzed
bimolecular reaction and a catalyzed termolecular reaction. The
kinetics of curing of the acrylate runs according to a first-order reaction. 163
In the mixture, the rate constants are lower than in the separate systems.
Also the activation energies in the mixtures are higher. It is believed
that chain entanglements between the two networks cause a steric
hindrance for the curing process. The vitrification restrains the chain mobility
that is reflected as a decrease of the rate constants. The incorporation
of the methacryloyl moiety in an epoxide resin improves the weathering
stability and the photostability of the system.
178, 179
3.3.7.4 Urethane-modified Bismaleimide
Urethane-modified bismaleimide (UBMI) can be introduced and partially
grafted to the epoxy oligomers by polyurethane grafting agents. Afterwards,
a simultaneous bulk polymerization technique can be used to prepare
interpenetrating networks. 180 The tensile strength increases to a maximum
value with increasing UBMI content, then decreases with further increasing
UBMI content. If the polyurethane grafting agent contains poly-
(oxypropylene) polyols the interpenetrating network shows a two-phase
system, whereas in the case of poly(butylene adipate) a single phase system
is observed. The better compatibility of poly(butylene adipate) base
networks results in a higher impact strength.
An intercrosslinked network of bismaleimide-modified polyurethane-epoxy
systems was prepared from the bismaleimide having ester link-

Epoxy Resins 167
ages, polyurethane-modified epoxy, and cured in the presence of 4,4 ′ -diaminodiphenylmethane.
Infrared spectral analysis was used to confirm the
grafting of polyurethane into the epoxy skeleton. The prepared matrices
were characterized by mechanical, thermal, and morphological studies.
The changes of the properties depend on the relative amounts of the
moieties used. The incorporation of polyurethane into the epoxy skeleton
increases the mechanical strength and decreases the glass transition temperature,
thermal stability, and heat distortion temperature. On the other
hand, the incorporation of bismaleimide with ester linkages into a polyurethane-modified
epoxy system increases the thermal stability, tensile and
flexural properties, and decreases the impact strength, glass transition temperature,
and heat distortion temperature. 181
3.3.7.5 Electrically Conductive Networks
Electrically conductive polymers could find use in rechargeable batteries,
conducting paints, conducting glues, electromagnetic shielding, antistatic
formulations, sensors, electronic devices, light-emitting diodes, coatings,
and others. Low concentrations of polyaniline can make the polymer
electrically conductive when a co-continuous microstructure could be
achieved.
For the preparation of conductive polyaniline epoxy resin composites,
a doped polyaniline is blended with the epoxy resin. Plasticizers are
added to assist in the dispersion of the conductive polymer. The curing
agent must be selected in order to avoid dedoping. 168
The grafting onto the nitrogen of polyaniline was achieved by the
ring-opening graft copolymerization of 1,2-epoxy-3-phenoxypropane. By
the degree of grafting, the solubility, the optical and the electrochemical
properties of the grafted polyaniline can be tailored. 182
3.3.8 Organic and Inorganic Hybrids
An organic-inorganic hybrid interpenetrating network has been synthesized
from an epoxide-amine system and tetraethoxysilane (TEOS). The
kinetics of the formation of the silica structure in the organic matrix, and its
final structure and morphology, depend on the method of preparation of the
interpenetrating network. In the sol gel process, hydrolysis and polymerization
of TEOS are performed at room temperature in isopropyl alcohol.
The hybrid network can be prepared by two procedures.

168 Reactive Polymers Fundamentals and Applications
In the one-step procedure, all reaction components are mixed simultaneously.
In the two-step procedure, TEOS is hydrolyzed in the first step,
then mixed with the organic epoxy components and polymerized under the
formation of silica and epoxide networks.
Large compact silica aggregates, with 100 to 300 nm diameter, are
formed by the one-stage process of polymerization. In the two-stage process
the partial hydrolysis of TEOS effects an acceleration of the gelation.
This results in somewhat smaller silica structures. The most homogeneous
hybrid morphology with the smallest silica domains of size 10 to 20
nm can be achieved in a sequential preparation of the interpenetrating network.
165, 183
An increase in modulus by two orders of magnitude was
achieved at a silica content below 10%. 184 Phenolic novolak/silica and
cresol novolak epoxy/silica hybrids can be prepared in a similar manner
with TEOS. 185
3.3.9 Flame Retardants
Flame retardancy can be imparted by suitable monomers and curing agents.
Flame retardants can be grouped into halogen-containing compounds, the
most important being tetrabromobisphenol A, halogen free systems containing
aluminum trihydrate with red phosphorus, and phosphate esters. 186
Flame retardants that are used in epoxide resins are shown in Table 3.7.
Triglycidyloxy phenyl silane cured with 4,4 ′ -diaminodiphenylmethane
and others gives highly flame retardant polymers. 18 Heating in air
indicates that a silicon-containing carbon residue formed is superior in preventing
oxidative burning.
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is
synthesized by a multi step reaction from o-phenylphenol and phosphorus
trichloride.
From this compound, an adduct with p-benzoquinone, 2-(6-oxid-
6H-dibenz[c,e][1,2]oxa-phosphorin-6-yl)-1,4-benzenediol (ODOPB), can
be obtained. ODOPB can be used as a reactive flame-retardant in o-cresol
formaldehyde novolak epoxy resins for electronic applications. 19, 187 A related
compound, 2-(6-Oxid-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methanol
(ODOPM) can be used as flame-retardant hardener for o-cresol-formaldehyde
novolak epoxy (CNE) resin in electronic applications. 188 Some
phosphorous-containing flame retardants are shown in Figure 3.9.

Epoxy Resins 169
Compound
Table 3.7: Flame Retardants for Epoxide Resins
Remark/Reference
Tetrabromobisphenol A-based epoxies
Triglycidyloxy phenyl silane
18
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide
(DOPO)
10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-oxa-
190
10-phosphaphenanthrene-10-oxide (DHPDOPO)
19, 189
Bis(m-aminophenyl)methylphosphine oxide (BAMPO)
Bismaleimide(3,3 ′ -bis(maleimidophenyl))
192
phenylphosphine oxide (BMPPPO)
Bis(3-glycidyloxy)phenylphosphine oxide
193
Bis(4-aminophenoxy)phenylphosphine oxide (BAPP)
194
Tris(2-hydroxyphenyl)phosphine oxides
195, 196
Bis(3-diethylphosphono-4-hydroxyphenyl)sulfide (DPHS)
197
Benzoguanamine-modified phenol biphenylene components
198
Melamine phosphate
199
2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine
200 a
2,2 ′ -[(1-Methylethylidene)bis[(2,6-dibromo-4,1-phenylene)
200 a
oxy]]bis[4,6-bis[(2,4,6-tribromophenyl)oxy]]-1,3,5-triazine
Carbon black
201
a c.f. Figure 3.8
191

170 Reactive Polymers Fundamentals and Applications
Br
Br
Br
Br
O
N
O
Br
N
N
Br
O
Br
Br
Br
Br
Br
Br
Br
O
N
O
Br
N
N
Br
O
Br
Br
H 3 C
C
CH 3
Br
O
Br
Br
N
N
Br
O
N
O
Br
Br
Br
Br
Figure 3.8: Top: 2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine,
Bottom: 2,2 ′ -[(1-Methylethylidene)bis[(2,6-dibromo-4,1-phenylene)oxy]]
bis[4,6-bis[(2,4,6-tribromophenyl)oxy]-1,3,5-triazine 200

Epoxy Resins 171
O
P O
CH 2
OH
O
HO
P
O
OH
ODOPM
ODOPB
Figure 3.9: 2-(6-Oxid-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methanol
(ODOPM), 2-(6-Oxid-6H-dibenz[c,e][1,2]oxa-phosphorin-6-yl)-1,4-benzenediol
(ODOPB)
Other phosphorus-containing epoxy resins can be obtained from the
addition reaction of DOPO and the glycidyl ether of cresol-formaldehyde
novolak. 202, 203 The cured products are highly flame resistant.
In the presence of a phosphorous-containing hardener, bis(m-aminophenyl)methylphosphine
oxide (BAMPO), the volatilization of the cured
resin is reduced and aromatization is accelerated. This results in a larger
yield of stable char. This behavior is attributed to the flame retardant action
of BAMPO. However, at high content of BAMPO this effect is overwhelmed
by flame quenching due to the volatilization of the phosphoruscontaining
moieties from BAMPO. 191
Further, bismaleimide(3,3 ′ -bis(maleimidophenyl))phenylphosphine
oxide (BMPPPO), is a phosphorus-containing compound that is soluble in
organic compounds. Interpenetrating networks can be prepared by simultaneously
curing an epoxy/diaminodiphenylmethane system and BMPPPO.
The cured resin system exhibits a glass transition temperature around
212°C, thermal stability at temperatures beyond 350°C, and excellent flame
retardancy with a limiting oxygen index (LOI) of 40%. 192
Phosphorous-containing diamines have been prepared that act as
curing agents for epoxy resins. 204 The compounds and their synthesis
are shown in Figure 3.10. When cured with phosphorus-containing curing
agents, the epoxy resins show extremely high LOI values of up to 49.
Amine-based curing agents destabilize a brominated epoxy resin by
a mechanism of the nucleophilic substitution of bromine. As a result, a
brominated epoxy resin releases products of pyrolysis about 100°C lower
than a nonbrominated epoxy resin. 205

172 Reactive Polymers Fundamentals and Applications
H 2 N
O
C NH 2
O
P
+
H
O
P
O
H 2 SO 4 /HNO 3
O 2 N
O
P
NO 2
SnCl 2 /HCl/EtOH
H 2 N
O
P O
C NH 2
H 2 N
O
P
NH 2
O
P
O
2-DOPO-A
BAPPPO
Figure 3.10: 2-DOPO-A, Bis(4-aminophenyl)phenylphosphine oxide
(BAPPO)
204, 206

Epoxy Resins 173
Table 3.8: Global Production/Consumption Data of Important Monomers
and Polymers 207
Monomer Mill. Metric tons Year Reference
Ethylene oxide 14.7 2002
208
Ethyleneamines 0.248 2002
209
Epichlorohydrin 0.640 1999
210
Epoxy Resins 0.65 1999
211
3.3.10 Production Data
Global production data for the most important monomers used for unsaturated
epoxy resins are shown in Table 3.8.
3.4 CURING
3.4.1 Initiator Systems
The epoxide group reacts with several substance classes. Only a few of the
possible reactions are used for curing in practice. Curing agents of epoxy
resins can be subdivided into three classes:
1. Compounds with active hydrogens,
2. Ionic initiators, and
3. Hydroxyl coupling agents.
The most commonly used curing reaction is based on the polyaddition
reaction, thereby opening the epoxide ring. The glycidyl group can be
cured by amines and other nitrogen-containing compounds such as polyamides.
Many of the amines effect curing at room temperature. This type
of curing is called a cold curing.
The reactivity of an epoxy compound with an amine depends on the
structure of the compounds. The relative reaction rates of the secondary
amine to the primary amine can be explained in terms of substitution effects.
212 Anhydrides are active only at elevated temperatures. This type of
curing is addressed as hot curing.

174 Reactive Polymers Fundamentals and Applications
O
OH
R NH 2
+ CH 2 CH
R NH CH 2 CH
OH
OH
R
NH CH 2
O
CH 2 CH
CH
R
CH 2
N
CH 2
CH
CH
OH
O
OH
R OH + CH 2 CH
R O CH 2 CH
Figure 3.11: Reaction of the Glycidyl Group with an Amine and with a Hydroxy
Group
3.4.2 Compounds with Activated Hydrogen
3.4.2.1 Amines
Both primary and secondary amines can be used. From a chemical point of
view, the active hydrogen attached to the nitrogen group effects an addition
reaction, as the epoxide group is opened. The curing of the diglycidyl
oligomer with a diamine occurs in three stages:
1. Linear coupling of the oligomer,
2. Formation of a branched structure, and
3. Crosslinking.
The basic reaction between the glycidyl groups with a primary amine is
shown in Figure 3.11. The first reaction in Figure 3.11 is the addition
reaction of primary amine hydrogen with an epoxy group. The product
of this reaction is a secondary amine. The secondary amine may react
with another epoxy group to form a tertiary amine, as shown in the second
reaction, Figure 3.11. Usually the secondary amine is less reactive than
the primary amine. The ratio of the kinetic constants is approximately 1/2.
Both reactions are autocatalyzed by OH groups formed during the process.
The third reaction shown is the etherification reaction between epoxy
functions and hydroxyl groups. In most systems, this reaction can

Compound
Ethylene diamine
Diethylenetriamine
Triethylenetetramine
Hexamethylene diamine
Diethylaminopropylamine
Isophorone diamine
1,2-Diaminocyclohexane
Bis-p-aminocyclohexylmethane
Bisaminomethylcyclohexane
Menthane diamine
Table 3.9: Amines Suitable for Curing
Remarks
Epoxy Resins 175
Fast curing, low viscosity
Fast curing, low viscosity
Fast curing, low viscosity
Slower curing, needs elevated temperature,
flexible materials
Needs elevated temperature, good adhesive
Needs elevated temperature,
good potlife
N-aminoethyl piperazine
Fast curing
Diaminodiethyl toluene
Mixture of 2,6-diamino-3,5-diethyl
toluene and 2,4-diamino-3,5-diethyl
toluene
m-Phenylene diamine
Chemical resistant materials
4,4 ′ -Diaminodiphenylmethane Chemical resistant materials
3,3 ′ ,5,5 ′ -Tetraethyl-4,4 ′ -diamino Flame retardant 191
diphenylmethane
4,4 ′ -Diamino-3,3 ′ -dimethyl
Cycloaliphatic diamine213, 214
dicyclohexylmethane (DCM)
1,5-Naphthalene diamine
be neglected. However, it has been shown that this reaction takes place
using 4,4 ′ -methylene bis(3-chloro-2,6-diethylaniline) (MCDEA) as curing
catalyst. On the other hand, with 4,4 ′ -diaminodiphenylsulfone (DDS) and
4,4 ′ -methylenedianiline (MDA) as catalysts the etherification was not observed.
109, 215
Typical nitrogen compounds used for cold curing are shown in Tables
3.9, and 3.10, and in Figures 3.12 and 3.13. There are many possibilities
for formulating a curing system from primary and secondary amines,
and also with tertiary amines.
Tertiary amines catalyze the reaction. Other catalysts are complexes
of boron trifluoride complexes, quaternary ammonium salts, thiocyano
compounds, etc. Retarders are certain ketones and diacetone alcohol.

176 Reactive Polymers Fundamentals and Applications
Table 3.10: Polymeric Amines and Hetero Functional Amines
Compound
Remarks
Poly(propylene oxide)diamine
Trimercaptothioethylamine Optical applications23, 216
Polymercaptopolyamines
In combination with customary amine
hardeners 217
2,4-Diamino-4 ′ -methylazobenzene Optical applications 218
(DMAB)
4,4 ′ -Dithiodianiline Reversible crosslinking 219
Dicyandiamide
Common for adhesives
4,4 ′ -Diaminodiphenylsulfone Chemical resistant materials
bis(m-aminophenyl)methylphosphine
191
oxide (BAMPO)
4,4 ′ -Methylene bis[3-chloro-
67
2,6-diethylaniline]
Olefin oxide polyamine adducts Fast curing, low toxicity
Glycidyl ether polyamine adducts Fast curing
Diamide of dimerized linoleic acid For adhesives
and ethlyene diamine
Ketimines
Low viscosity, long potlife,
latent hardening catalysts
2,5-Bis(aminomethyl)bicyclo[2.2.1] Norbornane diketimine 220
heptane di(methylisopropyl
ketimine)
Substituted imidazolines, e.g., Wide range in stoichiometry
2-ethyl-4-methylimidazole, 1-methylimidazole
Sulfanilamide
45, 221–223
Polysilazane-modified polyamines Thermal resistant 224

Epoxy Resins 177
H 2 N CH 2 CH 2 NH CH 2 CH 2 NH 2
Diethylenetriamine
H 2 N CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 NH 2
Hexamethylenediamine
CH 3 CH 2
N CH 2 CH 2 CH 2 NH 2
CH 3 CH 2
Diethylaminopropylamine
H 2 N
CH 3 CH 3
C
CH 3
NH 2
H 2 N
CH 2
CH 2
N
H
Menthanediamine
N-Aminoethyl piperazine
Figure 3.12: Aliphatic Nitrogen Compounds for Curing: Diethylenetriamine,
Hexamethylene diamine, Diethylaminopropylamine, Menthane diamine, N-aminoethyl
piperazine

178 Reactive Polymers Fundamentals and Applications
H 2 N
NH 2
NH 2
H 2 N
m-Phenyenediamine
1,5-Napthalene diamine
H 2 N
O
S
O
NH 2
4,4’-Diaminodiphenylsulfone
H 2 N
CH 2 NH 2
4,4’-Diaminodiphenylmethane
Figure 3.13: Aromatic Nitrogen Compounds for Curing: m-Phenylene diamine,
1,5-Naphthalene diamine, 4,4 ′ -Diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenylmethane

Epoxy Resins 179
Certain cyclic amines, such as 1,2-bis(aminomethyl)cyclobutane and
isomers of diaminotricyclododecane increase the pot life time. Polyamines
and dicyanamide are preferably used for adhesive formulations.
Phenolic hydroxyl groups exert autocatalysis at low conversions with
respect to the ring opening of the epoxide group, thereby adding the amine
groups. In the later stage of curing the amine groups are largely consumed
and the phenolic hydroxyl groups start to react with the residual epoxide
groups. 225 A suitable accelerator for adhesive formulations is 2,4,6-tris(dimethylaminomethyl)phenol.
Most low molecular amines are toxic and also sensitive to the carbon
dioxide in air. Therefore, the various adducts of the amines have been
developed to mitigate this drawback.
3.4.2.2 Ketimines
Ketimines form the active amine structure by addition of water; thus they
act as delayed-action catalysts.
3.4.2.3 Amino Amides
Amide-based compounds are used to achieve special properties and desired
curing characteristics, such as lower toxicity, less sensitive final properties
to the stoichiometry, lower peak temperatures for large castings. The active
group in curing is not directly the amide group, but the attached primary
and secondary amino groups present in the molecule. The amide group
is helpful for achieving the other benefits, mentioned above. Examples
for amino amides are adducts of polyamines with fumaric acid or maleic
acid, or fatty acids. Similar to amines, in amine amides the reaction can be
accelerated with boron trifluoride complexes, Mannich bases, etc.
3.4.2.4 Metal salts
Zirconium tetrachloride catalyzes effectively the nucleophilic opening of
epoxide rings by amines. This has been used for the efficient synthesis
of β-amino alcohols. 226 Zinc bromide and zinc perchlorate are also active
in this manner. 227 However, it seems that this catalyst is not used for the
curing of epoxy resins.

180 Reactive Polymers Fundamentals and Applications
Anhydride
Table 3.11: Anhydrides for Hot Curing
Remark/Reference
Dodecenyl succinic anhydride Liquid
Hexahydrophthalic anhydride
3-Methyl-1,2,3,6-tetrahydrophthalic N,N-dimethylbenzylamine as accelerator
228
anhydride (MeTHPA)
Hexahydro-4-methylphthalic
anhydride
Tetrahydrophthalic anhydride
Methyltetrahydrophthalic anhydride
Phthalic anhydride
Methyl nadic anhydride
Liquid
HET anhydride
Pyromellitic dianhydride (PMDA)
5-(2,5-Dioxotetrahydrofuryl)-
229
3-methyl-3-cyclohexene-1,2-dicarboxylic
anhydride
(DMCDA)
Glutaric anhydride Biodegradable Formulations 230
Styrene-maleic anhydride
Low molecular weight copolymers
copolymers
3.4.2.5 Phenols
Bisphenol A is a main ingredient for the manufacture of glycidyl ethers.
Polyfunctional phenols can be used to cure epoxy resins. This method
did not find large commercial use, except in the development of highly
chemically resistant coatings. The curing reaction is completely similar to
the curing reaction of amines.
Phenoplasts. Polyfunctional phenols can be applied as phenol/formaldehyde
condensates of the novolak-type. In this field a wide variety has been
examined, including phenolic adducts of chloromethylated diphenyl oxide,
tetrabrominated bisphenol, and phenol adducts of poly(butadiene)
3.4.2.6 Anhydride Compounds
Typical anhydride compounds used for hot curing are shown in Table 3.11
and in Figure 3.14. Most anhydrides need elevated temperatures to be
active. The anhydride group is not active in the absence of acidic or basic

Epoxy Resins 181
C 12 H 23
O
O
O
O
O
O
Dodecenylsuccinic anhydride
Phthalic anhydride
O
O
O
O
O
O
Tetrahydrophthalic anhydride
Hexahydrophthalic anhydride
H 3 C
CH
O
O
O
O
O
O
O
O
O
Methylnadic anhydride
Pyromellithic anhydride
Figure 3.14: Anhydrides for Hot Curing

182 Reactive Polymers Fundamentals and Applications
catalysts; instead the anhydride group must be converted into the carboxyl
group. This can be achieved by hydrolysis by natural occurring moisture,
or by alcoholysis.
The reaction of an anhydride is accelerated by a tertiary amine or by
complexes of metal salts, such as ferric acetylacetonate. 231 The reaction
of the anhydride group, as well as the acid group with the epoxide group,
results in an ester linkage, with all the advantages and disadvantages of the
ester link.
Anhydrides are in some cases preferred over amines because they
are less irritating to the skin, have longer pot life times, and low peak temperatures.
Aromatic and cycloaliphatic anhydrides find wide applications
for molding and casting techniques.
3.4.2.7 Polybasic Acids
The carboxyl group is capable of opening the epoxide group. Theoretically,
the optimum stoichiometry is one acid group by one epoxide group. In
practice an excess of acid is used.
3.4.2.8 Polybasic Esters
To obtain tough materials, the epoxides can be cured by the insertion reaction
into ester groups. The curing agent is formed in-situ by the radical
polymerization of N-phenylmaleimide and p-acetoxystyrene. 232 2,5-Dimethyl-2,5-bis(benzoylperoxy)hexane
is suitable, because its decomposition
temperature of 110°C is close to the desired cure temperature of 100°C.
The two monomers copolymerize satisfactorily in the absence of the epoxy
compound. The advantage of using the in-situ technique of polymerization
is that the initial composition has low viscosity.
The insertion mechanism is shown in Figure 3.15. Compared to
epoxy systems cured with a phenol resin, the copolymer of N-phenylmaleimide
and p-acetoxystyrene shows a significantly higher glass transition
temperature.
3.4.3 Coordination Catalysts
Coordination catalysts consist of metal alkoxides, such as aluminum isopropyloxide,
metal chelates, and oxides. Coordinative polymerization results
in high molecular weight and stereospecific species.

Epoxy Resins 183
O
O
H 3 C C O + CH 2 CH CH 2
H 3 C
O
C
O
O CH 2 CH CH 2
CH CH 2
CH CH 2
O
N
O
O
N
O
Figure 3.15: Insertion of the Epoxide into a Pendent Ester Group
3.4.4 Ionic Curing
3.4.4.1 Anionic Polymerization
The anionic polymerization of epoxides can be initiated by metal hydroxides,
and secondary and tertiary amines. The rate of curing is low in comparison
to other curing methods. Therefore, anionic polymerization has not
found wide industrial application. Moreover, the mechanical properties of
the final materials are not satisfactory.
3.4.4.2 Cationic Polymerization
Cationic polymerization can lead to a crosslinking process if diepoxides
are taken as monomers. Thus, a wide variety of compounds can be used
catalytically as cationic curing initiators for epoxy resins that act at a high
rate. Moreover, their low initial viscosities and fast curing make them good
candidates for rapid reactive processing.
Cationic polymerization is initiated by Lewis acids. A lot of metal
halogenides have been shown to be active, such as AlCl 3 , SnCl 4 , TiCl 4 ,
SbCl 5 or BF 3 , but the most commonly used compound is boron trifluoride.
In practice, boron trifluoride is difficult to handle and the reaction runs
too fast. Therefore, the compound is used in complexed form, e.g., as
an ether complex or an amine complex. The strength of the ether and
amine complexes can be related to the base strength of the ether and amine,

184 Reactive Polymers Fundamentals and Applications
Compound
Table 3.12: Latent Catalysts
Reference
N-Benzylpyrazinium hexafluoroantimonate
233
N-Benzylquinoxalinium hexafluoroantimonate
233
Benzyl tetrahydrothiophenium hexafluoroantimonate
234
o,o-Di-tert-butyl-1-piperidinylphosphonamidate
235
o-tert-Butyl-di-1-piperidinylphosphonamidate
235
o,o-di-tert-Butyl phenylphosphonate
236
o,o-Dicyclohexyl phenylphosphonate
236
respectively. Since the reactivity of a complex depends on the dissociation
constant, some predictions on the activity of the complex can be made.
Water or alcohols cause chain transfer reactions. The alcohol attacks
the positively charged end of the growing polymer chain and forms an ether
linkage or a hydroxyl group, respectively. The released proton can initiate
the growth of another polymer chain. Diols and triols yield polymers with
pendent hydroxyl groups. Therefore, diepoxides or higher functional epoxides
are polymerized in the presence of diols or triols, etc.; branched and
crosslinked products may appear.
In the cationic UV curing of an aliphatic epoxy compound it was
observed that the polymerization rate decreased strongly after a conversion
level of less than 10%. This effect was not caused by the glass transition
temperature. However, the addition of 1,6-hexanediol (HD) raised the conversion
at room temperature. 237
There are photolatent and thermolatent catalyst systems. A great variety
of those catalysts have been reviewed. 238 Besides the direct thermolysis
of the initiator, also indirect methods are viable. Table 3.12 provides
a list of latent catalysts.
Spiroorthocarbonate. The cationic curing reaction of a bisphenol A-type
epoxy resin in the presence of a spiroorthocarbonate can be performed with
borontrifluoride dietherate. The spiroorthocarbonate undergoes a double
ring opening reaction. 239 The conversion of the epoxy groups increases as
the content of the spiroorthocarbonate increases.
3,9-Di(p-methoxybenzyl)-1,5,7,11-tetra-oxaspiro[5.5]undecane, c.f.
Figure 3.16 as spiroorthocarbonate, can be synthesized by the reaction of
2-methoxybenzyl-1,3-propanediol with dibutyltin oxide.
Differential scanning calorimetry shows two peaks that are attributed

Epoxy Resins 185
H 3 C
O O
O O CH 3
O O
3,9-Di(p-methoxy-benzyl)-1,5,7,11-tetra-oxaspiro(5,5)undecane
O
O
O
O
O
O
3,23-Dioxatrispiro[tricyclo[3.2.1.0]octane-6,5’-
1,3-dioxane-2’2"-1,3-dioxane-5",7’"-tricyclo[3.2.1.0octane]
Figure 3.16: 3,9-Di(p-methoxybenzyl)-1,5,7,11-tetra-oxaspiro[5.5]undecane
and 3,23-dioxatrispirotricyclo[3.2.1.0[2.4]]octane-6,5 ′ -1,3-dioxane-2 ′ 2 ′′ -
1,3-dioxane-5 ′′ ,7 ′′′ -tricyclo[3.2.1.0[2.4]octane]
to the polymerization of the epoxy group, and to the copolymerization of
the spiroorthocarbonate with epoxy groups or homopolymerization, respectively.
Copolymers containing a spiroorthocarbonate are capable of
yielding a hard, non-shrinking matrix resin. Examples of these copolymers
include a 2,3,8,9-di(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane
spiroorthocarbonate, and 3,23-dioxatrispirotricyclo[3.2.1.0[2.4]]octane-
6,5 ′ - 1,3-dioxane-2 ′ 2 ′′ -1,3-dioxane-5 ′′ ,7 ′′′ -tricyclo[3.2.1.0[2.4]octane] and
cis,cis-, cis,trans-, and trans,trans-configurational isomers of 2,3,8,9-di-
(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane.
These spiroorthocarbonates were determined to undergo an expansion
of 3.5% during homopolymerization and demonstrated acceptable cytotoxicity
and genotoxicity properties. These properties make them promising
components of composite resin matrix materials. 20
Trifluoromethanesulfonic acid salts. Triflic acid, i.e., trifluoromethanesulfonic
acid, CF 3 SO 3 H is a known strong acid. Lanthanide triflates
are Lewis acids and they maintain their catalyst activity even in aqueous
solution. The strong electronegativity of the trifluoromethanesulfonate anion
enhances the Lewis acid character of the initiator. Therefore, lanthanide
triflates are excellent catalysts in the ring opening of the epoxy compounds.
240

186 Reactive Polymers Fundamentals and Applications
Phosphonic Acid Esters. Phenylphosphonic esters decompose into phenylphosphonic
acid and the corresponding olefins at 150 to 170°C. In the
presence of ZnCl 2 they can initiate a cationic polymerization of glycidyl
phenyl ether (GPE) to molecular weights up to 2000 to 7000 Dalton. 236
Examples are o,o-di-1-phenylethyl phenylphosphonate, o,o-di-tertbutyl
phenylphosphonate, and o,o-dicyclohexyl phenylphosphonate. These
compounds can be synthesized from phenylphosphonic dichloride and the
corresponding alcohols.
Phosphonamidates. Phosphonamidates are thermally latent initiators,
suitable for the polymerization of epoxides. 235 These compounds, such
as o,o-di-tert-butyl-1-piperidinylphosphonamidate and further o-tert-butyl-di-1-piperidinylphosphonamidate
can be synthesized from phosphorus
oxychloride and piperidine in the presence of triethylamine, followed by
the reaction with tert-butyl alcohol in the presence of sodium hydride. No
polymerization of epoxide resins occurs below 110°C, whereas the curing
proceeds rapidly above 110°C. At room temperature a mixture of epoxide
and phosphonamidate is stable for months.
3.4.5 Photoinitiators
Photoinitiation is one of the most efficient methods for achieving very fast
polymerization. Often the reaction can be completed within less than one
second. 241 Curing with ultraviolet light has been developed for the coating
area, printing inks and adhesives. The mechanism of photo curing consists
mostly of a cationic photopolymerization of epoxides. The kinetics of the
photoinduced reactions can be monitored by differential photocalorimetry.
242 The major drawback of differential photocalorimetry is the rather
long response time in comparison to the curing rate.
The well-known use of radical generating photoinitiators in vinylcontaining
systems is not applicable in pure epoxy systems. There is an
exception when the epoxide resin is mixed with a vinyl monomer that bears
the hydroxyl functionality or the amide functionality. The radical generating
photoinitiator reacts then with the vinyl monomer. 243
Common photoinitiators for epoxy systems are shown in Table 3.13.
In the photoinduced curing of epoxides, the propagating polymer
cations cannot deactivate one another, but require a deactivation by another
species present in the polymerization mixture. Therefore, after the light

Compound
Table 3.13: Photoinitiators for Epoxides
Epoxy Resins 187
Reference
Aryl diazonium tetrafluoroborates
4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)-
244
ammonium hexafluoro antimonate)benzophenone
Calixarene derivatives
245
9-Fluorenyl tetramethylene sulfonium hexafluoroantimonate
246
Cyclopentadiene-Fe-arene hexafluorophosphate
247
is switched off, a pronounced postpolymerization reaction can be monitored.
248 The conversion in the dark may contribute up to 80% of the total
curing process. The overall polymerization quantum yield reaches ca. 200
mol per photon.
It has been shown that polyglycols, i.e., polyols from 1,2-diols, slow
down the cationic polymerization, whereas polyols made from 1,4-diols do
not show this effect. 234 Also the addition of small amounts of crown ethers
(12-crown-4 ether) retards the polymerization. This behavior is attributed
to complexes that are formed only with glycol-like structures that reduce
the effective concentration of cations available to initialize the polymerization.
3.4.5.1 Aryl Diazonium Tetrafluoroborates
The azo group in aryl diazonium tetrafluoroborates decomposes on ultraviolet
radiation into the aromatic compound, nitrogen and boron trifluoride.
The latter compound initiates a cationic polymerization of the epoxide resin.
The evolution of nitrogen limits the applications to thin films.
3.4.5.2 Aryl Salts
Other efficient photoinitiators are based on the photolysis of diaryliodonium
and triarylsulfonium salts, that when decomposed liberate strong
Brønsted bases. These bases initiate the cationic polymerization.
It has been shown that diaryliodonium hexafluoroantimonate initializes
photochemically the cationic copolymerization of 3,4-epoxycyclohexylmethyl-3
′ ,4 ′ -epoxycyclohexane carboxylate and triethylene glycol methylvinyl
ether. 249 Epoxy-functionalized silicones can be synthesized by

188 Reactive Polymers Fundamentals and Applications
O
S
Thioxanthone
Anthracene
Figure 3.17: Thioxanthone, Anthracene
rhodium-catalyzed, chemoselective hydrosilation of vinyl ethers with siloxanes
or silane. 250
Epoxidized soyabean oil accelerates the crosslinking reaction of aromatic
diepoxides in the presence of a triarylsulfonium photoinitiator. 251
The photoinitiated copolymerization leads within seconds to a fully cured
insoluble material showing increased hardness, flexibility, and scratch resistance.
In interpenetrating networks, constructed by vinyl polymers and epoxides
by photo curing, a mixture of a radically decomposing photoinitiator
and a cationic photoinitiator is used. Examples are a mixture of a hydroxyphenylketone
and a diaryliodonium hexafluorophosphate salt. During
the UV curing of a mixture of acrylate and epoxide monomers, the epoxides
react slower than acrylates. 173 The low efficiency of the initiation
process is caused by the low ultraviolet absorbance of cationic photoinitiators.
However, photosensitizers can improve the performance.
Combinations of photo curing and thermal curing in interpenetrating
networks of a vinyl polymer and an epoxide are possible. Such a combination
of crosslinkable resins allows the partial or complete cure of each
component independent of the other. 252
3.4.5.3 Photosensitizers
Photosensitizers can be used to improve characteristics of photo curing for
pigmented materials. These photosensitizers exhibit significant UV absorption
in the near UV and transfer the absorbed energy to a cationic photoinitiator.
253 Examples for photosensitizers are anthracene and thioxanthone
derivatives, such as 2,4-diethylthioxanthone, isopropylthioxanthone,
c.f. Figure 3.17. Photoinitiators are iodonium salts that exhibit a compara-

Epoxy Resins 189
CH 3
H 3 C
CH 2
CH 2
CH 3
OH
OH
HO
H 3 C
CH 2 CH 2
OH HO
OH
CH 2 CH 2 CH 3
CH 3
Figure 3.18: p-Methylcalix[6]arene
tively low triplet state energy.
3.4.5.4 Calixarenes
Calixarenes are by-products in the phenol/formaldehyde condensation to
prepare bakelite. They found attention for their application as surfactants,
chemoreceptors, electrochemical and optical sensors, solid-phase extraction
phases, and stationary phases for chromatography. 254
The hydroxyl groups in calixarenes (c.f. Figure 3.18) can be protected
with tert-butoxycarbonyl groups, trimethylsilyl groups, and cyclohexenyl
groups, respectively. In this way the hydroxyl group does not react
with an epoxide group. The phenol groups can be restored if a compound
is present that generates acids photolytically. 245
3.4.6 Derivatives of Michler’s Ketone
4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)ammonium hexafluoro
antimonate)benzophenone (MKEA) is synthesized from 4,4 ′ -bis(dimethylamino)benzophenone
(Michler’s ketone) and ethyl α-(bromomethyl)acrylate,
c.f. Figure 3.19. MKEA initiates cationic photopolymerization
of cyclic ethers, like cyclohexene oxide (CHO) via a conventional addition

190 Reactive Polymers Fundamentals and Applications
H 3 C
N
H 3 C
O
C
CH 3
N
CH 3
+
Br
CH 2 C CH 2
C O
O
CH 2
CH 3
H 2 C
O
C CH 2
CH 3
N + O
C
CH 3
N +
CH 2 C CH 2
C CH 3 CH 3 C O
O
-
SBF 6
-
SBF 6
O
CH 2 CH 2
CH 3 CH 3
MKEA
Figure 3.19: Synthesis of 4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)ammonium
hexafluoro antimonate)benzophenone (MKEA)
fragmentation mechanism. MKEA belongs to the group of addition-fragmentation
catalysts.
The mechanism of initiation of MKEA is shown in Figure 3.20. This
initiator does not require supplementary free radical sources. It is suggested
that radicals stemming from the photoinduced hydrogen abstraction
participate in addition fragmentation reactions to yield reactive species capable
of initiating cationic polymerization. 244
Monomers with strong electron donors such as N-vinyl carbazole,
isobutyl vinyl ether, and n-butyl vinyl ether undergo explosive polymerization
upon illumination of light. In the case of cyclohexene oxide there
is an induction period, owing to the trace impurities present, but afterwards,
the polymerization proceeds readily.
3.4.6.1 Photoinitiator Systems
Visible light photoinitiator systems include an iodonium salt, a visible light
sensitizer, and an electron donor compound. 20

Epoxy Resins 191
R*
+ H 2 C
C
CH 2
CH 3
N +
O
C
CH 3
O
CH 2
CH 3
R*
H 2 C
C*
CH 2
CH 3
N +
O
C
CH 3
O
CH 2
CH 3
R*
H 2 C
C*
CH 2
+
CH 3
N*+
O
C
CH 3
O
CH 2
CH 3
Figure 3.20: Mechanism of Initiation of 4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)ammonium
hexafluoro antimonate)benzophenone (MKEA)

192 Reactive Polymers Fundamentals and Applications
Examples of useful aromatic iodonium complex salt photoinitiators
include diaryliodonium hexafluorophosphates and diaryliodonium hexafluoroantimonates,
such as (4-(2-hydroxytetradecyloxyphenyl))phenyliodoniumhexafluoroantimonate,
(4-octyloxyphenyl)phenyliodonium hexafluoroantimonate
(OPIA), and (4-(1-methylethyl)phenyl)(4-methylphenyl)-
iodonium tetrakis pentafluorophenylborate. These salts are more thermally
stable, promote faster reaction, and are more soluble in inert organic solvents
than are other aromatic iodonium salts of complex ions. Diphenyl
iodonium hexafluoroantimonate has a photoinduced potential greater than
N,N-dimethylaniline.
The second component in the photoinitiator system is the photosensitizer.
Desirably, the photoinitiator should be sensitized to the visible
spectrum to allow the polymerization to be initiated at room temperature
using visible light. The sensitizer should be soluble in the photopolymerizable
composition, free of functionalities that would substantially interfere
with the cationic curing process, and capable of light absorption within
the range of wavelengths between about 300 and about 1000 nanometers.
Suitable sensitizers include compounds in the following categories:
• α-Diketones
• Ketocoumarins
• Aminoarylketones
• p-Substituted aminostyrylketones
For applications requiring deep cure (e.g., cure of highly filled composites),
it is preferred to employ sensitizers having an extinction coefficient
below about 1000 lmol −1 cm −1 at the desired wavelength of irradiation
for photopolymerization, or alternatively, the initiator should exhibit
a decrease in absorptivity upon light exposure. Many of the α-diketones
exhibit this property, and are particularly preferred for dental applications.
A suitable photosensitizer is camphorquinone.
The third component of the initiator system is an electron donor
compound. The electron donor compound should be soluble in the polymerizable
composition. Further, suitable compatibility and interplay with
the photoinitiator and the sensitizer and other properties, like shelf stability,
should be fulfilled. The donor is typically an alkyl aromatic polyether
or an alkyl, aryl amino compound wherein the aryl group is optionally substituted
by one or more electron withdrawing groups. Examples of suitable
electron withdrawing groups include carboxylic acid, carboxylic acid ester,

Epoxy Resins 193
ketone, aldehyde, sulfonic acid, sulfonate, and nitrile groups.
In practice, the following compounds find application:
4,4 ′ -Bis(diethylamino)benzophenone,
4-Dimethylaminobenzoic acid (4-DMABA),
Ethyl-4-dimethylamino benzoate (EDMAB),
3-Dimethylaminobenzoic acid (3-DMABA),
4-Dimethylaminobenzoin (DMAB),
4-Dimethylaminobenzaldehyde (DMABAL),
1,2,4-Trimethoxybenzene (TMB), and
N-Phenylglycine (NPG).
3.4.7 Epoxy Systems with Vinyl Groups
Besides pure epoxy systems, mixed systems such as epoxy acrylates are
in use. These systems can be cured with radical photoinitiators. Examples
for such initiators are 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-
butan-1-one (BDMB), 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one
(TPMK), 2,2-dimethoxy-1,2-diphenylethan-1-one (BDK),
and hydroxy-2-methyl-1-phenyl-propanone. 255
3.4.8 Curing Kinetics
There are various methods to investigate the kinetics of curing, including
1. Viscometry,
2. Differential scanning calorimetry,
3. Modulated differential scanning calorimetry,
4. Dielectric analysis,
5. Dynamic mechanical analysis,
6. In-situ Fourier transform infrared spectroscopy, and
7. Fluorescence response.
3.4.8.1 Viscometry
In the course of curing, the crosslinking density and the viscosity as well
as the modulus of the resin system increase. The viscoelastic properties
can be measured in a torsional motion. 256

194 Reactive Polymers Fundamentals and Applications
3.4.8.2 Differential Scanning Calorimetry
Differential scanning calorimetry is the only direct reaction rate method
which operates in two modes: constant temperature or linear programmed
mode. Several methods to evaluate the data obtained by differential scanning
calorimetry are available. 257 The isoconversional method 258 is frequently
used to calculate the energies of activation and evaluating the dependence
of the effective activation energy on the extent of conversion. 259
Relations are available between the degree of conversion, the time
dependence of the conversion, and the direct measurable parameters, i.e.,
viscometry, differential scanning calorimetry and dynamic mechanical analysis.
The equation is always second-order although the coefficients to this
equation are different for the individual methods. The DSC technique becomes
insensitive at conversions shortly after the gel point. 260 However,
changes in the heat capacity can be indicators of the onset and the finishing
of the vitrification. 214
Differential scanning calorimetry allows statements concerning the
reaction mechanism of curing. The ring opening reaction between phenyl
glycidyl ether and aniline was investigated by DSC. The reaction resembles
the diepoxy-diamine cure mechanism. However, it was detected that
besides that from the epoxy ring opening reaction, another exothermic process
at the last stages of the reaction takes place. It was concluded that the
reaction of epoxy ring opening by aniline occurs by two concurrent pathways,
261, 262 an uncatalyzed one and an autocatalyzed one.
3.4.8.3 Temperature Modulated Differential Scanning Calorimetry
In temperature modulated differential scanning calorimetry (TMDSC), the
sample is subjected to a sinusoidal temperature change. The instruments
are called differential AC-calorimeters. This particular method can measure
the storage heat capacity and the loss heat capacity, i.e., the reversible
part of heat that can be withdrawn again by cooling, and a part of heat
consumed by chemical reaction. A complex heat capacity with a real part
(storage heat capacity) and an imaginary part (loss heat capacity) can be
defined. 263 The treatment is similar to other complex modules in mechanics.
During the curing, the glass transition temperature rises steadily.
The reaction induced vitrification takes place when the glass transition
temperature rises above the curing temperature. This transition can be fol-

Epoxy Resins 195
lowed simultaneously with the reaction rate in TMDSC.
264, 265
Modulated differential scanning calorimetry allows detecting of reaction
induced phase separations. The apparent heat capacity changes, as
phase separation occurs. The cloud point can be determined with optical
microscopy, and there is a correspondence between the optical method
and the calorimetry method.
266, 267
In an amine curing system, a complex
formed from the primary amine and the epoxide was postulated that
initiates the curing reaction. The reactions of the primary amine and the
secondary amine with an epoxy-hydroxyl complex are comparatively slow
and thus rate determining during the whole curing process.
264, 268
In an
epoxy-anhydride system some complications have been elucidated. 269
Temperature modulated DSC can be used with advantage during isothermal
curing of semi-interpenetrating polymer networks. 270
3.4.8.4 Dielectric Analysis
Dielectric analysis 271 is based on the measurement of the dielectric permittivity
ε ′ and the dielectric loss factor ε ′′ in the course of curing. The
complex dielectric constant ε ∗ may be expressed by
ε ∗ = ε ′ − iε ′′ (3.1)
The permittivity is proportional to the capacitance and depends on
the orientation polarization. The orientation polarization results from the
change in the dipole moment due to the chemical reaction and also from
the change of the concentration of dipoles due to the volume contraction
during the curing reaction. The loss factor corresponds to the energy loss.
Both dielectric and mechanical measurements are suitable techniques
for monitoring the curing process. Also, phase-separation processes
can be monitored by dielectric analysis, because dielectric measurements
are sensitive to interfacial charge polarization. Dipolar relaxation indicates
the vitrification through the α-relaxation process in both phases. 272 Further,
dielectric sensor measurements have the advantage that they can be
made in the laboratory as well as in-situ in the fabrication tool in a production
line. 273 A relation between the dielectric response and other methods
measuring the gel point has been established in epoxy systems. 214
Dielectric analysis, in combination with other experimental techniques,
can be used to establish a time-temperature-transition (TTT) diagram.
The curing must be measured in a series of experiments at differ-

196 Reactive Polymers Fundamentals and Applications
ent temperatures. In such a diagram gelation, vitrification, full cures, and
phase-separation are marked. 274
A technique involving simultaneous dielectric and near infrared measurements
has been used for monitoring the curing of blends of a diglycidyl
ether bisphenol A epoxy resin with a 4,4 ′ -diaminodiphenylmethane hardener
and various amounts of poly(methyl methacrylate) as modifier. 275
3.4.8.5 In-Situ Fourier Transform Infrared Spectroscopy
During the curing reaction, the appearance or disappearance of various
characteristic infrared bands can be monitored. This method yields more
information than a single parameter, e.g., as obtained from a DSC measurement.
However, there is more work needed to calibrate the system properly
than in a DSC experiment. Multivariate analysis, in particular alternating
least squares (ALS), allows calculation of the concentration profiles and
the spectra of all species involved in the reaction of curing epoxy resins. 276
During curing, the intensity of the epoxy group, at 789 to 746 cm −1
decreases. 277 For example, based on such experiments, in the curing of a
dicyanate ester (1,1-bis(4-cyanatophenyl)ethane) with a bisphenol A epoxide,
the formation of an oxazoline structure has been proposed. 278
3.4.8.6 Fluorescence Response
Fluorescence is a very sensitive and non-destructive technique to monitor
the curing. The fluorescence response from chemical labels and probes
enables the changes to be followed in the surroundings of the chemical
label. In the curing process, the viscosity may change about six orders of
magnitude.
A change in the viscosity of the medium leads to a decrease in the
non-radiative decay rate and consequently a change in the fluorescence
quantum yield. The reaction medium acts as a thermal bath for the excited
fluorescent molecule. When the monomers become fixed in forming
a crosslinked polymer, a reduction of translational, rotational, and vibrational
degrees of freedom in the bath takes place. Therefore, a reduction
in the number of non-radiative deactivation pathways and an increase in
fluorescence intensity occurs.
1-Pyrenesulfonyl chloride (PSC) was used as a chemical label for
silica epoxy interfaces, the surface coated with (3-aminopropyl)triethoxysilane,
because it reacts easily with amine groups, yielding sulphonamide

Epoxy Resins 197
C
O OH
CH 2
H 3 C CH 3
N
S O
NH 2
DNS-EDA
O
CH 2
NH
9-Anthroic acid
Figure 3.21: 9-Anthroic acid, 5-dimethylaminonaphthalene-1-(2-aminoethyl)-
sulfonamide (DNS-EDA)
derivatives. 279 Also 9-anthroic acid, its ester derivatives and 5-dimethylaminonaphthalene-1-(2-aminoethyl)sulfonamide
(DNS-EDA), c.f. Figure
3.21 are common fluorescence dyes.
280, 281
3.4.9 Thermal Curing
By investigating the curing of a commercial epoxy prepolymer with imidazole
curing agents, it has been verified that the cure schedule influences
the properties of the end product. The highest thermal stability of the polymers
can be achieved by isothermal cure schedules. Samples cured by a
temperature program showed lower glass transition temperatures. In a series
of temperature programmed curing experiments, a lower heating rate
resulted in higher transition temperatures and superior thermal stability.
The initial and postcure schedules are thus of critical importance for the
final properties of the polymer. 282
3.4.10 Microwave Curing
Due to increasing application in the aerospace and microelectronics industries
the demand for accelerated curing has emerged. In particular, for the
microelectronics industry, the curing of thermoset systems has become a
bottleneck of the whole production process. Besides photo curing, curing
with γ-rays and electron beams is an alternative.
Microwave curing of materials has the potential to deliver several
major advantages over conventional thermal processing. One of these is

198 Reactive Polymers Fundamentals and Applications
a decrease in the time necessary for manufacture since another potential
advantage is that the power is directed to the sample. The microwave energy
is absorbed throughout the body of the material rather than relying
on thermal conduction and convection. Therefore, the energy consumed is
less than thermal curing.
Experiments with the diglycidyl ether of bisphenol A and three types
of curing agents, i.e., 4,4 ′ -Diaminodiphenylsulfone, 4,4 ′ -Diaminodiphenylmethane,
and m-phenylene diamine with various energies of microwave
energy showed that in comparison to thermal curing microwave curing is
faster. The glass transition temperatures are somewhat lower in the case
of the products cured with microwave technology in comparison to those
cured by thermal methods. 283 However, the curing performance is strongly
dependent on the curing agent used. 284 The interfacial shear strengths in
those composites cured with microwave techniques are comparable with
being thermally postcured. 285
3.5 PROPERTIES
Mechanical properties of epoxy resins can be correlated and traced back
to the constituting monomers. The mechanical properties of epoxy resins
depend on the flexibility of the segments and on the crosslinking density.
Epoxy resins shrink in the course of curing less than vinyl resins.
It is important to distinguish between the shrinkage that occurs before
gelling and after gelling. Only a shrinkage that occurs after gelling
results in residual stress in the final product.
Epoxy resins can exhibit several thermal transition regions, depending
on the chemical nature of the monomers. These transitions influence
the curing. If a glass transition occurs during curing at the temperature applied,
the individual reactive parts of the pendant molecules can no longer
move sufficiently and the curing reaction freezes at this conversion. However,
raising the temperature effects further curing.
Cycloaliphatic epoxy resins have a low viscosity. The cured resins
exhibit a high glass transition temperature. On the other hand, they exhibit
low break elongation and toughness because of their high crosslinking density.
Epoxy resins show good electrical properties. Of course, the electrical
properties are affected by the moisture content. On the other hand,
the resins can be made electrically conductive, by metal particles such as

Table 3.14: Epoxies Based on Hybrid Polymers
Compounds
Epoxy Resins 199
Remark/Reference
Siloxane polymer with pendant epoxide rings
286–288
Epoxy polyurethane hybrid resins
Maleimide-epoxy resins
289
silver and copper. Epoxy resins adhere by forming strong bonds with the
majority of surfaces, therefore, an important application is in adhesives.
Epoxy resins have excellent resistance to acids, bases, organic and inorganic
solvents, salts, and other chemicals.
3.5.1 Hybrid Polymers and Mixed Polymers
Hybrid polymers and mixed polymers are summarized in Table 3.14. These
include silicone-epoxy hybrid polymers, urethane-epoxy hybrid polymers,
and maleimide-epoxy polymers.
3.5.1.1 Epoxy-Siloxane Copolymers
A siloxane polymer with pendant epoxide rings on the side chain of
the polysiloxane polymer backbone, when blended with diglycidyl bisphenol
A ether and cured, increases the mobility of the crosslinked network
and the thermal stability. Graft siloxane polymer with pendant epoxide
rings can be synthesized by the hydrosilylation of poly(methylhydrosiloxane)
with allyl glycidyl ether. 286
Aminopropyl-terminated poly(dimethylsiloxane) blended in an epoxy
resin shows an outstanding oil and water repellency in coatings. 290 The
peel strength of a pressure-sensitive adhesive affixed to the modified epoxy
resin also decreases. Polyether/poly(dimethylsiloxane)/polyether triblock
copolymers added in amounts of 5 ca. phr, efficiently reduce the static
friction coefficient of the cured blends upon steel. 291
Silsesquioxanes are organosilicon compounds with the general formula
[RSiO 3/2 ] n , c.f. Figure 8.1, at page 323. Silsesquioxane (SSO) solutions
were reacted with diglycidyl either of bisphenol A with 4-dimethylaminopyridine
as initiator, to result in SSO-modified epoxy networks. The
modification with SSO increased the elastic modulus in the glassy state.
This is explained by an increase in the cohesive energy density. 292

200 Reactive Polymers Fundamentals and Applications
3.5.1.2 Maleimide-Epoxy Resins
Maleimide-epoxy resins are based on N-(p-carboxyphenyl)maleimide and
allyl glycidyl ether. 289 The resin can be cured thermally and is suitable as
one component resin.
3.5.2 Recycling
3.5.2.1 Solvolysis
The recycling of wastes of epoxy resins is very difficult, because of the
inherent infusibility and insolubility of the materials. Often the composite
materials contain reinforcing fibers, metals, and fillers. 293
Efficient destruction of the organic material in composites can be
achieved by thermolysis processes or by incineration processes. These
methods yield considerable amounts of non-combustible residues or decomposition
products that are not attractive for further use.
Valuable recycled materials can be obtained by solvolysis methods.
Here, the depolymerization products and reinforcing fibers can be retrieved.
By glycolysis with diethylene glycol, the ester linkages of a bis epoxide
(diglycidyl ether of bisphenol A) that is cured with a di anhydride,
are cleaved. The transesterification is catalyzed by titanium n-butoxide.
In the case of 70% glass fiber/epoxide-anhydride composites, the
glass fibers can be recovered. The liquid depolymerization products may
be converted to polyols, components for unsaturated polyester resins, etc.
The glycolysis of amine cured epoxide resins shows no volatile nitrogen
compounds. The most favored path of degradation is the decomposition
of the ether linkage of bisphenol A to yield oligomers with phenol
groups. 294 The separation of the phenolic compounds from the glycolysis
products can be achieved by liquid-liquid extraction.
The glycolysis products can be basically used as a polyol in production
of polyurethane. However, the hydroxyl value is much too high for
polyurethane production.
It has been suggested to use the solvolysis products from epoxide
resins in combination with other solvolysis products, e.g., solvolysis products
from wastes from PET for semi interpenetrating networks based on
PET hydrolyzate and epoxies. 295

Epoxy Resins 201
3.5.2.2 Reworkable Epoxies for Electronic Packaging Application
Epoxy resins show excellent longevity and resistance to ageing. This is due
to the formation of an insoluble and infusible crosslinked network during
the cure cycle. This property is sometimes seen as a drawback from the
repairability standpoint.
During the manufacture of expensive electronic parts, such as multi
chip modules, several chips are mounted onto one high density board. If
one chip is damaged, then the whole board will become useless. The same
is true if some special electronic parts in a board need to be modified because
of progress in technology.
Therefore, the availability of a reworkable material, that is, one that
undergoes controlled network breakdown, expands the potential routes to
repairing, replacing, or removing assembled structures and devices. Implementing
reworkable materials early could expand recycling concerns that
could be faced in the near future.
An effective solution is to use thermally reworkable epoxide resins
for underfilling.
296, 297
In such systems, the cured epoxy network can be
degraded by locally heating to a suitable temperature, and the faulty chip
could be replaced.
Commercial cycloaliphatic epoxides degrade at about 300°C. Epoxides
with secondary or tertiary ester bonds (as shown in Figure 3.22)
have been demonstrated to decompose at temperatures between 200°C and
300°C. 216, 298 The epoxides are cycloaliphatic compounds and can be basically
derived by the esterification of cyclohexenoic acid with α-terpineol
with subsequent epoxidation. Diepoxides with carbamate and carbonate
groups 299 also degrade in this temperature range. In comparison to chemical
degradation methods, heat to degrade the network can be localized
more easily in the rework process, thereby allowing for more precise control
over the region of the board that will be reworked.
Instead of branched ester structures, ether structures, c.f. Figure
3.22, bottom, are also suitable candidates for thermolabile linkages in epoxides.
231
Thio links can be used to form a reversible network. 219 Further diepoxides
connected via acetal links can be used for the introduction of reversible
chemical links. 300 This type of network can be degraded in acidic
solvents.

202 Reactive Polymers Fundamentals and Applications
O
O
O
O
O
CH 3
O
O
O
O
CH 3
O
O
CH 3
O
O
CH 3
O
O
CH 3 O
CH 3
O
CH 3
O O
CH CH2
O
1,2-Bis (2,3-epoxycyclohexyloxy)
propane
O CH 3 CH 3
O
C CH
CH 3
O
O
2-Methyl-2,4-bis (2,3-epoxycyclohexyloxy)
pentane
Figure 3.22: Epoxides with Thermally Cleavable Groups for Controlled Network
Breakdown: Top Esters, Bottom Ethers. 1,2-Bis(2,3-epoxycyclohexyloxy)propane,
2-Methyl-2,4-bis(2,3-epoxycyclohexyloxy)pentane

Epoxy Resins 203
3.6 APPLICATIONS AND USES
3.6.1 Coatings
The largest applications of epoxy resins are in coatings. Epoxy resin coatings
have excellent mechanical strength and adhesion to many kinds of
surfaces. They are corrosion resistant and resistant to many chemicals.
Coatings find applications in various paints, white ware, and automotive
and naval sectors, for heavy corrosion protection of all kinds. Epoxy coating
formulations are available both as liquid and solid resins. Epoxy acrylic
hybrid systems are used as coatings for household applications, e.g., indoor
and outdoor furniture and metal products.
Waterborne coatings are dispersions of special formulations of the
resins with suitable surfactants. These materials can be applied by electrodeposition
techniques. Powders can be applied as coatings by fluidizedbed
techniques.
3.6.2 Foams
Epoxy resins can be fabricated to make foams. Foamable compositions
have been described from a novolak resin, an epoxy resin, and a blowing
agent. Water can act as a blowing agent, especially when higher density
foams are required. Novolak resins are typically suspended in an aqueous
solution, that is the blowing agent. 301 Encapsulated calcium carbonate or
anhydrous sodium bicarbonate are suitable blowing agents. 302 Phosphoric
acid is used to catalyze the polymerization of resin and it also reacts with
the carbonate core to generate a blowing gas to form voids.
3.6.3 Adhesives
Approximately 5% of total epoxy resin production is used in adhesive applications.
Epoxide resin adhesives are formulated two-component systems
that cure at room temperature, and as hot curing systems in the form
of films and tapes. Among others, acrylates are suitable modifiers for epoxy
adhesives.
3.6.4 Molding Techniques
Epoxy resins are used in all known reactive molding techniques. Non-reinforced
articles can be molded with aluminum molds. This is used for

204 Reactive Polymers Fundamentals and Applications
electrical coil covering, etc. In electronic industries various embedment
techniques, i.e., casting and potting, and impregnation are important applications.
Laminated sheets are used for the fabrication of printed circuit
boards in the electronics industry.
Pultrusion and lamination are common techniques. Laminated articles
are also used in building constructions for concrete molds, honeycomb
cores, reinforced pipes, etc. Epoxy resins are superior to polyesters where
adhesion and underwater strength are important.
3.6.5 Stabilizers for Polyvinyl Chloride
Epoxy resins with monofunctional epoxy groups in the prepolymer are effective
in stabilizing polyvinyl chloride against dehydrochlorination during
processing and use, in comparison to tribasic lead sulphate. Lead-based
stabilizers for polyvinyl chloride are mostly banned and only allowed for
a few applications. For example, the replacement of lead-based stabilizers
by epoxy stabilizers will improve the environmental toxicity of lead in
water flowing through PVC pipes. 303
3.7 SPECIAL FORMULATIONS
3.7.1 Development of Formulations
In practice, epoxy resins are composed of a wide variety of individual components.
To obtain a composition with the desired properties, a great deal
of know-how is required.
A solid knowledge of the structure-property relationships can serve
as a valuable tool for the art of formulation. 304
On the other hand, there are methods that are helpful in the development
of formulations. In particular, statistical methods can save time.
An overview of such methods is given in the standard book of Box and
Hunter. 305 Instead, most studies on epoxy formulation are done by the
“one variable at a time” method. This means that only one parameter of
interest is changed while the other remaining parameters are kept constant.
This strategy provides admittedly valuable information, however, it does
not allow a good insight into mutual interactions of formulation parameters.
The usefulness of statistical methods in the field of formulation of
epoxy adhesives has been demonstrated in the literature. 306

Epoxy Resins 205
3.7.2 Restoration Materials
A variety of epoxy resins are used for the consolidation of stone monuments
in an outdoor environment. For these applications good weathering
resistance and sufficient penetration depth is mandatory.
A suitable epoxy monomer for restoration materials is 3-glycidoxypropyltrimethoxysilane
(GLYMO) and amine curing agent is (3-aminopropyl)triethoxysilane
(ATS). This monomeric composition penetrates
deep enough to exceed the maximum moisture zone and creeps beyond the
damaged layers.
The alkoxysilane groups are hydrolytically unstable and generate
silanol groups which may crosslink with one another, and also form bonds
to the hydroxyl groups present in the stone, thus anchoring the organic
polymer onto the lithic matrix.
307, 308
The curing kinetics of hybrid materials prepared from diglycidyl
ether of bisphenol A and GLYMO has been investigated using poly(oxypropylene)diamine
as a hardener. 309 The total conversion of epoxy groups
was found to decrease with increasing content of GLYMO. The experimental
data scattered, which was attributed to an uncontrolled initial hydrolysis
of GLYMO caused by the varying air humidity during the sample preparation.
3.7.3 Biodegradable Epoxy-polyester Resins
Biodegradable epoxy-polyester resins consist of polyesters with pendent
epoxidized allyl groups. 230 These polyesters are synthesized from succinic
anhydride and allyl glycidyl ether and butyl glycidyl ether with benzyltrimethylammonium
chloride as catalyst.
The butyl glycidyl ether acts as a diluent for the allyl functionalities,
in order to reduce the amount of pendant allyl groups in the chain. The
epoxidation of the polyesters is achieved by m-chloroperbenzoic acid. The
epoxy-polyester resins can be cured with glutaric anhydride.
3.7.4 Swellable Epoxies
Hydrophilic polymers find applications in medicine and agriculture, owing
to their biocompatibility. 310
Crosslinked structures, prepared from sucrose and 1,4-butanediol diglycidyl
ether (1,4-BDE) are hydrogels with water regain values of 30%. 311

206 Reactive Polymers Fundamentals and Applications
The crosslinking is achieved with triethylamine or sodium hydroxide. Triethylamine
gives rise to end-capped diethylamine groups. By this reaction
the ethyl group is left behind as ethyl ether in the sucrose.
The ring-opening polymerization of epoxy end-terminated poly(ethylene
oxide) (PEO) can serve to synthesize crosslinked materials with an
exceptional swelling behavior. 312 These gels have attracted interest for use
as drug delivery platforms.
3.7.5 Reactive Membrane Materials
Reactive membrane materials can be prepared from 2-hydroxyethyl methacrylate
and glycidyl methacrylate by radical photopolymerization.
Enzymes, such as cholesterol oxidase, can be directly immobilized
on the membrane by the reaction of the amino groups of the enzyme and
the epoxide groups of the membrane. The immobilization improves the pH
stability of the enzyme as well as its thermal stability. The immobilized
enzyme activity remains quite stable. 313
Poly(2-hydroxyethyl methacrylate) membranes can be also activated
by direct treatment with epichlorohydrin. On such materials poly(L-lysine)
could be immobilized. 314 Such a membrane with immobilized poly(Llysine)
can be utilized as an adsorbent for DNA adsorption experiments.
3.7.6 Controlled-release Formulations for Agriculture
In order to introduce pendant dichlorobenzaldehyde functionalities as acetals,
the epoxide functionalities in linear and crosslinked poly(glycidyl
methacrylate) are hydrolyzed to diol groups. In the second step the pendant
diol groups in the polymers are acetalized by dichlorobenzaldehyde. 315 Dichlorobenzaldehyde
is a bioactive agent that is slowly released under various
conditions.
3.7.7 Electronic Packaging Application
In flip-chip manufacturing, filled polymers serve as underfilling. Underfilling
is the plastic material which is inserted in the gap between integrated
circuit and the substrate. The gap is approximately 50 to 75 µm wide. The
underfilling is used to couple the chip and the substrate mechanically. It decreases
the residual stress in the solder joints caused by thermal expansion.

Epoxy Resins 207
The materials used for underfilling should have good wetting characteristics,
significant adhesion, high conductivity, and should not form voids.
The prevention of void formation is essential for thermal conductivity. Low
viscosity of the monomeric resin is essential to achieve void-free underfillings.
A resin with a lower viscosity allows the addition of a greater amount
of filler. The viscosity of a benzoxazine resin can be reduced by the incorporation
of a low-viscosity epoxy resin. The benzoxazine resin imparts a
low water uptake, a high char yield, and mechanical strength. The epoxy
resin reduces the viscosity of the mixture and results in higher crosslinking
density and improved thermal stability of the material. A melt viscosity of
about 0.3 Pas at 100°C can be achieved. 316
3.7.8 Solid Polymer Electrolytes
The interest in solid polymer electrolytes arises from the possibility of applications
of polymer ionic conductors in energy storage systems, electrochromic
windows, and fuel cells or sensors operating from subambient to
moderate temperatures. 317
Hosts for solid polymer electrolytes are poly(ethylene oxide) (PEO),
segmented polyurethanes with poly(ethylene oxide)/ poly(dimethylsiloxane)
318 and with poly(ethylene oxide)/perfluoropolyether 319 blocks, respectively,
as well as crosslinked epoxy-siloxane polymer complexes.
320, 321
The copolymers are immersed in a liquid electrolyte (1 M LiClO 4 in propylene
carbonate) to form gel-type electrolytes.
Solvent-free solid polymer electrolytes are based on polyether epoxy
crosslinked with poly(propylene oxide) polyamines. 322 The crosslinked
polyether networks are doped with LiClO 4 . The network is prepared by
mixing epoxy monomer, the curing agent dissolved in acetone and LiClO 4 .
To obtain films the mixture is poured on plates and cured at elevated temperatures.
The electric conductivity of the polymer electrolyte is dependent
on interactions between ions and the host polymer.
3.7.9 Optical Resins
3.7.9.1 Lenses
In comparison to glasses, plastics have low density, i.e., comparative low
weight, are fragmentation-resistant and can be easily dyed. Therefore, optical
materials made from organic polymers are attractive for optical ele-

208 Reactive Polymers Fundamentals and Applications
ments such as lenses of eyeglasses and cameras. However, the refractive
index of the standard resins is relatively small. Therefore, there is a need
to use materials with high refractive index and low chromatic aberration.
The introduction of sulfur into the monomers raises the refractive index.
Sulfur-containing resins have a high refractive index, low dispersion,
and a good heat stability. 23, 216 Components for epoxy resin with high refractive
index are obtained from bis(3-mercaptophenyl)sulfone (BEPTPhS)
and epichlorohydrin.
A sulfur-containing curing agent is trimercaptotriethylamine
(TMTEA) which can be obtained from triethanolamine. Besides sulfurcontaining
epoxies, with tailor-made polyphosphazenes, refractive indices
ranging from 1.60 to 1.75 can be achieved. 323
3.7.9.2 Liquid Crystal Displays
In liquid crystal displays (LCDs), control of the alignment of the liquid
crystal (LC) molecules is one of the most important issues with respect
to the quality of LCDs. The rubbing method does not satisfy the recent
demands for alignment quality. The photoalignment method reduces contaminations
that lower the contrast ratio and electrostatic buildup that can
cause failure of thin film transistors. 324
Nematic liquid crystalline materials can be aligned homogeneously
on a photoreactive polymer film when exposed to linearly polarized light.
Thermal stability and photostability of the alignment layer is a crucial parameter
and the alignment layer must be transparent in the visible region
for a display device. Certain photocrosslinkable polymer systems meet
these demands. Derivatives of cinnamic ester and cinnamic acid are suitable
candidates for phototransformations. In particular, the anisotropic
[2+2] cycloaddition of the cinnamate moiety can induce an irreversible
alignment of a low molecular weight liquid crystal. Polymers with the
chalcone group in the side chain react in a similar way. A chalcone-epoxy
compound can be synthesized from 4,4 ′ -Dihydroxychalcone and epichlorohydrin
in the same way as with bisphenol A. In this photoreactive epoxy
oligomer, the photosensitive unsaturated carbonyl moieties are located in
the main chain. For the polymerization of the epoxy groups, triarylsulfonium
hexafluoroantimonate (TSFA) is a suitable photoinitiator.
The photodimerization of the chalcone precedes the photopolymerization
of the epoxy groups. Under continuous irradiation, the anisotropic

Epoxy Resins 209
O
HO
C
CH
CH
OH
1,3-Bis-(4-hydroxy-phenyl)-propenone
Figure 3.23: 4,4 ′ -Dihydroxychalcone
photocrosslinked chain molecules can be frozen by the photopolymerization
of the epoxy groups at both ends of the compound. Without a photoinitiator,
the end groups of the oligomer are not fixed. Therefore, there are
two kinds of photochemical reactions that enhance the photostability of the
induced optical anisotropy. 24
3.7.9.3 Holography
Materials for high-resolution holograms, which can be used on holographic
optical elements such as heads-up display, consist of a bisphenol-type epoxy
resin and a radically polymerizable aliphatic monomer. A diaryliodonium
salt and 3-ketocoumarin (KCD) are used as a complex initiator. The
formation of the image is based on the radical polymerization of the monomer
initiated by a holographic exposure, followed by the cationic polymerization
of the epoxy resin by UV-exposure after post-exposure baking. 325
3.7.9.4 Nonlinear Optical Polymers
Second-order nonlinear optical (NLO) polymeric materials are of interest
because of their potential applications in integrated optical devices, such as
waveguide electro-optic modulators, switches, and optical frequency doubling
devices. The interest in these polymeric materials is mainly due to
their large optical nonlinearities, low dielectric constants, and ease of production.
For practical use, the poled polymers must possess large secondorder
optical nonlinearities which should be sufficiently stable at ambient
temperature for a long period of time.
A high crosslinking density and stiffness makes interpenetrating networks
attractive for such applications. The possibility of introduction of
chromophores that impart the nonlinear optical properties is essential.

210 Reactive Polymers Fundamentals and Applications
An example for an NLO active interpenetrating polymer network is
an epoxy prepolymer and a phenoxy-silicon polymer. 4,4 ′ -Nitrophenylazoaniline
(Disperse Orange 3) functionalized with crosslinkable acryloyl
groups is incorporated into the epoxy prepolymer. The epoxy prepolymer
forms a network through acryloyl groups which are reactive at high temperatures
without the aid of any catalyst or initiator. The phenoxy-silicon
polymer is based on an alkoxysilane dye made of (3-glycidoxypropyl)trimethoxysilane
and Disperse Orange 3, and 1,1,1-tris(4-hydroxyphenyl)-
ethane, as a multifunctional phenol. The two networks are formed simultaneously
and separately at 200°C. 326
Interpenetrating polymer networks based on crosslinked polyurethane/epoxy
based polymer can be obtained by simultaneously crosslinking
phenol-capped isocyanates with 2-hydroxypropyl acrylate and curing epoxy
prepolymers. To each of these components phenylazo-benzothiazole
chromophore groups are linked. The crosslinked polyurethane and the epoxy
based polymer show glass transition temperatures of 140 and 178°C,
respectively, whereas the interpenetrating network shows two T g ’s at 142
and 170°C. Thin, transparent poled films of the crosslinked polymers can
be prepared by spin-coating, followed by thermal curing and corona poling
at 160°C. The polymers exhibit a long-term stability of the dipole alignment
at 120°C. 327
3.7.10 Reactive Solvents
Polymers can be processed more easily by using solvents. The disadvantage
the necessary removal of the solvent. This might be tedious and a
time consuming step. Also, environmental hazards may arise. Reactive
solvents are those that polymerize after the molding process. In this case,
no removal is necessary. Accordingly, intractable polymers can be processed
by the utilization of reactive solvents. The polymers are dissolved
in a liquid curable resin. Then the homogeneous solution is transferred into
a mold. The curing of the reactive solvent takes place in the mold.
In the course of curing, molecular weight of the resin increases. A
phase separation and phase inversion are likely to take place. The dissolved
polymer should become the continuous matrix, and the reactive solvent is
dispersed as particles in the matrix. So the final properties of the system
are dominated by the properties of the thermoplastic phase.
The main advantage of this procedure is a lower processing temper-

Epoxy Resins 211
ature because of decrease with viscosity. There is no need to remove the
solvent which is bounded to the polymer.
3.7.10.1 Poly(butylene terephthalate)
Although poly(butylene terephthalate) can be relatively easily processed,
a further improvement of the processing is required when a difficult flow
length or mold geometry has to be mastered. 328
3.7.10.2 Poly(phenylene ether)
Poly(2,6-dimethyl-1,4-phenylene ether) (PPE) can be dissolved at elevated
temperatures in an epoxy resin and the solution can be easily transferred
into a mold or into a fabric. 329
During the curing of epoxy resin, a phase separation and a phase
inversion occurs. The originally dissolved PPE then becomes the continuous
phase. The dispersed epoxy particles become an integral part of the
system and act as fillers or as toughening agents, depending on the type of
epoxy resin. An important parameter for the final physical and mechanical
properties is the size of the dispersed particles.
The size of the dispersed phase is governed by the competition between
the coalescence of dispersed droplets, and the vitrification or gelation
rate, respectively, induced by the curing process. For the coalescence,
the viscosity of the system plays an important role which is dependent on
the curing temperature. The viscosity can be further controlled by adding
another thermoplastic material such as poly(styrene).
Blends of poly(phenylene ether) and an epoxy resin cured with dicyandiamide
materials show a two-phase morphology. To improve the uniformity
and miscibility, triallyl isocyanurate (TAIC) can be used as an insitu
compatibilizer. 330 Also the fracture toughness of the modified systems
is improved by adding TAIC.
3.7.11 Encapsulated Systems
Photopolymerizable liquid encapsulants (PLE) for microelectronic devices
may offer important advantages over traditional transfer molding compounds.
A PLE is comprised of an epoxy novolak-based vinylester resin,
fused silica filler, a photoinitiator, a silane coupling agent, and optionally
of a thermal initiator. 331

212 Reactive Polymers Fundamentals and Applications
3.7.12 Functionalized Polymers
The epoxy group can be used to functionalize various polymers, to achieve
certain desired properties.
3.7.12.1 Tougheners
Vinylester-urethane hybrid resins (VEUH) can be toughened by functionalized
polymers. 332 Suitable basic materials for toughening are nitrile rubber,
hyperbranched polyesters, and core/shell rubber particles. These materials
can be functionalized with vinyl groups, carboxyl groups, and epoxy
groups.
Toughness is improved in VEUH when the functional groups of the
modifiers react with the secondary hydroxyl groups of a bismethacryloxy
vinylester resin and with the isocyanate groups of the polyisocyanate compound.
Functionalized epoxy and vinyl hyperbranched polymers are less
efficient as toughness modifiers in comparison to functionalized liquid nitrile
rubber. They show no adverse effect on the mechanical properties.
3.7.13 Epoxy Resins as Compatibilizers
Most polymers are not miscible with one another. This lack of miscibility
results in poor properties of polymeric blends. However the properties can
be improved by adding compatibilizers. Due to the inherent reactivity of
the epoxy group, an interfacial chemical bonding can be achieved which
results in small particle sizes of the blend. This enhances the properties of
the blends. Some compatibilizers based on epoxy compounds are shown
in Table 3.15.
3.7.13.1 Polyamide Blends
Blends of polyamide 6 and epoxidized ethylene propylene diene (e-EPDM)
can improve the toughness of polyamide 6. The particle size of e-EPDM
is much smaller than that of unepoxidized EPDM (u-EPDM) rubber in a
polyamide 6 matrix. It is believed that the epoxy group in e-EPDM reacts
with the polyamide 6 to form a graft copolymer. Thus an interfacial
compatibilization takes place. 333
Styrene/glycidyl methacrylate (SG) copolymers are miscible with
syndiotactic poly(styrene) (s-PS). In blends of polyamide 6 (PA6) with
syndiotactic poly(styrene), the epoxide units in the SG phase are capable

Epoxy Resins 213
Table 3.15: Compatibilizers Based on Epoxy Compounds for Various
Polymers
Polymer 1 Polymer 2 Compatibilizer
PA6 PS Styrene/glycidyl methacrylate copolymers
PA6 ABS Glycidyl methacrylate/ methyl methacrylate copolymers
(GMA/MMA)
PA6 PP Poly(ethylene) functionalized with maleic anhydride
PBT PPE Low molecular weight epoxy compounds
PBT SAN Terpolymers of methyl methacrylate, glycidyl
methacrylate (GMA), and ethyl acrylate
PA6 Polyamide 6
PS Poly(styrene)
PBT Poly(butylene terephthalate)
ABS Acrylonitrile butadiene styrene (ABS) copolymers
PP Poly(propylene)
SPE Poly(phenylene ether)
SAN Styrene/acrylonitrile copolymers
of reacting with the PA6 end groups. Copolymers of styrene/glycidyl methacrylate
are effective in reducing the s-PS domain size and improving the
interfacial adhesion. The best compatibilization is found with a content of
5% glycidyl methacrylate (GMA) in the SG copolymer. Both the strength
and modulus of the blend are improved by the addition of the SG copolymers.
However, a loss in toughness is observed at loadings of copolymer.
The addition of SG copolymer to the blend has little influence on the crystallization
behavior of the polyamide component. The crystallinity of s-PS
is reduced. 334
Blends of nylon 6 with acrylonitrile/butadiene/styrene (ABS) copolymers
and with styrene/acrylonitrile copolymers (SAN) can be prepared
using glycidyl methacrylate/methyl methacrylate (GMA/MMA) copolymers
as compatibilizing agents. 335
Known compatibilizers for blends of low density poly(ethylene)
(LDPE) and polyamide 6 (PA6) are ethylene/acrylic acid copolymers
(EAA), maleic anhydride functionalized polyethylenes, and an ethylene-
/glycidylmethacrylate copolymer (EGMA). The effectiveness of EGMA
as a reactive compatibilizer is comparable to that of the EAA copolymers.
However the effectiveness is lower than that of poly(ethylene) functionalized
with maleic anhydride. A possible reason is the reaction of the pendent

214 Reactive Polymers Fundamentals and Applications
epoxy groups with the amide groups that attach the polyamide molecules
together and hinder the dispersion in this way. 336
In blends of poly(propylene) and polyamide 6, poly(ethylene) functionalized
with maleic anhydride showed better compatibilization than
glycidyl methacrylate. The compatibilizing effect of the PP-MA for the
PP/Ny6 blends was more effective than poly(propylene) functionalized
with glycidyl methacrylate. 337
Glycidyl methacrylate copolymers are miscible with SAN. The epoxide
unit can react with the polyamide end groups. The compatibilizer
can form graft copolymers at the polyamide/SAN interface during melt
processing. Incorporation of the compatibilizer does not significantly improve
the impact properties of nylon 6/ABS blends.
The direct mixing of polyamide and poly(propylene) leads to incompatible
blends with poor properties. Poly(propylene) functionalized with
glycidyl methacrylate can be used as a compatibilizer in the blends of PP
and nylon 6. 338
3.7.13.2 Poly(butylene terephthalate)
Poly(butylene terephthalate) (PBT) and poly(phenylene ether) (PPE) can
be compatibilized by low molecular weight epoxy compounds. 339 Terpolymers
of methyl methacrylate, glycidyl methacrylate (GMA), and ethyl
acrylate are effective reactive compatibilizers for blends of (Poly(butylene
terephthalate) (PBT) with styrene/acrylonitrile copolymers (SAN) or ABS
materials. 340 During melt processing, the carboxyl end groups of PBT react
with epoxide groups of GMA to form a graft copolymer.
In blends of poly(butylene terephthalate) with an ethene/ethyl acrylate
copolymer (E/EA), which show the general features of uncompatibilized
polymer blends, such as a lack of interfacial adhesion and a relatively
coarse unstabilized morphology, no evidence of transesterification reaction
was found. In contrast, blends containing both virgin and modified
E/MA/GMA terpolymers show a complex behavior. Two competitive reactions
take place during the melt blending:
1. Compatibilization due to interfacial reactions between PBT chain
ends and terpolymer epoxide groups, resulting in the formation of
E/MA/GMA/PBT graft copolymer, and
2. Rapid crosslinking of the rubber phase due to the simultaneous
presence of hydroxyl and epoxide groups on E/MA/GMA chains.

Epoxy Resins 215
The competition reactions between compatibilization and crosslinking
are dependent on the type of the terpolymer, since the modified E/-
MA/GMA contains hydroxyl groups before mixing. The in-situ compatibilization
reaction of the pendent epoxy groups with PBT causes the formation
of E/MA/GMA hydroxyl groups. 341
The concentration of carboxyl groups at the PBT chain ends influences
the rate of compatibilization but not the final morphology. The lower
the concentration, the slower the morphology development. Ternary blends
of PBT/(E-MA-GMA/E-MA) exhibit a very fine morphology. Here the development
of the morphology is mildly influenced by the crosslinking rate
of the rubber phase caused by the shear rate in the mixing chamber. 342
3.7.14 Surface Metallization
Established methods for the metallization of a polymer surface are 343
1. Electroless plating,
2. Vacuum deposition or metal spraying, and
3. Coating using a metallic paint.
A more recent method has been described that utilizes the reduction
of metal ions incorporated directly in the polymer. It has been shown that
cobalt or nickel ions integrated in an epoxy network could be reduced to
the pure metal by dipping the film in an aqueous NaBH 4 solution. 229
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4
Phenol/formaldehyde Resins
Phenolic resins are known as the oldest thermosetting polymers. They
still have many industrial applications in sectors such as automotive, computing,
aerospace, and building. Reviews concerning phenolic resins are
given, for example, by Gardziella and by Burkhart. 1–3
Phenolic resins are thermosetting resins produced by the condensation
of a phenol with an aldehyde wherein water is produced as a byproduct.
Typically, the phenol is phenol itself and the aldehyde is formaldehyde,
but substituted phenols and higher aldehydes have been used to
produce phenolic resins with specific properties such as reactivity and flexibility.
The variety of phenolic resins available is quite large as the ratio of
phenol to aldehyde, the reaction temperature, and the catalyst selected can
be varied. 4
Phenolic resins fall into two broad classes:
1. Novolak resins,
2. Resol resins.
Resol resins are single stage resins and novolak resins are two-stage
resins. Resol resins are typically produced with a phenol, a molar excess of
formaldehyde, and an alkaline catalyst. The reaction is controlled to create
a non-crosslinked resin that is cured by heat without additional catalysts to
form a three-dimensional crosslinked insoluble, infusible polymer. In contrast,
novolak resins are typically produced with formaldehyde, at molar
excess of phenol, and an acid catalyst.
241

242 Reactive Polymers Fundamentals and Applications
Table 4.1: Types of Novolak Resins
Novolak Resin Type
Ratio ortho:para
High ortho novolak 75:25
General-purpose novolak 45:55
High para novolak 38:62
Suitable acid catalysts include the strong mineral acids such as sulfuric
acid, phosphoric acid, and hydrochloric acid as well as organic acid
catalysts such as oxalic acid, p-toluenesulfonic acid, and inorganic salts
such as zinc acetate or zinc borate.
The reaction produces a thermoplastic polymer that can be melted
but will not crosslink upon the application of heat alone. The resulting
novolak thermoplastic resin can be crosslinked by the addition of a novolak
curing agent.
There are various types of novolak resins with different ortho-to-para
ratios of the methylene linkages: high ortho novolak resins (HON), general-purpose
novolak resins (GPN), and high para novolak resins (HPN).
The characterization is listed in Table 4.1.
Resol resins require no additional curing agents. They can be cured
by heat reactive. However, they have a low shelf life. Curing for resols and
hexamine-cured novolaks proceeds at 150 to 200°C.
4.1 HISTORY
As early as in 1872, Baeyer ∗ reported about reactions of phenols and aldehydes
that give resinous substances. In 1899, Arthur Smith patented phenol/formaldehyde
(PF) resins to replace ebonite as electrical insulation. In
1899, Arthur Smith filed patent application for a method for substituting
ebonite, wood, etc. 5 In 1907 Baekeland † mixed phenol and formaldehyde
and obtained phenol/formaldehyde resins. In 1907 he filed the first of 117
patents on phenol/formaldehyde resin systems. 6
Before he was engaged in phenolic resins, Baekeland worked on the
development of copying papers. Such a product became famous under
the name Velox. Formica was first produced by Herbert Faber and Daniel
O’Conor as an electrical insulator in 1910. Formica is a composite that
∗ Adolf von Baeyer, born in Berlin 1835, died in Starnberg 1917
† Leo Hendrick Baekeland, born in Gent 1863, died 1944

Phenol
Phenol/formaldehyde Resins 243
Table 4.2: Phenolic Monomers
Remark/Reference
Phenol
Most common
Bisphenol A
2,2-Bis(4-hydroxyphenyl)propane
Bisphenol F
Bis(4-hydroxyphenyl)methane
Bisphenol B
2,2-Bis(4-hydroxyphenyl)butane
Resorcinol
Cresols
Methylphenols
m-Cresol Photoresists 7
p-Cresol Photoresists 7
2-Cyclohexyl-5-methylphenol Photoresists 7
Xylenols
m-Aminophenol
8
m-Methoxyphenol
8
β-Naphthol
Cardanol
Cardol
Aldehyde
Table 4.3: Aldehyde-type Components
Remark/Reference
Formaldehyde
Most common
Paraformaldehyde
9
Butyraldehyde
Hot-melt adhesives and as binders for
non-wovens 10
Glyoxal Improved optical properties 11
Multihydroxymethyl ketones
12, 13
consists of layers of paper impregnated with phenolic and melamine resins.
In 1952 the first long-playing records and singles were manufactured from
polyvinyl chloride which replaced shellacs and phenolics previously used.
4.2 MONOMERS
Derivatives of phenol that are suitable for use for phenol/formaldehyde
resins are listed in Table 4.2. They include bisphenol A, bisphenol B, resorcinol,
cresols, and xylenols. Derivatives of formaldehyde that are suitable
for use for phenol/formaldehyde resins are listed in Table 4.3. They
include paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde
and glyoxal, trioxane, furfural, and furfurol.

244 Reactive Polymers Fundamentals and Applications
CH 3
CH 3
+
CH
CH
CH 2
CH 3
O
CH 3
C
H + -H 2 O
CH 3
C O
OH
CH 3
CH 3
OH
CH 3 C CH 3
O
Figure 4.1: Synthesis of Phenol and Acetone
4.2.1 Phenol
The peroxidation of cumene is the preferred route to phenol, accounting
for over 90% of world production. The process which is also referred to as
the Hock Process or Cumox Process, consists of
1. Liquid-phase oxidation of cumene to cumene hydroperoxide
(CHP), and
2. Decomposition of the concentrated CHP to phenol and acetone.
The synthesis is shown in Figure 4.1. The main use of phenol is as
a feedstock for phenolic resins, bisphenol A, and caprolactam. It is also
used in the manufacture of many products including insulation materials,
adhesives, lacquers, paint, rubber, ink, dyes, illuminating gases, perfumes,
soaps, and toys.
4.2.2 o-Cresol
o-Cresol is used mostly as an intermediate for the production of pesticides,
epoxy resins, dyes, and pharmaceuticals, but also as a component of disinfectants
and cleaning agents. o-Cresol is readily biodegradable and has a

Phenol/formaldehyde Resins 245
Table 4.4: Uses of Formaldehyde
Chemical
Phenol/formaldehyde resins
urea/formaldehyde resins
Wood adhesives
Foundry materials
Polyacetal resins
1,4-Butanediol
Methylene bis(4-phenyl isocyanate)
Pentaerythritol
Controlled-release fertilizers
Melamine/formaldehyde resins
Paraformaldehyde
Chelating agents
Herbicides
Trimethylolpropane
Pyridine chemicals
Neopentyl glycol
Nitroparaffin derivatives
Textile chemicals
Trimethylolethane
low bioaccumulation or geoaccumulation potential.
Approximately 60% of o-cresol is obtained from coal-tar and crude
oil by using classical techniques such as distillation, stripping, and liquid-liquid
extraction. The remaining 40% is obtained synthetically by the
alkylation of phenol with methanol.
4.2.3 Formaldehyde
Formaldehyde is a basic industrial chemical. It is used for the production
of a variety of chemicals, as shown in Table 4.4. Formaldehyde is a colorless,
highly flammable gas that is sold commercially as 30 to 50% aqueous
solutions.
Formaldehyde is used predominantly in the synthesis of resins, with
urea/formaldehyde resins, phenolic-formaldehyde resins, pentaerythritol,
and other resins. About 6% of uses are related to fertilizer production.
Formaldehyde find application in a variety of industries, including the medical,
detergent, cosmetic, food, rubber, fertilizer, metal, wood, leather, petroleum,
and agricultural industries. 14

246 Reactive Polymers Fundamentals and Applications
O
H 3 C C CH 2 CH 2 (O CH 2 )n OH
CH 2 O
O
H 3 C C CH 2 CH 2 (O CH 2 ) n-1
OH
Figure 4.2: Multihydroxymethylketones
Table 4.5: Global Production/Consumption Data of Important Monomers
and Polymers 15
Monomer Mill. Metric tons Year Reference
Formaldehyde 24 2003
16
Benzene 44 2003
17
Bisphenol A 2 1999
18
Phenol 6.4 2001
19
Phenolic resins 2.9 2001
20
Resorcinol 0.046 2002
21
4.2.4 Multihydroxymethylketones
Multihydroxymethylketones are the reaction products of ketones with a
large excess of formaldehyde. 13 They are used as reactive solvents for melamine
and other applications, but also can act as a source of formaldehyde,
because they will decompose back, as shown in Figure 4.2.
A mixture of phenol in a multihydroxymethylketone produces a special
type of a modified phenol/formaldehyde resin.
4.2.5 Production Data of Important Monomers
Production data of raw materials for phenolic resins are shown in Table 4.5.
Only a minor part of the formaldehyde produced is consumed for making
phenol resins. Bisphenol A is also used in other resin systems, mainly for
epoxide resins.

Phenol/formaldehyde Resins 247
4.2.6 Basic Resin Types
4.2.6.1 Novolak Resins
A novolak resin is a precondensate consisting of at least one phenol, or a
phenol derivative, and at least one aldehyde. Novolak resins are used, for
example, in rubber preparations which serve the production of belts, tubes
and tires.
These resins can reinforce the rubber preparations by contributing
hardness and high moduls with low deformation after curing. The reinforcement
is explained by the formation of a three-dimensional network
within the rubber upon curing.
4.2.6.2 Resol Resins
Phenolic resol resins are typically made by condensation polymerization
of phenol and formaldehyde in the presence of a catalyst at temperatures
between 40°C and 100°C. An alkaline catalyst is essential. If an acid catalyst
would be used, an uncontrolled curing during the preparation of the
prepolymer would occur. On the other hand, in principle, curing of the
resol prepolymer could be achieved by acidifying.
Due to the low yield of the phenol and formaldehyde condensation
under the normal reaction conditions, a typical resol resin contains a high
percentage of free monomers, i.e., phenol and formaldehyde. These free
monomers are volatile and highly toxic. Reducing the level of free monomers
in such resins, thus reducing their emissions into the environment
during application processes, has been one of the most heavily researched
areas by both phenolic resin producers and resin users for many years. 22
Resol refers to phenolic resins that contain useful reactivity, as opposed
to the cured resins. At this stage, the product is fully soluble in one
or more common solvents, such as alcohols and ketones, and is fusible at
less than 150°C.
4.2.7 Specialities
4.2.7.1 Modification with Lignin
Lignin (poly(phenylpropane) units) from waste black can be used for a partial
substitution of the phenol in a phenol/formaldehyde resin. The amount

248 Reactive Polymers Fundamentals and Applications
C 4 H 9
S H 2 C
OH
OH HO C 4 H 9
OH
CH 2 S
H 9 C 4
Figure 4.3: 2,14-Dithiacalix[4]arene
C 4 H 9
of replaced phenol with lignin in the resin can be increased by hydrolysis
of the lignin with hydrochloric acid. 23
The modification of PF resins with cornstarch and lignin promotes
the condensation reactions. Increased molar masses and a high yield of
methylene bridges are found. 24
4.2.7.2 Hydrogen peroxide modifier for particleboards
The addition of H 2 O 2 to a phenolic resin results in greater reactivity of the
phenolic resin and increases the mechanical properties of particleboards.
No significant influence of H 2 O 2 on the water resistance of the particleboards
has been observed. 25
4.2.7.3 Calixarenes
Calixarenes are cyclic phenol/formaldehyde oligomers. They have unusual
and interesting properties. 2,14-Dithiacalix[4]arene, c.f. Figure 4.3, can be
prepared by acid-catalyzed cyclocondensation of 2,2 ′ -thiobis[4-tert-butylphenol]
with formaldehyde. 26

Phenol/formaldehyde Resins 249
OH
O
O
O
OH -
O
HCHO
O
CH 2
H
OH
O -
CH 2 OH
O
O
O -
HCHO
H
CH 2
OH
CH 2 OH
Figure 4.4: Reaction Mechanism for the Addition of Formaldehyde on Phenol in
Basic Medium 27
4.2.8 Synthesis
4.2.8.1 Mechanism
The basic mechanism of the addition of formaldehyde is shown in Figure
4.4. The catalyst can be a hydroxide anion and a metal cation. The hydroxide
anion contributes to the formation of phenates by abstracting the
alcoholic proton.
The rate constants correlate with the radius of the metal cation, as
shown in Table 4.6. The metal hydroxide catalysts can be classified into
two families according to the valency of the cation: KOH, NaOH, and
LiOH; and Ba(OH) 2 and Mg(OH) 2 .
4.2.8.2 Kinetic Models
The kinetics of the polymerization of resol has been modelled taking into
account the phenol and formaldehyde equilibria. The kinetic parameters

250 Reactive Polymers Fundamentals and Applications
Table 4.6: Rate Constants, and Ionic Radius 27
Cation k[lmol −1 h −1 ] Ionic radius [Å]
K + 0.106 3
Na + 0.119 4
Li + 0.153 6
Ba 2+ 0.164 5
Ca 2+ 0.226 6
Mg 2+ 0.413 8
have been obtained by adjusting the experimental data. The influence of
the type and amount of catalyst, the initial pH, the initial molar ratio of
formaldehyde to phenol and the condensation temperature on the kinetic
rate constants can be described. 28
4.2.8.3 Preparation
A resol type phenol/formaldehyde resin may be prepared by reacting a molar
excess of formaldehyde with phenol under alkaline reaction conditions.
Formaldehyde is used in an amount between about 0.5 and 4.5 mol per mol
of phenol, with the preferred ranges dependent on the application. The free
formaldehyde is typically between 0.1% and 15%. The free phenol content
is typically between 0.1% and 20%.
Reaction Conditions. Alkaline reaction conditions are established by
adding an alkaline catalyst to an aqueous solution of the phenol and formaldehyde
reactants. During the initial reaction of the phenol and formaldehyde,
only that amount of alkaline catalyst necessary to produce a resin
need be added to the reaction nature. Typically, an amount of 0.005 to 0.01
mol of alkaline catalyst per mol of phenol is used. Sodium hydroxide is
the most popular catalyst.
Polycondensation of phenol and formaldehyde is typically carried
out at a temperature in the range from about 30°C to about 110°C, over a
reaction time of about 1 hour to about 20 hours, using a formaldehyde to
phenol mole ratio in the range from about 1 to about 6. 22
Formaldehyde to Phenol Ratio. A typical phenolic resin to be used as a
binder for fiberglass is made at a formaldehyde/phenol mole ratio as high

Phenol/formaldehyde Resins 251
as 6, to virtually eliminate free phenol in the resin. The high formaldehyde/phenol
ratio required to achieve the very low free phenol concentration
results in free formaldehyde concentrations as high as 20%. The high percentage
of free formaldehyde in the resin must be scavenged by the addition
of a large amount of urea or any other formaldehyde scavengers. 22
4.2.8.4 Structure
A part of a structure of a novolak resin and a resol resin is shown in Figure
4.5. A resol prepolymer differs from a novolak resin in that it contains not
only methylene bridges but also reactive methylol groups and dimethylene
ether bridges.
13 C-NMR spectroscopy has proven to be the most successful and
informative analytical tool to analyze resol resins. Using chromium(III)acetylacetonate
as a relaxation agent, quantitative 13 C-NMR spectra can be
obtained. 29
4.2.9 Catalysts
The common catalysts for the phenol/formaldehyde resol synthesis are
shown in Table 4.7. The catalyst type influences the rate of reaction of
phenol and formaldehyde and the final properties of the resins. 27
The substitution of phenol with formaldehyde in the ortho-position
versus para-position increases in the following sequence of hydroxide catalyst
metals: K < Na < Li < Ba < Sr < Ca < Mg. 30
Among the tetraalkylammonium hydroxides, it is advantageous to
use tetramethyl- or tetraethylammonium hydroxides as catalysts rather than
tetrapropyl- or tetrabutylammonium hydroxides, because the resins prepared
with the last two catalysts have a limited miscibility of the resins
obtained with water. 30
4.2.9.1 Inorganic Catalysts
Phenolic resins are widely used as binders in the fiberglass industry. Most
resins for the fiberglass industry are catalyzed with inorganic catalysts because
of their low cost and non-volatility.
When an inorganic base-catalyzed phenolic resin is mixed with urea
solution, a so-called premix or prereact, certain components of the phenolic
resin, such as tetradimers, crystallize out, causing the blockage of lines,

252 Reactive Polymers Fundamentals and Applications
OH
OH
OH
CH 2
CH 2
CH 2
OH
CH 2
OH
CH 2
Novolak
OH
OH
OH
CH 2
CH 2
CH 2
CH 2
OH
O
CH 2
CH 2
OH
CH 2 OH
Resol
Figure 4.5: Structure of Novolak and Resol Resins

Phenol/formaldehyde Resins 253
Table 4.7: Common Catalysts for the Phenol/formaldehyde Resol Synthesis
Catalyst
Reference
Sodium hydroxide, potassium hydroxide, lithium hydroxide
31, 32
Magnesium hydroxide, calcium hydroxide, barium hydroxide
Sodium carbonate
Calcium oxide, magnesium oxides
Tertiary amines, triethylamine
2-Dimethylamino-2-methyl-1-propanol,
32
2-(dimethylamino)-2-(hydroxymethyl)-1,3-propanediol
Tri(p-chloro phenyl)phosphine,
32
triphenylphosphine
Tetraalkylammonium hydroxide
30
interrupting normal operations, and the loss of resin. The crystallized material
is difficult to dissolve and hinders uniform application of the resin to
the glass fiber.
The tetradimer tends to crystallize in premix solutions of inorganic
base-catalyzed resins and urea. Precaution must be taken with the inorganic
base-catalyzed resins to avoid tetradimer crystal growth. For example,
problems can be minimized by regular cleaning of the storage tanks
and lines, and by shortening the time between the preparation and use of
the premix solution. 22
4.2.9.2 Organic Catalysts
Phenolic resins catalyzed with an organic catalyst are especially useful
for applications where high moisture resistance and higher mechanical
strength are required. When a phenolic resin such as PF resin catalyzed
with an organic catalyst is mixed with an amino resin such as urea/formaldehyde
(UF) resin, the resultant PF/UF or PF/U is expected to be much
more storage stable and to have much less tetradimer precipitation or crystallization.
The organic catalyst, unlike an inorganic base, will increase the solubility
of the phenolic resin in the PF/UF solution. A PF/UF mixture or
premix is often used as a binder in the fiberglass industry. 22
The activation energy of curing of UF resins is generally higher than
that of PF resins, but the curing rates of UF resins are faster than those

254 Reactive Polymers Fundamentals and Applications
of PF resins. 33 Tertiary amino alcohols have been found to be very effective
catalysts for the polycondensation of phenol and formaldehyde, and
yet they are essentially non-volatile so that attendant amine emissions are
negligible. Because the tertiary amino alcohols are organic catalysts, they
produce resins which are essentially ashless, and thus are particularly useful
in the manufacture of resins suitable for use in many industries.
The resulting phenol/formaldehyde resol resin is characterized by
the high moisture resistance and high mechanical strength of resins produced
with the use of organic rather than inorganic catalysts. These organic
catalysts also produce phenol/formaldehyde resol resins having superior
tetradimer storage stability, when mixed with a formaldehyde scavenger
such as urea. 22
The tertiary amino alcohol catalyst remains in the resulting reaction
product, and at least a portion of the catalyst becomes chemically bound to
the polymeric matrix in the resol resin. The presence of the hydroxyl functionality
on the amino alcohol molecule acts as a plasticizer and increases
the flow of the hot resin melt, thereby increasing the resin efficiency and
yielding a stronger bond of the resin with materials which are integrated
with the resin, such as fiberglass. The chemical bonding of the catalyst to
the polymeric matrix also further inhibits catalyst emissions in the finished
product. 22
4.2.10 Manufacture
4.2.10.1 Exothermic Hazards
The reaction of phenol with formaldehyde is highly exothermic. Therefore,
there is a hazard situation owing to the high released heat in case of
improper operation in industrial scale. From kinetic data, the conditions of
a thermal explosion has been modelled. 34
4.2.10.2 Distillation
When a distillation step is required, the distilled resin can be solvated in
an alcohol, such as methanol, isopropanol, or ethyl alcohol. This is typical
for paper saturating resins. 35 These resins are usually neutralized to a pH
of 6.5 to 7.5 with acid to give lighter color cure.

4.3 SPECIAL ADDITIVES
4.3.1 Low Emission Types
Phenol/formaldehyde Resins 255
It is often desirable to scavenge the free formaldehyde prior to application.
This is done for several reasons:
1. To reduce the extent of human exposure during manufacture,
2. To reduce the free formaldehyde emissions during the forming and
curing of the insulation product,
3. To reduce the free formaldehyde prior to the addition of an acid
catalyst,
4. To reduce the cost of the binder, and
5. To improve the anti-punk properties of the resin.
4.3.1.1 Release of Phenol
A problem is the release of volatile organic components, such as phenol,
into the atmosphere during curing. Typical levels of free phenol in a
phenol/formaldehyde resin are in the range of 5 to 15%. One method of
reducing the free phenol level in the base phenol/formaldehyde resin is to
increase the amount of formaldehyde (relative to the phenol) in the resin as
manufactured. Unfortunately this usually results in a more brittle resin that
when cured is unacceptable for manufacturing postforming laminates. 35
4.3.1.2 Urea Scavenger
Often urea cannot be added to the phenolic resin by the manufacturer, because
the mixture of phenolic resin and urea, i.e., the premix, is not sufficiently
stable to permit its storage for two to three weeks without tetradimer
precipitation. 22
If urea is added as scavenger to the phenolic resin in a premix system,
it lasts many days before the resin has to be used. During this time,
virtually all the free formaldehyde in the resin reacts with the added urea.
The free formaldehyde content in the premix can then be as low as 0.1%.
The use of such a ready-for-sale premix system reduces the emission of
free monomer. 22

256 Reactive Polymers Fundamentals and Applications
4.3.1.3 Scavengers for Formaldehyde
The most common scavengers for formaldehyde are chemical species containing
a primary or secondary amine functionality. Examples include urea,
ammonia, melamine, and dicyandiamide. The most common, and the
most economical, amine species is urea. 35
The addition of formaldehyde scavengers to a phenol/formaldehyde
resin requires a finite period of time to achieve equilibrium with the free
formaldehyde in the resin. The process of reaching this equilibrium is
referred to as prereaction, and the time to reach the equilibrium is referred
to as the prereact time. Prereact times vary with temperature and amine
species. When urea is used, the prereaction times range from 4 to 16 hours,
depending on temperature.
The mole ratio of formaldehyde to formaldehyde scavenger is important,
and the conditions must be optimized to achieve the best performance
of the binder resin. With urea, the mole ratio of formaldehyde
to urea is optimally maintained between 0.8 and 1.2. At a lower level,
the opacity increases significantly along with the ammonia emissions. At
higher levels the formaldehyde emissions increase and the risk of precipitation
of dimethylolurea is greatly increased. That is why in traditional
binders using urea as the formaldehyde scavenger, the extension level is
dictated by the amount of free formaldehyde in the base resin.
However, disadvantages arise when the resins are prereacted with
urea prior to forming the binder. Because free formaldehyde stabilizes the
tetradimer in the resin, prereacting with urea will reduce the amount of free
formaldehyde in the resin, hence reducing the shelf life of the formulation.
In addition, prereacting with urea takes time, requires prereact tanks and
binder tanks, and urea needs to be stored in heated storage tanks.
4.3.1.4 Over-condensing
The reduction of residual free formaldehyde can be achieved by over-condensing
the resin. 36 An over-condensed resol denotes a resin in which a
relatively high proportion of large oligomers is formed at the end of the
condensation stage. It has a high average molecular weight, higher than
500 Dalton. Such a resol is obtained by increasing the reaction time or the
reaction temperature to ensure a virtually quantitative conversion of the
initial phenol while going beyond the monocondensation to monomethylolphenols.
It contains a very low proportion of free phenol and volatile

Phenol/formaldehyde Resins 257
phenolic compounds capable of polluting the atmosphere at the site of use.
4.3.1.5 Aqueous Dispersions of Phenol/formaldehyde Resins
Aqueous dispersions of phenol/formaldehyde resol resins are frequently
used in the manufacture of mineral fiber insulation materials, such as insulating
glass fiber batts for walls, in roofs and ceilings, and insulating
coverings for pipes.
Typically, after the glass fiber has been formed, the still hot fiber
is sprayed with aqueous binder dispersion in a forming chamber or hood,
with the fibers being collected on a conveyer belt in the form of a wool-like
mass associated with the binder. In some cases, a glass fiber web is sprayed
with the aqueous dispersion.
Both resol and urea-modified resol resins have been employed for
this purpose. The urea contributes to the punking resistance of the binder
(i.e., resistance to exothermic decomposition at elevated temperatures), and
reduces volatile compounds when the resin is cured at elevated temperatures.
37 To improve the performance of the binder for glass fibers, a lubricant
composition, such as a mineral oil emulsion, and a material promoting the
adhesion of the resol resin to the glass fibers, such as a suitable silane, can
be added. An example of an adhesion-improving silane is (3-aminopropyl)triethoxysilane.
37
4.3.2 Boric Acid-modified Types
Boric acid-modified phenolic resins (BPFR) show excellent performance,
such as thermal stability, mechanical strength, electric properties and further
shielding of neutron radiation. 38
Because bisphenol F has a methylene group, it shows a higher freedom
of rotation in contrast to bisphenol A-based materials. The reaction
of bisphenol F, formaldehyde and then with boric acid is shown in Figure
4.6. At elevated temperatures the boric acid forms a six-membered ring
structure containing a boron oxygen coordination bond. 39 The curing reaction
of BPFR follows an autocatalytic kinetics mechanism. 40 The cured
structure of BPFR formed from the paraformaldehyde method is different
from BPFR formed from the formalin method. The structure in this curing
BPFR does not contain ether bonds and carbonyl groups. The thermal
stability of this BPFR is better than BPFR formed from formalin. 41

258 Reactive Polymers Fundamentals and Applications
HO
CH 2
OH
CH 2 O
HO
CH2
CH 2
OH
HO
CH 2
OH
H 3 BO 3
HO
CH 2
OH
HO
CH 2
CH 2
O
B
OH
HO
CH 2
CH 2
O
HO
CH 2
OH
H 2 C
CH 2 O O CH 2
B
O O
H
CH 2
Figure 4.6: Reaction of Bisphenol F with Formaldehyde and Boric Acid

Phenol/formaldehyde Resins 259
CH 2
R
O
CH 2
R
Figure 4.7: Formation of Xanthens 42
The weight loss for a common bisphenol F resin is more than 99%
at 580°C, while the boron-modified resin shows only 45% at 700°C. The
situation is completely similar for a bisphenol A resin. 38
4.3.3 Fillers
Many fillers are known for PF resins, such as glass fibers, ceramic material,
and organic fiber materials.
4.3.3.1 Jute Reinforcement
Jute textile can be recycled into composites using 12 to 30% of phenol/-
formaldehyde (PF) resin. The dimensional stability of the produced composites
can be improved by acetylating or by steam treatment of the jute
textile. Steaming the jute textile is superior to acetylation in improving the
dimensional stability. A steamed jute textile exhibits much less irreversible
and reversible swelling than acetylated or untreated jute textile. 43
4.3.4 Flame Retardants
4.3.4.1 Pyrolysis products
The main products of pyrolysis of both novolaks and resols are phenol,
2-methylphenol, 4-methylphenol, 2,4,6-trimethylphenol, and xanthens. 42
Xanthens arise because of cyclization reactions, as shown in Figure 4.7.

260 Reactive Polymers Fundamentals and Applications
OH
OH
H 3 C CH 2
O
H 2 C CH 3
OH
OH
H 3 C CH 2
CH 3
CH 3
OH
OH
CH 3
H 3 C
H 2 C
CH 3
CH 3
CH 3
Figure 4.8: Self-condensation of 2-Hydroxymethyl-4,6-dimethylphenol
4.3.4.2 Brominated Phenol/formaldehyde Resin
A brominated phenol/formaldehyde resin with ca. 10% bromine has been
shown to be a good plywood adhesive that shows a high shear strength,
good flame retardancy, and good resistance to both hot and cold water. 44
4.4 CURING
4.4.1 Model Studies
The mechanism of curing has been investigated using model compounds.
2-Hydroxymethyl-4,6-dimethylphenol condenses at 120°C into bis(2-hydroxy-3,5-dimethylbenzyl)ether
and bis(2-hydroxy-3,5-dimethyl-benzyl)-
methylene as shown in Figure 4.8. The ether is formed much faster than
the methylene compound. Phenol does not act as an acid catalyst for ether
hydrolysis.
Previous results suggest that during curing at temperatures above
150°C, quinone methides have been proposed as key intermediates. However,
at temperatures below 150°C, quinone methides have not been considered
as important, which has been contradicted. 45 Figure 4.9 illustrates
the formation of quinone methides. Quinone methides can be formed by
the intramolecular dehydration of 2-hydroxymethyl-4,6-dimethylphenol.
Further, they can be formed by a retro Diels-Alder reaction of a trimer.
With phenol and 2-methylphenol, a quinone methide attacks exclusively

Phenol/formaldehyde Resins 261
OH
OH
O
H 3 C CH 2
-H 2 O
H 3 C CH 2
CH 3
CH 3
O
OH
OH
OH
H 3 C CH 2
H 3 C CH 2
CH 3
CH 3
Figure 4.9: Formation and Reaction of Quinone Methides
the free ortho site of the phenol. Therefore, a high ortho bridged resin
should be formed under conditions that favor the formation of an ortho
quinone methide. This would require a resin which contains predominately
ortho hydroxymethyl substituents, and condensation at high temperature,
preferably in solvents which encourage the dehydration of the ortho hydroxymethyl
functionality. 45 Phenoxy bridges are shown to be formed by
ether exchange between phenolic OH and a bridging ether.
Evaluation of nonisothermal DSC curing data by isoconversional
analysis revealed that the activation energy changes with conversion in the
course of curing. The data were interpreted to show that the curing process
of phenol/formaldhyde resins undergoes a change in the reaction mechanism
from a kinetic to a diffusion regime. 46
4.4.2 Experimental Design
Factorial experiments have been conducted to find the effect of the monomer
feed on the structure of resol resins.
47, 48
The amount of ortho and
para methylol phenols increases with the F/P ratio. An increased condensation
viscosity also increases the weight-average molecular weight.
Among the parameters investigated, the viscosity has the strongest effect
on the molecular weight. Several other useful relations could be established
by the statistical approach.

262 Reactive Polymers Fundamentals and Applications
4.4.3 Water Content
The amount of water in a powder resol resin was shown to play an important
part in the curing kinetics. In the initial curing stages, water acts as a
diluent and retards the curing. At the higher conversions, water acts as a
plasticizer and contributes to enhancing the final conversion. 49
4.4.4 Influence of Pressure
Curing under high-pressure conditions reveals competition between the
oxidation and polymerization reactions. This results in fewer methylene
bridges and more free ortho-positions. Thus, a consequent lower degree of
polymerization is reached. 50
4.4.5 Wood
The activation energy of the curing reaction of a PF resin generally increases
when PF resin is mixed with wood. This is caused mainly by the
decrease of the pH resulting from the presence of wood. 51 Further, wood
decreases the curing enthalpy. This effect can be interpreted in that the
final conversions are lowered.
4.4.6 Novolak Curing Agents
Several curing agents for novolak resins are known in the art, including
formaldehyde, paraformaldehyde, and hexamethylenetetramine. The most
common curing agent is hexamethylenetetramine, which reacts upon heating
to yield ammonia and cured resin. These curing agents complete the
crosslinking reaction to convert a thermoplastic novolak resin to an insoluble
infusible state. 4
4.4.6.1 Hexamethylenetetramine
When hexamethylenetetramine is used, ammonia evolves during curing of
the novolak resin. In addition, novolak curing agents like hexamethylenetetramine
typically require curing temperatures as high as 150°C. The cure
temperatures can be lowered by the addition of acids, but this often introduces
other problems such as die staining, die sticking, and sublimation of
organic acids into the atmosphere.

Phenol/formaldehyde Resins 263
4.4.6.2 Triazine-type Hardeners
Hardeners of the triazine-type are alkoxylated melamine/formaldehyde resins
or alkoxylated benzoguanamine-formaldehyde resins.
These hardeners have a water solubility of less than 15% by weight
and contain from 1 to 2.5 melamine or benzoguanamine rings per molecule.
About 7% to 15% of triazine hardener is used.
The triazine hardeners are prepared from melamine or benzoguanamine
and formaldehyde with at least 4 mol formaldehyde per mol melamine
or benzoguanamine to produce melamine/formaldehyde resins or
benzoguanamine-formaldehyde resins, e.g., hexakis(methylol)melamine in
the case of a melamine/formaldehyde resin. These formaldehyde resins are
subsequently alkoxylated with, e.g., butoxymethyl groups. 52
Melamine resins typically require either an acid catalyst or elevated
temperatures to cure a novolak resin. Melamine resin curing agents
also tend to cure novolak resins more slowly than hexamethylenetetramine.
They produce a lesser extent of cure, and frequently produce formaldehyde
in a side reaction. 4
4.4.6.3 Substituted Melamines
The most common methylene donor for crosslinking novolak resins is
hexamethylenetetramine (HMTA), but it has the following drawbacks:
• It raises problems of health and safety.
• When novolak resins are used with HMTA in the presence of rubbers
intended to adhere to metal reinforcements, this bond may
take deteriorate.
HMTA as hardener can be replaced by another methylene donor,
hexa(methoxymethyl)melamine (H3M). 8 This can be used in conjunction
with a urea, amide, or imide, such as propionamide. This compound liberates
methanol instead of ammonia in the course of curing. 8
4.4.7 Resol Resin Hardeners
Resol resins have also been used as a curing agent for novolak resins. 53
A comparatively large amount of resol is required to achieve a reasonable
crosslink density.

264 Reactive Polymers Fundamentals and Applications
A disadvantage is that resol resins have a limited shelf life, caused
by self-condensation wherein the phenolic nuclei are bridged by methylene
groups. Resol resins may contain significant levels of free phenol
and formaldehyde that may present environmental concerns. Conventional
resol resins typically contain 4 to 6% free phenol and may contain approximately
1% free formaldehyde. 4
4.4.7.1 Benzoxazine Curing Agent
An alternative curing agent for a novolak resin is a benzoxazine polymer. 54
Benzoxazine may be an intermediate product in the reaction of hexamethylenetetramine
(HMTA) and phenol or substituted phenols. Benzoxazine
is the Mannich product of a phenolic compound, an aldehyde and a primary
amine. A benzoxazine polymer composition may be manufactured
by combining an alcoholate of an amino triazine such as melamine, guanamine,
benzene guanamine, an aldehyde and a resol, and allowing these
to react under conditions favorable to benzoxazine formation.
4.4.8 Ester-type Accelerators
Certain esters can accelerate the curing of PF resins, for example, ethyl
formate, propylene carbonate, γ-butyrolactone, and triacetin. 55 A mechanism
for the action of these accelerators has been proposed. The first step
consists of transesterification with the methylol group of the resin. Then,
the ester group is attacked by another aromatic compound in the ortho or
para position, or it is converted to a reactive quinone methide intermediate,
which reacts by the quinone methide mechanism.
4.4.9 Ashless Resol Resins
Ashless resins are prepared from organic ingredients; no inorganic catalyst
should be used. The catalysts commonly used in phenolic resin production
are sodium hydroxide and triethylamine (TEA). TEA is very volatile
and toxic. Its emission into the atmosphere is regulated by government
agencies.
Ashless and low-ash phenolic resol resins having no amine odor can
be prepared by reacting phenol and formaldehyde in the presence of a low
volatile and strongly basic tertiary amino alcohol, such as 2-dimethylamino-2-methyl-1-propanol
(DMTA) or 2-(dimethylamino)-2-(hydroxymeth-

Amine
Phenol/formaldehyde Resins 265
Table 4.8: Basicity of Amines and Aminoalcohols
pH a
Triethylamine 10.8
2-Dimethylamino-2-methyl-1-propanol 10.7
2-(Dimethylamino)-2-(hydroxymethyl)-1,3-propanediol (80%) 10.6
a 0.010 N aqueous solution
yl)-1,3-propanediol (DMAMP). 22 These tertiary amino alcohols have a
boiling point above 250°C. A comparison of the pH of 0.010 N solutions
of these amino alcohols along with that of triethylamine is shown in Table
4.8, indicating that DMTA and DMAMP (80%) are as basic as TEA. 22
4.4.10 Recycling
4.4.10.1 Porous Fiberboard from Waste Newspapers
Flame retardant and waterproof porous fiberboards can be manufactured
from waste newspapers by using a foaming agent and a reinforcing phenol/formaldehyde
resin. 56 A water-soluble phenol/formaldehyde resin of the
resol type is used in amounts of 11% to obtain best quality product. To
increase the porosity, a foaming agent is admixed.
4.4.10.2 Sewage Treatment Process
Modified wastes from phenol/formaldehyde resins and expanded poly(styrene)
can be used in sewage treatment processes. 57 Amino derivatives of
novolak wastes and sulfonated derivatives of novolak and expanded polystyrene
wastes are synthesized. These compounds are basically anionic
polyelectrolytes, and they exhibit good flocculation properties in purification
processes of a sewage waters of coal-mines, or steel plants. The purification
is effected in that the impurities in the waste water interact with
the polymeric material thus forming insoluble particles. The main mechanisms
of destabilization of the polymeric electrolyte are bridging of the
individual molecules by the impurity mosaic flocculation, and charge neutralization.
In mosaic flocculation, the polyelectrolyte adsorbs locally onto
the impurity, so that opposite charged regions may be formed. 58

266 Reactive Polymers Fundamentals and Applications
Use
Table 4.9: Uses for Phenol/formaldehyde Resins 35
Insulation
Plywood and engineered lumber
Oriented strand board
High pressure laminating resins
Paper saturating resins
Open or closed cell foams
Abrasive binders
Friction binders
Coated foundry sand binders
Remarks
Coating fibers
Wafer board resins
Use for flat surfaces
Oil filter, overlay, paint roller tubes
Floral foam supports
4.5 APPLICATIONS AND USES
Phenol/formaldehyde resins are used to make a variety of products including
consolidated wood products such as plywood, engineered lumber,
hard board, fiberboard, and oriented strand board. Other products include
fiberglass insulation, laminates, abrasive coatings, friction binders, foams,
foundry binders, and petroleum recovery binders. They are also used as
paper saturating resins for oil filters, overlay, paint roller tubes, etc. 35 Uses
of phenol/formaldehyde resins are summarized in Table 4.9.
Phenol/formaldehyde foam resins are used to make open or closed
cell foams when cured. Such foams are primarily used to make floral foam
supports for retaining flower stems in water. The foam is able to soak
up water many times its original weight to provide water for the flowers.
These foams are primarily open cell (with openings in cell walls).
Other uses for phenol/formaldehyde foams are dense foams used
for models (similar to balsa wood), to hold jewelry, and to make molds
for foot prosthetics. Closed cell foams find use in barrier and insulation
applications.
Further uses of phenol/formaldehyde resins include abrasive binders,
friction binders, and phenol/formaldehyde coated foundry sand binders.
4.5.1 Binders for Glass Fibers
Glass fibers are generally mass produced in two types:
1. Bulk or blown fiber for insulation and allied applications,
2. Continuous-filament, or reinforcing fibers.

Phenol/formaldehyde Resins 267
In either form, the raw fiberglass is abrasive and fragile. Damage to
the individual glass fibers can occur as a result of the self-abrasive motion
of one fiber passing over or interacting with another fiber. The resulting
surface defects cause reduction in the overall mechanical strength of the
fiberglass.
Consequently, binders have been developed to prevent these problems.
A typical binder may prevent the destructive effects of self-abrasion
without inhibiting the overall flexibility of the finished glass fiber product.
Good resistance and resilience to extreme conditions of elevated humidity
and temperature are beneficial in view of the wide variety of applications
of glass fiber/binder compositions.
The amount of binder present in a fiberglass product is dependent on
several factors including the product shape, the type of service required,
compressive strength requirements, and anticipated environmental variables
such as temperature. 59
4.5.1.1 Phenolic Binders
Traditionally, the performance parameters required for insulation fibers
have been satisfied only with phenol/formaldehyde resins.
Therefore, glass fiber binders have been almost exclusively based on
phenol/formaldehyde resins. These systems typically include aminoplast
resins such as melamine and urea, silicone compounds, soluble or emulsified
oils, wetting agents, and extenders or stabilizers.
Typically phenolic binders contain large amounts of low molecular
weight species including phenol, formaldehyde, and volatile phenol/formaldehyde
adducts such as 2-methylolphenol and 4-methylolphenol.
During the curing process, these volatile low molecular weight components
are released into the atmosphere in substantial volumes as volatile
organic compounds (VOCs).
Since the process of manufacturing fiberglass typically involves spraying
large volumes of phenol/formaldehyde binders into high volume air
streams, and then curing the product in convection ovens that involve high
volumes of air, fiberglass manufacturers have an urgent need to reduce their
VOC emissions, particularly with regard to formaldehyde. 59
Reducing the free formaldehyde content of typical phenol/formaldehyde
binders affects the final product quality, because an excess of formaldehyde
is essential for curing and bonding in such systems. Attempts

268 Reactive Polymers Fundamentals and Applications
to convert free formaldehyde into less obnoxious and dangerous chemicals
have involved the addition of ammonia or urea. Such additions were
intended to convert free formaldehyde into hexamethylenetetramine or a
mixture of mono and dimethylol ureas.
Unfortunately, urea, hexamethylenetetramine, and mono and dimethylol
ureas can all contribute to the production of trimethylamine, which
gives the cured phenolic binder and finished product an undesirable fishy
odor. In addition, nitrogen-containing compounds can decompose to yield
ammonia and other potentially harmful volatile compounds. Phenol/formaldehyde
resins require careful handling procedures. Since the cooked resin
must be refrigerated until use, refrigerated trucks and holding tanks are
required. Even with refrigeration, the storage time of a phenolic resin is
typically 15 days.
4.5.2 Molding
In the plastics molding field, phenolic resins have been a preferred choice
as molding material for precision parts that must function in hostile environments.
Phenolic resins form crosslinked structures with excellent dimensional,
chemical, and thermal stability at elevated temperature.
4.5.3 Novolak Photoresists
A positive photoresist composition can comprise a 1,2-naphthoquinonediazide
compound and a novolak resin. The composition is sensitive to
ultraviolet rays.
7, 60
The photosensitizer is mainly a naphthoquinonediazidesulfonic acid
ester. The content of the photosensitizer is 20 to 60 parts per 100 parts
by weight of the substituted phenol novolak resin. Suitable phenols for
this special application are mixtures of 2-cyclohexyl-5-methylphenol, m-
cresol, and p-cresol. The phenols are condensed with formaldehyde. Suitable
solvents include methylisobutylketone or 2-heptanone. 7
The unexposed photoresist is not soluble in alkaline medium. The
insolubility is attributed due to an azo coupling of the sensitizer with the
novolak polymer. Exposure to UV-light converts the o-diazonaphthoquinone
into an indene carboxylic acid, c.f. Figure 4.10. The carboxylic groups
enhance the solubility of the lacquer, so that the material becomes soluble
in an alkaline medium.

Phenol/formaldehyde Resins 269
O
N + N -
hν
O
C
SO 3 H
H 2 O
SO 3 H
O
C OH
SO 3 H
Figure 4.10: Conversion of o-Diazonaphthoquinone by Radiation
4.5.4 High Temperature Adhesives
Resol melamine dispersions in which melamine is solubilized are used as
high temperature adhesives, e.g., for glass fibers. The resin has low formaldehyde
content and a high alkali ratio. The uncured resins compositions
show improved water solubility. 61
4.5.5 Urethane-modified Types
Cured phenol/formaldehyde resins show considerable fragility and a low
impact resistance. The hydroxymethyl groups present enable a chemical
modification with urethane oligomers with isocyanate end groups.
The addition of polyurethane improves the elasticity of the compositions
and introduces coupling sites that increase the adhesion properties. 62
In order to decrease the reactivity of the PF resin with oligomer isocyanate
groups and to expand the shelf life of such compositions, the methylol
groups can be etherified with butanol. The etherification with butanol
proceeds in the presence of phosphoric acid.

270 Reactive Polymers Fundamentals and Applications
4.5.6 Carbon Products
Phenol/formaldehyde polymers are increasingly used as precursors for the
production of carbon replacing ceramic and pitch-based materials in refractory
applications.
4.5.6.1 Mechanism of Carbonization
The pore sizes of carbons obtained from phenol/formaldehyde resins depend
strongly on the ratio of formaldehyde to phenol (FP) in the initial formulation.
Higher formaldehyde-to-phenol ratios result in higher surface
areas when measured with nitrogen, but similar surface areas measured
with carbon dioxide. 63 This leads to the conclusion that the microporous
structure of the carbon powder is extremely narrow. A comparison of a resin
with a molar ratio of phenol to formaldehyde (F/P) F/P=1.2 and F/P=1.8
showed that the differences between the cured resins persisted after heating
to 400°C, when methylene bridge degradation becomes significant. However,
no substantial differences are observable after heating to 500°C.
4.5.6.2 Carbon Membranes
Carbon membranes have gained great interest because of their thermal and
chemical stability. Carbon membranes are classified according to pore size
as microfiltration membranes. The mean pore diameter ranges from 0.02 to
10 µm, usually from 0.1 to 1 µm. Ultrafiltration membranes have a mean
pore diameter from 1 to 100 nm: gas separation membranes have a mean
pore diameter of less than 1 nm.
Activated carbons can be prepared by controlled pyrolysis of either
natural products, such as coconut shell at 800°C, coal at 400 to 600°C,
wood at 300 to 500°C, or polymeric materials, such as phenol/formaldehyde
resins at 900°C, poly(furfuryl alcohol) at 600°C, or polyimide at 550
to 800°C. 64
Carbon molecular sieve membranes for the separation of hydrogen
- nitrogen and hydrogen - methane mixtures have been prepared from a
novolak phenol/formaldehyde resin. The liquid resin is used to form a film
on a porous substrate by dip-coating. A carbon molecular sieve membrane
is then obtained by carbonization of the film.
The pore structure of the carbon membranes can be closely controlled
by adjusting the degree of curing of the raw material. The final pore

Phenol/formaldehyde Resins 271
diameter increases with the amount of hexamethylenetetramine used for
curing.
65, 66
Porous carbon membranes can also be formed on a macroporous
clay support. The process consists of carbonizing a solvent-containing
non-interpenetrating crosslinked resol-type phenol/formaldehyde (PF) resin
film on a macroporous clay substrate. The porous structure of the membrane
seems to result from the evaporation of solvent at the film-making
stage, along with in-situ crosslinking and carbonization. 64
4.5.6.3 Porous Carbon Beads
Porous carbon beads can be prepared by carbonization at 1000°C of phenol/formaldehyde
beads under nitrogen or carbon dioxide atmosphere, followed
by oxidation with boiling nitric acid. 67 The carbonization atmospheres
have a remarkable influence on the porosity development and structural
changes of the resulting carbon spheres. In comparison with a N 2
atmosphere, a CO 2 atmosphere yields more surface pits, a higher surface
area, and a higher micropore volume of the carbon spheres.
4.5.6.4 Carbon Urea Impregnation
Carbons from phenol/formaldehyde resins, which are glass-like, contain a
high proportion of closed pores that are not accessible to gas molecules.
Opening of these closed pores contributes to an increase in the porosity.
Urea, which decomposes at 130 to 400°C, can be employed as an additive
to the resin precursor. The escape of the degradation gases produced by
the impregnated urea during resin carbonization promotes the formation of
micropores in the resulting char.
Carbons of ca. 2000 m 2 /g can be obtained at 70% burn-off by 10%
urea impregnation in the resin, while at a similar burn-off level, carbons
obtained from pure resin can have a surface area around 1400 m 2 /g. 68 The
burn-off level is the weight loss in % of the maximum weight loss.
4.5.6.5 Nitrogen-containing Carbon Catalysts
Activated carbons, because of their high accessible surface area, are used as
supports for certain catalysts. Often, the presence on the surface of heteroelements,
such as oxygen, nitrogen, and sulfur, stabilizes loaded metallic
catalysts. Surface oxygen or surface nitrogen can effectively catalyze the

272 Reactive Polymers Fundamentals and Applications
reduction of NO with NH 3 at low temperatures, compared to metal oxide
catalysts.
Carbon catalyst supports containing nitrogen can be prepared using
implantation of nitrogen by treatment with NH 3 or HCN of a carbon that
has been previously oxidized. Another method consists of the use of nitrogen-containing
polymers. For example, active carbons containing up to
4.5% nitrogen can be prepared by carbonization in argon and steam activation
of a vinylpyridine resin. 69
Activated carbon catalysts can be produced from the phenol/formaldehyde
resins that are prepared using ammonia. After synthesis, m-phenylene
diamine (MPDA) dissolved in alcohol is added to the resin as an
additional nitrogen source. Up to 30% of m-phenylene diamine is required
by the process.
The resin can be carbonized using a gasification method. This method
consists of carbonization of the resin in N 2 by heating at 10°C/min from
room temperature to 800°C, followed by gasifying the resulting carbon in
oxygen at 400°C. 70 The main difference between pyrolysis and gasification
as used here, is that pyrolysis is conducted in inert atmosphere, but
gasification is a combined thermal treatment in inert gas, ie., N 2 and an
oxidizing gas, i.e. O 2 . Ultimate analysis shows that up to 10% of nitrogen
can be incorporated in the carbon char.
4.6 SPECIAL FORMULATIONS
4.6.1 Chemical Resistant Types
Alkaline resistance can be improved by etherification of the phenolic hydroxyl
group. Not more than one third of the phenolic hydroxyl group
should be etherified, otherwise the reactivity would decrease too much.
4.6.2 Ion Exchange Resins
Commercially available ion exchange resins are produced from polymers
such as phenol/formaldehyde, styrene-divinylbenzene, acrylonitrile, acrylates,
and polyamines. 71
These polymers can be modified by halomethylation, sulfonation,
phosphorylation, carboxylation, etc. This additional reaction enables the
production of an ion exchange resin with specific reactive sites, thereby
exhibiting greater selectively towards particular metal ions or other anions

Phenol/formaldehyde Resins 273
or cations. In conventional practice, the ion exchange resins are produced
in bead or granular form, the bead size generally varying from 40 µm to
greater than 1 mm in diameter. A particular advantage of phenolic resins
is that they are chemically resistent.
4.6.3 Brakes
Phenolic-bonded composites for Industrial brake applications often contain
partially dehydrated vermiculite particles to generate friction. Dehydration
and rehydration processes of vermiculite should take place. The maximum
detected temperature on the friction surface of certain investigated composite
samples after friction test was 900°C. 72
4.6.4 Waterborne Types
Generally waterborne laminating resins are similar to the solvent-borne
types except they lack an organic solvent and have usually lower molecular
weight than their solvent-borne counterparts. Because they have lower
molecular weight, they typically have a higher level of free phenol.
4.6.5 High Viscosity Novolak
High molecular weight, thermoplastic phenol/formaldehyde is a suitable
compatibilizer for poly(propylene)-phenol/formaldehyde resins. The materials
can be blended by reactive extrusion.
A phenol/formaldehyde resin with high molecular weight is required
in reactive extrusion to obtain a favorable viscosity ratio. A mixture of
phenol and cresols, tert-butylphenols, and resorcinol is used as phenol
component. The resins are highly linear with a molecular weight in the
range of 10 to 30 kDalton. 73
4.6.6 Foams
In order to foam the resin, surfactants or wetting agents are mixed into the
resin to create bubbles. Then a low boiling liquid such as CFC, HCFC,
pentane or hexane is added to the mixture. A strong acid is added to the
resin to initiate curing of the phenol/formaldehyde resin. This reaction
generates heat causing the low boiling liquid to vaporize within the bubbles
in the resin. Consequently a foam is created from this mixture. Typically,

274 Reactive Polymers Fundamentals and Applications
within 10 minutes the foam rises to its maximum height and hardens when
fully cured.
4.6.7 Visbreaking of Petroleum
Mild thermal cracking (visbreaking) of the gas oil fraction boiling above
350°C can be achieved in the presence of 0.5% of a polymeric phenol/-
formaldehyde sulfonate (PFS) used as a promoter. The addition of PFS as
a promoter accelerates the free radical chain reaction. 23
4.7 TESTING METHODS
Several test methods are commonly used to characterize a phenolic resin. 22
Subsequently,these methods are described.
4.7.1 Water Tolerance
Distilled water at 25°C is gradually added to 10 g resin until the resin
solution turns hazy. The water tolerance of a resin is an indication of the
miscibility of the resin with water. It is an important parameter for resin
used in fiberglass binders since the phenolic resin is normally diluted with
water to a concentration as low as 2%. Maintaining a clear solution without
phase separation at such dilution is essential for trouble-free processing and
for high quality film properties. Typically a water tolerance of 25 times is
required. The higher the water tolerance of the resin is, the lower is the
molecular weight of the resin. A low molecular weight resin has more
polar end groups than a more condensed resin.
4.7.2 Salt Tolerance
For the salt tolerance test, a 10% sodium chloride solution is added to the
phenolic resin solution gradually until the resin solution turns hazy.
This is another method to measure the ability of the resin to mix with
water and remain clear without precipitation, similar to water tolerance
except that it is more challenging to the resin.

Phenol/formaldehyde Resins 275
4.7.3 Free Phenol Content
The free phenol content is measured by gas chromatography. It is the
amount of phenol in the resin at the end of synthesis. A lower number
is preferred for increased resin efficiency and lower emissions.
4.7.4 Free Formaldehyde
The free formaldehyde content is measured commonly by the hydroxylamine
titration method. This is the amount of formaldehyde left unreacted
with phenol in the resin at the end of synthesis. A lower number is preferred
for higher resin use efficiency and lower emissions.
4.7.5 pH
The pH measures the basicity of the resin. A certain basic pH should be
preferably maintained for the resin to be free of precipitation and to have a
high water tolerance.
4.7.6 Solids Content
The solids content measures the concentration of the phenolic resin which
is not evaporable at the test temperature for the duration of the test. The
phenolic resin placed in an aluminum dish and is kept in a 150°C oven for
2 hours.
4.7.7 o-Cresol Contact Allergy
The presence of o-cresol was established as a contact sensitizer in a phenol/formaldehyde
resin. 74
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55. A. H. Conner, L. F. Lorenz, and K. C. Hirth. Accelerated cure of phenolformaldehyde
resins: Studies with model compounds. J. Appl. Polym. Sci.,
86(13):3256–3263, December 2002.
56. C. P. Chang and S. C. Hung. Manufacture of flame retardant foaming board
from waste papers reinforced with phenol-formaldehyde resin. Bioresour.
Technol., 86(2):201–202, January 2003.
57. W. M. Bajdur and W. W. Sulkowski. Application of modified wastes from
phenol-formaldehyde resin and expanded polystyrene in sewage treatment
processes. Macromol. Symp., 202:325–337, September 2003.
58. G. Tchobanoglous, F. L. Burton, and H. D. Stensel, editors. Wastewater
Engineering : Treatment and Reuse. McGraw-Hill series in civil and environmental
engineering. McGraw-Hill, Boston, 4th edition, 2003.
59. T. J. Taylor, W. H. Kielmeyer, C. M. Golino, and C. A. Rude. Emulsified
furan resin based glass fiber binding compositions, process of binding
glass fibers, and glass fiber compositions. US Patent 6 077 883, assigned to

280 Reactive Polymers Fundamentals and Applications
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Lafayette, IN), June 20 2000.
60. H. Sawada, A. Nishino, and A. Uesugi. Support for lithographic printing
plate and method of manufacturing the same. US Patent 6 670 099, assigned
to Fuji Photo Film Co., Ltd. (Minami-Ashigara, JP), December 30 2003.
61. W. R. Walisser. Resole melamine dispersions as adhesives. US Patent
5 296 584, assigned to Borden, Inc. (Columbus, OH), March 22 1994.
62. A. Žmihorska Gotfryd. Coating compositions based on modified phenolformaldehyde
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63. K. Lenghaus, G. G. Qiao, and D. H. Solomon. The effect of formaldehyde
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64. N. Kishore, S. Sachan, K. N. Rai, and A. Kumar. Synthesis and characterization
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65. W. Wei, H. Hu, G. Qin, L. You, and G. Chen. Pore structure control of phenol-formaldehyde
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66. W. Wei, H. Hu, L. You, and G. Chen. Preparation of carbon molecular
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67. M. I. Kim, C. H. Yun, Y. J. Kim, C. R. Park, and M. Inagaki. Changes
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68. M.-C. Huang and H. Teng. Urea impregnation to enhance porosity development
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69. J. Lahaye, G. Nanse, A. Bagreev, and V. Strelko. Porous structure and surface
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70. M.-C. Huang and H. Teng. Nitrogen-containing carbons from phenol-formaldehyde
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Phenol/formaldehyde Resins 281
74. M. Bruze and E. Zimerson. Contact allergy to o-cresol—a sensitizer in
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198–200, December 2002.

5
Urea/formaldehyde Resins
Urea/formaldehyde glue resins are the most important type of urea/formaldehyde-resins.
Monographs on the chemistry of urea/formaldehyde resins
include those by Dunky, Meyer and Pizzi, Dijk. 1–4
The industrial production of urea/formaldehyde glue resins for the
wood-working industry started in 1931. Environmental concerns demanded
a change of the formulation of urea/formaldehyde-resins to decrease the
molar ratio of formaldehyde to urea to avoid formaldehyde emissions.
5.1 HISTORY
The reaction of urea with formaldehyde was first noted in 1884, with commercial
interest in the polymers commencing at about 1918 with a patent
issued to Hanns John (1891–1942). 5–7 However, in 1896 Carl Goldschmidt
described precipitates formed when aqueous solutions of urea and formaldehyde
were reacted under acidic conditions. 8 It is believed that the
primary precipitate formed by Goldschmidt and empirically identified as
C 5 H 10 O 3 N 4 was, in fact, a cyclically structured condensation product. 9
5.2 SYNTHESIS OF RESIN
5.2.1 Formaldehyde
Formaldehyde is available in many forms. Paraform (solid, polymerized
formaldehyde) and formalin solutions (aqueous solutions of formaldehyde,
283

284 Reactive Polymers Fundamentals and Applications
sometimes with methanol, in 37%, 44%, or 50% formaldehyde concentrations)
are commonly used forms. Formaldehyde is also available as a gas.
Typically, formalin solutions are the preferred source of formaldehyde.
5.2.2 Urea
Solid urea, such as prill, and urea solutions, typically aqueous solutions,
are commonly available. Further, urea may be combined with another moiety,
typically formaldehyde, often in an aqueous solution.
5.2.3 Ammonia
Ammonia is used to reduce the free formaldehyde content. Ammonia is
available in various gaseous and liquid forms, particularly including aqueous
solutions at various concentrations. Any of the commercially-available
aqueous ammonia-containing solutions are the preferred form.
Such solutions typically contain between 10 to 35% ammonia. A
solution having 35% ammonia can be used, providing stability and control
problems can be overcome. An aqueous solution containing about 28%
ammonia is particularly preferred.
Ammonia or late additions of urea are commonly used to reduce free
formaldehyde levels in urea/formaldehyde polymer systems. Ammonia
reduces the cured polymers’ resistance to hydrolysis. The addition of urea
tends to produce a polymer that releases smoke during the cure cycle. 10
5.2.4 Diketones
Small additions of acetylacetone and ammonia to urea/formaldehyde resin
can bind the free formaldehyde. 11 The addition causes the formation
of 2,6-dimethyl-3,5-diacetyl-1,4-dihydropyridine (3,5-diacetyl-1,4-dihydrolutidine)
by a Hantz reaction, as shown in Figure 5.1.
5.2.5 Specialities
5.2.5.1 Cationic Urea Formaldehyde Resins
A water soluble cationic resin is prepared by initially reacting urea and
formaldehyde at a formaldehyde to urea mole ratio of 2 to 3 together with
triethanolamine in a urea to triethanolamine mole ratio of 2 to 3. The
resin formed is made cationic by acidifying it to a pH of 1.5, with a strong

Urea/formaldehyde Resins 285
CH 3
C O
CH 2
C O
CH 3
CH 2 O, NH 4 OH
H 3 C
H N
H 3 C
CH 3
C
O
O
C
CH 3
Figure 5.1: Binding of Formaldehyde by Acetylacetone
inorganic acid such as hydrochloric, sulfuric, or nitric acid, followed by
prompt neutralization to a pH of 6 to 7. A pH above 7 is discouraged as
this retards the cure of the resin.
Cationic urea formaldehyde resins with polymers containing vinylamine
units improve the properties of paper with respect to dry strength
and wet strength. 12
Suitable polymers containing polymerized vinylamine units can be
prepared by hydrolysis of homopolymers and copolymers containing polymerized
N-vinylamide units.
Examples for such polymers are a homopolymer of N-vinylformamide
and a copolymer of methacrylic acid and N-vinylformamide. The
amide group is often only partly hydrolyzed, say to an extent of 25%. The
cationic urea/formaldehyde resins are infinitely dilutable with water.
Aqueous solutions of cationic urea/formaldehyde resins typically
have a solid content between 25 and 45%. The aqueous resin solutions or
the solid products obtained therefrom are used as additives for increasing
the dry and wet strength of paper in papermaking. The resins, in the form
of aqueous solutions, are added to the paper stock prior to sheet formation.
Water-soluble Resins. Water-soluble cationic urea/formaldehyde resins
are obtained by condensing urea and formaldehyde in the presence of polyamines.
The reactants are first precondensed in alkaline pH range, then condensed
in acidic pH range until gel formation begins. They are subjected to
post-condensation, for example, with formaldehyde, and are subsequently
neutralized. 12

286 Reactive Polymers Fundamentals and Applications
5.2.5.2 Melamine-modified Resins
Urea is the standard nitrogen-containing component in urea/formaldehyde
resins. Resins with improved properties can be obtained by substitution of
the urea with melamine. Sulfitation of the methylol groups can improve the
resin properties. Still another approach is the co-condensation with amines
and the introduction of urea-terminated amines. Melamine improves the
resistance against attack by humidity and water, especially at elevated temperatures.
Melamine contents up to 25% are used. 1,1,2,2-Tetramethoxyethane
(TME) is a high boiling point diacetal (165°C). It can be synthesized
from glyoxal. Such acetals improve the performance of melamine/urea/-
formaldehyde resins. The acetal as cosolvent increases the solubility of
both the unreacted melamine and the oligomers in water. Thus a more effective
reaction can be achieved. 13 The improvement of mechanical properties
by the addition of acetals such as methylal and ethylal occurs because
of the by increased effectiveness and participation of the melamine to the
crosslinking reactions. 14
Iminoamino methylene base intermediates are obtained by the decomposition
of hexamethylenetetramine in the presence of strong anions
such as SO 2−
4
and HSO − 4
. These compounds improve the weathering resistance
of hardened melamine/urea/formaldehyde resins. 15
5.2.6 Polymerization
The synthesis of a urea/formaldehyde (UF) resin proceeds via the methylolation
of urea and condensation of the methylol groups. The reaction
can be conducted in an aqueous medium because of the good solubility
of both urea and formaldehyde. The basic reactions are shown in Figure
5.2. The methylolation of urea is done in alkaline or slightly acidic
solution in a two-fold excess of formaldehyde. Following methylolation,
further condensation into methylene urea oligomers occurs, with a degree
of oligomerization of 4 to 8. Because of the functionality of the nitrogen,
branched products can be formed. Ether bridges also may be formed.
These ether bridges can be rearranged into methylene bridges, expelling
formaldehyde. Dimethylol urea is not a stable compound. In the presence
of another formaldehyde reactive compound, dimethylol urea will donate
its two formaldehyde groups to the more stable phenol, ammonia, melamine,
etc. This leaves raw urea in the resin which reduces the durability
significantly. 10

Urea/formaldehyde Resins 287
O
C
H 2 N NH 2
+
H 2 C O C
H 2 N NH CH 2 OH
O
O
C
H 2 N NH CH 2 OH
O
C
O
C
H 2 N NH CH 2 O CH 2 N NH 2
O
O
C
C
H 2 N NH CH 2 N NH 2
Figure 5.2: Basic Reactions of Urea and Formaldehyde

288 Reactive Polymers Fundamentals and Applications
Table 5.1: Feed for a Urea Formaldehyde Resin 16
Reactant
mol
Formalin solution, 50% CH 2 O 14.5
Ethylene diamine 0.3
Urea (first charge) 12.1
NH 4 OH, 28% 6.1
UFC 85: water a 14.4
CH 2 O 34.5
Urea 7.2
Urea (second charge) 3.5
Alum (KAlSO 4 × 12H 2 O) 50% 0.2
NaOH 25% 0.02
Latent catalyst 0.02
Water 1.6
a : 25% urea, 60% formaldehyde and 15% water
5.2.6.1 UF three-step preparation
The resin is prepared by reacting urea and formaldehyde in a three-step
process.
1. Urea and formaldehyde are reacted in the presence of ammonia,
at an excess formaldehyde of 1.2 to 1.8. A cyclic triazone/triazine
polymer is formed at 85 to 95°C within 2 hours.
2. A thermosetting polymer is formed from the cyclic polymer. To
the reaction mixture containing triazole/triazine polymer, an additional
portion of formaldehyde is added, preferably with additional
urea, to yield a higher cumulative F/U mole ratio of 2 to 2.7. The
pH is adjusted to 6.0 to 6.4.
3. If the resin is not used immediately, a third neutralization step
should be employed, preferably with sodium hydroxide.
Use of ammonia or late additions of urea are common techniques
for reducing free formaldehyde content of urea/formaldehyde polymer systems.
5.2.6.2 Synthesis Procedure
An example of a synthesis procedure is given here. The reactants that are
used to prepare a urea/formaldehyde resin are listed in Table 5.1. The re-

Urea/formaldehyde Resins 289
sin is prepared by charging the 50% formalin, ethylene diamine, and urea
into a reactor and heating the mixture to 45°C to dissolve the urea. Then
NH 4 OH is added which causes the mixture to have an exothermic reaction
reaching a temperature of 83°C. The reaction mixture is heated further to
95°C and maintained at that temperature for 90 minutes. A cyclic polymer
is formed in this initial phase of the chemical reaction. The triazone
concentration can be over 50% of the total polymer mix at this stage of
the synthesis, depending on the molar ratios of the ingredients. The pH
of the mixture is maintained between 8.7 and 9.3 by adding 25% NaOH
as needed ( a total of 0.4 mol). The reaction mixture is then cooled to
85°C. UFC 85 (25% urea, 60% formaldehyde, and 15% water) and a second
charge of urea are added to the reaction mixture. The temperature
is thereafter maintained at 85°C for 10 minutes. The pH is adjusted from
about 6.2 to 6.4 by adding a total of 0.2 mol of alum (KAlSO 4 ×12H 2 O) in
increments over a course of 25 minutes. The reaction mixture was cooled
to 80°C, and after 15 minutes, further cooled to 75°C. After 7 minutes, the
reaction mixture is cooled to 55°C, 26.9 g 25% NaOH is added, and then
the mixture is further cooled to 35°C. A latent catalyst was added and the
reaction mixture is cooled to 25°C. The pH is finally adjusted to 7.6 to 8.2
with 25% NaOH. The free formaldehyde content of the resin is 0.59%. After
24 hours the free formaldehyde content drops to 0.15%. The viscosity
of the resin is 573 cP.
5.2.6.3 Cyclic Melamine/urea/formaldehyde Prepolymer
Cyclic urea prepolymers may be used as modifiers of thermosetting phenol/formaldehyde
and melamine/formaldehyde-based resins for a variety of
end uses. These prepolymers are urea/formaldehyde polymers containing
at least 20% triazone and substituted triazone compounds. The use of cyclic
urea prepolymer in such resin binders provides properties superior to
those obtained from using the resin alone, in many applications. The resins
are modified with the cyclic urea prepolymer, either by reacting into
the base resin system, blending with the completed base resin system, or
blending into a binder preparation. Suitable primary amines can be used in
the formulation, such as methylamine, ethylamine, and propylamine, ethanolamine,
cyclopentylamine, ethylene diamine, hexamethylene diamine,
and linear polyamines.
A methylolated cyclic urea prepolymer is typically prepared by re-

290 Reactive Polymers Fundamentals and Applications
acting urea, ammonia, and formaldehyde and then reacting with 2 mol of
formaldehyde to produce a methylolated cyclic urea prepolymer having
50% solids. 13 C-NMR indicates that 42.1% of the urea is contained in the
triazone ring structure, 28.5% of the urea was di/tri-substituted, 24.5% of
the urea is mono-substituted, and 4.9% of the urea is free. This cyclic urea
prepolymer is then reacted into a standard phenol/formaldehyde resin during
the cook cycle of the phenol/formaldehyde resin. In many systems, a
cyclic prepolymer is either cooked into the resin or added to a resin. 10
5.2.7 Manufacture
The production of UF resins is usually achieved in three stages. 3
1. Methylolation: urea reacts with aqueous formaldehyde under alkaline
conditions at temperatures up to 100°C.
2. Condensation: the condensation of methylols in slightly acidic
medium yields oligomers with different molar mass and various
functionalities. The condensation is then stopped by adding alkaline
substances.
3. Post treatment: evaporation of excess water and formaldehyde, or
addition of secondary urea to decrease the ratio of formaldehyde
to urea.
The multistage process is useful to fulfill the requirements of retaining
the reactivity and the strength of the cured resin under the condition of
minimal emission of formaldehyde during service.
5.3 SPECIAL ADDITIVES
5.3.1 Modifiers
A requirement is that the additives does not increase the viscosity of the
suspension significantly, but would improve the toughness and the moisture
resistance of UF resin. Thermoplastic acrylic copolymers with different
degrees of hydrophilicity were added to a UF resin. The copolymers consist
of two or three monomers selected from methyl methacrylate, acrylamide,
acrylic acid, 1-vinyl-2-pyrrolidinone, ethyl acrylate, and vinyl acetate.
The SEM micrographs of cured thermoplastic-modified UF showed
a phase-separated thermoplastic structure in a continuous UF phase when

Urea/formaldehyde Resins 291
Table 5.2: Global Production/Consumption Data of Important Monomers
and Polymers 17
Monomer Mill. Metric tons Year Reference
Urea 110 2002
18
Formaldehyde 24 2003
19
Amino resins 8.4 2002
20
UF was modified with a self-dispersed and surfactant-stabilized polymer
type. However, when the UF was modified with a water-soluble polymer,
a single phase was detected.
21, 22
A water soluble, styrene-maleic anhydride copolymer can be used a
modifier for binder resins. Glass fiber mats made with the modified binder
composition exhibit an enhanced wet tensile strength, wet mat strength,
tear strength, and dry tensile strength. Because of this strength improvement,
the mat processing speeds through the cure oven can be significantly
increased without risking breakage of the continuous mat. 23
5.3.2 Flame Retardants
As flame retardants, ammonium hydrogenphosphate ((NH 4 ) 2 HPO 4 ) and
sodium tetraborate (Na 2 B 4 O 7 ) were tested together with mineral fillers
such as vermiculite, phlogopite, clay, etc. The increased flame resistance
results from the evolution of noncombustible gases. 24
5.3.3 Production Data of Important Monomers
Production data of important raw materials are shown in Table 5.2. Urea is
mostly used as a fertilizer. Only a small fraction is used for urea/formaldehyde
resins. Formaldehyde is used not exclusively for urea/formaldehyde
resins. Other major uses are phenol/formaldehyde resins, polyacetal resins,
pentaerythritol 1,4-butanediol and hexamethylenetetramine. Amino resins
include melamine/formaldehyde resins and melamine/urea/formaldehyde
resins, besides urea/formaldehyde resins.
5.4 CURING
During curing, an insoluble, infusible, three-dimensional network is constructed.
Curing is initiated by lowering the pH. This is achieved by the ad-

292 Reactive Polymers Fundamentals and Applications
N
H 2 C O
+
(NH 4 ) 2 SO 4
N
N
+
H 2 SO 4
N
Figure 5.3: Reaction of Ammonium Sulfate with Formaldehyde
dition of acids, such as phosphoric acid or maleic acid. Acidic salts, e.g.,
aluminum sulfate, or urea phosphate can be added. Further anhydrides,
such as maleic anhydride, decompose in aqueous medium into acids. Ammonium
sulfate reacts with formaldehyde to form hexamethylenetetramine
and sulfuric acid, as shown in Figure 5.3.
Ammonium chloride is now avoided for acidification in favor of ammonium
sulfate. Residual ammonium chloride forms hydrochloric acid
during the combustion of wood-based panels. It is suspected that the chlorine
promotes the formation of chlorodioxins. Usually 2 to 3% of ammonium
salt-based on the solid content of resin are sufficient as catalyst. Excess
catalyst causes over-curing. Brittle resins are then formed, with less water
resistance. Formaldehyde is the primary reactive component in urea/formaldehyde
resins.
A higher reactivity and a higher crosslinking density of the final network
formation can be achieved by a higher formaldehyde-to-urea ratio.
On the other hand, free formaldehyde is undesirable for toxicological reasons.
Resins with very low formaldehyde content exhibit several drawbacks
of the final product. These can be minimized, however by a special
condensation process, the use of special accelerators, and by the modification
of the formulation with melamine.
5.5 MEASUREMENT OF CURING
Curing can be monitored by thermal methods, as well as utilizing spectroscopic
methods. The curing reaction in an ammonium chloride catalyzed
system starts at around 100°C, whereas in an uncatalyzed system the curing
reaction starts between 120 to 180°C. 25 In comparison to PF resins, the
activation energy of curing of UF resins is generally higher. Nevertheless,

Urea/formaldehyde Resins 293
the curing rates of UF resins are faster. 26 The pH values in UF formulations
have a significant influence on the rate constants, but they affect the
activation energy of curing marginally.
The curing reaction in the presence of wood has been measured using
15 N-distortionless enhancement by polarization transfer nuclear magnetic
resonance spectroscopy (DEPT NMR). 27 A DEPT pulse sequence
was employed to follow the curing of urea/formaldehyde resin.
5.6 PROPERTIES
5.6.1 Formaldehyde Release
Typically, when urea/formaldehyde resins are cured, they release formaldehyde
into the environment. Formaldehyde can also be released from the
cured resin, particularly when the cured resin is exposed to acidic environments.
Such formaldehyde release is undesirable, particularly in enclosed
environments. Formaldehyde is malodorous and is considered hazardous
to human and animal health. Various techniques have been used to reduce
formaldehyde emission from urea/formaldehyde resins.
Use of formaldehyde scavengers and methods for resin formulation,
including addition of urea as a reactant late in the resin formation reaction,
are techniques used to reduce formaldehyde emission. However, the use
of formaldehyde scavengers often is undesirable, not only because of the
additional cost, but also because it affects the properties, of the resin. For
example, using ammonia as a formaldehyde scavenger reduces the resistance
of the cured resin to hydrolysis. Later addition of urea to reduce free
formaldehyde concentration in the resin generally yields a resin that must
be cured at a relatively low rate to avoid smoking. The stability of the resin
can also be adversely affected by such treatments. 16 Instead of urea,
triethanolamine can be added to a mixture of urea and formaldehyde.
5.6.2 Storage
During storage, urea/formaldehyde resins undergo reactions that result in
structural changes. Methylene groups adjacent to secondary amino groups
are formed by the main reaction. This reaction proceeds between the free
terminal hydroxymethyl and amino groups. 28

294 Reactive Polymers Fundamentals and Applications
5.7 APPLICATIONS AND USES
5.7.1 Glue Resins
The main application of urea/formaldehyde resins is in the adhesive industry.
Urea/formaldehyde glues are used in pressed wood products such
as particle board, and plywood as laminating resins. Because of the potential
for formaldehyde release, UF resins have been modified for indoor
applications. Formaldehyde is a potent primary irritant.
5.7.2 Binders
Typical binders used to bind glass fiber mats include urea/formaldehyde
resins, phenolic resins, melamine resins, bone glue, polyvinyl alcohols,
and latices. These binder materials are impregnated directly into the fibrous
mat and set or cured by heating to obtain the desired integrity in
glass fibers. The most widely used glass mat binder is urea/formaldehyde,
because it is relatively inexpensive. 16
5.7.3 Foundry Sands
In the manufacturing of low nitrogen-containing foundry sands, the hexamine
crosslinker is replaced partly with another crosslinking agent that
does not contain nitrogen. Nitrogen, when present in coated foundry sand
can give rise to nitrogen defects during steel casting. It is preferable to
have as low of nitrogen content as possible. Usually this other crosslinking
agent is a thermosetting resol phenol/formaldehyde resin. During the
manufacturing of low nitrogen-containing sands, a novolak resin is added,
followed by the resol resin and then the hexamine. 10
5.8 SPECIAL FORMULATIONS
5.8.1 Ready-use Powders
For small scale applications, e.g., as adhesive, ready-use powders of urea/formaldehyde
resins are dissolved in water. The formulation contains
fillers, extenders, hardeners, scavengers, and other additives which have to
be mixed with water only.

Urea/formaldehyde Resins 295
5.8.2 Cyclic Urea Prepolymer in PF Laminating Resins
Phenol/formaldehyde resins used to manufacture high pressure laminates
are typically produced by reacting phenol and formaldehyde by means of
an alkaline catalyst such as sodium hydroxide. 10
Typical mole ratios of formaldehyde to phenol range from 1.2 to 1.9
mol of formaldehyde per mol of phenol. Catalyst levels range from 0.5 to
3%.
The materials are reacted to a suitable endpoint, cooled under vacuum,
and usually distilled to remove the water present from the formaldehyde
solution as well as the water of condensation from the polymerization
reaction. They may be used in this state or an organic solvent such as methanol
can be added to reduce the solids concentration and viscosity of the
mixture.
A cyclic urea prepolymer in phenol-formaldehyde resins acts as a
plasticizer for the resin. This makes the laminate more post-formable and
tougher. Products produced with such resins resist chipping and breakage
during machining steps. Diluting the phenol-formaldehyde resin with
cyclic urea prepolymer reduces the free phenol and other volatile phenolic
moiety levels of the phenol-formaldehyde resin which reduces air pollution.
Because of the plasticizing effect achieved with the cyclic urea prepolymer,
higher F/P mole ratio PF resins (traditionally more brittle) can be
used which further reduces the free phenol and volatile phenolic moiety
levels.
5.8.3 Liquid Fertilizer
Urea/formaldehyde-based liquid fertilizers can provide nitrogen to the soil.
In addition to nitrogen, phosphorous and potassium are considered major
nutrients essential for plant growth. Long-term stability of high nitrogen
liquid urea/formaldehyde fertilizers can be achieved by forming either a
high percentage (more than 30%) of cyclic triazone structures or by condensing
the urea/formaldehyde resin into small urea/formaldehyde polymer
chains. 29
5.8.4 Soil Amendment
Urea/formaldehyde resin foams are used as a soil amendment for agricultural
applications. The amendment by UF foams does not influence the pH

296 Reactive Polymers Fundamentals and Applications
and causes insignificant alterations to the physical properties of the soil by
slightly increasing total porosity, water availability, and the porosity, and
by reducing the bulk density. 30
5.8.5 Microencapsulation
Self-healing polymers and composites with microencapsulated healing agents
offer a possibility for long-lived polymeric materials. Healing agents
have been microencapsulated using urea/formaldehyde resins. The microcapsules
must have sufficient strength to remain intact during polymer processing.
However, the microcapsules should break when the polymer is
damaged. 31
REFERENCES
1. A. Pizzi. Urea-formaldehyde adhesives. In A. Pizzi, editor, Advanced Wood
Adhesives Technology. Marcel Dekker, New York, 1994.
2. B. Meyer. Urea-Formaldehyde Resins. Addison-Wesley, London, 1979.
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Polymeric Materials Encyclopaedia: Synthesis, Properties and Applications,
pages 1598–1599. CRC Press, Boca Raton, FL, 1999.
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December 26 1995.
13. M. Zanetti, A. Pizzi, and P. Faucher. Low-volatility acetals to upgrade the
performance of melamine-urea-formaldehyde wood adhesive resins. J. Appl.
Polym. Sci., 92(1):672–675, April 2004.
14. M. Zanetti, A. Pizzi, M. Beaujean, H. Pasch, K. Rode, and P. Dalet. Acetalsinduced
strength increase of melamine-urea-formaldehyde (MUF) polycondensation
adhesives. II. solubility and colloidal state disruption. J. Appl.
Polym. Sci., 86(8):1855–1862, November 2002.
15. C. Kamoun, A. Pizzi, and M. Zanetti. Upgrading melamine-urea-formaldehyde
polycondensation resins with buffering additives. I. the effect of hexamine
sulfate and its limits. J. Appl. Polym. Sci., 90(1):203–214, October
2003.
16. L. R. Graves. Urea-formaldehyde resin composition and method of preparation
thereof. US Patent 5 674 971, assigned to Georgia-Pacific Resins, Inc.
(Atlanta, GA), October 7 1997.
17. R. Gubler, editor. Chemical Economics Handbook (CEH). SRI Consulting, a
Division of Access Intelligence, Menlo Park, CA, 1950–to present. (Internet:
http://ceh.sric.sri.com/).
18. D. H. Lauriente. Report “Urea”. In Chemical Economics Handbook (CEH).
SRI Consulting, a Division of Access Intelligence, Menlo Park, CA, July
2004. (Internet: http://ceh.sric.sri.com/).
19. S. Bizzari. Report “Formaldehyde”. In Chemical Economics Handbook
(CEH). SRI Consulting, a Division of Access Intelligence, Menlo Park, CA,
January 2004. (Internet: http://ceh.sric.sri.com/).
20. E. Greiner. Report “Amino Resins”. In Chemical Economics Handbook
(CEH). SRI Consulting, a Division of Access Intelligence, Menlo Park, CA,
February 2004. (Internet: http://ceh.sric.sri.com/).
21. P. Rachtanapun and P. Heiden. Thermoplastic polymers as modifiers for urea-formaldehyde
(UF) wood adhesives. I. procedures for the preparation and
characterization of thermoplastic-modified UF suspensions. J. Appl. Polym.
Sci., 87(6):890–897, February 2003.
22. P. Rachtanapun and P. Heiden. Thermoplastic polymers as modifiers for urea-formaldehyde
(UF) wood adhesives. II. procedures for the preparation and
characterization of thermoplastic-modified UF wood composites. J. Appl.
Polym. Sci., 87(6):898–907, February 2003.

298 Reactive Polymers Fundamentals and Applications
23. S.-G. Chang, L. R. Graves, C. R. Hunter, and S. L. Wertz. Modified ureaformaldehyde
binder for making fiber mats. US Patent 6 084 021, assigned
to Georgia-Pacific Resins, Inc. (Atlanta, GA), July 4 2000.
24. A. N. Egorov, Y. I. Sukhorukov, G. V. Plotnikova, and A. K. Khaliullin. Fireproofing
coatings based on urea resins for metallic structures. Russ. J. Appl.
Chem., 75(1):152–155, January 2002.
25. J. Lisperguer and C. Droguett. Curing characterization of urea formaldehyde
resins by differential scanning calorimetry (DSC). Bol. Soc. Chilena Quim.,
47(1):33–38, March 2002.
26. G. B. He and B. Riedl. Phenol-urea-formaldehyde cocondensed resol resins:
Their synthesis, curing kinetics, and network properties. J. Polym. Sci., Part.
B: Polym. Phys., 41(16):1929–1938, August 2003.
27. B. D. Gill, M. Manley-Harris, and R. A. Thomson. Use of natural abundance
15 N DEPT NMR to investigate curing of urea-formaldehyde resin in
the presence of wood fibers. Magn. Reson. Chem., 41(8):622–625, August
2003.
28. P. Christjanson, K. Siimer, T. Pehk, and I. Lasn. Structural changes in urea-formaldehyde
resins during storage. Holz als Roh- und Werkst., 60(6):
379–384, December 2002.
29. K. D. Gabrielson. Controlled release urea-formaldehyde liquid fertilizer resins.
US Patent 6 632 262, assigned to Georgia-Pacific Resins, Inc. (Atlanta,
GA), October 14 2003.
30. P. A. Nektarios, A.-E. Nikolopoulou, and I. Chronopoulos. Sod establishment
and turfgrass growth as affected by urea-formaldehyde resin foam soil
amendment. Scientia Horticulturae, 100(1-4):203–213, March 2004.
31. E. N. Brown, M. R. Kessler, N. R. Sottos, and S. R. White. In situ poly(ureaformaldehyde)
microencapsulation of dicyclopentadiene. J. Microencapsul.,
20(6):719–730, November–December 2003.

6
Melamine Resins
Melamine resins rely on 1,3,5-triazine-2,4,6-triamine and formaldehyde.
They are similar to urea formaldehyde polymers.
6.1 HISTORY
The industrial use of melamine resin started in the late 1930s when the
Swiss company CIBA began the industrial production of melamine from
dicyandiamide. 1, 2 Earlier, the use of this resin was limited because of its
high price. Now melamine can be produced cheaper from urea, so the
economical situation is improved.
6.2 MONOMERS
6.2.1 Melamine
Melamine may be partially or totally replaced with other suitable aminecontaining
compounds. Alternatives to melamine include urea, thiourea,
dicyandiamide, 2,5,8-triamino-1,3,4,6,7,9,9b-heptaazaphenalene (melem),
(N-4,6-diamino-1,3,5-triazin-2-yl)-1,3,5-triazine-2,4,6-triamine (melam),
melon, ammeline, ammelide, substituted melamines, and guanamines. 3
The melamine homologues melam, melem, and melon have higher thermal
stability than pure melamine. These compounds are also used as flame
retardants.
299

300 Reactive Polymers Fundamentals and Applications
Substituted melamines include alkyl melamines and aryl melamines.
Representative examples of some alkyl-substituted melamines include
methylmelamine, dimethylmelamine, trimethylmelamine, ethylmelamine,
and 1-methyl-3-propyl-5-butylmelamine. Typical examples of an
aryl-substituted melamine are phenylmelamine or diphenylmelamine. Melamine
and related compounds are shown in Figure 6.1. Foams and fibers
exhibit increased elasticity, when some of the melamine is replaced by
a substituted melamine, e.g., N-mono-, N,N ′ -bis- and N,N ′ ,N ′′ -tris(5-hydroxy-3-oxapentyl)melamine.
4 However, based on considerations of cost
and availability, standard melamine is generally preferred.
6.2.2 Other Modifiers
Suitable resin modifiers are ethylene diamine, melamine, ethylene ureas,
and primary, secondary, and tertiary amines. Dicyandiamide can be also
incorporated into the resin.
The concentrations of these modifiers in the reaction mixture may
vary typically from 0.05 to 5.00%. All these modifiers promote hydrolysis
resistance, polymer flexibility, and lower formaldehyde emissions. 5
6.2.3 Synthesis
Similar to urea, melamine reacts with formaldehyde in weakly alkalineaqueous
media to form methylol compounds. Melamine is hexafunctional,
so up to hexamethylol monomers can be formed. Hexamethylol melamine
is shown in Figure 6.2.
The further condensation proceeds under neutral and acidic conditions,
thereby forming methylene or dimethylene ether bonds. A pure melamine
resin gels within a few days at room temperature. Because of this
undesired property, melamine resins are blended with urea resins.
6.2.3.1 Etherified Resins
Etherified resins are prepared by the reaction of melamine with formaldehyde
under the conditions of pH around 6 and reflux temperature in the
presence of a large amount of butanol. Xylene cycles out the water formed
by the condensation reaction by azeotropic distillation and accelerates the
etherification in this way.

Melamine Resins 301
H
H 2 N N NH 2
N N
NH 2
H 2 N
N
N
N
NH 2
N
N
N NH 2
N
NH 2
Melamine
Melam
NH 2
NH 2
NH 2
N
N
N
N
N
N
N
N
N
N
H 2 N
N
N
H 2 N
N
N
NH
n
Melem
Melon
H 2 N N NH 2
N
N
Benzoguanamine
H
HH
N N
H
C C
N
N
H
Dicyandiamide
Figure 6.1: Melamine, Melam, Melem, Melon, Benzoguanamine, Dicyandiamide

302 Reactive Polymers Fundamentals and Applications
H 2 N N NH 2
H 2 C O
N
N
+
NH 2
HOH 2 C
N
HOH 2 C
N
N
CH 2 OH
N
CH 2 OH
N
HOH 2 C
N
CH 2 OH
Figure 6.2: Hexamethylol melamine from Melamine and Formaldehyde
6.2.4 Manufacture
Melamine is mixed with neutralized formaldehyde solution. The excess
of formaldehyde is about threefold. The mixture is heated to 75 to 85°C.
When the solution becomes cloudy, water is admixed. Then fillers can be
admixed for molding resins. The mixture is dried at 70 to 80°C. while the
condensation reaction still proceeds.
In the co-condensation of melamine and urea, due to the difference
in reactivity of melamine and urea, the condensation of melamine moiety
is quicker than the urea moiety.
6.3 PROPERTIES
Phenol/formaldehyde resins and melamine/formaldehyde resins are standard
resins used for many products. The choice of resin depends on the
desired properties. Phenol/formaldehyde resins are strong and durable and
relatively inexpensive, but are generally colored resins. Melamine resins
are water clear but are more expensive. They are generally used for products
where the color or pattern of the substrate is retained with a transparent

Melamine Resins 303
melamine protective coating or binder.
The emission of formaldehyde in melamine/urea/formaldehyde resins
is decreased as the melamine content is increased. 6 This is explained
due to the stronger bonding between triazine carbons of melamine than
those of urea carbons. Sulfonated melamine/formaldehyde resins exhibit
good solubility in water. 7
6.4 APPLICATIONS AND USES
Melamine based resins are widely used as adhesives for wood, as resins for
decorative laminates, varnish, and moldings, and for improving the properties
of paper and cellulosic textiles. In comparison to urea formaldehyde
resins, a melamine-based resin has higher resistance against heat and moisture.
Etherified melamine resins are often used in combination with alkyd
resins for production of decorative laminates. Modification of textiles
by melamine is used to impart crease resistance and shrinkage. The wet
strength of paper is greatly improved by the use of melamine resins as
wet-end additives.
Acoustic ceiling tiles are backcoated with melamine resins in order
to make them more rigid and humidity-resistant when installed in suspended
ceilings. Melamine resins are also used for the preparation of decorative
or overlay paper laminates. This application is due to their excellent
color, hardness, and solvent, water, and chemical resistance, heat resistance,
and humidity resistance.
Molded articles, such as dinnerware, are prepared with a combination
of melamine/formaldehyde resins and urea/formaldehyde resins. The
resins are combined because the melamine/formaldehyde resin is too expensive
by itself. The such articles made from these resins are generally
not very water-resistant or dimensionally stable. 5
6.4.1 Wood Impregnation
Melamine/formaldehyde (MF) belongs to the hardest and stiffest isotropic
polymeric materials used for decorative laminates, molding compounds,
adhesives, coatings, and other products. Due the high hardness and stiffness,
and low flammability, MF resins can be used to improve the properties
of solid wood. An MF resin can penetrate the amorphous region of

304 Reactive Polymers Fundamentals and Applications
wood. It has been established that significant portions of a suitable MF
resin penetrate the secondary cell wall layers and middle lamella of softwoods.
8
6.5 SPECIAL FORMULATIONS
6.5.1 Resins with Increased Elasticity
In foams and fibers, with increased elasticity, the melamine is partly replaced
by a hydroxy alkyl substituted melamine. To prepare these resins,
melamine and substituted melamine are polycondensed together with
formaldehyde. The feed may also contain small amounts of customary
additives, such as disulfite, formate, citrate, phosphate, polyphosphate, urea,
dicyandiamide, or cyanamide. 4 Moldings are produced by curing the
resins in a conventional manner by adding small amounts of acids, preferably
formic acid. Foams can be produced by foaming an aqueous solution
or dispersion containing the melamine/formaldehyde precondensate,
an emulsifier, a blowing agent and a curing agent.
6.5.2 Microspheres
Monodisperse melamine/formaldehyde microspheres have been prepared
via a dispersed polycondensation technique. The nucleation and growth
of the particles were achieved within short periods. A continuous coagulation
occurred even in the presence of surfactants. 9 Microcapsules are
interesting because of the controlled-release properties of the respective
encapsulated substances. A fragrant oil could be microencapsulated by an
in-situ polymerization. 10 The particle sizes ranged from 12 to 15 µm. The
efficiency of encapsulation of the fragrant oil reached up to 67-81%.
Microcapsules were prepared in a capillary flow microreactor and
also in a batch experiment. The microcapsules obtained from the microreactor
showed smaller particle diameters and a narrower particle size distribution
than those obtained in a batch experiment. 11
REFERENCES
1. M. Higuchi. Melamine resins (overview). In J. C. Salamone, editor, The
Polymeric Materials Encyclopaedia: Synthesis, Properties and Applications,
pages 837–838. CRC Press, Boca Raton, FL, 1999.

Melamine Resins 305
2. Gesellschaft für Chemische Industrie in Basel. Verfahren zur Herstellung
von 2.4.6-Triamino-1.3.5-triazin (Melamin). CH Patent 189 406, assigned to
Ciba AG, February 28 1937.
3. G. M. Crews, S. Ji, C. U. Pittman, Jr., and R. Ran. Ammeline-melamineformaldehyde
resins (amfr) and method of preparation. US Patent 5 254 665,
assigned to Melamine Chemicals, Inc. (Donaldsonville, LA), October 19
1993.
4. J. Weiser, W. Reuther, G. Turznik, W. Fath, H. Berbner, and O. Graalmann.
Melamine resin moldings having increased elasticity. US Patent 5 162 487,
assigned to BASF Aktiengesellschaft (Ludwigshafen, DE), November 10
1992.
5. F. C. Dupre, M. E. Foucht, W. P. Freese, K. D. Gabrielson, B. D. Gapud,
W. H. Ingram, T. M. McVay, R. A. Rediger, K. A. Shoemake, K. K. Tutin,
and J. T. Wright. Cyclic urea-formaldehyde prepolymer for use in phenolformaldehyde
and melamine-formaldehyde resin-based binders. US Patent
6 379 814, assigned to Georgia-Pacific Resins, Inc. (Atlanta, GA), April 30
2002.
6. S. Tohmura, A. Inoue, and S. H. Sahari. Influence of the melamine content
in melamine-urea-formaldehyde resins on formaldehyde emission and cured
resin structure. J. Wood Sci., 47(6):451–457, 2001.
7. L. H. Su, S. R. Qiao, J. Xiao, X. Tang, G. D. Zhao, and S. W. Fu. Synthesis
and properties of high-performance and good water-soluble melamine-formaldehyde
resin. J. Appl. Polym. Sci., 81(13):3268–3271, September 2001.
8. W. Gindl, F. Zargar-Yaghubi, and R. Wimmer. Impregnation of softwood
cell walls with melamine-formaldehyde resin. Bioresour. Technol., 87(3):
325–330, May 2003.
9. I. W. Cheong, J. S. Shin, J. H. Kim, and S. J. Lee. Preparation of monodisperse
melamine-formaldehyde microspheres via dispersed polycondensation.
Macromol. Res., 12(2):225–232, April 2004.
10. H. Y. Lee, S. J. Lee, I. W. Cheong, and J. H. Kim. Microencapsulation of
fragrant oil via in situ polymerization: effects of ph and melamine-formaldehyde
molar ratio. J. Microencapsul., 19(5):559–569, September–October
2002.
11. T. Sawada, M. Korenori, K. Ito, Y. Kuwahara, H. Shosenji, Y. Taketomi,
and S. Park. Preparation of melamine resin micro/nanocapsules by using
a microreactor and telomeric surfactants. Macromol. Mater. Eng., 288(12):
920–924, December 2003.

7
Furan Resins
Furan resins are condensation products of furfuryl alcohol (FA). The resins
are derived from vegetable cellulose, a renewable resource. 1 Furans as
constituents of polymers have been reviewed. 2
7.1 HISTORY
In Latin, furfur means bran. Furfural was first isolated in 1832 (or 1821)
by Döbereiner ∗ , as a by-product of the synthesis of formic acid. In 1840
the ability of furfural to form resins was discovered by Stenhous. 3 The
industrial production of furfural started in 1922, and one year later the first
furan-based resins emerged. Early patents on furan resins include that of
Claessen 4 and one for synthetic resins, (actually mixed phenol furan resins)
suitable for use in molding gramophone records. 5
7.2 MONOMERS
Monomers suitable for furan resins are listed in Table 7.1. One of the chief
advantages in furan resins stems from the fact that they are derived from
vegetable cellulose. Suitable sources of vegetable cellulose are corn cobs,
sugar cane bagasse, oat hulls, paper mill by-products, biomass refinery
1849
∗ Johann Wolfgang Döbereiner, born in Hof an der Saale 1780, in Germany, died in Jena
307

308 Reactive Polymers Fundamentals and Applications
Table 7.1: Monomers for Furan Resins 6
Furan Compound
Remarks or Reference
Furan
Furfural
Furfuryl alcohol
5-Hydroxymethylfurfural (HMF)
5-Methylfurfural
2-Furfurylmethacrylate
7
Bis-2,5-hydroxymethylfuran Glass fiber binder
2,5-Furandicarboxylic acid
O
OH
OH
OH
HO
OH
OH
OH
OH
OH
OH
O
C H
O
Figure 7.1: Mechanism of the Formation of Furfural
eluents, cottonseed hulls, rice hulls, and food stuffs such as saccharides
and starch. 6
Pentoses hydrolyze to furfural and hexoses give 5-hydroxymethylfurfural
on acid digestion. 8
7.2.1 Furfural
Furfuraldehyde is a by-product from the sugar cane bagasse which produces
resins with an excellent chemical stability and low swelling. 2-Furan
formaldehyde or furfural is made from agricultural materials by means of
hydrolysis.
The mechanism of formation of furfural is shown in Figure 7.1. It
is a light yellow to amber colored transparent liquid. Its color gradually
deepens to brown during storage. It tastes like apricot kernel. It is mainly

Furan Resins 309
used in lubricant refinement, furfuryl alcohol production, and pharmaceutical
production.
Furfural is the chief reagent used to produce materials such as furfuryl
alcohol, 5-hydroxymethylfurfural (HMF), bis(hydroxymethyl)furan
(BHMF), and 2,5-dicarboxyaldehyde-furan. The furan-containing monomers
in turn can undergo reactions to produce various furan-containing
monomers with a wide variety of substituents as shown in Table 7.1.
7.2.2 Furfuryl Alcohol
Furfuryl alcohol is made from furfural by reduction with hydrogen. It is a
colorless transparent liquid and becomes brown, light yellow, or deep red,
when exposed in the air. It can be mixed with water and many organic solvents
such as alcohol, ether, acetone, etc., but not in hydrocarbon products.
7.2.3 Specialities
7.2.3.1 Furan-based Polyimides
Polyimides based on poly(2-furanmethanol-formaldehyde) can be prepared
by a Diels-Alder reaction (DA) of the respective furan resin with bismaleimides.
9 The Diels-Alder reaction proceeds in tetrahydrofuran (THF) or
in bulk. The tetrahydrophthalimide intermediates aromatize in the presence
of acetic anhydride. Polyimides based on the furan resin exhibit good
thermal stability.
7.2.4 Synthesis
Furan-based monomers can polymerize through two well-known mechanisms.
The first involves chain or polyaddition polymerization, which is
initiated by free radical, cationic or anionic promoters. Polymerization
produces macromolecules with furan rings pendant on the main chain.
The second method is a polycondensation, also referred to as polymerization
condensation. Polymers and copolymers resulting from acid
catalyzed condensation reactions result in macromolecules with furan rings
in the main chain. 6
As a general rule, the furan resins formed by polycondensation reactions
have stiffer chains and higher glass transition temperatures. These
reactions may involve self-condensation of the furan monomers described

310 Reactive Polymers Fundamentals and Applications
O
CH 2
OH
H +
O
CH 2
+
O
CH 2
+
O
CH 2
OH
O
CH 2
O
CH 2
OH
Figure 7.2: Acid Catalyzed Self-condensation of Furfuryl Alcohol
above, as well as condensation reactions of such monomers with aminoplast
resins, organic anhydrides, and aldehydes such as formaldehyde, ketones,
urea, phenol, and other suitable reagents. Most common, furan resins
are produced by acid catalyzed condensation reactions.
The condensation results in linear oligomers, the furan rings being
linked with methylene and methylene-ether bridges, c.f. Figure 7.2.
The synthesis of furan resins proceeds in a pH range of 3 to 5, at
a temperature range of 80 to 100°C. The condensation is stopped, when a
desired viscosity value is reached, by neutralizing the liquid resin.
Furfuryl alcohol can also be condensed with formaldehyde to obtain
furan-formaldehyde resins. The content of free formaldehyde can be
lowered by the addition of urea at the late stages of synthesis.
7.3 SPECIAL ADDITIVES
7.3.1 Reinforcing Materials
Aramid fibers were used as reinforcing material for a phenol resin and a
furan resin. A comparative study of the mechanical performance of the
materials showed that the furan resin is more suitable as a matrix than the
phenol resin. 10

Furan Resins 311
Table 7.2: Global Production Data of Furan Resins Related Components 11
Monomer Mill. Metric tons Year Reference
Formaldehyde 24 2003
12
Furfural 0.225 1999
13
7.3.2 Production Data of Important Monomers
The most important industrial furan resins are based on 2-furfuryl alcohol.
The largest producers of furfural are China and the Dominican Republic.
Production data are shown in Table 7.2. Around 30% of the furfural consumption
is used to produce furfuryl alcohol, which is mainly consumed
by the production of furan resins.
7.4 CURING
Materials known to be suitable for curing furan resins include inorganic
and organic acids. Examples of suitable organic and inorganic acids include
hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, tartaric
acid, and maleic acid. Friedel-Crafts catalysts include aluminum trichloride,
zinc chloride, aluminum bromide, and boron fluoride.
Resins with improved fire resistance are cured with a mixture of
trimethylborate, boric anhydride, and p-toluenesulfonic acid. 14
Salts of both inorganic and organic acids may also be used. Ammonium
sulfate is preferred. Ammonium sulfate is a latent catalyst which may
become active at approximately 110 to 150°C. Suitable organic salts are the
urea salt of toluenesulfonic acid, the polyammonium salts of polycarboxylic
acids such as the diammonium salts of citric acid, and the ammonium
salts of maleic acid. Cyclic anhydrides such as maleic anhydride are also
suitable for use as catalysts.
It is believed that polyester co-polymers are formed between the anhydride
and the free hydroxylated species present in the resin. Maleic
acid promotes the polymerization reaction. Furthermore, it is believed that
maleic acid may preferentially reduce the emission of bis(hydroxymethyl)furan
monomer during the curing process. A significant reduction of
volatile organic compounds (VOCs), will use a catalyst system comprised
of maleic acid and ammonium sulfate. 6

312 Reactive Polymers Fundamentals and Applications
O
O
CH CH 2
O
CH 2
O
CH CH 2
Figure 7.3: Crosslinked Methylene Bridges
7.4.1 Acidic Curing
The resin can be crosslinked by an acidic catalyst. The reaction is not
sensitive to air. The main route of curing is an additional condensation reaction
at the free α-hydrogen of furan rings. These positions are connected
by methylene bridges.
7.4.2 Oxidative Curing
The oxidative crosslinking of furfuryl alcohol (FA) polycondensates proceeds
at temperatures of 100 to 200°C. Structures with tertiary carbon
atoms, as shown in Figure 7.3, could be identified.
7.4.3 Ultrasonic Curing
Ultrasonic treatment, i.e., sonication during the curing process of a furan
resin, showed changes of the curing performance. p-Toluenesulfonic acid
was added as curing catalyst in the proportion of 0.3%. Fine carbons were
also incorporated.
Using an ultrasonic homogenizer in the presence of carbonaceous
fine particles showed an increased curing rate of the furan resin. This, in
turn, increased the polymerization degree with an increase in ultrasound
intensity. The increase of curing rate was also observed by small additions
of carbonaceous fine particles. In this case, the curing accelerated with an
increase in the specific surface area of the additives. 15
The increase of curing rate is believed to result from cavitation. The
curing reaction proceeds slowly in the absence of cavitation and simple
stirring fails to produce such a marked increase in the rate of reaction. The
curing is accelerated by heat, oxygen, and the addition of phenol and urea.

Furan Resins 313
7.5 PROPERTIES
7.5.1 Recycling
Research has been conducted to introduce pendent furan groups into polymers
such as poly(styrene) via copolymerization with a suitable comonomer.
The pendent furan moieties can be crosslinked with a bismaleimide
to achieve polymers with better performance. In order to recycle these
crosslinked materials, heating experiments with an excess of 2-methylfuran
were performed in order to induce the retro Diels-Alder reaction
and break-up the network. The reaction proceeded in this manner and the
original copolymers could be recovered from the treatment. Therefore,
the introduction of furan units is a potential path of recycling crosslinked
polymers by thermal treatment with a diene in excess. 16
The Diels-Alder reaction between styrene-furfuryl methacrylate copolymer
samples and bismaleimide can be monitored the ultraviolet absorbance
of the maleimide group at 320 nm or by 13 C-NMR spectroscopy. 7
7.6 APPLICATIONS AND USES
Furan resins are used mainly in the foundry industry, as sand binders for
casting molds and cores. Furan resins are often used in combination with
other resins. Furan resins are highly corrosion resistant. Therefore, they
have found use in mortars and in cements. Improved mechanical properties
are implemented by reinforcing with glass fibers.
7.6.1 Carbons
Porous Carbon. Furan resins form a porous carbon by pyrolysis at 450°C.
Glass-like Carbon. Glass-like carbon is identified as an excellent carbon
artifact due to its characteristics such as hardness and shape stability. The
microstructure of glass-like carbon consists of a non-graphitic alignment of
hexagonal sheets. It has unique properties such as great hardness compared
with other carbon materials and impermeability for gases. 17
Glass-like carbon is of interest in the battery and semiconductor industries.
Glass-like carbon is prepared by heat-treatment on thermosetting
resins in inert atmosphere.

314 Reactive Polymers Fundamentals and Applications
Figure 7.4: SEM photographs of glass-like carbon derived from furan resin. (a)
300, (b) 600 °C. 18 (Reprinted with permission from Elsevier)
During the heat-treatment of a furan resin, weight loss is very rapid
up to 500°C, then continues gradually up to 1000°C, and then the weight
stays almost constant above 1000°C. SEM photographs of heat treated
glass-like carbon reveal a large increase of micro-grain size in the range
of 60 to 105 nm when treated at 2000°C. Up to 2500°C, the grain size
decreases to 27 to 40 nm due to graphitization. 18 There is a structural
correlation between the micro-texture of the furan resin and the glass-like
carbon formed from the particular resin. The pore structure in glass-like
carbon can be characterized by small-angle X-ray scattering (SAXS) technique.
The scattering intensities grow gradually with increasing heat-treatment
temperature up to 1600 to 1800°C, and then the intensities increase
abruptly at a temperature higher than 1800°C.
The dependence of the structural change of a glass-like carbon from
a furan resin is almost the same as that of a phenolic resin. However, it
was found that the carbon prepared at 1200°C from furan resin shows the
largest interlayer spacing in the carbon matrix and at the same time the
smallest value of the gyration radius for the pores. 17
7.6.2 Chromatography Support
Conventionally used packing materials for liquid chromatography are a
chemically bonded type of packing material based on silica gel and a pack-

Furan Resins 315
ing material based on synthetic resin. The silica gel-based packing material
has relatively strong in mechanical properties and in its swelling or shrinking
characteristics against various organic solvents. Therefore, it has a high
resolving power and is superior in exchangeability of eluent for analysis.
However, the silica gel-based packing material has problems in that the silica
gel dissolves under acidic or alkaline conditions and the solubility of
the silica gel in an aqueous solution increases when warmed, resulting in
durability problems.
The packing material of synthetic resin, on the other hand, is known
to be high in acid- and alkali-resistivity, and has a good chemical durability
as a packing material. However, since the mechanical strength of the particles
is small, it has been difficult to convert them into finer particles. Raw
materials which are highly chemically stable and exhibit high mechanical
strength are graphitized carbon black.
A packing material for liquid chromatography is produced by mixing
carbon black, a synthetic resin which can be graphitized, and pitches.
Suitable synthetic resins are phenolic resins, furan resins, furfural resins,
divinylbenzene resins, or urea resins. 19 The pitches can be petroleum
pitches, coal-tar pitches, and liquefied coal oil. The mixture is granulated
and heated up to 3000°C in an inert atmosphere.
7.6.3 Composite Carbon Fiber Materials
Impregnation of carbon fibers and subsequent pyrolysis at 1000°C improves
strength of carbon fibers. 20 A yarn is passed through a bath containing
a carbonizable resin precursor, such as a partially polymerized furfuryl
alcohol. It is advantageous to add a latent catalyst along with the precursor.
Suitable catalysts are a complex of boron trifluoride and ethylamine or
maleic anhydride.
The use of a latent catalyst allows the application of a low-viscosity
solution to the fiber with subsequent polymerization at the elevated temperatures.
If the precursor were to polymerize significantly prior to application,
the treating bath would be so viscous that would allow only a coating
to be formed.
For high performance composite carbon fiber reinforced carbonaceous
material which is compositely reinforced with carbon fibers, prepregs
of woven fabrics of carbon fibers are impregnated with a resin such as
phenol resin, furan resin, epoxy resin, urea resin, etc. They then are lamin-

316 Reactive Polymers Fundamentals and Applications
ated as a matrix and molded under heat and pressure, and after carbonization,
they are further graphitized by heating to a temperature of 3000°C. 21
7.6.4 Foundry Binders
Furans are somewhat more expensive than other binders, but the possibility
of sand reclamation is advantageous. One of the most commercially
successful no-bake binders is the phenolic-urethane no-bake binder. This
binder provides molds and cores with excellent strengths that are produced
in a highly productive manner.
Furan-based binders have less VOC, free phenol level, low formaldehyde,
and produce less odor and smoke during core making and castings.
However, the curing performance of furan binders is much slower than the
curing of phenolic urethane no-bake binders.
Furan binders can be modified to increase their reactivity, for instance
by formulating with urea/formaldehyde resins, phenol/formaldehyde
resins, novolak resins, phenolic resol resins, and resorcinol. Nevertheless,
these modified furan binders do not provide the cure speed needed
in foundries that require high productivity. Therefore, an activator, which
promotes the polymerization of furfuryl alcohol, is added. Resorcinol pitch
is used for this purpose. 22 Further components in such a formulation are
polyester polyols or polyether polyols, and a silane, such as (3-aminopropyl)triethoxysilane.
The curing process of urea-modified furan resins in sands has been
investigated by infrared spectroscopy. 23
7.6.5 Glass Fiber Binders
An alternative to phenol/formaldehyde-based fiberglass binders is furanbased
binders. Furan binders provide many of the advantages of phenolic
binders while resulting in substantially reduced VOC emissions. Water as
a significant component can be used. Formaldehyde is not a significant
curing or decomposition by-product, and the furan resins form very rigid
thermosets.
Emulsified furan resins can be used. Emulsified furan-based glass
fiber binding compositions are advantageous since they allow the use of
furan resins that have high molecular weights or the addition of other materials
which would give rise to the formation of two-phase systems. 6 A
suitable surfactant to be added to the furan binder compositions is sodium

Furan Resins 317
dodecyl benzene sulfonate. It may be added in an amount from 0.05 to
1.0%.
7.6.6 Oil Field Applications
Wells in sandy, oil-bearing formations are frequently difficult to operate
because the sand in the formation is poorly consolidated and tends to flow
into the well with the oil. Sand production is a serious problem because the
sand causes erosion and premature wearing out of the pumping equipment.
It is a nuisance to remove from the oil at a later point in the operation.
Furan resin formulations can be used for in-situ chemical sand consolidation.
24
7.6.7 Plant Growth Substrates
Conventional mineral wool plant growth substrates are based on a coherent
matrix of mineral wool of which the fibers are mutually connected by a
cured binder.
There is a need to reduce the phytotoxicity of the chemicals used.
The phytotoxicity may result from the phenolic binder materials. If a phenolic
resin is used as binder, a wetting agent must be added in order to impart
the hydrophobic mineral wool matrix with hydrophilic properties. However,
the use of a furan resin allows the abandonment of the use of a wetting
agent.
A disadvantage of the use of a furan resin is its comparatively high
price. Therefore, the traditional phenol/formaldehyde resin substituted
only partly by a furan resin, is sufficient to maintain or to achieve the desired
properties.
25, 26
7.6.8 Photosensitive Polymer Electrolytes
Both conjugated furan chromophores and polyethers can be grafted onto
chitosan to result in a photosensitive polymer electrolyte. The furan chromophore
consists of conjugated furan chromophores of 5-[2-(5-Methyl furylene
vinylene)]furancarboxyaldehyde, 27 c.f. Figure 7.5. The graft polymer
can be photocrosslinked. The photochemical reaction consists of a π 2 +π 2
cycloaddition reaction of the vinylene double bonds of the furan moiety so
that two pendent vinylene groups form a four membered ring. The crosslinking
reaction is shown in Figure 7.6

318 Reactive Polymers Fundamentals and Applications
H 3 C
O
O
O
C
H
Figure 7.5: 5-[2-(5-Methyl furylene vinylene)]furancarboxyaldehyde
OH
OH
O
O
O
O
NH
CH 2
O
CH 3
O
NH
CH 2
O
CH 3
O
O
CH 3
O
O
O
CH 3
CH 2
NH
CH 2
NH
O
O
O
O
OH
OH
Figure 7.6: Photo Crosslinking of the Furylene Vinylene Units Grafted on Chitosan

Furan Resins 319
REFERENCES
1. Z. László-Hedvig and M. Szesztay. Furan resins (2-furfuryl alcohol based).
In J. C. Salamone, editor, The Polymeric Materials Encyclopaedia: Synthesis,
Properties and Applications, pages 548–549. CRC Press, Boca Raton, FL,
1999.
2. A. Gandini and M. N. Belgacem. Furans in polymer chemistry. Prog. Polym.
Sci., 22(6):1203–1379, 1997.
3. I. F. C. B.V. Historical overview and industrial development. (Internet:
http://www.furan.com).
4. C. Claessen. Process for the treatment of wood or other substances containing
cellulose for the purpose of obtaining cellulose and artificial resin, asphalt,
lac and the like. GB Patent 160 482, March 17 1921.
5. J. S. Stokes. Improvements in and relating to synthetic resin composition.
GB Patent 243 470, December 3 1925.
6. T. J. Taylor, W. H. Kielmeyer, C. M. Golino, and C. A. Rude. Emulsified
furan resin based glass fiber binding compositions, process of binding
glass fibers, and glass fiber compositions. US Patent 6 077 883, assigned to
Johns Manville International, Inc. (Denver, CO); QO Chemicals, Inc. (West
Lafayette, IN), June 20 2000.
7. E. Goiti, F. Heatley, M. B. Huglin, and J. M. Rego. Kinetic aspects of the
Diels-Alder reaction between poly(styrene-co-furfuryl methacrylate) and bismaleimide.
Eur. Polym. J., 40(7):1451–1460, July 2004.
8. C. Moreau, M. N. Belgacem, and A. Gandini. Recent catalytic advances in
the chemistry of substituted furans from carbohydrates and in the ensuing
polymers. Top. Catal., 27(1-4):11–30, February 2004.
9. K. S. Patel, K. R. Desai, K. H. Chikhalia, and H. S. Patel. Polyimides based
on poly(2-furanmethanol-formaldehyde). Adv. Polym. Technol., 23(1):76–80,
2004.
10. K. Kawamura and S. Ozawa. Characterization of fiber reinforced plastics
made from aramid and phenol resin or furan resin. Kobunshi Ronbunshu,
59(1):51–56, 2002.
11. R. Gubler, editor. Chemical Economics Handbook (CEH). SRI Consulting, a
Division of Access Intelligence, Menlo Park, CA, 1950–to present. (Internet:
http://ceh.sric.sri.com/).
12. S. Bizzari. Report “Formaldehyde”. In Chemical Economics Handbook
(CEH). SRI Consulting, a Division of Access Intelligence, Menlo Park, CA,
January 2004. (Internet: http://ceh.sric.sri.com/).
13. J. Levy and Y. Sakuma. Report “Furfural”. In Chemical Economics Handbook
(CEH). SRI Consulting, a Division of Access Intelligence, Menlo Park,
CA, July 2001. (Internet: http://ceh.sric.sri.com/).

320 Reactive Polymers Fundamentals and Applications
14. N. Meyer and M. Cousin. Furan resins of improved fire resistance. US
Patent 4 355 145, assigned to Societe Chimique des Charbonnages SA (Paris
La Defense, FR), October 19 1982.
15. K. Hoshi, T. Akatsu, Y. Tanabe, and E. Yasuda. Curing properties of furfuryl
alcohol condensate with carbonaceous fine particles under ultrasonication.
Ultrason. Sonochem., 8(2):89–92, April 2001.
16. C. Gousse, A. Gandini, and P. Hodge. Application of the Diels-Alder reaction
to polymers bearing furan moieties. 2. Diels-Alder and retro-Diels-Alder reactions
involving furan rings in some styrene copolymers. Macromolecules,
31(2):314–321, January 1998.
17. K. Fukuyama, T. Nishizawa, and K. Nishikawa. Investigation of the pore
structure in glass-like carbon prepared from furan resin. Carbon, 39(13):
2017–2021, November 2001.
18. Y. Korai, K. Sakamoto, I. Mochida, and O. Hirai. Structural correlation between
micro-texture of furan resin and its derived glass-like carbon. Carbon,
42(1):221–223, 2004.
19. H. Ichikawa, A. Yokoyama, T. Kawai, H. Moriyama, K. Komiya, and Y. Kato.
Packing material for liquid chromatography and method of manufacturing
thereof. US Patent 5 270 280, assigned to Nippon Carbon Co., Ltd. (Tokyo,
JP); Tosoh Corporation (Yamaguchi, JP), December 14 1993.
20. M. Katz. Improvement of carbon fiber strength. EP Patent 0 251 596, assigned
to Du Pont, January 7 1988.
21. T. Kawakubo and E. Oota. Process for preparation of carbon fiber composite
reinforced carbonaceous material. US Patent 5 096 519, assigned to
Mitsubishi Pencil Co., Ltd. (JP), March 17 1992.
22. K. K. Chang. Furan no-bake foundry binders and their use. US Patent
6 593 397, assigned to Ashland Inc. (Dublin, OH), July 15 2003.
23. M. Bilska and M. Holtzer. Application of fourier transform infrared spectroscopy
(FTIR) to investigation of moulding sands with furan resins hardening
process. Arch. Metall., 48(2):233–242, 2003.
24. P. Shu. Water compatible chemical in situ and sand consolidation with furan
resin. US Patent 5 522 460, assigned to Mobil Oil Corporation (Fairfax, VA),
June 4 1996.
25. E. L. Hansen and J. F. De Groot. Process for the manufacture of a mineral
wool plant growth substrate. US Patent 6 562 267, assigned to Rockwool
International A/S (Hedenhusene, DK), March 13 2003.
26. J. F. De Groot and T. B. Husemoen. Hydrophilic plant growth substrate,
comprising a furan resin. US Patent 6 032 413, assigned to Rockwool International
A/S (DK), March 7 2000.
27. A. Gandini, S. Hariri, and J.-F. Le Nest. Furan-polyether-modified chitosans
as photosensitive polymer electrolytes. Polymer, 44(25):7565–7572, December
2003.

8
Silicones
In contrast to most organic polymers, in silicones the backbone is made of
silicon and oxygen. Silicon is together with carbon in the fourth group of
the periodic system, therefore a similar behavior of these elements can be
expected.
8.1 HISTORY
Kipping ∗ started with the synthesis of organic silicon compounds by treating
SiCl 4 with magnesium-based organometallic compounds. These compounds
are now called Grignard reagents, invented by Victor Grignard in
1900.
Hyde † , at Corning, developed a flexible, high temperature binder for
glass fibers and synthesized the first silicone polymer. The potential applications
in other fields, such as electric industries soon became apparent.
Eugene George Rochow ‡ at General Electric developed synthesis of
silicones that is now used. 1, 2 His first patent dates at 1941. 3, 4
In 1949,the silly putty was invented by James Wright when mixing
silicone oil with boric acid. Silly putty acts like both a rubber and a putty.
∗ Frederic Stanley Kipping, born in Upper Broughton (UK) 1863, died in 1949
† James Franklin Hyde, born in Solvay, New York 1903, died in 1999
‡ Eugene George Rochow, born in Newark, New Jersey 1909, died in 2002
321

322 Reactive Polymers Fundamentals and Applications
8.2 MONOMERS
8.2.1 Chlorosilanes
The synthesis of silanes and siloxanes starts from chlorosilanes such as dimethyldichlorosilane.
Other products are derived from this compound that
also serve as monomers. Thus, in silicone chemistry, the term monomer is
not as clearly defined as in other fields of polymer chemistry.
8.2.2 Silsesquioxanes
Silsesquioxane resins are used in industrial applications in the automotive,
aerospace, naval, and other manufacturing industries. Silsequioxane resins
exhibit excellent heat and fire resistant properties that are desirable for such
applications. These properties make the silsesquioxane resins attractive for
use in fiber-reinforced composites for electrical laminates, and structural
use in automotive components, aircraft, and naval vessels.
There is a need for rigid silsesquioxane resins that has increased
flexural strength, flexural strain, fracture toughness, and fracture energy,
without significant loss of modulus or loss of thermal stability. In addition,
rigid silsesquioxane resins have low dielectric constants and are useful
as interlayer dielectric materials. Rigid silsesquioxane resins are also
useful as abrasion resistant coatings. These applications require that the
silsesquioxane resins exhibit high strength and toughness. 5
The formation of silsesquioxanes is shown in Figure 8.1. Silsesquioxanes
are organosilicon compounds with the formula [RSiO 3/2 ] n .
[R 7 Si 7 O 9 (OH) 3 ], as shown in Figure 8.1, can be synthesized in one
step via the hydrolytic condensation of RSiCl 3 or RSi(OMe) 3 . A single
Si-O-Si linkage in a fully condensed R 8 Si 8 O 12 framework can be cleaved
selectively by strong acids (e.g., HBF 4 /BF 3 or triflic acid. 6
8.2.3 Hydrogen Silsesquioxanes
Hydrogen-silsesquioxane resins are useful precursor substances for silicacontaining
ceramic coatings. Hydrogen silsesquioxane resins are ladder or
cage polymers. 7 The general structure is shown in Figure 8.2. When trichlorosilane
is subjected to hydrolytic condensation caused by direct contact
with water, the reaction occurs abruptly, and gels are formed. Accordingly,
various methods for manufacturing hydrogen-silsesquioxane resins

Silicones 323
R
Si
OH
R
Cl
Si
Cl
Cl
H 2 O
O
R
O
Si
O
Si
O
O
Si
R
R O
OH
R
O
Si OH
Si
R
O
O
Si
R
Figure 8.1: Formation of Silsesquioxanes: [R 7 Si 7 O 9 (OH) 3 ]
H
HO
Si
O
Si
HO
H
H H
O
Si
O Si
O O
O Si O
Si
H H
H H
O Si
O Si
O O
O
Si
O
H
n
Si
H
OH
OH
H
Si
O
O
O
O
H
Si
O
H
Si Si
H
O
O
O
O
O
H
Si
O
Si
H
H
Si
O
Si
H
Figure 8.2: Hydrogen silsesquioxane resins. 7 Top: Ladder Form, Bottom: Cage
Form

324 Reactive Polymers Fundamentals and Applications
that do not form gels have been proposed. The hydrogen-silsesquioxane
resin can be manufactured in an aromatic hydrocarbon solution of trichlorosilane.
The hydrolytic condensation is then performed as a two-phase
reaction with concentrated sulfuric acid.
Concentrated sulfuric acid and aromatic hydrocarbon react to produce
an arylsulfonic acid hydrate, and the water in this hydrate contributes
to the hydrolytic condensation of trichlorosilane. Therefore, the hydrogensilsesquioxane
resin produced by this hydrolytic condensation is obtained
from the organic phase.
When water is added to the concentrated sulfuric acid phase in order
to recover and reuse the arylsulfonic acid, precipitation occurs, thus
rendering the arylsulfonic acid unsuitable for reuse. For this reason, large
quantities of organic solvent and sulfuric acid are lost using this method.
A method for complete reuse of the solvent, the sulfuric acid and surfactants,
essentially without loss of these compounds, has been described. The
method utilizes a two-phase system consisting of an aqueous phase:
1. An aqueous solution consisting of sulfuric acid and an organic
sulfonic acid, e.g., p-toluenesulfonic acid monohydrate, and
2. The organic phase consisting of a diluted solution of organic sulfonic
acid in a halogenated hydrocarbon solvent. The trichlorosilane
must be soluble in this solvent, and the solvent should not react
with sulfuric acid. Examples are isopropyl chloride, chlorobenzene,
and others.
This method results in hydrogen-silsesquioxane resins at a high yield.
The loss of the organic solvent used in the organic phase is small, and the
precipitation of benzenesulfonic acid, etc., in the aqueous phase due to supersaturation
can also be eliminated. The organic solvent, the sulfuric acid
and the organic sulfonic acid used in the aqueous phase can be effectively
reused. 8
8.2.4 Alkoxy Siloxanes
Examples of alkoxy siloxanes are listed in Table 8.1. Trifunctional siloxane
units and tetrafunctional siloxane units are used to improve the physical
properties of curable epoxy resins. Branched silicone resins with trifunctional
siloxane units are highly heat-resistant and have an excellent capacity
for film-formation, which is why they are used as electrical insulating

Table 8.1: Epoxy-containing Siloxanes 9
Siloxane
Methyltrimethoxysilane
Methyltriethoxysilane
Ethyltrimethoxysilane
Ethyltriethoxysilane
Vinyltrimethoxysilane
Phenyltrimethoxysilane
3,3,3-Trifluoropropyltrimethoxysilane
Dimethyldimethoxysilane
Methylphenyldimethoxysilane
Methylvinyldimethoxysilane
Diphenyldimethoxysilane
Dimethyldiethoxysilane
Methylphenyldiethoxysilane
Tetramethoxysilane
Tetraethoxysilane (TEOS)
Tetrapropoxysilane
Dimethoxydiethoxysilane
Silicones 325
materials, and heat-resistant paints and coatings. 9
8.2.5 Epoxy-modified Siloxanes
Siloxanes with pendent epoxy groups are listed in Table 8.2. Epoxy-containing
silicone resins are prepared either by the co-hydrolysis and condensation
of epoxy-containing trialkoxysilane and diorganodialkoxysilane or
by the base-catalyzed equilibration polymerization of cyclic diorganosiloxane
and epoxy-containing trialkoxysilane. 9 Epoxy-containing silicone
resins have broad molecular weight distributions and do not exhibit a softening
point or a distinct glass transition temperature.
8.2.6 Silaferrocenophanes
Silaferrocenophanes are of considerable interest because they may serve
as precursors to unusual ceramic materials. Polymers can be made by
ring opening polymerization as shown in Figure 8.3. Other ferrocenophanes
bridged by heteroatoms such as germanium and phosphorus have
been synthesized. In the presence of methylphenylchlorosilane or diphenylchlorosilane,
i.e., silanes with pendent hydrogen, telechelic polymers can

326 Reactive Polymers Fundamentals and Applications
Siloxane
Table 8.2: Epoxy-containing Siloxanes 9
3-Glycidoxypropyl(methyl)dimethoxysilane
3-Glycidoxypropyl(methyl)diethoxysilane
3-Glycidoxypropyl(methyl)dibutoxysilane
2-(3,4-Epoxycyclohexyl)ethyl(methyl)dimethoxysilane
2-(3,4-Epoxycyclohexyl)ethyl(phenyl)diethoxysilane
2,3-Epoxypropyl(methyl)dimethoxysilane
2,3-Epoxypropyl(phenyl)dimethoxysilane
3-Glycidoxypropyltrimethoxysilane (GLYMO)
3-Glycidoxypropyltriethoxysilane
3-Glycidoxypropyltributoxysilane
2-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane
2-(3,4-Epoxycyclohexyl)ethyltriethoxysilane
2,3-Epoxypropyltrimethoxysilane
2,3-Epoxypropyltriethoxysilane
Fe
CH 3
Si
CH 3
Fe
CH 3
Si
CH 3
Figure 8.3: Ring Opening Polymerization of Silaferrocenophanes

Silicones 327
Table 8.3: Products Obtained by the Rochow Synthesis 10
Silane Yields [%] Boiling Points [°C]
Methyldichlorosilane 0.5 41
Methyltrichlorosilane 8–18 66
Dimethyldichlorosilane 80–85 70
Trimethylchlorosilane 2–4 57
be produced with the hydrogen bearing silanes as end group 11, 12 Apart
from silaferrocenophanes, ferrocenophanes with conjugated double bonds
instead of silicon are of interest because of their electrical properties. 13
8.2.7 Synthesis
8.2.7.1 Direct Synthesis
Silicones are synthesized via methylchlorosilanes by the Müller-Rochow
process. The reaction is carried out at temperatures of 250 to 300°C and
2 to 5 bars. A copper catalyst used with antimony, cadmium, aluminum,
zinc, and tin is effective for improving the activity. However, lead would
act as an inhibitor.
A finely homogenized mixture of silicon and copper is introduced
into a fluidized bed reactor. The reactor is fluidized by gaseous methylchloride.
The reactants are separated from the solid components and on
cooling a crude liquid silane mixture is obtained. Silicon conversions of
90 to 98% and methylchloride conversions of 30 to 90% can be achieved.
The reaction is strongly exothermic and requires a precise control. Dimethyldichlorosilane
is the main product. Other major products obtained are
shown in Table 8.3. The selectivity for producing dimethyldichlorosilane
is highly sensitive to trace amounts of other metals present. The selectivity
for dimethyldichlorosilane is reduced if the Cu, Zn, or Sn concentrations
exceed the generally used concentrations or if the reaction temperature
exceeds 300°C. A silver promoter increases the selectivity to dimethyldichlorosilane.
14, 15 The crude silane mixture is then separated in distillation
columns. A high separating capacity is needed, because the boiling
points of CH 3 SiCl 3 and (CH 3 ) 2 SiCl 2 differ by only 4°C. A high purity is
required, because even a small amount of CH 3 SiCl 3 leads to branched and
eventually gelled products.

328 Reactive Polymers Fundamentals and Applications
8.2.7.2 Hydrosilylation
The hydrosilylation reaction consists of the addition of hydrogen-containing
silanes to products with double or triple bonds. This reaction is suitable
for introducing organo functions into silicone compounds. Therefore, hydrosilylation
is extensively used to synthesize organofunctional silicones
with pendant vinyl groups, amino groups, etc. 16 In a further step, chlorine
atoms, hydrogen atoms, and alkoxy groups can undergo a nucleophilic
substitution. The hydrosilylation reaction requires often high temperatures.
Vinyl Groups. The hydrosilylation of aromatic compounds containing
vinyl unsaturation can lead to radical polymerization of the monovinylaromatic
compounds, especially at elevated temperature. The use of radical
polymerization inhibitors, such as phenols or quinones, is often necessary,
however, most of these inhibitors are not sufficiently active at elevated
temperatures and require the presence of oxygen to improve their activity.
However, special conditions and precautions make the use of a radical
polymerization inhibitor unnecessary. Styrene and α-methylstyrene can be
hydrosilylated with heptamethyltrisiloxane with a Karstedt platinum catalyst
at 90°C. 17
When 4-vinyl-1-cyclohexene is reacted with a hydrogenchlorosilane,
both the vinylic double bond and the double bond in the cyclohexene
ring react. Thereby an organic silicon compound of the formula given in
Figure 8.4 is obtained in which the hydrogenchlorosilane is added to each
of the two double bonds in 4-vinyl-1-cyclohexene. The cyclohexane ring
within the molecule imparts a high hardness and scratch resistance and is
useful as a coupling agent to be added to paints for use in automobiles,
buildings and adhesives. The compound is also useful as an intermediate
to an alkoxysilane coupling agent. 18
8.2.7.3 Grignard Synthesis
The Grignard synthesis is suitable to introduce organic groups to silicon.
The Grignard synthesis is used on a laboratory scale. An example for a
Grignard synthesis is shown in Figure 8.5. With water, methylphenyldichlorosilane
condenses to a linear polymer.

Silicones 329
H
CH 3
Si Cl
+ + H
CH 3
Si Cl
Cl
Cl
CH 3
CH 3
Si Cl
Cl
Si
Cl
Cl
+
CH 3
Cl
Si
CH 3
Si Cl
Cl
Cl
Figure 8.4: Hydrosilylation of 4-Vinyl-1-cyclohexene
Cl
Cl
Mg Br + Cl Si Cl
Si Cl + MgClBr
Cl
Cl
Cl
CH 3
CH 2
Mg
Br + Cl
Si
Cl
Cl
CH 3
CH 2
Si
+ MgClBr
Cl
Figure 8.5: Grignard Synthesis

330 Reactive Polymers Fundamentals and Applications
8.2.7.4 Condensation
Hydrolysis of chlorosilanes results in silanols. These silanols are not stable
and undergo a polycondensation. Intramolecular and intermolecular condensation
takes place. Intermolecular condensation yields linear siloxanes,
and intramolecular condensation yields cyclic products. When trichlorosilanes
undergo hydrolysis, highly crosslinked silicone resins are obtained.
The reaction can be catalyzed by acids. An equilibrium between the linear
siloxanes and cyclic siloxanes can be established.
If the catalyst is deactivated, the condensation stops and the cyclic
products that consist mostly of a tetramer can be removed by distillation.
On the other hand, cyclic siloxanes can be transformed to polymers in the
presence of alkali. If the catalyst is not deactivated then cyclic siloxane
forms until the equilibrium is established. In equilibrium ca. 20% of cyclic
products are present, which is relevant to the recycling of polysiloxanes.
Chain Stoppers. To obtain stable or functional terminal groups, chain
stoppers are added. The reaction proceeds under continuous cleavage and
recombination of siloxane bonds. The reaction is catalyzed by acids.
Bodying. Bodying is a technology that consists of the base-catalyzed
depletion of the silanol groups in a silicone resin prepared by the hydrolysis
and condensation of organoalkoxysilane. In this process the molecular
weight of the silicone resin is simply increased, while control of the
molecular weight, softening point, and glass transition temperature is not
possible. 9
Crosslinking. The degree of crosslinking depends on the presence of
either tetrachlorosilane SiCl 4 for the production of very rigid resins, or
(CH 3 ) 2 SiCl 2 for softer grades.
8.2.8 Manufacture
Commercially produced silicone resins comprise:
• Non-meltable solids
• Soluble reactive resins
• Silsesquioxanes
• High reactive alkoxysiloxanes with molecular weight.

Silicones 331
8.3 MODIFIED TYPES
8.3.1 Chemical Modifications
Reactive alkoxysiloxanes can undergo a reaction with functional organic
resins. The modification of methylpolysiloxanes is achieved by substituting
the methyl groups with other organic groups, e.g., lower alkyl chains or
functional groups like vinyl groups, or by copolymerization with organic
polymers, e.g., poly(ethylene oxide) or poly(propylene oxide).
8.3.1.1 Amine Functions
Aminofunctional silicones impart extreme softness. Such materials are appreciated
in textiles because of the improved wear comfort. In textile dyeing
uniformity of color fixation is achieved by efficient control of foaming
in the dyeing bath.
8.3.1.2 Functionalized Silanes
Reactive silanes or siloxanes can also include functionalities such as: vinyl,
hydride, allyl, or other unsaturated groups. For surface coating, hexamethyldisiloxane
and tetramethyldivinyldisiloxane are used. 5 Mixtures of
siloxanes with trimethyl silyl groups and dimethylvinyl silyl groups are
also common.
8.3.1.3 Crosslinking Agents
Crosslinking agents include alkoxysilanes such as methyltrimethoxysilane,
dimethyldimethoxysilane, etc., or oxime silanes, for example, methyltris-
(methylethylketoxime)silane. 19 Crosslinking accelerators include amines,
tin compounds such as dibutyltin diacetate, or dibutyltin dilaurate. 19
8.3.2 Fillers
The silicone network does not exhibit much mechanical strength. Mechanical
strength is imparted by the interaction of a filler with the polymer.
Fumed silica shows the strongest reinforcing effect. Other fillers include
quartz flour, iron oxide, and carbon black.

332 Reactive Polymers Fundamentals and Applications
8.3.3 Reinforcing Materials
Fiber reinforced, silicone matrix resin composites find many applications
in structural components. Fiber reinforcement often takes the form of woven
glass fiber mats. Woven carbon fiber mats offer a higher modulus
reinforcing media, but they are more expensive than glass fibers. Other
fiber compositions such as aramid, nylon, polyester, and quartz fibers may
be used for reinforcement. Other fibrous forms, such as non-woven mats
and layers of loose fibers, may also be used in silicone-based composite
applications. 20
Fiber reinforced, silicone matrix resin composites in multilayer laminated
form are strong and fire resistant. They find applications in interiors
of airplanes and ships. They are also used in electrical applications, such
as wiring boards and printed circuit boards, requiring flexural strength and
low weight.
Suitable resin types are typically highly branched and crosslinked
polymer molecules, when cured. To facilitate the impregnation process,
silicone precursor formulations may be diluted with toluene. The toluene
is then evaporated from the composite.
8.4 CURING
8.4.1 Curing by Condensation
Curing by condensation releases alcohol, amines, acetic acid, or other
volatile reaction products.
The polymerization reaction does proceed in the absence of water.
This fact is utilized in one component systems that form polymers
by means of atmospheric humidity. To avoid premature curing, the components
are packed in compartments that are free of moisture and tight to
permeation of moisture.
Methoxysilanes can condense with chlorosilanes releasing methylchloride,
21 as shown in Figure 8.6. The reaction is catalyzed by ferric
chloride.
8.4.1.1 Platinum Complexes for Hydrosylilation
Additional crosslinking occurs by reaction of compounds with pendant
vinyl groups. Certain platinum complexes catalyze the hydrosylilation re-

Silicones 333
CH 3
CH 3
Si O CH 3
+ Cl Si O
CH 3 CH 3
CH 3
Si O
CH 3
CH 3
Si O
CH 3
CH 3 Cl
Figure 8.6: Condensation of Methoxysilanes with Chlorosilanes
action.
Suitable platinum catalysts are chloroplatinic acid, dichlorobis(triphenylphosphine)platinum(II),
platinum chloride, platinum oxide, and also
complexes of platinum compounds. For example, a Karstedt catalyst is a
complex of chloroplatinic acid with 1,3-divinyl-1,1,3,3-tetramethyldisiloxane
and 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane. 5
Synergistic catalyst systems are mixtures of the compounds H 2 PtCl 6
and RuCl 3 × nH 2 O. 22 The hydrosilylation reaction proceeds at room temperature.
However, using inhibitors the temperature can be increased.
8.4.1.2 Hydrosilylation Inhibitors
Hydrosilylation inhibitors fall into two general classes. 23 One class is composed
of materials that effectively inhibit hydrosilylation over a wide range
of temperatures and can be volatilized out of the organosilicon composition
to allow hydrosilylation to proceed. Examples of this class are pyridine,
acrylonitrile, 2-ethenylisopropanol, and perchloroethylene.
The other class of inhibitors is materials that are non-volatile. The
inhibitory effect of these materials is overcome by heating, whereupon
hydrosilylation takes place. Examples of this latter class are the reaction
product of a siloxane having silicon-bonded hydrogen atoms, a platinum
catalyst, and an acetylenic alcohol, organic phosphines and phosphites,
benzotriazole, organic sulfoxides, metallic salts, aminofunctional
siloxanes, ethylenically unsaturated isocyanurates olefinic siloxanes, dialkyl
carboxylic esters, and unsaturated amides. Examples of inhibitors
are shown in Table 8.4.
In polyethers, oxidation impurities inhibit the hydrosilylation of the
polyethers, however, the exact identities of these inhibitors are unknown.
They are believed to include acetal hydroperoxides, allyl hydroperoxides
and free radicals localized at the tertiary carbon atoms in the hydrophobic

334 Reactive Polymers Fundamentals and Applications
Table 8.4: Inhibitors for Platinum Catalysts
Inhibitor
Remarks
Methylbutynol
Ethynyl cyclohexanol Most preferred 5
Diphenylphosphine
3-Methyl-1-dodecyn-3-ol Release coatings 24
3,7,11-Trimethyl-1-dodecyn-3-ol
segments (e.g., propylene oxide) of unsaturated polyethers. Oxidation impurities
are most likely to occur in polyethers which have been stored for a
long period with no or insufficient quantities of antioxidant. However, they
may also be present in freshly prepared polyethers which may have gotten
too hot in the presence of air or oxygen. Polyethers can be stabilized with
mixtures of ascorbic acid and sodium ascorbate and allyl polyethers. 25
8.4.1.3 Salts
A commercially available curing catalyst material comprises zinc octoate
and choline octoate. 20
8.4.1.4 Polymethylsilazanes
Polymethylsilazanes are synthesized by the reaction of ammonia with dimethyldichlorosilane
and methyltrichlorosilane. They are effective room
temperature curing agents for silicone resins. However, ammonia is released
in the course of curing. 26
8.5 CROSSLINKING
Crosslinking can be achieved by different reactions at high temperatures
for HTV-rubber and at room temperature for RTV-rubber. The liquid RTVsilicone
rubber can crosslink both by condensation and by addition mechanisms.
8.5.1 Condensation Crosslinking
Condensation crosslinking occurs between α,ω-dihydroxypoly(dimethylsiloxane)s
and silicates in the presence of inorganic compounds. The cross-

Silicones 335
linking density depends on the functionality and concentration of the crosslinking
agent and the nature of the catalyst.
8.5.2 Peroxides
Crosslinking at higher temperatures in the range 100 to 160°C is achieved
by the addition of peroxides. Suitable formulations contain a small amount
of vinyl groups.
8.5.3 Hydrosilylation Crosslinking
The hydrosilylation reaction is suitable for final crosslinking or curing reactions.
8.5.3.1 Thermoplastic Elastomers
Hydrosilylation crosslinking can be used to prepare a thermoplastic elastomer.
A thermoplastic elastomer is a polymer or polymeric blend that can
be processed and recycled in the same way as a conventional thermoplastic
material. However, it has some properties and functional performance
similar to those of vulcanized rubber at the service temperature.
Elastomeric rubber blends are used in the production of high performance
thermoplastic elastomers, particularly for the replacement of thermoset
rubbers in various applications. High performance thermoplastic
elastomers, in which a highly vulcanized rubbery polymer is intimately
dispersed in a thermoplastic matrix, are generally known as thermoplastic
vulcanizates. Hydrosilylation crosslinking of a rubber acts via the unsaturated
groups present from norbornene and diene components. Even at low
concentrations of hydrosilylation agent and catalyst, a rubber can be fully
crosslinked in a dynamic vulcanization process and provide a thermoplastic
elastomer product with excellent physical properties and oil resistance.
Suitable hydrosilylation agents are methylhydrogen polysiloxanes,
methylhydrogen dimethyl-siloxane copolymers, bis(dimethylsilyl)alkanes,
and bis(dimethylsilyl)benzene. 27 Platinum catalyst concentrations of 0.1
to 4 ppm are sufficient. The preparation is done by mixing the rubber
and silicone hydride at 180°C. Then a solution of the platinum catalyst is
added. The rubber is dynamically vulcanized by mixing until maximum
torque is reached.

336 Reactive Polymers Fundamentals and Applications
8.6 PROPERTIES
8.6.1 Silicone Rubber
Silicone rubber consists essentially of silicone polymers and fillers. Silicone
rubber formulations with molecular weights of more than 100 kDalton
and can flow, in contrast to other polymers.
8.6.1.1 HTV-silicone rubber
Silicone polymers for solid silicone rubber (HTV-silicone rubber) have
molecular weights of 500 kDalton to 1000 kDalton, yet exhibit a pasty
consistency.
8.6.1.2 RTV-silicone rubber
Pourable silicone rubber (RTV-silicone rubber) has a liquid consistency
and molecular weights in the range of 10 kDalton to 20 kDalton.
8.6.2 Thermal Properties
The service temperatures of silicones cover a wide range, from −60 to
+250°C. Silicone rubber retains its elasticity to temperatures down to
−60°C. The glass transition temperature is 120°C. At temperatures greater
than 150 °C silicone rubbers are superior to other elastomers with respect to
their thermal properties. 28 Silicone rubber exhibits a flash point of 750°C
and an excellent flame retardancy. However, on combustion, it releases
toxic or corrosive gases.
8.6.2.1 Boron Siloxane Copolymers
Polymers containing boron within the polymer are high temperature oxidatively
stable materials. It has been known that the addition of a carborane
within a siloxane polymer significantly increases the thermal stability of
such siloxane polymers. 29 Hybrids of organic and inorganic components,
made from 1,7-Bis(chlorotetramethyldisiloxy)-m-carborane, 1,3-dichlorotetramethyldisiloxane
and 1,4-dilithio-1,3-butadiyne are shown in Figure
8.7. Oxidative crosslinking in air is found for poly(m-carborane-di-methylsiloxane)
around 420°C. 21 Such polymers can be converted into ceramics

Silicones 337
H 3 C
Si
CH 3
CH 3
Si O
CH 3
CH 3
Si C
CH 3
Z
CH 3
Si O
CH 3
CH 3
Si Cl
CH 3
Cl C
H 3 C
O
Si
C
CH 3
C
Z=B 10 H 10
C
C
H 3 C
Si
CH 3
Li
C C C C Li
O
H 3 C
Si
CH 3
CH 3 CH 3
C
C
Z
Cl
Si O Si Cl
H 3 C
Si
CH 3
CH 3 CH 3
O
H 3 C
Si
CH 3
B
B
C
B
C
B
B
B
B
B
B
B
Figure 8.7: Polymers from 1,7-Bis(chlorotetramethyldisiloxy)-m-carborane,
1,3-dichlorotetramethyldisiloxane and 1,4-dilithio-1,3-butadiyne

338 Reactive Polymers Fundamentals and Applications
by pyrolysis. Carbon fibers coated with poly(carborane-siloxane-acetylene)
can be protected against oxidation at elevated temperatures. 30
8.6.2.2 Microcellular Ceramics
Microcellular foams were produced by means of poly(methyl methacrylate)
as a sacrificial templating agent. Poly(methyl methacrylate) microbeads,
were mixed in with a methylsilicone resin powder. The samples
were heated up to 300°C and after one hour pyrolyzed at 1200°C. A silicon
oxycarbide (SiOC) ceramic microcellular foam was obtained. 31
8.6.3 Electrical Properties
Silicone rubbers and resins are very efficient in insulating. The dielectric
strength, the resistivity, and the dielectric constant do not change significantly
with temperature.
8.6.4 Surface Tension Properties
Unmodified silicones exhibit hydrophobic properties. When spread out
as films they impart water repellency to the carrier material. The surface
tension is only around 30 mN/m.
Silazanes significantly improve water-repellent properties of silicone
resins. 19 Examples of hexaorganodisilazanes include hexamethyldisilazane,
1,3-dihexyltetramethyldisilazane, 1,3-di-tert-butyltetramethyldisilazane,
1,3-di-n-butyltetramethyldisilazane, and 1,3-diphenyltetramethyldisilazane.
8.6.5 Antioxidants
Iron-containing polysilazanes exhibit an antioxidation effect on silicone oil
and rubber. 32 This type of polymer was synthesized by the polycondensation
of silazane lithium salts with iron trichloride. The synthesis is shown
in Figure 8.8. The gelling time of a silicone oil increased from 3 to 1000
hours at 300°C in air by an addition of 5% of polysilazane.
8.6.6 Gas Permeability
Silicones have an extraordinarily high gas permeability. They find use in
medical applications, e.g., as contact lenses, so that the oxygen in air can

Silicones 339
H
Li
H 3 C CH 3 H
N
3 C CH 3
N
Si Si BuLi Si Si
H 3 C CH 3
H 3 C CH 3
N N
N N
H Si H
H Si H
H 3 C CH 3
H 3 C CH 3
Li
H 3 C CH 3
N
Si Si
H 3 C CH 3
N N
H Si Li
H 3 C CH 3
BuLi
BuLi
Li
H 3 C CH 3
N
Si Si
H 3 C CH 3
N N
Li Si Li
H 3 C CH 3
H 3
C CH
Si Si 3
N
H 3 C CH 3
Li
H 3 C
CH 3
Si
N
Li
Si
CH 3
CH 3
FeCl 3
H 3 C
Li Si
N
H 3 C
Si
H 3 C
CH 3
H 3 C CH
Si Si 3
N
H 3 C CH 3
Li
H 3 C
CH 3 Fe H 3 C
Si
N
Si
Li
CH 3
Li
H 3 C
N Si
Si
CH 3 H 3 C
CH 3
Figure 8.8: Synthesis of Iron-containing Polysilazanes

340 Reactive Polymers Fundamentals and Applications
contact the cornea of the eye. Another medical application is the use as
permeable membrane in heart-lung machines.
8.6.7 Weathering
Silicone rubber is highly resistant to ozone and radiation. Therefore, it
exhibits good weathering properties.
8.7 APPLICATIONS AND USES
Silicone products are used for a wide variety of applications, including
building and construction material, medical applications, sealing, impregnation,
putty, surface treatments, and painting applications. Silicone rubbers
can be fabricated into tubing, hose, gaskets, and seals.
Silicone oils are oligomeric chains of poly(dimethylsiloxane). The
fluids are thermally stable and chemically resistant. They can serve as
excellent lubricants.
8.7.1 Antifoaming Agents
The low surface tension enables silicones to be used as antifoaming agents,
foam stabilizers, and free-flowing agents, e.g., in paints.
8.7.1.1 Antifoaming Agents
Suspension polymerization of PVC, silicone antifoaming agents are an important
constituent. Also, foaming in spinning baths of man-made fibers
can be controlled by silicone antifoaming agents.
8.7.2 Release Agents
8.7.2.1 Mold Release Agents
Silicones are used as mold release agents in the rubber and plastics industries.
Molds made from silicone rubber itself are common.
Silicone resins are typically applied to surfaces by dissolving the
silicone resin in volatile solvents. Evaporation of the solvent leaves behind
the silicone resin in the desired location, e.g., on the surface of the mold
for release, or in the cavities and interstices of the port as a sealant. Then,

Silicones 341
with the application of heat or chemicals, the resin is cured in-situ, forming
a hard, polymeric network.
Waterborne silicone release agents are common. An advantage of
using water as a carrier is that the presence of water can prevent or delay
silanol condensation of the resin. A catalyst may be added and stored in a
water-based composition without inducing immediate curing. Hence, the
use of water as a carrier improves the shelf life of the composition.
The most significant difficulty associated with using water as a carrier
is that silicone resins are relatively immiscible in water. Water-based
silicone resin compositions can be formulated using conventional surfactants.
Large amounts of surfactant, however, are usually required, and the
dispersion formed may not be very stable. The dispersion can be stabilized
with a hydrophobically modified polycarboxylic acid. 33
8.7.2.2 Paper Release Agents
Crosslinkable silicone polymers are used as silicone release papers. These
have a wide range of applications for labels and coatings.
8.7.3 Sealing and Jointing Materials
Silicone seals have found widespread uses in cars, gaskets, household engines,
and medical devices. Silicone jointing materials are used for expansion
joints on building facades, connecting aluminum or plastic, and in the
sanitary field, e.g., for bathroom tiles. Various silicone rubber grades have
been developed with different curing systems.
8.7.4 Electrical Industry
The high insulating power of silicones is appreciated in the electrical industry.
Applications are in cables, electrical motors, seals, and heating
elements. Silicone rubber rollers are used in photocopying devices, and
facsimile devices.
8.7.5 Medical Applications
Silicones are mostly inert to living organisms. They are considered nontoxic
materials and can be used in pharmaceutical and medical applications.

342 Reactive Polymers Fundamentals and Applications
8.8 SPECIAL FORMULATIONS
8.8.1 Polyimide Resins
Polyimide resins are commonly used as materials for printed circuit
boards and heat-resistant adhesive tapes because of their high
heat resistance and superior electrical insulation properties. Common
basic materials are 3,3 ′ ,4,4 ′ -diphenylsulfone tetracarboxylic dianhydride
(DSDA) 4,4 ′ -hexafluoropropylidenebisphthalic dianhydride (6FDA),
2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP) and 3,3 ′ -dihydroxy-
4,4 ′ -diaminobiphenyl (HAB).
They are used as resin varnish to form surface protective films and
interlayer insulating films of electronic parts and semiconductor materials.
Commonly a solution is prepared by dissolving a polyimide precursor such
as polyamic acid.
The solution is coated on a substrate, followed by removal of the
solvent. Then high-temperature treatment effects the dehydration cyclization
and the product obtained is used as polyimide resin. To improve the
solubility of a polyimide resin in solvents, improve its adhesive force to
substrates and impart flexibility, a siloxane group can be introduced into
the polyimide skeleton.
Such siloxane materials are diaminosiloxanes, i.e., straight chain silicones
having amino groups at both terminals. Therefore, types with a
small content of cyclic siloxane oligomers have been developed. 34
8.8.2 Thermal Transfer Ribbons
Thermal transfer printing is advantageous because relatively low noise levels
are attained during printing. Thermal transfer printing is widely used
in special applications such as printing of machine readable bar codes and
magnetic alpha-numeric characters. Most thermal transfer ribbons employ
poly(ethylene terephthalate) (PET) polyester as a substrate. The functional
layer which transfers ink, also referred to as the thermal transfer layer, is
deposited on one side of the substrate, and a protective backcoat is deposited
on the other side of the poly(ethylene terephthalate) substrate.
Untreated poly(ethylene terephthalate) will not pass under a thermal
print head without problems. The side of the poly(ethylene terephthalate)
substrate which comes in contact with the print head, i.e., the side opposite
the thermal transfer layer, must be protected during the printing process.

Silicones 343
Failure to do so will result in the sticking of poly(ethylene terephthalate)
to the heating elements during the heating cycle. Poly(ethylene terephthalate)
is also an abrasive material which will cause unacceptable wear on the
print head. Therefore, conventional thermal transfer ribbons which employ
a poly(ethylene terephthalate) substrate have treated backsides. The substrate
is coated on the reverse side to form a barrier between the poly(ethylene
terephthalate) and the print head.
The backcoats are usually comprised of silicone polymers. The most
common backcoats are silicone oils and UV cured silicones. The silicone
oils can be delivered directly to the PET substrate or via an organic solvent.
However, for environmental reasons solvent-free coatings are used.
A water-soluble silicone block copolymer consists of silicone resin blocks
and water-soluble poly(ethylene oxide) blocks or poly(propylene oxide)
blocks. 35
8.8.3 Self-Assembly Systems
The adhesion between a substrate and a polymer can be improved by using
molecular self-assembling polymers. Typical self-assembly systems
include silanes on hydroxylated substrates, such as glass surfaces or silicon
wafers. The mechanical stability of a self-assembled polymer film can
be increased by incorporating sticker groups in the polymer chain to introduce
additional interactions between the sticker groups and the substrate
solid surface.
This is why silane functionalized poly(styrene) and poly(methyl
methacrylate) were polymerized in the presence of a silane coupling agent,
mercaptopropyltrimethoxysilane (MPS), which is also an effective chain
transfer agent in the radical polymerization. 36
8.8.4 Plasma Grafting
Cornstarch granules could be surface functionalized in a high frequency
plasma with ethylene diamine. In the second step the material was grafted
with dichlorodimethylsilane.
A poly(dimethylsiloxane) graft-copolymer layer on the modified surface
was detected. 37 The starch graft-copolymer might find use as a reinforcing
component in silicone-rubber materials.

344 Reactive Polymers Fundamentals and Applications
8.8.5 Antifouling Compositions
Aquatic animal and plant organisms such as barnacles, oysters, ascidians,
polyzoans, serupulas, sea lettuces and green layers adhere and grow on the
surface of marine structures, resulting in damage. For example, the aquatic
organisms can adhere to the bottom of a ship, increasing the frictional resistance
between the ship body and water. The increased resistance results
in higher fuel costs. Some industrial plants use sea water for cooling.
Fouling of intake pipes by aquatic animals and plants can hinder
the induction of cooling water resulting in a drop in cooling effectiveness.
A wide range of marine structures such as undersea construction, piers,
buoys, harbor facilities, fishing nets, ships, marine tanks, water conduit
raceway tubes of power plants and coastal industrial plants are affected.
8.8.5.1 Biopolymers
Marine organisms are initially attracted to and subsequently attach to a surface
by chemical and physical means. Biopolymers such as polypeptides
and polysaccharides comprise the outermost layer of marine organisms,
and in some cases the marine organism exudes a glue, which is typically
comprised of similar material, by which it attaches to a substrate.
Biopolymers are very polar, and initial physical attachment to a substrate
easily occurs when the substrate contains polar groups to which these
biopolymers can form hydrogen-bonds. Further chemical attachment can
take place by reactions between the biopolymers and a substrate. A hydrophobic
surface is one which contains very little to no polar groups; thus,
a hydrophobic surface expresses very few toeholds for marine organisms to
adhere. The only type of attraction would be Van der Waals forces, which
are very weak.
8.8.5.2 Toxicants
Various antifouling compositions have been developed to prevent the adherence
of the aquatic organisms. Toxicants containing copper, tin, arsenic
and mercury, and others been proposed. Further, strychnine, atropine, creosote,
and phenol have been proposed.
However, even the effective compositions have disadvantages. These
compositions prevent fouling by a toxic mechanism. Effectiveness of the

Silicones 345
compositions requires that a lethal concentration of poison be maintained
in the water immediately adjacent to the surface of the marine structure.
Eventually, the poison is completely leached into the water and the
composition is exhausted and must be replaced. Further, the poisons are
toxic to humans and aquatic life and can be a major source of pollution in
busy harbors and in waterways.
8.8.5.3 Fouling Release Coatings
Fouling release coatings, i.e., coatings which do not allow organisms to
adhere to the marine body surface, have been proposed as alternatives to
the toxicity-based antifouling agents.
Particularly suitable are curable fluorinated silicone resins formed
by replacing some but not all of SiH groups in an end-capped fluoroalkyl
group-containing polyalkylhydrosiloxane. Otherwise, a fluorinated silicon
resin can be blended with a non-fluorinated organopolysiloxane resin prior
to crosslinking.
Examples of suitable unsaturated fluoroalkyls include nonafluorohexene,
1H-1H-2H-perfluoroheptene, 1H-1H-2H-perfluorooctene, 1H-1H-
2H-perfluorononene and 3,3,4,4,5,5,5-heptafluoro-1-pentene.
Fluorosilicons are prepared by reacting a polyalkylhydrosiloxane
and an unsaturated fluoroalkyl compound. A suitable catalyst is an organic
transition metal salt, such as zinc octoate.
The fluorinated silicon resin is then crosslinked either by the pendant
groups of the silicon resin itself, or with added compounds.
Such added components can be methyltriethoxysilane or octyl triethoxysilane
or a tetraethoxysilane or a fluoroalkyltriethoxysilane.
The coating consists of more than one layer, an anticorrosive layer,
the adhesion promoting layer, and the release layer. Adhesion promoting
layers include a moisture curable grafted copolymer that further includes
poly(dialkylsiloxane) and n-butyl acrylate, styrene, vinyl chloride and vinylidene
chloride that is grafted onto the siloxane backbone. An aminofunctionalized
polysiloxane is active as adhesion promoter. The release
layer consists of the fluorinated polysiloxane. 38
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(Tokyo, JP), June 12 2001.
19. S. Akamatsu and M. Sasaki. Curable silicone resin composition. US Patent
6 255 373, assigned to Dow Corning Toray Silicone Company, Ltd. (Tokyo,
JP), July 3 2001.
20. F. J. McGarry, B. Zhu, and D. E. Katsoulis. Silicone resin based composites
interleaved for improved toughness. US Patent 6 660 395, assigned to Dow
Corning Corporation (Midland, MI), December 9 2003.
21. M. Patel and A. C. Swain. Thermal stability of poly(m-carborane-siloxane)
elastomers. Polym. Degrad. Stabil., 83(3):539–545, March 2004.
22. K. D. Klein, W. Knott, and D. Windbiel. Synergistic catalyst system and process
for carrying out hydrosilylation reactions. US Patent 6 307 082, assigned
to Goldschmidt AG (Essen, DE), October 23 2001.
23. J. R. Keryk, P. Y. K. Lo, and L. E. Thayer. Silicone release coatings containing
higher alkenyl functional siloxanes. US Patent 4 609 574, assigned to
Dow Corning Corporation (Midland, MI), September 2 1986.
24. J.-M. Frances, R. S. Dordick, and A. Soldat. Silicone compositions comprising
long chain α-acetylenic alcohol hydrosilylation inhibitors. US Patent
5 629 387, assigned to Rhone-Poulenc Chimie (Courbevoie Cedex, FR), May
13 1997.
25. K. M. Lewis and R. A. Cameron. Treatment of polyethers prior to hydrosilylation.
US Patent 5 986 122, assigned to Witco Corporation (Greenwich,
CT), November 16 1999.
26. Y. M. Zhang, Y. Huang, X. L. Liu, and Y. Z. Yu. Studies on the silicone resins
cured with polymethylsilazanes at ambient temperature. J. Appl. Polym. Sci.,
89(6):1702–1707, August 2003.
27. R. E. Medsker, D. R. Hazelton, G. W. Gilbertson, S. Abdou-Sabet, K.-S.
Shen, R. L. Hazelton, and Ravishanka. Hydrosilylation crosslinking of thermoplastic
elastomer. US Patent 6 251 998, assigned to Advanced Elastomer
Systems, L.P. ; Exxon Chemical Patents, Inc., June 26 2001.

348 Reactive Polymers Fundamentals and Applications
28. P. R. Dvornic and R. W. Lenz. High Temperature Siloxane Elastomers.
Hüthig & Wepf, Basel, New York, 1990.
29. T. M. Keller and D. Y. Son. High temperature ceramics derived from linear
carborane-(siloxane or silane)-acetylene copolymers. US Patent 6 265 336,
assigned to The United States of America as represented by the Secretary of
the Navy (Washington, DC), July 24 2001.
30. T. M. Keller. Oxidative protection of carbon fibers with poly(carborane-siloxane-acetylene).
Carbon, 40(3):225–229, March 2002.
31. P. Colombo, E. Bernardo, and L. Biasetto. Novel microcellular ceramics
from a silicone resin. J. Am. Ceram. Soc., 87(1):152–154, January 2004.
32. Y. M. Li, Z. M. Zheng, C. H. Xu, C. Y. Ren, Z. J. Zhang, and Z. M. Xie. Synthesis
of iron-containing polysilazane and its antioxidation effect on silicone
oil and rubber. J. Appl. Polym. Sci., 90(1):306–309, October 2003.
33. J. Wang. Water-based silicone resin compositions. US Patent 5 804 624,
September 8 1998.
34. M. Sugo and H. Kato. Polyimide silicone resin, process for its production,
and polyimide silicone resin composition. US Patent 6 538 093, assigned to
Shin-Etsu Chemical Co., Ltd. (Tokyo, JP), March 25 2003.
35. J. D. Roth. Water soluble silicone resin backcoat for thermal transfer ribbons.
US Patent 6 245 416, assigned to NCR Corporation (Dayton, OH), June 12
2001.
36. F. Zhou, W. M. Liu, T. Xu, S. J. Liu, M. Chen, and J. X. Liu. Preparation
of silane-terminated polystyrene and polymethylmethacrylate self-assembled
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37. Y. H. C. Ma, S. Manolache, M. Sarmadi, and F. S. Denes. Synthesis of
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38. A. E. Mera and K. J. Wynne. Fluorinated silicone resin fouling release composition.
US Patent 6 265 515, assigned to The United States of America as
represented by the Secretary of the Navy (Washington, DC), July 24 2001.

9
Acrylic Resins
Acrylic resins are polymers of acrylic or methacrylic esters. They are
sometimes modified with monomers such as acrylonitrile and styrene. The
most common acrylates are methyl acrylate, ethyl acrylate, n-butyl acrylate
and 2-ethylhexyl acrylate. Methacrylates include methyl methacrylate,
ethyl methacrylate, butyl methacrylate, and higher alcohol esters.
The resins are used either as molding powders or casting syrups.
Acrylic resins are often used as hybrid resins in combination with urethanes,
epoxides and silicones.
Since coatings are not the primary goal of this topic, coating applications
will be dealt with only marginally, even when acrylic resins contribute
highly to this topic. Acrylic resins are also widely used for dental applications.
We treat this topic because of its importance in a special chapter.
Here we focus on non-dental applications of acrylic resins.
An overview on acrylic and methacrylic ester polymers is given in
the literature. 1, 2
9.1 HISTORY
Acrylic acid was obtained through the air oxidation of acrolein by Redtenbacher
in 1843. Methacrylic acid was first prepared in 1865. Otto Röhm
observed the polymerization of acrylics. The production of acrylates
started in 1927 by Röhm&Haas. In 1936 poly(methyl methacrylate) was
prepared by a casting process.
349

350 Reactive Polymers Fundamentals and Applications
O
CH 2 CH C
O CH 3
O
CH 2 CH C
O CH 2 CH 3
Methyl acrylate
Ethyl acrylate
O
CH 2 CH C
O CH 2 CH CH 2 CH 2 CH 2 CH 2 CH 3
CH 2
CH 3
CH 2
2 CH 3
2-Ethylhexyl acrylate
O
CH C O
O
CH 2
CH 2 CH C O CH 2 C CH
CH 2 CH C O
O CH 2
Trimethylolpropane triacrylate
Figure 9.1: Acrylate-based Monomers
9.2 MONOMERS
A large variety of monomers is known, because of the possibility of esterifying
the acrylic acid and methacrylic acid with various alcohols. The
most common monomers are shown in Table 9.1. Some acrylate-based
monomers are shown in Figure 9.1.
9.2.1 Specialities
9.2.1.1 Cyclohexyl methacrylates
Polymers containing cyclohexyl methacrylate and related compounds such
as 4-methylcyclohexylmethyl methacrylate exhibit high weather resistance.
This is due to its low hygroscopic functional group. It is used for
coating materials.

Acrylic Resins 351
Table 9.1: Monomers for Acrylic Resins
Monomer Remarks Reference
Acrylic Monomers
Acrylic acid
Methyl acrylate
Ethyl acrylate
n-Butyl acrylate
2-Ethylhexyl acrylate
Trimethylolpropane triacrylate (TMPTA)
a 3
Aziridine derivatives
a 4
Methacrylic Monomers
Methyl methacrylate
b
Ethyl methacrylate
2-Hydroxyethyl methacrylate (HEMA)
n-Butyl methacrylate
c
Ethylene glycol dimethacrylate
a
Poly(ethylene glycol)dimethacrylate
3-Methacryloxypropyl-trimethoxysilane (MPTS)
5
Cyclohexyl methacrylate
d 6
4-Methylcyclohexylmethyl methacrylate
7
Methacryloyl isocyanate
7
2-Methacryloyloxyethyl isocyanate
7
Methyl N-methacryloylcarbamate
8
Phenyl N-methacryloylcarbamate
8
2-Ethylhexyl N-methacryloylcarbamate
9
2-Isocyanatoethyl methacrylate (IEM)
10
a Crosslinker
b Standard
c Flexible
d Improved weatherability

352 Reactive Polymers Fundamentals and Applications
9.2.1.2 Methacryloyl Isocyanate and Derivatives
Alkenoylcarbamates can be readily polymerized by themselves or with any
other vinyl compounds. The carbamates formed from alcohols with a small
number of carbon atoms are available in a stable solid form under the atmospheric
condition and can be dissolved easily in various solvents.
The acylurethane structure contributes to an enhancement of cohesion.
Therefore, copolymers containing alkenoylcarbamate units show various
advantageous properties such as high elasticity and good adhesion.
The introduction of an epoxy or aziridino group introduces further
reactive moieties. The modification to a blocked isocyanate structure provides
the alkenoylcarbamate compounds with the latent reactivity of an
isocyanate group, which will be actualized from the blocked isocyanate
structure under heating.
Methyl N-methacryloylcarbamate, phenyl N-methacryloylcarbamate,
benzyl N-methacryloylcarbamate, and a series of other methacryloyl
carbamates can be synthesized from methacryloyl isocyanate by adding the
appropriate alcohols to methacryloyl isocyanate. 8 The synthesis is shown
in Figure 9.2. The reaction is conducted at low temperatures. Also an exchange
of the alcohol group in the carbamate is possible. For example,
ethyl N-methacryloylcarbamate can be reacted with 2-ethylhexyl alcohol
in the presence of a radical polymerization inhibitor such as hydroquinone
at 120°C. The ethoxy moiety is then replaced by the 2-ethylhexyloxy moiety
to result in 2-ethylhexyl N-methacryloylcarbamate. This product is a
viscous liquid. 9
9.2.2 Synthesis
9.2.2.1 Monomers
Acrylic acid is synthesized by the oxidation of propene via acrolein.
Methyl methacrylate is synthesized from acetone via the acetone cyanhydrin
(ACH). The reactions are shown in Figure 9.3. The conventional
process for the synthesis of methyl methacrylate runs via the acetone cyanhydrin.
Other technical processes include
• The ACH-based process (Röhm&Haas, Mitsubishi Gas Chemical),
• The i-butylene oxidation process (Lucky, Japan Methacrylic),
• The tert-butanol oxidation process (Kyodo, Mitsubishi Rayon),

Acrylic Resins 353
CH 2
CH 3
C C N C O
CH 3 OH
CH 2
CH 3 H
C C N C O
O
O
O
CH 3
N-Methacryloylcarbamate
CH 2
CH 3
C C N C O
OH
CH 2
CH 3 H
C C N C O
O
O
O
Phenyl N-methacryloylcarbamate
Figure 9.2: Synthesis of Methyl N-methacryloylcarbamate and Phenyl N-methacryloylcarbamate
8
• The propyne carbonylation (Shell, ICI), and
• The hydrocarbonylation of ethene. 11
9.2.2.2 Esterification
The reaction of methacrylic acid with an alcohol results in the respective
ester. Also, an olefin can be added to the acid in the presence of anhydrous
catalysts. Ethylene oxide reacts to form the hydroxy alkyl esters. Diazomethane
reacts to the methyl esters. The reactions are shown in Figure 9.4.
9.2.3 Manufacture
Various structural elements, such as rods, sheets, tubes, and molding powders
are produced by bulk polymerization. The most common method for
the production of sheets is the batch cell method. The polymerization process
releases a lot of heat and has to be carried out slowly, in order to
avoid an adverse effect on the optical properties. If the polymerization in
bulk quantities proceeds too fast, even the boiling point can be crossed and

354 Reactive Polymers Fundamentals and Applications
O 2
CH 2 CH C
O
CH 2 CH CH 3 CH 2 CH C
H
O
CH 2 CH C
H
O 2
O
OH
CH 3
CH 3
C O HCN HO C C N H CH
2SO 2 4
C C NH 2
CH 3 CH 3
CH 3
H 2 SO 2
CH 3
OH
CH 2
CH 3
C C
O
OCH 3
Figure 9.3: Synthesis of Acrylic acid and Methyl methacrylate

Acrylic Resins 355
CH 2
CH 3
C C
O
CH 3
OH + HO R CH 2 C C
O
OR
CH 2
CH 3
C C
OH + CH 2 CH R
O
CH 2
CH 3
C C
O
CH 2 CH 2 R
O
CH 2
CH 3
C C
O
O
OH + H 2 C CH 2
CH 2
CH 3
C C
O
O CH 2 CH 2 OH
CH 2
CH 3
C C
CH 3
OH + CH 2 N 2 CH 2 C C
OCH 3
O
O
Figure 9.4: Esterification Reactions of Methacrylic Acid

356 Reactive Polymers Fundamentals and Applications
Table 9.2: Ultraviolet Absorbers for Acrylic Resins 12
Compound
Benzotriazole Ultraviolet Absorbers
2-(5-Methyl-2-hydroxyphenyl)benzotriazole
2-[2-Hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole
2-(3,5-Di-tert-butyl-2-hydroxyphenyl)benzotriazole
2-(3-tert-Butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzothiazole
2-(3,5-Di-tert-Butyl-2-hydroxyphenyl)-5-chlorobenzothiazole
2-(3,5-Di-tert-amyl-2-hydroxyphenyl)benzotriazole
2-(2 ′ -Hydroxy-5 ′ -tert-octylphenyl)benzotriazole
2-Hydroxybenzophenone Ultraviolet Absorbers
2-Hydroxy-4-methoxybenzophenone
2-Hydroxy-4-octoxybenzophenone
2,4-Dihydroxybenzophenone
2-Hydroxy-4-methoxy-4 ′ -chlorobenzophenone
2,2 ′ -Dihydroxy-4-methoxybenzophenone
2,2 ′ -Dihydroxy-4,4 ′ -dimethoxybenzophenone
Salicylic Acid Phenyl Ester Ultraviolet Absorbers
p-tert-Butylphenyl salicylate
p-Octylphenyl salicylate
thus bubbles are formed. Inhomogeneous temperature distribution during
polymerization my cause streaks in the material.
9.3 SPECIAL ADDITIVES
9.3.1 Ultraviolet Absorbers
Examples of ultraviolet absorbers are shown in Table 9.2.
9.3.2 Flame Retardants
Flame resistance can be imparted by incorporating certain organic phosphoric
acid esters to acrylic resins. Some flame retardants are shown in
Table 9.3 and in Figure 9.5.
However, these organic phosphoric acid esters usually have a plasticizing
effect. They are likely not only to substantially lower the heat
distortion temperature of the acrylic resin products, but also to lower its

Acrylic Resins 357
Table 9.3: Flame Retardants13, 14
Compound Remarks Reference
Phosphoric acid esters
13
Chlorinated polyphosphates
13
Halogenated polyphosphonate
13
Alkyl acid phosphate Synergist
13
Tetrabromobisphenol A
14
2,2-Bis(4-hydroxy-3,5-dibromophenyl)propane
14
Tricresyl phosphate
14
Tris(2-chloroethyl)phosphate
14
Antimony trioxide Inorganic
14
Zirconium hydroxide Inorganic
14
Barium metaborate Inorganic
14
Tin oxide Inorganic
14
O O O
CH 2 O P O CH P O CH P O CH 2
CH 2 CH 2 CH 3 O CH 3 O CH 2
Cl CH 2
Cl
CH 2
CH 2
CH 2
CH 2
Cl
Cl Cl
Figure 9.5: Chlorinated Polyphosponate (Phosgard C-22 R, Monsanto)

358 Reactive Polymers Fundamentals and Applications
Table 9.4: Global Production Data of Important Monomers and Polymers
15 Monomer Mill. Metric tons Year Reference
Methyl methacrylate 2 2002
16
Acrylic surface coatings 0.92 2003
17
Acrylic resins and plastics 0.85 2000
18
mechanical strength. Further, the water absorptivity of the resin products
tends to increase by the incorporation of such flame retardants, and when
used outdoors, the resin products are likely to undergo deformation or crazing
upon absorption of water.
For a copolymer of methyl methacrylate, α-methylstyrene, styrene,
maleic anhydride, and methacrylic acid, a synergism has been observed.
When two types of flame retardants, i.e., a halogen-containing condensed
phosphoric acid ester or a halogenated polyphosphonate and an alkyl acid
phosphonate, are combined, superior flame resistance and physical properties
will be imparted by the synergistic effect of the components.
Here, it is possible to reduce the amount of the main flame retardant
to a level of about 20% even when the flame resistance should meet the
standard of V-0 of the UL Standards. 19
Therefore, it is possible to avoid the deterioration of the physical
properties, particularly the deterioration of the heat resistance, which is a
serious problem when a great amount of the flame retardant is added. 13
9.3.3 Production Data of Important Monomers
Global production data of the most important monomers used for acrylic
ester resins are shown in Table 9.4.
9.4 CURING
The polymerization of acrylic resins occurs essentially by a radical mechanism.
9.4.1 Initiator Systems
Traditional radical polymerization initiators may be used for the casting
polymerization. Common catalysts are shown in Table 9.5. Polymerization

Acrylic Resins 359
Table 9.5: Polymerization Initiators for Casting
Initiator
Azobis-type Catalysts 13
Remarks
2,2 ′ -Azobis(isobutyronitrile) preferred
2,2 ′ -Azobis(2,4-dimethylvaleronitrile) preferred
Diacylperoxide-type Catalysts 13
Lauroyl peroxide
Dibenzoyl peroxide
Bis(3,5,5-trimethylhexanoyl)peroxide
Perester-type Catalysts 20
tert-Amylperoxy-2-ethylhexanoate
tert-Butylperoxy-2-ethylhexanoate
Percarbonate-type Catalysts 13
bis(4-tert-Butylcyclohexyl)peroxydicarbonate
UV Curing Catalysts 3
2,2-Dimethoxy-2-phenylacetophenone (DMPA)
benzophenone (BP) and
methyldiethanolamine (MDEA)
Acyl-phosphine oxide
21
preferred
preferred

360 Reactive Polymers Fundamentals and Applications
initiators particularly suitable for the continuous sheet-forming process are
those having a decomposition temperature, at a half-life of 10 hours, in the
range of 40°C to 80°C.
9.4.2 Promoters
Special initiator systems for cold curing were developed. An effective initiator
promoter system consists of a zinc 2-ethylhexanoate solution, a cobalt
2-ethylhexanoate, and as peroxide source tert-butylperoxybenzoate. 22
9.5 PROPERTIES
Acrylic resins are appreciated for their exceptional clarity and optical properties.
Acrylics show a slow burning behavior and can be formulated as
self-extinguishing.
Acrylic resins are excellent in transparency, translucency, surface
gloss, and weather resistance and further have a high surface hardness and
a superior design adaptability.
Therefore, they find a wide variety of applications in interior materials
for vehicles, exterior materials for household electrical appliances and
building materials (exterior) for example, regardless of whether they are
outdoor or indoor applications.
However, acrylic resins generally exhibit poor flexibility and low
impact resistance and, therefore, pose a problem in that they are prone to
fracture when given an extraneous load or impact.
9.5.1 Electrical Properties
Acrylic resins are easily electrically charged by friction because of their
high surface resistivity. Thus they are deteriorated in appearance by adhesion
of rubbish or dust, or they bring about an undesirable situation
by electrostatic electrification in parts of electronic equipment. Antistatic
properties to the acrylic resin can be imparted by 23
• Kneading a surfactant with the acrylic resin, or applying a surfactant
on the surface of the acrylic resin,
• Kneading a vinyl copolymer having a poly(oxyethylene) chain and
a sulfonate, carboxylate or quaternary ammonium salt structure,
with an acrylate resin,

Acrylic Resins 361
• Kneading a polyether ester amide with a methyl methacrylatebutadiene-styrene
copolymer,
• Adding a functional polyamide elastomer,
• Adding a polyamide-imide elastomer having a low content of hard
segments.
9.5.2 Hydrolytic and Photochemical Stability
Methacrylate-based polymers have a better hydrolytic stability than the
corresponding acrylate polymers. They are much more stable than vinyl
acetate polymers.
Acrylic and methacrylic resins are not very sensitive to ultraviolet
radiation. However, ultraviolet absorbers improve stability. Adding ultraviolet
absorbers, e.g., to arcylic windows, also protects the interior from
UV radiation.
9.5.3 Recycling
Poly(methyl methacrylate) depolymerizes nearly qualitatively (ca. 96%)
on pyrolysis into the monomer. This property is attractive for thermal recycling
of unmixed poly(methyl methacrylate) wastes. The situation in the
case of acrylates is different.
9.6 APPLICATIONS AND USES
Acrylic resins have been widely used as materials for various parts of electronics
products, household appliances, office automation appliances, etc.
because of their excellent transparency and stiffness. 23 They are used in
the sanitary sector, as surrogate for ordinary glass.
9.6.1 Acrylic Premixes
An acrylic resin composition can be used as raw material for an acrylic
premix for producing an acrylic artificial marble. Acrylic artificial marbles
are obtained by blending an acrylic resin with inorganic fillers such as aluminium
hydroxide. They have an excellent appearance, soft feeling and
weatherability and are widely used for kitchen counters, lavatory dressing
tables, waterproof pans, etc.

362 Reactive Polymers Fundamentals and Applications
Artificial marbles are generally produced by filling a slurry mold.
This mold is obtained by dispersing inorganic fillers in an acrylic syrup.
The filled slurry must be cured at relatively low temperature. The acrylic
syrup has a comparatively low boiling temperature. Consequently a long
time is required for molding which causes low productivity. To overcome
these drawbacks, the acrylic syrup can be blended with a crosslinked resin
powder having a specific degree of swelling.
On the other hand, an acrylic premix for an artificial marble, with excellent
low shrinking properties has been prepared by blending the acrylic
syrup with a thermoplastic acrylic resin powder, which is poorly soluble
in the syrup. The acrylic syrup consists essentially of methyl methacrylate
or a (meth)acrylic monomer mixture and poly(methyl methacrylate) or an
acrylic copolymer.
To impart strength, solvent resistance, and dimension stability to a
molded article, instead of pure methyl methacrylate monomer, a polyfunctional
(meth)acrylic monomer may be added. It is preferable to replace
the methyl methacrylate monomer by neopentyl glycol dimethacrylate up
to 50%, since the molded article then has a remarkably excellent surface
gloss. 24 The acrylic syrup may be obtained by dissolving the component
acrylic polymer in the monomer, or a syrup can be obtained by partial
polymerization of the component in the monomer.
To the premix curing agents, such as dibenzoyl peroxide, lauroyl
peroxide, tert-butyl hydroperoxide, cyclohexanone peroxide, methylethylketone
peroxide, tert-butylperoxyoctoate, tert-butylperoxybenzoate,
dicumyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane,
2,2 ′ -azobis(isobutyronitrile) are added. The filler then is added and
heat and pressure curing takes place for 10 minutes under conditions of
a mold temperature of 130°C and a pressure of 100 kg/cm 2 to obtain an
acrylic artificial marble with a thickness of 10 mm.
9.6.2 Protective Coatings in Electronic Devices
In semiconductor devices including a ferroelectric film or a dielectric film
with a high dielectric constant, a surface coating has been proposed. This
coating is made of an acrylic resin which prevents the degradation of the
polarization properties of the ferroelectric or a film with a high dielectric
constant, respectively, on the semiconductor device. 25

Acrylic Resins 363
9.6.3 High-performance Biocomposite
An environmentally friendly acrylic resin has been examined with respect
to a high-performance biocomposite. Parameters such as the onset of curing
reaction, the degree of cure at certain temperatures, and the swelling
equilibrium data were analyzed. The crosslinking density after curing the
resin at 180°C for 10 min indicates the completion of curing to a major
extent under those conditions. 26
9.6.4 Solid Polymer Electrolytes
In conventional batteries with electrolytic solutions, the possible leakage
of the electrolyte solution or elution of the electrode substance outside the
battery presents a problem in long-term reliability. Batteries and electric
double-layer capacitors using a solid polymer electrolyte are free of these
problems. Also, these can be easily reduced in thickness.
For installing a solid polymer electrolyte into a battery or electric
double-layer capacitor, a method of using an electrolyte and a trifunctional
methacrylic compound as the main components for the solid polymer electrolyte
has been developed. The monomer for the solid polymer electrolyte
is prepared from 2-isocyanatoethyl methacrylate and a branched oligo
glycol. Such a glycol can be prepared by the etherification of glycerol,
ethylene glycol, and propylene glycol. The isocyanate group adds with the
pendent hydroxyl groups resulting in a trifunctional methacrylate ester. 10
The synthesis is shown in Figure 9.6. Also, a mixture of poly(ethylene glycol)dimethacrylate
and methoxypoly(ethylene glycol) mono methacrylate
can serve as a monomer for solid polyelectrolyte polymers. 27
It is desirable for a three-dimensional network structure to be
formed. The polymerization is initiated by conventional peroxides or azo
compounds. The whole formulation for a battery consists of:
1. Methacrylic monomer,
2. Polymerization initiator,
3. Polymerization retarder,
4. Electrolyte salt,
5. Organic solvent, and
6. Inorganic particles.
The process for manufacturing a complete battery is described in detail
elsewhere. 10

364 Reactive Polymers Fundamentals and Applications
CH 2
CH 3
CH C
O CH 2 CH 2 NCO
HOR
CH 2
CH 2
CH 3
CH C
O CH 2 CH 2 NCO
HOR
CH
O
CH 2
CH 3
CH C
O CH 2 CH 2 NCO
HOR
CH 2
O
O
CH 2
CH 3
CH C
O CH 2 CH 2 N C
OR
CH 2
H
O
CH 3
O
H
O
CH 2
CH
C
O
CH 2
CH 2
N
C
OR
CH
CH 2
CH 3
CH C
O CH 2 CH 2 N C
OR
CH 2
O
H
O
O
R = (CH 2 CH 2 O) n (CH 2 CHO) m
CH 3
Figure 9.6: Synthesis of a Methacrylate Monomer for a Solid Electrolyte 10

Acrylic Resins 365
9.7 SPECIAL FORMULATIONS
9.7.1 Silane and Siloxane Acrylate Resins
Weather resistant resin coatings can be prepared by an addition polymerization
reaction of n-butyl acrylate, methyl methacrylate, n-butyl
methacrylate, and 3-methacryloxypropyl-trimethoxysilane (MPTS). The
weather resistant silicone/acrylic resin coatings are then blended with
TiO 2 . The viscosity of the resin decreases with increasing content of
MPTS, whereas the thermal stability at high temperature increases.
5, 28, 29
Coatings with 30% MPTS have especially good weather resistant properties.
UV-curable formulations for UV-transparent optical fiber coatings
have been developed. Poly(dimethylsiloxane-acrylate) resins showed the
best performance with respect to the monomer reactivity and the UV-transparency
of the polymer coating. An acyl-phosphine oxide proved to be
the best suited because of its high reactivity, fast photolysis, and lack of
absorbing of the by-products of photo curing at the wavelength of operation.
21
9.7.2 Marble Conservation
Marble and stone used as building materials are susceptible to environmental
damage. Acrylic resins can be used as carriers of suitable pigments for
the protection of the surface of a monument. Copolymers of ethyl methacrylate
and methyl acrylate have been extensively applied as a protective
agent for stone building materials since the 1950s.
The photodegradation of acrylic resins containing titanium dioxide
pigments has been studied under UV irradiation. Two kinds of TiO 2 ,
anatase and a mixture of anatase and rutile, were used in different concentrations.
The changes caused by the irradiation treatment were monitored
by Fourier transform infrared spectroscopy, gel permeation chromatography,
and solubility measurements. The presence of anatase pigment
significantly improved the photostability. 30 Films of acrylic resins of varying
compositions were applied both on a dolomitic white marble support
and on potassium bromide disks and exposed to UV light. The main degradation
pathway under ultraviolet irradiation is the chain scission. The rates
of photodegradation may be related to the type of ester group and to the
presence of the α-methyl group in the main chain. 31

366 Reactive Polymers Fundamentals and Applications
Blends of acrylic resins and fluoroelastomer are also suitable materials
in stone protection. Films of a copolymer of ethyl methacrylate
and methyl acrylate blended with a copolymer of vinylidene fluoride and
hexafluoropropene were investigated by means of FT-IR spectroscopy and
FT-IR microspectroscopy before and after UV and thermal treatments. A
high content of fluoroelastomer increases the stability of these blends. A
solution of a blend described above in tetrahydrofuran was successfully applied
to a marble surface of the Saint Maria Cathedral in Lucca, Toscana. 32
9.7.2.1 Degradation by Lipase
Layers of an aged acrylic resin, a fifteenth-century tempera painting on
panel and a nineteenth-century oil painting on canvas have been removed
by the action of lipases. Lipases are hydrolytic enzymes that act on glycerol
ester bonds. These enzymes are a less aggressive alternative to highly polar
organic solvents or alkaline mixtures. 33
9.7.3 Tackifier Resins
Acrylic resins are suitable as tackifier resins in pressure-sensitive adhesive
applications. They can be prepared by free-radical polymerization. The
acrylic tackifier is then blended with a natural rubber base in various ratios.
Investigation of the mechanical properties showed that blends with a good
pressure-sensitive adhesive performance have a higher loss of tangent-δ at
higher frequencies. 34
9.7.4 Drug Release Membranes
The feasibility of a transdermal delivery system (TDS) for 17-β-estradiol
was investigated by in vitro release studies. Unilaminate adhesive devices
capable of releasing 17-β-estradiol in a controlled fashion over a period up
to 216 hours have been developed using acrylic resins. The release of drug
from the adhesive devices seems to obey a zero-order kinetics.
Acetyltributyl citrate (ATBC), triethyl citrate (TEC), propylene glycol
(PG) and myristic acid (MA) are plasticizers that can modify the release
patterns of the drug. The study demonstrated that the acrylic resins
are suitable polymers for the preparation of 17-β-estradiol TDS adhesive
devices. 35

Acrylic Resins 367
9.7.5 Support Materials for Catalysts
Palladium-tin catalysts can be deposited on acrylic resins bearing carboxylic
functional groups. The resins act as support materials for the catalysts.
The catalysts are suitable for the selective hydrogenation of 100 ppm aqueous
nitrate solutions. The materials exhibit different Sn contents and show
different reduction temperatures.
A high COOH content in the support is important in the control of
the selectivity of the catalysts limiting ammonia formation. 36
Copper ion catalysts can be immobilized on acrylic resins (rather
than acrylonitrile resins) with aminoguanidyl groups. They are prepared
by modification of the nitrile groups in an acrylonitrile, vinyl acetate, and
divinylbenzene terpolymer using aminoguanidine carbonate.
The catalysts act on the oxidation of hydroquinone to p-benzoquinone
with hydrogen peroxide as oxidant. The catalytic activity and selectivity
in the Cu(II)-resin system increases in comparison to the reaction
without a catalyst and the reaction with native Cu(II) ions. 37
9.7.6 Electron Microscopy
Acrylic resins can be used for low-temperature embedding of samples in
electron microscopy. 38
9.7.7 Stereolithography
Three-dimensional objects can be built without the use of molds by stereolithography.
The objects are obtained layer by layer by polymerizing a
low-viscosity liquid resin under a laser beam. The kinetic behavior of the
resin is essential for a complete curing which occurs in the small zone
exposed to laser irradiation.
The isothermal kinetic behavior of a commercial acrylic resin for
stereolithography has been analyzed by differential photocalorimetric analysis.
A kinetic model accounting for the effect of autoacceleration, the
vitrification, and light intensity has been set up. 39
9.7.8 Laminated Films
Laminated films of acrylic resins are constituted of a soft layer formed of
an acrylic resin with rubber particles incorporated and a hard layer also
formed of an acrylic resin.

368 Reactive Polymers Fundamentals and Applications
By incorporating rubber particles into an acrylic resin, the flexibility
is improved while all other positive properties, such as transparency and
surface gloss, are maintained. To have a hard outer surface two films, one
of them filled with rubber particles and one being unfilled, are combined.
The laminated film is excellent in surface hardness, flexibility and
ability to prevent whitening from occurring during molding or forming and
hence is suitable for use as a surface material for moldings, such as interior
materials for vehicles, exterior materials for household electrical appliances
and building materials (exterior), which are obtained by a molding
or forming process requiring bending or stretching. 12
9.7.9 Ink-jet Printing Media
An ink-jet printing system is one wherein ink droplets are jetted onto a
surface of a printing medium and attached thereon.
Therefore, the surface of the printing medium needs to rapidly absorb
the jetted ink droplets. The printing media for use in the ink-jet printing
system are not limited to paper but include various materials such as
transparent resin films for overhead films and metals. Some of these printing
media have no hydrophilic surfaces. Therefore, in order to clearly print
information, an ink-receiving layer needs to be provided on the surface of
a substrate constituting the printing medium. The ink-jet printing media
are required to have the following characteristics:
• Permeation of ink inside the ink-receiving layer must be rapidly
made, color running should not take place, and clear color having
high chromaticity can be reproduced.
• In the multi-color printing using a combination of ink components,
each ink component must be rapidly absorbed even if ink dots are
superposed on the same surface of the printing medium, and in the
high-speed printing, the printed surface must be free from staining,
and the ink absorption rate and the ink absorption quantity both
must be satisfactory.
• The printing medium must have water resistance, and even if the
printed image is contacted by water, running or bleeding of ink of
the image must not take place.
• Even if the ink-jet printing media are stored in the superposed
state, they must be free from blocking.

Acrylic Resins 369
• Even if the printed matter is stored for a long period of time, color
fading should not take place.
Proposals for forming an ink-receiving layer containing hydrophilic
resins include 40
• Starch and other water-soluble cellulose derivatives,
• Polyvinyl alcohol, modified polyvinyl alcohol,
• Polyvinyl pyrrolidone,
• Polyvinyl acetal, and
• Hydrophilic acrylic copolymer having a crosslinked structure on
the substrate surface.
A hydrophilic acrylic copolymer having a crosslinked structure consists
of acrylamide, methacrylamide and other amides, acrylic acid and
acrylic esters, such as glycidyl acrylate and the corresponding methacrylate
derivatives, respectively. Examples of crosslinking agents include divinylbenzene,
ethylene glycol acrylate, and triethylene glycol diacrylate. A suitable
polymerization initiator is 2,2 ′ -azobis(2-amidinopropane)hydrochloride
or dibenzoyl peroxide in toluene. The polymerization is carried out
in aqueous isopropyl alcohol and poly(oxyethylene) nonylphenyl ether. 40
The copolymer was isolated and a dispersion was prepared that was applied
on wood-free paper and poly(ethylene terephthalate).
REFERENCES
1. J. W. Nemec and W. Bauer. Acrylic and methacrylic ester polymers. In
J. I. Kroschwitz, editor, Encyclopedia of Polymer Science and Engineering,
volume 1, pages 211–234. John Wiley & Sons, Inc., New York, 2nd edition,
1985.
2. H. W. Coover, Jr. and J. M. McIntire. Acrylic and methacrylic ester polymers.
In J. I. Kroschwitz, editor, Encyclopedia of Polymer Science and Engineering,
volume 1, pages 234–305. John Wiley & Sons, Inc., New York, 2nd
edition, 1985.
3. S. Yin, A. Merlin, A. Pizzi, X. Deglise, B. George, and M. Sylla. Structureproperty
relationship and influences of phenolic compounds on the mechanical
and thermomechanical properties of UV-cured acrylic resin networks. J.
Appl. Polym. Sci., 92(6):3499–3507, June 2004.
4. F. Xie, Z. H. Liu, and D. Q. Wei. Curing kinetics and properties of acrylic
resin cured with aziridine crosslinker. Chin. J. Polym. Sci., 20(1):65–70,
January 2002.

370 Reactive Polymers Fundamentals and Applications
5. H. S. Park, D. J. Chung, H. S. Hahm, S. K. Kim, W. B. Im, and S. J. Kim.
Preparation and physical properties of weather resistant silicone/acrylic resin
coatings. J. Chem. Eng. Jpn., 37(2):158–165, February 2004.
6. H. Nomura, Y. Kimata, H. Kanai, Y. Yokota, and M. Yoshida. Weatherability
of hals copolymerized acrylic resin precoated steel sheet. Tetsu To Hagane-J.
Iron Steel Inst. Jpn., 89(1):128–134, January 2003.
7. K. Nakamura, Y. Yokota, K. Takahashi, and M. Yoshida. Cyclohexylalkyl
(meth) acrylate ester-based resin composition. US Patent 6 686 413, assigned
to Nippon Shokubai Co., Ltd. (Osaka, JP), February 3 2004.
8. S. Urano, R. Mizuguchi, N. Tsuboniwa, K. Aoki, Y. Suzuki, and T. Itoh.
Carbamate physical property-improving reagent. US Patent 4 935 413, assigned
to Nippon Paint Co., Ltd. (Osaka, JP), June 19 1990.
9. E. Yamanaka, N. Tsuboniwa, T. Morimoto, M. Furukawa, and S. Urano.
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10. M. Takeuchi and S. Naijo. Thermopolymerizable composition for battery
use. US Patent 6 562 513, assigned to Showa Denki Kabushiki Kaisha
(Tokyo, JP), May 13 2003.
11. B. W. L. Jang, M. R. Gogate, J. J. Spivey, J. R. Zoeller, R. D. Colberg, and
G. N. Choi. Synthesis of methyl methacrylate from coal-derived syngas. US
Department of Energy Reports, Fischer Tropsch Archive 94065/20, Research
Triangle Institute, Research Triangle Park, NC, 1999.
12. K. Koyama and Y. Tadokoro. Acrylic resin laminated film and laminated
molding using the same. US Patent 6 692 821, assigned to Sumitomo Chemical
Company, Limited (Osaka, JP), February 17 2004.
13. S. Tayama and N. Kusakawa. Flame resistant acrylic resin composition
and process for its production. US Patent 4 533 689, assigned to Mitsubishi
Rayon Company, Limited (Tokyo, JP), August 6 1985.
14. F. Sawaragi and H. Sonezaki. Abrasion-resistant coating composition for
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15. R. Gubler, editor. Chemical Economics Handbook (CEH). SRI Consulting, a
Division of Access Intelligence, Menlo Park, CA, 1950–to present. (Internet:
http://ceh.sric.sri.com/).
16. S. Bizzari. Report “Methyl Methacrylate”. In Chemical Economics Handbook
(CEH). SRI Consulting, a Division of Access Intelligence, Menlo Park,
CA, August 2003. (Internet: http://ceh.sric.sri.com/).
17. E. Linak and A. Kishi. Report “Acrylic Surface Coatings”. In Chemical
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Menlo Park, CA, April 2004. (Internet: http://ceh.sric.sri.com/).
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vision of Access Intelligence, Menlo Park, CA, April 2001. (Internet:
http://ceh.sric.sri.com/).
19. Underwriter Laboratories. UL 94: Tests for Flammability of Plastic Materials
for Parts in Devices and Appliances. Underwriters Laboratories, Inc.,
333 Pfingsten Road, Northbrook, IL, 1.6th edition, 2000.
20. C. D. Diakoumakos, Q. Xu, F. N. Jones, J. Baghdachi, and L. M. Wu. Synthesis
of acrylic resins for high-solids coatings by solution and separation
polymerization. J. Coat. Technol., 72(908):61–70, September 2000.
21. F. Masson, C. Decker, S. Andre, and X. Andrieu. UV-curable formulations
for UV-transparent optical fiber coatings I. acrylic resins. Prog. Org. Coat.,
49(1):1–12, January 2004.
22. S.-I. Nonaka, R. B. Frings, C. Jaroszewski, and G. F. Grahe. Initiator composition
for polymerizing unsaturated monomers. US Patent 6 087 458, assigned
to Dainippon Ink and Chemicals, Inc. (Tokyo, JP), July 11 2000.
23. K. Kawakami, Y. Ishibashi, and T. Suzuki. Acrylic resin composition. US
Patent 5 574 101, assigned to Asahi Kasei Kogyo Kabushiki Kaisha (Osaka,
JP), November 12 1996.
24. Y. Ikegami, S. Koyanagi, Y. Kishimoto, and Y. Nakahara. Acrylic resin composition,
acrylic premix, process for producing acrylic artificial marble and
thickening agent. US Patent 6 323 259, assigned to Mitsubishi Rayon Co.,
Ltd. (Tokyo, JP), November 27 2001.
25. K. Umeda and K. Matsunaga. Semiconductor device including acrylic resin
layer. US Patent 6 730 948, assigned to Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP), May 4 2004.
26. T. Behzad and M. Sain. Cure study of an acrylic resin to develop natural fiber
composites. J. Appl. Polym. Sci., 92(2):757–762, April 2004.
27. T. Sato, K. Hata, and T. Maruo. Polymer battery and method of manufacture.
US Patent 6 696 204, assigned to Nisshinbo Industries, Inc. (Tokyo, JP),
February 24 2004.
28. H. S. Park, I. M. Yang, J. P. Wu, M. S. Kim, H. S. Hahm, S. K. Kim, and
H. W. Rhee. Synthesis of silicone-acrylic resins and their applications to
superweatherable coatings. J. Appl. Polym. Sci., 81(7):1614–1623, August
2001.
29. H. S. Park, S. R. Kim, H. J. Park, Y. C. Kwak, H. S. Hahm, and S. K. Kim.
Preparation and characterization of weather resistant silicone/acrylic resin
coatings. J. Coat. Technol., 75(936):55–64, January 2003.
30. P. Spathis, E. Karagiannidou, and A. E. Magoula. Influence of titanium dioxide
pigments on the photodegradation of paraloid acrylic resin. Stud. Conserv.,
48(1):57–64, 2003.
31. M. J. Melo, S. Bracci, M. Camaiti, O. Chiantore, and F. Piacenti. Photodegradation
of acrylic resins used in the conservation of stone. Polym. Degrad.
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32. E. Benedetti, A. D’ Alessio, M. F. Zini, E. Bramanti, N. Tirelli, P. Vergamini,
and G. Moggi. Characterization of acrylic resins and fluoroelastomer blends
as potential materials in stone protection. Polym. Int., 49(8):888–892, August
2000.
33. R. Bellucci, P. Cremonesi, and G. Pignagnoli. A preliminary note on the use
of enzymes in conservation: The removal of aged acrylic resin coatings with
lipase. Stud. Conserv., 44(4):278–281, 1999.
34. Y. C. Leong, L. M. S. Lee, and S. N. Gan. The viscoelastic properties of
natural rubber pressure-sensitive adhesive using acrylic resin as a tackifier. J.
Appl. Polym. Sci., 88(8):2118–2123, May 2003.
35. M. Rafiee-Tehrani, N. Safaii-Nikui, H. Peteriet, and T. Beckert. Acrylic resins
as rate-controlling membranes in novel formulation of a nine-day 17 β-
estradiol transdermal delivery system: In vitro and release modifier effect
evaluation. Drug Dev. Ind. Pharm., 27(5):431–437, 2001.
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acrylic resins for the selective hydrogenation of nitrate. Inorg. Chim. Acta,
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40. M. Sato and M. Yamagishi. Hydrophilic acrylic copolymers, hydrophilic
acrylic resin particles and ink-jet recording media. US Patent 6 063 488, assigned
to Soken Chemical & Engineering Co., Ltd. (JP), May 16 2000.

10
Cyanate Ester Resins
Cyanate ester resins are a comparatively new generation of thermosetting
resins. They are characterized by the cyanate group as a reactive group.
Most materials of this class are aromatic. Cyanate esters exhibit attractive
physical, electrical, thermal, and processing properties. Blends with epoxy
and bismaleimide are common. Major applications are in microelectronics,
aerospace, and related areas. 1–3
10.1 HISTORY
Cyanate chemistry was discovered in 1964. Cyanate ester resins have been
commercialized since the late 1970s.
10.2 MONOMERS
Cyanate esters bear basically two cyanate groups (-OCN) attached to an
aromatic ring. Also aryl cyanate esters with additional allyl groups are
known, e.g., 1-allyl-2-cyanatobenzene. Allyl-modified types act as reactive
diluents in combination with bismaleimide resins.
10.2.1 Specialities
Modifications in the thermal and mechanical properties are achieved by
blending cyanate esters with epoxies. This is used in particular for adjust-
373

374 Reactive Polymers Fundamentals and Applications
ing the tack, drape flow, and other rheological properties. Functionalized
thermoplastic oligomers can be also used for modification.
10.2.1.1 Monofunctional Cyanates
Monofunctional cyanates such as dinonylphenol cyanate can be used to
modify a fluorinated bisphenol A dicyanate monomer. The monofunctional
cyanate reduces the crosslink density in the cured network. Long network
chains between the branching points can be prepared by polymeric endcapped
dicyanates.
10.2.1.2 Alkenyl-modified Resins
Cyanate ester monomers, functionalized with alkenyl groups, raise the
glass transition temperature when used in conjunction with bismaleimide
resins. 4 Alkenyl groups are addressed as reactive modifiers because they
have the ability to react with both homopolymers (cyanate ester and bismaleimide)
to form networks.
10.2.1.3 Low-dielectric Cyanates
Fluoroaliphatic Cyanates. Fluoroaliphatic cyanates can be prepared from
a fluoro methylol precursor, such as HOCH 2 (CF 2 ) 6 CH 2 OH, and cyanogen
bromide. A solution of cyanogen bromide is reacted with a fluoromethylol
precursor with triethylamine as catalyst at −20°C. The product is recovered
by dilution with a water-immiscible organic solvent, extraction with water,
separation, drying, and concentration of the organic phase. 5
Resins from such materials have a very low permittivity to electric
fields, as needed for improving the performance in microelectronics. The
length of the fluoromethylene chain correlates with decreasing dielectric
constant, decreasing moisture absorption, and increasing thermal stability.
In general, fluoroaliphatic cyanate resins have dielectric constants in the
range of 2.3 to 2.6, tanδ loss lower than 0.02, and a low moisture absorption.
o-Methylated Cyanates. The ortho-methylation of a bis(4-cyanatocumyl)-
benzene cyanate ester showed a further decrease of the dielectric constant.
However, other physical properties are also affected. The glass transition

Cyanate Ester Resins 375
OH + Cl C N
- HCl
O C N
H 2 O
O
O C NH 2
Figure 10.1: Formation of Cyanates, Hydrolysis with Water to a Carbamide (not
desired)
temperature decreases by 40°C and the coefficient of thermal expansion
increases; thermal stability is reduced. 6
10.2.2 Synthesis
Cyanates are formed by the reaction of phenols with cyanogen halides. The
reaction is shown in Figure 10.1. A tertiary amine is catalytically active.
The reaction is sensitive to traces of water. Water hydrolyzes aryl cyanates
into carbamates. On the other hand, if the condensation is conducted at
temperatures near 0°C, the water seems not to affect the reaction. 7 Low
boiling esters can be purified by distillation. The impurities can be reduced
by proper selection of the solvent used in crystallization and washing steps
after the synthesis of the cyanate ester. Polymeric cyanate esters can be
purified by repeated precipitation processes.
The synthesis of various bisphenol dicyanate monomers has been reported.
Several cyanate esters are commercially available. Monomers for
cyanate ester resins are listed in Table 10.1 and shown in Figure 10.2. Most
of the monomers are based on bisphenols. Other cyanates are obtained by

376 Reactive Polymers Fundamentals and Applications
NCO
CH 3
C
OCN
CH 3
2,2-Bis(4-cyanatophenyl)propane
CH 3
NCO
C
OCN
H
1,1-Bis(4-cyanatophenyl)ethane
H 3 C
CH 3
H
NCO
C
OCN
H
H 3 C
CH 3
Bis(3,5-dimethyl-4-cyanatophenyl)methane
NCO
S
OCN
Bis(4-cyanatophenyl)thioether
NCO
CH 3
C
NCO
C CH CH 3
CH 3
CH 3
3
C
CH 3
1,3-Bis(4-cyanatophenyl-1-(methylethylidene))benzene
Figure 10.2: Bisphenol-based Cyanate Esters

Compound
Table 10.1: Monomers
Cyanate Ester Resins 377
Remark/Reference
2,2-Bis(4-cyanatophenyl)propane AroCy B-10
1,1-Bis(4-cyanatophenyl)ethane AroCy L-10
Bis(4-cyanatophenyl)methane
Bis(3,5-dimethyl-4-cyanatophenyl)methane
1,3-Bis(4-cyanatophenyl-1-(methylethylidene))benzene
Bis(4-cyanatophenyl)thioether
7
Bis(4-cyanatophenyl)ether
1,3-Bis(4-cyanatophenyl-1-(1-methylethylidene))benzene XU 366
1,1-Dibromo-2,2-bis(4-cyanatophenyl)ethylene
8 a
1,1-Dichloro-2,2-bis(4-cyanatophenyl)ethylene
8 a
2,2-Bis(4-Cyanatophenyl)1,1,1,3,3,3-hexafluoropropane
4,4-Dicyanatobiphenyl
Resorcinol dicyanate
2,7-dihydroxynaphthalene dicyanate
9
1,1-bis(3-methyl-4-cyanatophenyl)cyclohexane
10
a Flame Retardant
reactions of novolak and cyan halides. 11 The carbon atom in the cyanato
group is highly electrophilic. It is therefore prone to a nucleophilic reagent
attack.
10.3 SPECIAL ADDITIVES
10.3.1 Fillers
10.3.1.1 Silica
In semiconductor encapsulation, a large amount of inorganic filler, typically
65% is used. As is the case of epoxy based encapsulants, and also in
cyanate ester composites, a silica filler increases the conductivity, Young’s
modulus, and dielectric constant. The filler decreases the thermal expansion.
A high degree of interfacial adhesion between the untreated silica
filler and the cyanate ester matrix is obtained. 12
10.3.1.2 Silicate Nanocomposites
Nanocomposites improve the properties of cyanate resins. 13 The addition
of silicate nanocomposites increases the onset of the thermal decompo-

378 Reactive Polymers Fundamentals and Applications
sition. The glass transition temperature T g increases from 354°C for the
neat resin, to 387°C for a 2.5% loading with nanocomposites. The fracture
toughness and the flexural modulus increase by 30% with a loading of 5%.
10.3.2 Flame Retardants
In general, cyanate ester resins exhibit a better flame retardancy than epoxy
resins. In electronic applications, laminates are generally required to
possess a wide range of favorable properties, including high mechanical
strength, good thermal stability, good chemical resistance, low heat distortion,
a high resistance to aging, good electric insulation properties, consistent
dimensional stability over a wide temperature range, good adhesion to
glass and copper, a high surface resistivity, a low dielectric constant and
loss factor, ease of drillability, low water absorption, and a high corrosion
resistance. Additionally or even equally important is the limited flammability.
Epoxy resins alone or in combinations with cyanate esters or other
additives, which are widely used in the electronic industry for printed circuit
board (PCB) laminate applications, meet these requirements only because
they contain approximately 30 to 40% brominated aromatic epoxy
components. This is 17% to 32% as elemental bromine.
Antimony and halogen compounds have been added to resins in order
to impart flame retardancy. The problem with these brominated compounds
is that, although they have excellent flame-retardant properties,
they also have some undesirable properties. The chemical decomposition
of aromatic bromine compounds releases free bromine radicals and hydrogen
bromide, which are highly corrosive. Additionally, when highly
brominated aromatics decompose in the presence of oxygen, they may
form the highly toxic brominated dibenzofurans as some past studies have
shown. Consequently, interest in displacing the use of brominated aromatic
epoxies emerged.
Fillers with an extinguishing flame effect, such as antimony trioxide,
aluminum oxide hydrates, aluminum carbonates, magnesium hydroxides,
borates, and phosphates, have been proposed for the replacement of brominated
aromatics. However, all these fillers have the disadvantage that they
often seriously impair the mechanical, chemical, and electrical properties
of the laminates. In the case of antimony trioxide, it is listed as a carcinogen.

Cyanate Ester Resins 379
The flame-retardant effect of red phosphorus has also been investigated
in some cases combined with finely divided silicon dioxide or aluminum
oxide hydrate. Such compositions when used in electronic applications
may lead to corrosion due to the formation of phosphoric acid in the
presence of moisture.
In addition, organic phosphorus compounds, such as phosphoric acid
esters, phosphonic acid esters and phosphines, were proposed as flame-retardant
additives. These alternatives have not been promising due to plasticization
effects that they impart to the base resin. Other useful phosphorus-containing
compounds include propanephosphonic anhydride, and
ethylmethylphosphinic anhydride. 14 These flame retardants are allowed
to react with the epoxide component. Monomers with the phenylphosphine
oxide structure exhibit good thermooxidative properties and increased
yields of char when heated.
10.4 CURING
Essentially no volatile by-products are formed in the course of curing.
Many cyanate esters do not shrink during cure.
10.4.1 Thermal Curing
Cyanate ester resins are polymerized by a cyclotrimerization of the cyanato
functions. The cyclotrimerization produces aryloxytriazine rings which
serve as the crosslink sites in the final thermoset matrix. The cyclotrimerization
is shown in Figure 10.3. Very high temperatures, beyond 300°C, are
usually required for the crosslinking by cyclotrimerisation of cyanate ester
groups in uncatalyzed systems. 15 However, suitable catalysts are available
and usually catalysts are added. Then, the triazine rings are formed around
180°C. 16 In fact, the mechanism of cyclotrimerization is much more complicated.
17 Analysis of the initial products of curing by gel permeation
chromatography indicates that the dimer is a straight chain with a primary
amino group. The triazine ring in the trimers seems to exert a strong catalytic
effect on the remaining cyanate groups so that the reactivity from the
stage of trimers is significantly increased. The reactivities of the higher
intermediates decrease up to the heptamer. The monomer consumption in
the initial stage of curing follows a second-order rate kinetics. 18 In the
case of a novolak-type cyanate ester monomer, an autocatalytic behavior

380 Reactive Polymers Fundamentals and Applications
O
C
N
N
C
O
C
N
O
O
N
O
N
N
O
Figure 10.3: Cyclotrimerization of Cyanate Esters

Compound
Table 10.2: Curing Agents
Cyanate Ester Resins 381
Reference
Zinc octoate
Bis(1-methyl-imidazole)zinc(II)dicyanate
19
Bis(1-methyl-imidazole)zinc(II)dioctoate
Bis(1-methyl-imidazole)zinc(II)diacetyl-acetonate
Aluminium(III)acetylacetonate and dodecylphenol
20
Cobalt(II)acetylacetonate and nonylphenol
21
Dibutyltin dilaurate
22
2,2 ′ -Diallyl bisphenol A (DBA)
15
was observed. 23 The same is true for epoxy blends. 24
Various techniques for monitoring the curing of a bisphenol A dicyanate
ester resin have been screened, including UV, fluorescence, phosphorescence,
and IR techniques. During curing, a very strong luminescence
emission has been found.
The fluorescence emission intensity around 420 nm first increases
followed by a decrease with a small red shift as the cure reaction proceeds.
The aromatically substituted cyanurates formed during curing exhibit an
inner filter effect and are thus responsible for the observed emission and its
trend in intensity. 25
As catalysts, Lewis acids and carboxylic salts of transition metal are
suitable. For example, zinc naphthenate and nonylphenol cure the ester at
149°C. Further catalysts are given in Table 10.2. Besides trimerization, the
formation of dimers and higher oligomers was observed in small amounts.
Aryl cyanates are converted cleanly at 25°C to 1,3,5-triazines by
catalytic amounts of titanium tetrachloride in dichloromethane. A mechanism
has been proposed involving a rate-limiting nucleophilic attack of the
cyanate nitrogen on the cyanato carbon of a cyanate-titanium tetrachloride
complex. The subsequent steps are fast. 26
10.4.2 Curing with Epoxy Groups
Curing by the reaction with epoxy groups is also possible. The reaction is
shown in Figure 10.4. The reaction is proposed to run via an intermediate
trimer of the cyanate ester. The epoxy component acts as a toughener for
cyanate ester resins.
The chemical structure of the cyanate monomer can affect the cur-

382 Reactive Polymers Fundamentals and Applications
O C N
CH 2
+
O
CH
O
C
N
O
Figure 10.4: Reaction of Cyanate Esters with an Epoxide to Produce an Oxazoline
Structure
ing reactions and thermal properties of the final product. In a comparative
study, 2,2 ′ -bis(4-cyanatophenyl)propane was blended and cured with epoxy
based bisphenol or tetramethyl bisphenol.
The oxazolidinone ring structure is dominant when curing the bisphenol
epoxy system, whereas a cyanurate ring is predominant in the curing
reaction of a tetramethyl bisphenol epoxy system. This is attributed to
the bulky methyl groups. The crosslinked cyanurate structure has a higher
thermal stability than the linear oxazolidinone structure. 27
In epoxy/dicyanate blends containing an amine curing agent, the
cure rate increases with increasing dicyanate content. The reaction mechanism
is autocatalytic and is second-order. 24
10.4.3 Curing with Unsaturated Compounds
Figure 10.5 shows the reaction of cyanate esters with unsaturated compounds,
exemplified with a maleimide and an acetylenic compound. Phenolic
hydroxy groups have a catalytic effect on the cyclotrimerisation of
cyanate esters. 2,2 ′ -Diallyl bisphenol A (DBA), with two phenolic hydroxy
groups, has been used as a catalyst for the crosslinking of a cyanate
ester (CE). The double bonds on DBA can readily copolymerize with bismaleimide
to form an interpenetrating polymer network (IPN). 15 This type
of resin system is addressed as self-catalytic. The crosslinks are formed by
different reactions. By such a combination, cyanate esters can be cured
at a lower temperature while largely maintaining their superior dielectric
properties.

Cyanate Ester Resins 383
O
R
N
O
O
N
N
O
O
R
N
O
O C N N C O
R
C
C
R
O
N
O
N
R
R
Figure 10.5: Reaction of Cyanate Esters with Unsaturated Compounds

384 Reactive Polymers Fundamentals and Applications
However, these resins exhibit somewhat lower mechanical properties.
The flexural strength, flexural strain at break, and impact strength of
the BMI/DBA-CE IPN cured resin systems are relatively lower than that
calculated by the rule of mixtures, i.e., BMI/DBA and CE. 28
10.4.4 Initiator Systems
10.4.4.1 Encapsulated Initiators
To combine properties such as long pot life, short cure time, and high glass
transition temperature, small particles of effective hardeners were encapsulated
to make them insoluble and nonreactive when mixed with the resin
at room temperature. By this technique, pot lifes of more than 3 months
could be reached, whereas the same cyanate ester gels and becomes solid
within 30 min at the room temperature, if a neat hardener is used instead
of the capsules.
However, on heating, the capsules open and the curing reaction starts
immediately. Low-temperature systems with cure times less than 5 min
at 80°C can reach glass temperatures of about 140°C. A glass transition
temperature of 220°C after only 10 sec curing time can be achieved with
certain formulations. Such systems are also addressed as snap cure resin
systems. They can be easily mixed with a lot of common additives such as
minerals, tougheners, metallic powders, and others to cover a wide range
of performance characteristics. 29
10.4.4.2 Photoinitiators
Cyanate esters can be rendered photosensitive by mixing with a cationic
photoinitiator. Photosensitive compositions containing cyanate esters can
be used as permanently retained etch masks, solder masks, plating masks,
dielectric films, and protective coatings. The cured products can withstand
temperatures up to 360°C. The materials, depending upon the type of photoinitiator
selected, can be used as both positive and negative resists.
Suitable photoinitiators are arylacyldialkyl and hydroxyaryldialkyl
sulfonium salts. When a negative working photoresist is desired, the photoinitiator
employed is one which will generate a Lewis acid upon exposure
to actinic light. Examples of such photoinitiators are iron arenes. Furthermore,
photosensitizers can be added. Suitable photosensitizers include perylene(peri-dinaphthalene),
anthracene derivatives (e.g., 9-methylanthrac-

Cyanate Ester Resins 385
ene), dyes (e.g., acridine orange, acridine yellow, benzoflavin), and titanium
dioxide. 30 Modified resins, containing epoxy acrylate, a cyanate ester
compound, and an anhydride are used. 11
10.5 PROPERTIES
Cyanate monomers have a low toxicity with an LD 50 of 3 g/kg. 31 Cyanate
ester resins are superior to epoxy resins, phenolic resins, and bismaleimide
resins. They combine the advantages of epoxies, the fire resistance
of phenolics, and the high-temperature performance of polyimides. The
crosslinked networks of cyanacrylate resins can exhibit a T g higher than
300°C. They are thermally stable up to 475°C.
A systematic study on the effect of silica fillers in an AroCy B cyanate
ester polymer in the range from 15% to 70% on the thermal, mechanical,
and conductivity properties has been presented. 12
10.5.1 Modelling
The prediction of the physical and mechanical properties of new potential
poly(cyanurate)s prior to synthesis is an important issue for future technological
application. Several important properties have been predicted by
molecular dynamics programs. For example, the glass transition temperature
(T g ) can be simulated by monitoring changes in cell volume while
keeping the number of the atoms, the pressure, and the total energy constant.
31 Also, the curing behavior under process conditions has been modelled.
32
10.6 APPLICATIONS AND USES
10.6.1 Composites
Dicyanates of bisphenol derivatives are currently used in composites with
established reinforcements such as carbon fiber, glass fiber, silica cloth,
and pitch-based graphite fibers.
10.6.2 Electronic Industry
Cyanate ester laminates are primarily used in the electronic industry for
printed circuit boards. These laminates show a low dielectric constant, loss
factor, and superior peel strength with respect to copper.

386 Reactive Polymers Fundamentals and Applications
10.6.3 Spacecraft
High-temperature composite solar array substrate panels for spacecraft applications
to orbit the planet Mercury are made from pitch-fiber composite
material containing cyanate ester resins. The thermal, mass and stiffness
requirements suggested the panels should be fabricated from a high conductivity
and stiffness pitch-fiber composite material capable of withstanding
short-term temperatures as high as 270°C. 33
10.7 SPECIAL FORMULATIONS
10.7.1 PT Resins
To obviate certain disadvantages attendant to phenolic resins, a modified
multifunctional phenolic cyanate/phenolic triazine copolymer (PT) has
been developed. This resin type has greater oxidative, mechanical, and
thermal stability than conventional phenolic resins. Further, it did not produce
volatile by-products during crosslinking. In addition, the PT resins
possess better elongation properties and higher glass transition temperatures
than the conventional phenolic resins. 34
10.7.2 Blends with Epoxies
Blending of cyanate esters with epoxy resins is one of the most important
modifications. Most commercial cyanate ester prepregs are, in fact, made
from cyanate ester/epoxy blends. During curing, a complicated reaction
occurs in the blends. The cyanate resin can act here as a latent catalyst
for the epoxy resin. 35 In blends, the following mechanisms of curing have
been postulated:
1. Polycyclotrimerization,
2. Formation of oxazoline,
3. Insertion of epoxy groups into cyanurate,
4. Formation of tetrahydrooxazolooxazole, and
5. Ring cleavage and reformation of oxazoline.
In dicyanate-novolak epoxy resin blends, most of the oxazolidinone
is formed by isomerization of oxazoline rather than by insertion of epoxy
into isocyanurate. 36 The moisture uptake of certain dicyanate-epoxy novolak
blends is substantially lower than that of the homopolycyanate. 37

Cyanate Ester Resins 387
Formulations made from bisphenol A cyanate ester and diglycidyl ether of
bisphenol A epoxy resin, or o-cresol formaldehyde novolak epoxy resin,
have enhanced processing characteristics. 38
Resins of high crosslink density and high glass transition temperature
appeared to exhibit a larger reduction in glass transition temperature
upon plasticization by moisture compared to those with lower crosslink
density. 39
Epoxy backbones with hard-soft segments were tailored to improve
the toughness. Epoxide and cyanate ester resins with isophthalic
and terephthalic groups in the backbone, i.e., 1,3-[di(4-glycidyloxy diphenyl-2,2
′ -propane)]isophthalate (DGDPI) and 1,4-[di(4-cyanato diphenyl-2,2
′ -propane)]terephthalate (DCDPT) exhibit higher T g compared to a
standard epoxy system. The increase in the T g is attributed to the cyanate
ester and rigid aromatic backbones present.
40, 41
10.7.3 Bismaleimide Triazine Resins
Bismaleimide triazine resins (BT) are used for high density circuit boards
because of their good thermal stability. Bismaleimide triazine resins consist
of bismaleimide, a cyanate ester, and epoxy compounds. 42 A BT resin
can be cured with peroxide initiators, such as dicumyl peroxide or dibenzoyl
peroxide, or metal salt catalysts.
Cuprous oxide at a prepreg surface layer attracts more cyanate ester
resins but less bismaleimide resin from the prepreg to its surface than the
cupric oxide. A copper surface affects the curing extent of the BT resin in
contact and the cupric oxide has a more pronounced effect than the cuprous
oxide. This surface effect can extend at least two microns deep into the BT
prepreg from the contacted interface. 43 The thermal degradation of BT
resins results mainly from the epoxy constituent. However, in the presence
of copper oxides, the degradation in the BT occurs not only in the epoxy
resin but also in the cyanate ester component.
The incorporation of cyanate ester into an epoxy resin improves the
flexural and impact strength. The incorporation of bismaleimide (BMI)
increases the stress strain properties with a reduction in impact strength.
The moisture resistance increases with both increasing cyanate ester and
BMI content.
44, 45
However, glass transition temperature and heat deflection temperature
decrease with increasing cyanate ester content. The incorporation of

388 Reactive Polymers Fundamentals and Applications
bismaleimide into an epoxy resin enhances the thermal properties according
to its percentage of content. 46
The addition of bismaleimide to a cyanate ester results in an increase
in fracture toughness. Dynamic mechanical analysis suggests two glass
transition temperatures. This indicates that the material has a two-phase
morphology and can be addressed as an interpenetrating network. 47
For interpenetrating polymer networks based on BMI resin and cyanate
ester resins, a BMI resin modified with 2,2 ′ -diallyl bisphenol A was
utilized. Thermal curing with a cyanate ester resin results in an interpenetrating
network.
The flexural strength, flexural strain at break, and impact strength
of such a cured resin is lower than that calculated by a linear contribution.
Single damping peaks are detected for the cured resin systems, which
suggests a substantial degree of interpenetration between two networks. 28
At the gel point, the storage modulus G ′ and loss modulus G ′′ of the IPN
follow a power law with the oscillation frequency. 48 BMI/ DBA-CE IPN
resin systems combine a low dielectric constant and loss, high-temperature
resistance, and good processability. 49
2,2-bis(4-cyanatophenyl)propane, and a 2,2-bis[4-(4-maleimido
phenoxy)phenyl]propane, have a similar backbone structure. The monomer
blend shows a eutectic point at equimolar composition with a melting
point of 15°C. When cured together in a bismaleimide-triazine network,
polymers of varying compositions can be obtained. The simultaneous curing
of the blend can be transformed to a sequential curing by catalyzing
the dicyanate curing process using dibutyltin dilaurate. The cured blends
undergo a two-stage decomposition, corresponding to the poly(cyanurate)
and poly(bismaleimide). 50
10.7.4 Siloxane Crosslinked Resins
Cyanate ester monomers linked to dimethylsiloxane are cured in the same
way as cyanate esters by a cyclotrimerization of the cyanate group to a
cyanurate structure.
The cured resins are homogeneous rubbery castings with T g ranging
from 15 to −43°C. The dielectric constants show a strong dependence on
frequency. The tanδ increases with the chain length of the siloxane but
exhibits only a small frequency dependence. 51

Cyanate Ester Resins 389
Table 10.3: Thermoplastic Modifiers for Cyanate Ester Resins
Thermoplastic Modifier
Reference
Poly(ether imide)
52
Maleimide-styrene terpolymers
53
Polyarylates
54
Polysulfones
55
Polyoxypropylene glycol
56
10.7.5 Alloys with Thermoplastics
Cyanate esters can be alloyed with thermoplastics. This improves the fracture
toughness and the moisture resistance. Thermoplastic modifiers are
summarized in Table 10.3
10.7.5.1 Poly(ether imide)
Bisphenol A dicyanate blends with a poly(ether imide) exhibit a phase separation
during curing. The poly(ether imide) phase separates at the early
stages of curing, before gelation, but this phase separation does not affect
the kinetics of the cyclotrimerization. 57
The phase structure changes from a separated phase, via a co-continuous
phase, to phase inversion with the increase of the content of poly(ether
imide). The co-continuous phase morphology is attributed to a spinodal
decomposition. The admixture of poly(ether imide) increases the tensile
strength and elongation at break. Time resolved light scattering indicates
that the evolution of the phase separation is governed by a viscoelastic relaxation
process.
52, 58
10.7.5.2 Maleimide-Styrene Terpolymers
A terpolymer composed of N-Phenylmaleimide, N-(p-hydroxy)phenylmaleimide
and styrene has pendent reactive p-hydroxyphenyl groups. This
polymer was used to improve the toughness of cyanate ester resins. Copolymers
composed of N-phenylmaleimide and styrene are also effective.
An increase in the fracture toughness up to 135% could be achieved, with
a slight loss of flexural strength but retention of flexural modulus and glass
transition temperature. 53

390 Reactive Polymers Fundamentals and Applications
The styrene-hydroxyphenyl maleimide copolymer does not impair
the mechanical properties of cyanate ester resins, in contrast to other modifiers.
22
10.7.5.3 Polyarylates
Polyarylates prepared from bisphenol A and phthaloyl chloride and the
diacid dichlorides are soluble in a cyanate ester resin and can be used to
improve the brittleness of the resin.
The polyarylates include poly(2,2-di(4-phenylene)propane phthalate)
(PPA), poly(2,2-di(4-phenylene)propane phthalate-co-2,2-di(4-phenylene)propane
isophthalate) (IPPA), and poly(2,2-di(4-phenylene)propane
phthalate-co-2,2-di(4-phenylene)propane terephthalate) (TPPA). The most
effective modification of the cyanate ester resin can be attained under the
condition of a co-continuous phase structure of the modified resin.
54, 59
10.7.5.4 Polysulfones
The miscibility of bisphenol A dicyanate and polysulfone decreases with
an increase in molecular weight of the polysulfone. Concomitantly, the
viscosity of the blend increases. During curing, the phase separation mechanism
depends on the viscosity of the blends. At the onset point of phase
separation, the viscosity determines the morphology of the blends.
Increasing viscosity suppresses the nucleation and growth. Therefore,
the viscosity of the blends at the onset point of phase separation is the
critical parameter that determines the morphology of the blends. 55
10.7.5.5 Reactive Blending
Inhomogeneous modified poly(cyanurate)s have been created by reactive
blending of a bisphenol A dicyanate ester and polyoxypropylene glycol
(PPG). A finely divided morphology with highly interpenetrated phases,
i.e., a poly(cyanurate) rich phase, a mixed phase, and a polyoxypropylene
glycol rich phase is formed.
The glass transition temperature of the modified network matrix at
increasing PPG content is lowered. This is attributed due to the incorporation
of PPG in the network, the decrease of the final conversion of the
cyanate, and the increase of the free polyoxypropylene glycol which acts
as plasticizer. 56

Cyanate Ester Resins 391
10.7.6 Coupling Agents for Cyanate Ester Resins
Cyanate ester resins have utility in a variety of composite, adhesive, and
coating applications, where adhesion between the cyanate ester resin and a
surface is of critical importance. A coupling agent to enhance the adhesion
is 3-glycidoxypropyltrimethoxysilane.
3-(2-cyanatophenyl)propyltrimethoxysilane or 3-(4-cyanatophenyl)-
propyltrimethoxysilane can be synthesized from 2-allylphenol or 4-allylphenol,
respectively and trimethoxysilane. A Karstedt catalyst is used for
the hydrosylilation. 60
The cyanate ester formulations including the coupling agent can be
coated or mixed with a substrate to provide coated composites or filled
molded articles.
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50. C. P. Reghunadhan Nair and T. Francis. Blends of bisphenol A-based cyanate
ester and bismaleimide: Cure and thermal characteristics. J. Appl. Polym.
Sci., 74(14):3365–3375, December 1999.
51. E. M. Maya, A. W. Snow, and L. J. Buckley. Oligodimethylsiloxane linked
cyanate ester resins. Macromolecules, 35(2):460–466, January 2002.
52. Q. S. Tao, M. H. Wang, W. J. Gan, Y. F. Yu, X. L. Tang, S. J. Li, and J. H.
Zhuang. Studies on the phase separation of poly(ether imide)-modified cyanate
ester resin. J. Macromol. Sci.-Pure Appl. Chem., A40(11):1199–1211,
2003.
53. T. Iijima, T. Maeda, and M. Tomoi. Toughening of cyanate ester resin
by N-phenylmaleimide-N-(p-hydroxy)phenylmaleimide-styrene terpolymers
and their hybrid modifiers. Polym. Int., 50(3):290–302, March 2001.
54. T. Iijima, T. Kunimi, T. Oyama, and M. Tomoi. Modification of cyanate ester
resin by soluble polyarylates. Polym. Int., 52(5):773–782, May 2003.
55. J. W. Hwang, K. Cho, T. H. Yoon, and C. E. Park. Effects of molecular weight
of polysulfone on phase separation behavior for cyanate ester/polysulfone
blends. J. Appl. Polym. Sci., 77(4):921–927, July 2000.
56. A. Fainleib, O. Grigoryeva, and D. Hourston. Synthesis of inhomogeneous
modified polycyanurates by reactive blending of bisphenol A dicyanate ester
and polyoxypropylene glycol. Macromol. Symp., 164:429–442, February
2001.
57. I. Harismendy, M. Del Rio, A. Eceiza, J. Gavalda, C. M. Gomez, and I. Mondragon.
Morphology and thermal behavior of dicyanate ester-polyetherimide
semi-ipns cured at different conditions. J. Appl. Polym. Sci., 76(7):
1037–1047, May 2000.
58. Q. Tao, W. Gan, Y. Yu, M. Wang, X. Tang, and S. Li. Viscoelastic effects on
the phase separation in thermoplastics modified cyanate ester resin. Polymer,
45(10):3505–3510, May 2004.
59. T. Iijima, T. Kaise, and M. Tomoi. Modification of cyanate ester resin by
soluble polyimides. J. Appl. Polym. Sci., 88(1):1–11, April 2003.
60. J. B. Hall, F. B. McCormick, K. M. Vogel, and H. Yamaguchi. Aromatic
cyanate ester silane coupling agents. US Patent 6 217 943, assigned to 3M
Innovative Properties Company (Saint Paul, MN), April 17 2001.

11
Bismaleimide Resins
Bismaleimide resin systems are noted for their high-strength, high-temperature
performance, particularly as matrix resins in fiber-reinforced prepregs
and composites. They are bridging the gap between the relatively low temperature-resistant
epoxy systems and the very high temperature-resistant
polyimides. Unfortunately, bismaleimides are somewhat brittle, and thus
subject to impact induced damage.
11.1 MONOMERS
Monomers for bismaleimide resins are summarized in Table 11.1 and are
shown in Figure 11.1.
11.1.1 4,4 ′ -Bis(maleimido)diphenylmethane
The most important monomer is 4,4 ′ -bis(maleimido)diphenylmethane
(BMI). BMI has a melting temperature of 155 to 156°C and it polymerizes
radically above the melting point. Networks resulting from BMI are very
brittle.
11.1.2 2,2 ′ -Diallyl bisphenol A
BMI can be used together with 2,2 ′ -Diallyl bisphenol A (DBA). DBA copolymerizes
with BMI. The reaction is an ene reaction that leads to a chain
397

398 Reactive Polymers Fundamentals and Applications
Compound
Table 11.1: Monomers for Bismaleimide Resins
4,4 ′ -Bis(maleimido)diphenylmethane (BMIM) a
Bisphenol A bismaleimide (BMIP) b
2,2-Bis[4-(4-maleimido phenoxy)phenyl]propane (BMIP) b
2,2 ′ -Diallyl bisphenol A (DBA)
1,3-Bis(maleimidomethyl)cyclohexane
1
Multi Ring Maleimides
2
N,N-4,4-Diphenylmethanebismaleimide
3
N,N-4,4-Diphenyl ether bismaleimide (BMIE)
3
N,N-4,4-dibenzylbismaleimide
3
Bis(4-maleimidophenyl)sulfone (BMIS)
1,6-Hexane bismaleimide
4
Divalent metal bismaleimides
5
4-(N-maleimidophenyl)glycidyl ether (MPGE)
6
4,4 ′ -Bismaleimidophenylphosphonate
7
Reference
Bismaleimide bisimides
8
Imides with pendant naphthalene
9
Ester-containing bismaleimides
10, 11
Cardo ester bismaleimides
12
Poly(aminoaspartimide)s
12
a also BMI, BMDPM and BDM, however BMI is used in general
for bismaleimides
b BMIP is not uniquely used in the literature. BMIP stands for
either Bisphenol A bismaleimide or 2,2-Bis[4-(4-maleimido
phenoxy)phenyl]propane

Bismaleimide Resins 399
O
O
N
CH 2
N
O
O
BMIM
O
O
N
O
N
O
O
BMIE
O
O
O
N
S
N
O
O
O
BMIS
O
O
CH 3
N
O
C
O
N
O
CH 3
BMIP
O
O
O
N
O
S
O
O - M2+ - O
O
S
O
Divalent metal bismaleimide
N
O
O
Figure 11.1: Bis(4-maleimidophenyl)methane (BMIM), Bis(4-maleimidophenyl)ether
(BMIE), Bis(4-maleimidophenyl)sulfone (BMIS), 2,2-Bis[4-(4-maleimido
phenoxy)phenyl]propane (BMIP), Divalent metal bismaleimide

400 Reactive Polymers Fundamentals and Applications
extension reaction. Subsequently a Diels-Alder reaction follows. Such copolymers
exhibit less brittleness, because the crosslinking density is less
than that of pure BMI resins. Mixtures of 2,2 ′ -Diallyl bisphenol A ether
and 1,4-diallyl phenyl ether also have been used. These compounds are
reactive diluents for BMI because they reduce the apparent viscosity of the
BMI. 13 N,N ′ -Diallyl p-phenyl diamine (DPD) is a reactive diluent in this
sense. Reducing the viscosity is important for the preparation of the advanced
composites by techniques such as resin transfer molding (RTM). 14
For example, instead using diallyl bisphenol A, a novolak resin can
be obtained from diallyl bisphenol A and formaldehyde using p-toluenesulfonic
acid as catalyst. The resin is then reactively blended with bisphenol
A bismaleimide (BMIP) and cured through an Alder-ene reaction
at high temperatures. The materials are useful as adhesives. 15 The lap
shear strength properties are not significantly affected by the structure of
the particular BMI used. It has been demonstrated that using 2,2 ′ -Diallyl
bisphenol A gives products with better adhesion at elevated temperature. 16
11.1.3 Poly(ethylene glycol) End-capped with Maleimide
The addition of maleimido end-capped poly(ethylene glycol) (PEG) to
a bismaleimide resin (4,4 ′ -bis(maleimido)diphenylmethane) (BDM) enhances
the processability of the BDM resin significantly. The processing
temperatures of the BDM resin increase from approximately 20 to 80°C.
However, the modified resins show a decreased thermal stability of the
blended BDM resin, and the coefficient of thermal expansion increases.
The curing behavior and the thermal and mechanical properties are independent
of the molecular weight of the PEG segment. 17
11.1.4 Bismaleimide Bisimides
The monomers for bisimide resins are prepared by reacting N,N ′ -(4-aminophenyl)-p-benzoquinone
diimine (QA) with maleic anhydride or 5-norbornene-2,3-dicarboxylic
anhydride (also called nadic anhydride) in glacial
acetic acid as shown in Figure 11.2. The cured resins exhibit a char residue
at 800°C in nitrogen atmosphere greater than 55%. Chain-extended types
with flexible ether linkages, i.e., 1,3-bis(4-maleimido phenoxy)benzene or
1,4-bis(4-maleimido phenoxy)benzene, show a lower thermal stability than
the neat resins. 8

Bismaleimide Resins 401
O
O
N
N
N
N
O
O
O
O
O
H 2 N
N N
NH 2
O
O
O
O
O
N
N
N
N
O
O
Figure 11.2: Bismaleimide Adducts of N,N ′ -(4-Aminophenyl)-p-benzoquinone
diimine with Maleic anhydride and Nadic anhydride 8

402 Reactive Polymers Fundamentals and Applications
11.1.5 Maleimide Epoxy Monomers
The use of 4-(N-maleimidophenyl)glycidyl ether (MPGE) is a convenient
approach for synthesizing BMIs with epoxy linkage backbones. 6 MPGE is
synthesized from N-(4-hydroxyphenyl)maleimide and epichlorohydrin by
using benzyltrimethylammonium chloride as a catalyst. 18
In a similar manner, maleimide-modified epoxy compounds can be
prepared from N-(4-hydroxyphenyl)maleimide (HPM) with the diglycidyl
ether of bisphenol A. 19 The reaction scheme is shown in Figure 11.3. Triphenylphosphine
and methylethylketone were utilized as catalyst and solvent,
respectively. The resulting compounds bear both the oxirane ring and
the maleimide group.
Curing can be achieved by amine curing agents, such as 4,4 ′ -diaminodiphenylmethane
(DDM) and dicyandiamide (DICY). The incorporation
of maleimide groups into epoxy resins provides a cyclic imide structure
and high crosslinking density. The cured resins show high char yields
and high LOI values up to 30.
Further, specific chemical groups can be introduced into the BMI
bridging linkages, such as silicon groups and phosphorus groups. The dimerization
is shown in Figure 11.4. The cured resin with silicone exhibits
a limiting oxygen index of greater than 50.
11.1.6 Phosphorous-containing Monomers
A phosphorus-containing bismaleimide (BMI) monomer, bis(3-maleimidophenyl)phenylphosphine
oxide (BMIPO), can be accessed by the
imidization of bis(3-aminophenyl)phenylphosphine oxide. This bismaleimide
exhibits a good solubility in common organic solvents and a wide
processing window. 20, 21 It is an excellent flame retardant with a high glass
transition temperature, high onset decomposition temperature, and high
limiting oxygen index. Copolymers with BMIPO, BMI, and epoxy based
4,4 ′ -methylenedianiline (DDM) are homogeneous products without phase
separation. 22
Epoxy resins can be modified by 3,3 ′ -bis(maleimidophenyl)phenylphosphine
oxide. The cured resins have good thermal properties. 23 Further,
phenyl-(4,4 ′ -bismaleimidophenyl)phosphonate and ethyl-(4,4 ′ -bismaleimidophenyl)phosphonate
were tested as flame retardants in epoxy
systems. The flame retardancy of phosphonate-containing epoxy systems
was improved significantly with BMI. 24 An increase of the BMI com-

Bismaleimide Resins 403
O
O
O + H 2 N
OH
N
OH
O
O
O
CH 2
CH
O
CH 2
CH
CH 2
CH 2
O
O
H 3 C
C CH 3
H 3 C
C CH 3
O
N
O
O
+
O
CH 2
O
CH 2
O
CH
CH 2
OH
N
O
CH OH
CH 2
O
Figure 11.3: Synthesis of Epoxy-modified Maleimide Monomers 19

404 Reactive Polymers Fundamentals and Applications
O
N
O
O CH 2 CH CH 2
O
MPGE
HO
R
OH
O
OH
N
O CH 2 CH
O
CH 2
O
R
O
O
CH 2
CH CH 2 O
N
OH
O
R= one of the following groups
CH 3
C
CH 3
O P O
Si
Figure 11.4: Dimerization of 4-(N-maleimidophenyl)glycidyl ether (MPGE) with
Functional Diols

Reaction Type
Table 11.2: Reactions of Maleimides
Bismaleimide Resins 405
Radical polymerization
Diels-Alder reaction with a pentamathylcyclopentadiene
derivative
25
Diels-Alder reaction with furans
26
Reference
pounds also increased the storage modulus and glass transition temperature
but reduced the mechanical strength of the epoxy blends.
More bulky phosphorous-containing bismaleimides have been obtained
by the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-
10-oxide (DOPO) and 4,4 ′ -bis(maleimido)diphenylmethane.
27, 28
The
glass transition temperatures of the cured resins decrease with phosphorus
content. The limiting oxygen index (LOI) is improved by the incorporation
of DOPO.
11.1.7 Multiring Monomers with Pendant Chains
The synthesis of multiring monomers with long pendant chains is shown
in Figure 11.5. The synthesis runs via a two-fold Friedel-Crafts reaction,
followed by a reduction of the dinitro compounds. The diamines are then
reacted with maleic anhydride into bismaleimides. The properties of the
crosslinked poly(benzylimide) are not strongly affected by the presence
of the long alkyl chains. Therefore, linear thermoplastic polyimides with
good thermal stability can be obtained. 2
11.1.8 Reactions of Maleimides
We summarize some of the reactions of maleimides, all of them suitable
for obtaining polymers. The reactions are given in Table 11.2.
11.1.8.1 Radical Polymerization
The double bond in the maleic group undergoes an ordinary radical polymerization.

406 Reactive Polymers Fundamentals and Applications
CH 3
+ Cl CH
H CH 2
NO 2
3 C
3
R
R=C 16 H 33 ;C 8 H 17 ;C 6 H 13
O 2 N
CH 3
H 2 C CH 2
NO 2
H 3 C
R
CH 3
H 2 N
CH 3
H 2 C CH 2
NH 2
H 3 C
R
CH 3
O
O
O
O
O
CH 3
N
H 2 C
CH 2
N
O
H 3 C
R
CH 3
O
Figure 11.5: Multiring Monomers with Flexible Side Chains 2

Bismaleimide Resins 407
11.1.8.2 Michael Addition
The Michael addition is an addition of resonance-stabilized carbanions to
activated double bonds. The Michael addition is thermodynamically controlled.
It was first described in 1887. 29
α,ω-Polyaminoglycols. Amino-terminated oligomers based on propylene
glycol, ethylene glycol, and dimethylsiloxane, have been chain-extended
via Michael additions with bismaleimides. The polymers have a degree
of polymerization up to 15. The polymers are either linear or crosslinked,
depending on the starting materials and the conditions of preparation.
30, 31
Maleimide-urethanes. The reaction of 4-maleimidophenyl isocyanate
and oligoether diols or oligoester diols results in bismaleimide-containing
urethane groups. The bismaleimides can be chain-extended by means of a
Michael reaction into linear polymers. 32 The reaction scheme is shown
in Figure 11.6. Chain extenders are 4,4 ′ -diaminodiphenylmethane and
4,4 ′ -oxydianiline. Elastic films are obtained that show good mechanical
properties and a better thermal stability than the traditional polyurethane
elastomers.
11.1.8.3 Diels-Alder Reaction
Chain Extension. Bismaleimide oligomers can be synthesized by chain
extension reaction utilizing a Diels-Alder reaction as shown in Figure 11.7.
In the first step, a bisfuranylmethylcarbamate is formed from toluene diisocyanate
(TDI), or hexamethylene diisocyanate with two mol of furfuryl
alcohol. The furan (via its double bonds) then reacts with a bismaleimide,
such as 4,4 ′ -bis(maleimido)diphenylmethane using a Diels-
Alder reaction. 33 These bismaleimide oligomers can be used as a toughness
modification agent for other BMI resins. Finally, the ether link in the
original furan moiety is eliminated by acetic anhydride, and replaced by an
aromatic group.
Furan-containing Adducts. Furan-terminated compounds react with
BMI at 70°C to an oxygen-containing cycloadduct. The simple adducts are
obtained from the monofunctional dienophiles. Crosslinked products are
obtained from the coupling of furanic polymers with the bisdienophiles. 26

408 Reactive Polymers Fundamentals and Applications
O
O
N
NCO + HO OH + OCN
N
O
O
O
O
C
O
O
O
C
O
N
NH
HN
N
O
O
H 2 N
O NH 2
4,4’-Oxydianiline
H 2 N
CH 2 NH 2
4,4’-Diaminodiphenylmethane
Figure 11.6: Dimaleimide urethanes and Michael Reaction with aromatic Diamines

Bismaleimide Resins 409
O
CH 2 OH OCN R
NCO+
HO
CH 2
O
O
O
O
CH 2
O C
HN
R
C O
NH
CH 2
O
O
N
O
O O
CH 2 O C C O
O
HN R NH
CH 2
O
O O
O O
N
N
O
O
CH 3
C
O
C
CH 3
O
O
CH 2
O
C
C
O
CH 2
O
N
O
HN
R
NH
O
N
O
Figure 11.7: Chain Extension Reaction

410 Reactive Polymers Fundamentals and Applications
On heating the polymerized materials in various solvents with high boiling
points, no soluble products were obtained. This indicates the absence of a
retro Diels-Alder reaction.
It was concluded that aromatization of the imino heterocycles arising
from the cycloaddition took place, resulting in irreversible crosslinks. For
example, 1,1 ′ -(1-methylethylidene)bis(4-(1-(2-furanylmethoxy)-2-propanolyloxy))benzene
reacts with several bismaleimides, such as N,N ′ -hexamethylenebismaleimide
and N,N ′ -p-phenylenedimaleimide. In a subsequent
polymerization in the presence of acetic anhydride the aromatization
of the tetrahydrophthalimide intermediates occurs. 34
Networks from the linear copolymer Poly(styrene-co-furfuryl methacrylate)
can be prepared by Diels-Alder reaction at 25°C by adding bismaleimide.
35 In such a crosslinked copolymer, an endothermic peak without
a glass transition is observed. On reheating the sample, a glass transition
is found. This is attributed to the formation of a linear copolymer
produced by the retro Diels-Alder reaction in the course of the first heat
treatment. 36
Bisdienes. Phenylated poly(dihydrophthalimide)s have been synthesized
from 3,3 ′ -(oxydi-p-phenylene)bis(2,4,5-triphenylcyclopentadienone),
3,3 ′ -(p-phenylene)bis(2,4,5-triphenylcyclopentadienone), N,N ′ -o-phenylenedimaleimide,
N,N ′ -m-phenylenedimaleimide, and N,N ′ -p-phenylenedimaleimide.
37 Ketonic adducts are formed as intermediates, but the carbon
monoxide evolution proceeds spontaneously. Difunctional cyclohexadienes
with dihydrophthalimide as central units can act as bisdienes in Diels-Alder
polymerization polyadditions with bis(4-(1,2,4-triazoline-3,5-dione-4-yl)phenyl)methane
as the difunctional dienophile. The introduction
of phenyl side groups increases the solubility. 38
Pyrones. Pyrones also behave as diene and react with bismaleimides,
thus forming a bis-cycloadduct. 39
Diabietylketone. Another bisdiene is the dehydrodecarboxylation product
of abietic acid, also addressed as diabietylketone. 40 The dehydrodecarboxylation
reaction is shown in Figure 11.8. A Diels-Alder polymerization
of diabietylketone with 4,4 ′ -diphenylmethanedimaleimide (bismaleimide)
is possible. The resulting polymer is expected to be a poly-
(ketoimide) with hydrophenanthrene moieties in the backbone. However,

Bismaleimide Resins 411
C
O
COOH
Figure 11.8: Dimerization of Abietic Acid by Dehydrodecarboxylation
it was found that the repeating units are bismaleimide and diabietylketone
units not in a molar ratio of 1:1, but in a ratio of 5:1 to 6:1. This
observation was explained by the difference between the rates of the two
concomitant reactions, i.e., the homopolymerization of bismaleimide and
the Diels-Alder polymerization.
On the other hand, a polymer of the two monomer units in a ratio
of 1:1 can be obtained by the dehydrodecarboxylation of the diacid resulting
from the Diels-Alder reaction between abietic acid and 4,4 ′ -diphenylmethanedimaleimide
and also by the polycondensation of the ketone of
maleated abietic acid with 4,4 ′ -diaminodiphenylmethane. The polymers
are stable in air up to 360°C.
Photochemical Generation of Dienes. Certain dienes, such as o-quinodimethanes
can be generated by photochemical reactions. 41 When the photochemical
generation occurs in the presence of bismaleimides, the dienes
may react immediately with the bismaleimide in a Diels-Alder reaction,
thus forming a polymer.
Naphthols. Several 2-naphthols undergo a Diels-Alder addition reaction
with maleimides. This reaction can be utilized in curing bismaleimides.
For example, 7-allyloxy-2-naphthol satisfactorily cures bismaleimides. 42

412 Reactive Polymers Fundamentals and Applications
Urethane-imides. Poly(ester-urethane-imides) can be prepared by the
Diels-Alder polyaddition of 1,6-hexamethylene-bis(2-furanylmethylcarbamate)
with various bismaleimides that contain ester groups in the backbone.
43
Triol Extenders. Poly(bismaleimide-ether) polymers with functional
pendant groups can be obtained from a Michael polyaddition of flexible
bismaleimides, such as N,N-4,4-diphenylmethanebismaleimide, N,N-
4,4-diphenyl ether bismaleimide and N,N-4,4-dibenzylbismaleimide to trifunctional
monomers, such as glycerol and phenolphthalein. Additionally,
the hydroxyl functional poly(bismaleimide-ether) can be modified with
cinnamoyl moieties. 3
Hyperbranched Polyamides. Monomers that contain the diphenylquinoxaline
group are 2,3-bis(4-aminophenyl)quinoxaline-6-carboxylic acid
(BAQ) and 2,3-bis(4-(4-aminophenoxy)phenyl)quinoxaline-6-carboxylic
acid (BAPQ), c.f. Figure 11.9.These compounds form hyperbranched aromatic
polyamides on polycondensation.
Although the monomers are structurally similar, the properties of
both monomers and the respective hyperbranched polymers are different.
BAQ reacts normally with BMI in a Michael addition fashion, followed by
homopolymerization of the excess BMI. However, BAPQ seems to initiate
a free radical polymerization of BMI at room temperature. This unexpected
property of BAPQ suggests it can be used as a prototype for the development
of low-temperature, thermally curable thermosetting resin systems
for high-temperature applications. 44
11.1.9 Specialities
11.1.9.1 1,3-Bis(maleimidomethyl)cyclohexane
Imides are often substantially insoluble in ordinary organic solvents and
are soluble only in high boiling aprotic polar solvents, such as N-methyl-
2-pyrrolidone, N,N-dimethylacetamide, etc. This is a drawback when impregated
varnishes are prepared by dissolving the imides in these solvents.
High temperature is required for removing the solvents and the solvents
are liable to remain in the prepregs formed from the varnishes, causing
foaming in the laminates and considerably lowering the quality of flexible
printed circuits (FPC).

Bismaleimide Resins 413
COOH
N
NH 2
N
NH 2
2,3-Bis(4-aminophenyl)quinoxaline-6-carboxylic acid
COOH
N
O
NH 2
N
O
NH 2
2,3-Bis[4-(4-aminophenoxy)phenylquinoxaline-6-carboxylic acid
Figure 11.9: Monomers for Hyperbranched Oligoamides 44

414 Reactive Polymers Fundamentals and Applications
1,3-Bis(maleimidomethyl)cyclohexane is a bismaleimide compound
that is readily soluble in a variety of ordinary low boiling point organic solvents.
1 For instance, it is soluble in acetone, methylethylketone, tetrahydrofuran,
chloroform, and N,N-dimethylformamide. Despite its aliphatic
structure, the monomer can provide good heat-resistant bismaleimide resins
by thermal polymerization.
11.1.9.2 Siliconized Bismaleimides
Siliconized epoxy-1,3-bis(maleimido)benzene has been synthesized from
siloxanes.
45, 46
In the first step, epoxy based on the diglycidyl ether of
bisphenol A, and 4,4 ′ -diaminodiphenylmethane (DDM) was extended with
(3-aminopropyl)triethoxysilane.
The pendent ethoxysilane groups were further reacted with a hydroxy-terminated
poly(dimethylsiloxane) (HTPDMS) with dibutyltin dilaurate
as catalyst. The scheme is shown in Figure 11.10. 1,3-Bis(maleimido)benzene
is prepared from m-phenylene diamine and maleic anhydride.
Finally, the 1,3-bis(maleimido)benzene is dissolved in the siliconized epoxy
system at 125°C. To this mixture, a stoichiometric amount of DDM
is added homogenized. This mixture is cured at 120°C for 1 hour and
postcured at 205°C.
The curing is a comparatively complex process. It is proposed that
the curing is due to the following reactions: 46
1. Oxirane ring opening reaction with active amine hydrogens,
2. Autocatalytic reaction of the oxirane ring with pendent hydroxyl
groups of epoxy resin,
3. Addition reaction of the amine groups of DDM with double bonds
of BMI (Michael addition), and
4. Homopolymerization reaction of BMI.
Bismaleimides with silicone linkages can also be prepared via the
Diels-Alder reaction of bismaleimide-containing silicone and bisfuran containing
silicone. The bismaleimides are soluble in low boiling point solvents,
and the cured resins are stable up to 350 to 385°C. 47
Still another reaction path to prepare bismaleimides with silicone
groups is the reaction of N-(4-hydroxyphenyl)maleimide with dichlorodimethylsilane.
In a second step, the adduct is reacted with a polysiloxane
that is terminated with hydroxyl groups. 48

Bismaleimide Resins 415
CH 2
CH CH 2 + H N H + CH 2 CH 2
O
OCH
CH 2
CH 2
CH 3 CH 2
OH
Si
CH 2
CH 2 CH 3
O Si O
CH 2 OH
+ CH 3
+
+ Si
O
OH
Si
CH 2
CH
OH
N
CH 2
CH 2
CH
OH
CH 2
CH 2
CH 2
Si
O
CH 2
O
Si
O
Si
Si
Figure 11.10: Formation of a Silane-modified Epoxy Resin

416 Reactive Polymers Fundamentals and Applications
11.1.9.3 Maleimide Phenolic Resins
Phenolic novolak resins with pendant maleimide groups are accessible by
the polymerization of a mixture of phenol and N-(4-hydroxyphenyl)maleimide
(HPM) with formaldehyde in the presence of an acid catalyst. 49
HPM is less reactive than phenol toward formaldehyde. In fact, N-phenylmaleimide
is also reactive towards phenol and formaldehyde.
Curing is done by both possible typical reaction mechanisms for
these groups. Around 150 to 170°C, there is a condensation reaction of the
methylol groups formed in minor quantities on the phenyl ring of HPM.
The curing at around 275°C is associated with the addition polymerization
reaction of the maleimide groups.
Polymerization studies of non-hydroxy-functional N-phenyl maleimides
indicate that the phenyl groups of these molecules are activated
toward an electrophilic substitution reaction by the protonated methylol
intermediates formed by the acid-catalyzed reaction of phenol and formaldehyde.
Allyl-functional Novolak. The maleimide-functional phenolic resin can
be reactively blended with an allyl-functional novolak. This system undergoes
a multistep curing process over a temperature range of 110 to 270°C.
The presence of maleimide reduces the isothermal gel time of the blend.
Increasing the allylphenol content decreases the crosslinking in the
cured matrix, leading to an enhanced toughness and to improved mechanical
properties of the resultant composites. Increasing the maleimide content
results in an enhanced thermal stability. 50
Epoxy-functional Novolak. Epoxy-novolak (EPN) resins have been
cured together with a 1,1 ′ -(methylene di-4,1-phenylene)bismaleimide. A
suitably blended EPN and BMI with 30% bismaleimide shows higher T g
than the neat resin.
With an increase of bismaleimide, the thermal stability is increased.
A single exothermic reaction is observed on curing. The morphology of
the cured samples indicates the formation of a homogeneous network in
the blends.
51, 52

Compound
Table 11.3: Modifiers
Bismaleimide Resins 417
Reference
2,2 ′ -Diallyl bisphenol A (DBA)
Reactive rubbers
Polysulfone
Polyetherimide
53
Poly(hydantoin)
4,4 ′ -Bis(o-propenylphenoxy)benzophenone
N-Phenylmaleimide-styrene copolymer
Acetylene-terminated polymers
2,4-Di(2-allylphenoxy)-6-(2-naphthyloxy)-1,3,5-triazine (DAPNPT)
54
2,4-Di(2-allylphenoxy)-6-N,N-dimethylamino-1,3,5-triazine
55
2,6-Di(4-aminophenoxy)benzonitrile (DAPB)
56
Poly(propylene phthalate)
57
11.2 SPECIAL ADDITIVES
11.2.1 Tougheners and Modifiers
The toughness of bismaleimide resins is a major problem that is limiting
the field of application. The toughness can be improved by adding reactive
components that reduce the crosslinking density. Modifiers are summarized
in Table 11.3.
11.2.1.1 Reactive Rubbers
Blending with reactive liquid rubbers such as carboxyl-terminated butadiene
acrylonitrile rubbers increases the toughness.
11.2.1.2 Polyetherimide
Polyetherimide (PEI) is highly effective as a toughness improver for a bismaleimide
resin. Increasing the modifier content increases the miscibility
of the two phases. At a content of 20% PEI, the morphological structure
of the modified resin changes from a dispersed system to a particle cocontinuous
structure and eventually with still more PEI to a phase inverted
system. 53 Polyetherimide is also used in bismaleimide resins composed of
4,4 ′ -bis(maleimido)diphenylmethane and 2,2 ′ -Diallyl bisphenol A.
58, 59

418 Reactive Polymers Fundamentals and Applications
11.2.1.3 Polyesterimide
Polyesterimides can be used to improve the toughness of bismaleimide
resins, composed of 4,4 ′ -bis(maleimido)diphenylmethane (BDM) and
2,2 ′ -Diallyl bisphenol A (DBA). The fracture energy of the cured samples
increases with the increase of polyesterimide content in the modified
bismaleimide system. 60
11.2.1.4 Polysiloxanes
The addition of alkenylphenols such as 2-allylphenol, 2-propenylphenol,
and 2,2 ′ -diallyl bisphenol A increases the toughness of bismaleimide resin
systems, but the degree of toughness obtained is less than that ultimately
desirable. Polysiloxanes that are capped with alkenylphenols are compatible
with bismaleimide resins and can be used in appreciable amounts to
toughen such resins. The toughened systems maintain a high degree of
thermal stability.
A 2-allylphenoxy-terminated diphenyldimethylpolysiloxane can be
prepared from an epoxy-terminated siloxane, 2-allylphenol and triphenylphosphine
as catalyst. 61
11.2.1.5 Poly(ether ketone ketone)
Poly(ether ether ketones) (PEEK) to improve the brittleness of the bismaleimide
resin include poly(phthaloyl diphenyl ether) (PPDE), poly(phthaloyl
diphenyl ether-co-isophthaloyl diphenyl ether) (PPIDE), and phthaloyl diphenyl
ether-co-terephthaloyl diphenyl ether (PPTDE). The bismaleimide
resin is a mixture of 4,4 ′ -bis(maleimido)diphenylmethane and 2,2 ′ -Diallyl
bisphenol A. It was shown that PPIDE with 50 mol-% isophthaloyl unit
is more effective as a modifier for the bismaleimide resin than the other
poly(ether ketone ketone)s. The most effective modification for the cured
resins could be achieved with a co-continuous phase or a phase-inverted
structure of the modified resins. 62
Similarly, in a three-component bismaleimide resin composed
of 4,4 ′ -bis(maleimido)diphenylmethane (BDM), 2,2 ′ -diallyl bisphenol A
(DBA), and o,o ′ -dimethallyl bisphenol A, PPIDE and PPTDE are more
effective as modifiers than PPDE. 63

Bismaleimide Resins 419
11.2.1.6 Triazines
2,4-di(2-allylphenoxy)-6-(2-naphthyloxy)-1,3,5-triazine (DAPNPT) can
be prepared by the reaction of cyanuric chloride with 2-allylphenol followed
by a treatment with 2-naphthol. 54 The procedure is shown in
Figure 11.11.
Copolymers of DAPNPT with 4,4 ′ -bis(maleimido)diphenylmethane
(BMDPM) show improved mechanical properties compared to pure
BMDPM. The copolymer shows up to 10 times higher impact strength and
3 times higher shear strength. However, the impact strength and the shear
strength dramatically decrease when the molar ratio of DAPNPT/BMDPM
in the copolymer exceeds 1:2.
Completely analogous, as shown in Figure 11.11, 2,4-di(2-allylphenoxy)-6-N,N-dimethylamino-1,3,5-triazine
can be prepared by the reaction
of 2-allylphenol with cyanuric chloride and then by dimethylamine.
55 This monomer is a modifier for bismaleimide resins. It effectively
improves the mechanical properties of the resin without greatly decreasing
heat resistance of the resin.
11.2.1.7 Others
Polyamide-imide (PAI), poly(phenylene sulfide) cannot be used in BMI
allyl systems. These compounds have poor miscibilities with allyl compounds.
11.2.1.8 Boric Esters
Boron can be incorporated into allylic compounds by esterification of allylphenol
and boric acid. Such compounds are suitable as comonomers in the
polymerization of bismaleimide resins. The cured resins show an excellent
thermal stability.
No weight loss was observed when the copolymer was heated up to
465°C in nitrogen atmosphere. The char yields at 800°C in nitrogen are
more than 50%. 64 Allyl boron compounds improve the ablative properties
of bismaleimide resins. 65

420 Reactive Polymers Fundamentals and Applications
Cl
OH
N
N
+ +
HO
Cl
N
Cl
Cl
N
N
O
N
O
HO
O
N
N
O
N
O
Figure 11.11: Preparation of
2,4-Di(2-allylphenoxy)-6-(2-naphthyloxy)-1,3,5-triazine

Bismaleimide Resins 421
11.2.2 Fillers
11.2.2.1 Aluminum nitride Ceramic Powders
To prevent the failure of integrated circuites (IC) during processing and
operation, materials with a low dielectric constant, and a silicon compatible
coefficient of thermal expansion (CTE) ca. 4.0×10 −6 K −1 are needed.
A low dielectric constant reduces the delay time of signal transmission.
Further, a high glass transition temperature and a high conductivity is substantial,
especially in high powered ICs.
Silica has a high thermal conductivity, but it has a high dielectric
constant of around 40. Aluminum nitride 66 has a melting point of 2230°C
and is highly chemically inert. It is used in refractory materials, also in
conjunction with silica nitride and boron nitride. Aluminum nitride (AlN)
ceramic is superior to silica, since it not only has a high thermal conductivity
of up to 320 W/K and a compatible CTE with silicon, but it also has
a relatively low dielectric constant (ca. 8.9).
AlN ceramic powders, used as fillers in a modified bismaleimide resin,
change the curing performance. The addition of AlN increases the
activation energy of curing of the BMI. Also, the glass transition temperature
is raised slightly. 67
11.2.2.2 Silsesquioxane Nanofillers
Silsesquioxane nanofillers in a bismaleimide modified novolak resin exhibit
improvements in the glass transition temperature and the heat resistance
of the material. The modulus at high temperatures is also improved.
The particle size of the dispersed phase was about 100 nm, and particle
aggregates were observed. 68
11.2.3 Titanium dioxide
Ternary hybrids of bismaleimide-polyetherimide-titanium dioxide were
synthesized by sol-gel reaction. A 10% solution of BMI prepolymer in
N-methyl-2-pyrrolidone was mixed with 30 phr of polyetherimide.
Dibutoxybis(acetylacetonato)titanium(IV) was obtained from tetrabutyltitanate
and acetylacetone. This compound was added, and after stirring
again tetrabutyltitanate and acid were added. After drying, the resulting
film was thermally cured. The titanium dioxide particles were
dispersed uniformly in both the PEI-rich phase and the BMI-rich phase,

422 Reactive Polymers Fundamentals and Applications
Compound
Table 11.4: Flame Retardant Bismaleimides
Reference
Bis(3-maleimidophenyl)phenylphosphine
oxide (BMIPO)
3,3 ′ -Bis(maleimidophenyl)phenylphosphine oxide
23
Phenyl-(4,4 ′ -bismaleimidophenyl)phosphonate
24
Ethyl-(4,4 ′ -bismaleimidophenyl)phosphonate
24
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide
(DOPO)
20–22
27, 28
having a mean diameter of around 50 nm. 69 Increasing titanium dioxide
content improves the mechanical properties. However, the thermal decomposition
temperatures of the hybrids decrease from 374°C of the unfilled
resin to 294°C of a resin with a titanium dioxide content of 20 phr. It is
believed that titanium dioxide exerts a catalytic effect in this aspect.
11.2.4 Reinforcing Materials
11.2.4.1 Silica Coatings
The usual way to reinforce is to add the reinforcing material to polymeric
materials. For medical applications, ceramic coatings have been applied
to a bismaleimide. Non-reinforced BMI specimens are coated with a thin,
protective layer of a dense silicate ceramic material. Testing of the Vickers
hardness on the coated and uncoated BMI specimens indicates that the
coatings adhere well to the substrate. 70
11.2.5 Flame Retardants
Bismaleimide resins are flame retardant, because they are comprised of
aromatic groups and nitrogen. Therefore, for many applications, flame
retardancy is not a major problem. Phosphorous-containing monomers
have been described as flame retardants. They are used not only for bismaleimides,
but also for epoxy systems. Flame retardants are shown in
Table 11.4.

Bismaleimide Resins 423
11.3 CURING
11.3.1 Monitoring Curing Reactions
11.3.1.1 DSC
Experimental data for a kinetic model of a modified bismaleimide resin
were obtained by isothermal DSC. A curing mechanism involving multiple
reactions was established. The reaction is dominated by different mechanisms
at different stages of curing. At the beginning of curing, an autocatalytic
reaction was observed. 71 A reaction model was set up, and the
activation energy and the frequency factor were calculated. 72
11.3.1.2 Dielectric Method
A dielectric sensor for the cure monitoring of high temperature composites
has been developed. The on-line cure monitoring of a bismaleimide resin
was performed using a Wheatstone bridge type circuit and a high temperature
dielectric sensor. 73
11.3.1.3 Infrared Spectroscopy
An in-situ technique for studying the polymerization kinetics has been developed.
Fourier self-deconvolution of the spectra was used to enhance the
peak separations and the calculation of the peak areas needed for quantitative
monitoring of the curing process. During curing of 1,1 ′ -(methylene
di-4,1-phenylene)bismaleimide (MDP-BMI) with 4,4 ′ -diaminodiphenylmethane
(DDM), a substantial difference in the reactivity between primary
and secondary amine was observed. 74
11.3.2 Polymerization
11.3.2.1 Gel Point
When a monomer containing two double bonds is incorporated into a radically
growing chain, it is first incorporated with one double bond only. The
polymer chain then will bear pendant double bonds, but initially no crosslinks.
There are special cases where, after incorporation of the first double
bond, the second, now pendant double bond will be consumed by the same
growing radical. This behavior is termed backbiting, or if it occurs more
randomly, intramolecular cyclization.

424 Reactive Polymers Fundamentals and Applications
The pendant double bonds may react in a further stage of the polymerization
with another growing chain. Accordingly a complete polymer
chain becomes part of another growing chain by the reaction of a single
pendant double bond. The molecular weight of the polymer grows rapidly
until a certain stage of conversion is reached and a gel is formed.
The formation of networks during the copolymerization of styrene
with various maleimide compounds was investigated. 75 In particular, p-
maleimidobenzoic anhydride, or mixtures of p-maleimidobenzoic anhydride,
methyl-p-maleimidobenzoate, and styrene were studied.
In resin systems containing bismaleimides, during radical polymerization,
the concentrations of pendent double bonds in copolymers, calculated
from the consumption of monomers and copolymer composition,
follow the general trend typical for vinyl-divinyl copolymerization.
At the end of polymerization, a substantial fraction of pendent maleimide
bonds remains in the system. The conversions at the gel point are
much higher than for ring-free copolymerization due to cyclization and the
steric hindrance of the pendent double bonds.
11.3.2.2 Thermal Polymerization
In stoichiometric formulations of 1,1 ′ -(methylene di-4,1-phenylene)bismaleimide,
modified with 2,2 ′ -Diallyl bisphenol A, during the thermal curing,
copolymerization and homopolymerization do not overlap with each
other. 76 The reactions progress sequentially and homopolymerization occurs
only when the copolymerization is completed.
This conclusion is based on the T g –conversion relationship that was
modelled by the DiBenedetto equation. 77 The DiBenedetto equation, Eq.
11.1 is based on the corresponding states.
T g
α
C 1
C 2
T g,α=0
T g
= 1+C 1 α+C 1 α 2 (11.1)
Glass transition temperature
Conversion
Constant, characteristic for the system
Constant, characteristic for the mobility of the repeating units
In a modified diallyl bisphenol A/diaminodiphenylsulfone/bismaleimide
resin, the different temperature regimes were characterized by IR
spectroscopy. The major crosslinking occurs below 150°C. At 190°C the
maleimide moiety is converted into succinimide. 78

Bismaleimide Resins 425
Cure Reaction Pathways. In a homopolymerized bismaleimide resin
system, the maleimide ring addition is the only observable reaction with
conventional methods. When the maleimide is cured in the presence of
an amine, the Michael addition of the amine to the maleimide ring can be
observed.
In solution, using special reagents and conditions, a ring-opening
aminolysis reaction has been observed. Such a reaction has been postulated
as a curing mechanism for bismaleimides.
It has been verified that such an aminolysis reaction, accompanied
by ring opening, occurs to a significant extent during the cure of a neat BMI
resin. This partial structure can remain in the network even after a hightemperature
postcure treatment. The existence of the amide product has
been demonstrated in bismaleimide resin formulations selectively labelled
with 13 C atoms and 15 N atoms. 79
Cure Kinetics and Mechanism. Maleimide reacts with allylphenols in
an ene reaction via an intermediate Wagner-Jauregg reaction, followed by
a Diels-Alder reaction. 80, 81 The Wagner-Jauregg reaction is essentially a
Diels-Alder addition of BMI to the ene adduct of BMI and the allylphenol.
The reaction shows a strong dependency on the electron density of the
BMI. The Diels-Alder reaction is facilitated by an increased electrophilicity
of the dienophile. However, a reverse trend is observed for the Wagner-Jauregg
reaction. Therefore, it was concluded that this reaction could
follow a mechanism different from the conventional Diels-Alder reaction,
although the final product looks the same as in the Diels-Alder reaction. 82
In a mixture of 4,4 ′ -bis(maleimido)diphenylmethane and 2,2 ′ -diallyl-bisphenol
A (BMDM/DABPA) and other models, it was established that
the cure mechanism consists of a combination of step-wise and chain polymerization
and polycondensation reactions: 83
1. Step-wise ene addition reaction of allyl group to maleimide,
(shown in Figure 11.12).
2. Chain polymerization of the maleimide and the propenyl groups
generated by first reaction.
The chain polymerization is the main crosslinking reaction. The
mechanism of the reaction involving monofunctional model compounds
differs from the curing of the actual system because of steric hindrances in
2,2 ′ -diallyl bisphenol A, which retard reversible Diels-Alder reactions, and

426 Reactive Polymers Fundamentals and Applications
OH
O
OH
O
+
N
N
O
O
O
OH
O
N
O
N
O
O
N
O
O
O
OH
O
N
O
N
O
O
N
O
O
N
Figure 11.12: Ene Reaction of Allylphenol and Maleimide, Followed by
Wagner-Jauregg Reaction and a Diels-Alder Reaction

Bismaleimide Resins 427
different reactivity of maleimide groups. 84 Another mechanism of crosslinking
is the dehydration reaction of phenol groups. The dehydration of
phenolic groups necessarily involves the 1:1 adduct of maleimide and allyl
function as a reactant. 85
The homopolymerization of maleimide groups proceeds autocatalytically
under the action of free radicals generated by thermal decomposition
of maleimide propenyl groups donor-acceptor pairs. The steric hindrance
in 2,2 ′ -diallyl-bisphenol A prevents the reversible Diels-Alder reaction.
The methylated analog of 2,2 ′ -diallyl bisphenol A shows a higher
reactivity in thermal free-radical polymerization. 86 The curing kinetics of
bismaleimide modified with diallyl bisphenol A has been modelled by an
autocatalytic and n th -order model. 87
Microwave Curing. A comparative study between thermal and microwave
curing of bismaleimide resin was done. The degree of cure was
determined with differential scanning calorimetry. No difference in the
chemical reactions taking place during the microwave cure and the thermal
cure was detected. Samples that were cured with a conventional oven
showed slightly higher glass transition temperatures than the microwavecured
samples at higher conversions. 88
11.3.2.3 Photo Curing
N-alkylmaleimides homopolymerize in the absence of a photoinitiator
when exposed to UV light in solvents bearing a labile hydrogen. 89 Since
the maleimide is a chromophore, it is considered a photoinitiator together
with a co-initiator. A co-initiator may be methyldiethanolamine, trimethylolpropane
trismercaptopropionate, or poly(ethylene glycol).
Maleimide/vinyl ether systems belong to electron donor/electron acceptor
monomers. Maleimide acts as an electron acceptor and the vinyl
ether acts as an electron donor. With stoichiometric maleimide-vinyl ether
mixtures, the reaction proceeds within seconds upon UV exposure. 90 The
initiation reaction is shown in Figure 11.13.
The initiator radicals are formed by hydrogen abstraction from the
excited maleimide molecules. Highly crosslinked polymer networks can
be obtained.
The molecular structure of bismaleimides is quite rigid because of
the presence of aromatic rings. The presence of the aromatic rings, as well

428 Reactive Polymers Fundamentals and Applications
O
H
C
C
N R
C C
H
O
CH 2 CH O CH 2 R’
hν
O
H
C*
N R
H C
H
O
CH 2 CH O CH* R’
Figure 11.13: Photoinitiation in Donor Acceptor Systems 91
as the resultant high crosslinked density during thermal curing, give the
cured product its high heat-resistance, resulting in a high T g and a high
mechanical strength.
For the radiation curing of bismaleimides, comonomers such as
2,2 ′ -diallyl bisphenol A and 4-hydroxybutylvinyl ether have been tested.
Unlike N-alkylmaleimide and N-phenylmaleimide, BMI does not react
with vinyl ether without a photoinitiator. Triphenylphosphine oxide is a
suitable photoinitiator.
2,2 ′ -Diallyl bisphenol A, which is a good property modifier for BMI
in thermal curing formulation, does not polymerize with either BMI or
4-hydroxybutylvinyl ether, even in the presence of a photoinitiator. However,
2,2 ′ -diallyl bisphenol A is a co-initiator and speeds up the reaction of
a ternary system. 91
11.3.2.4 Anionic Initiators
Several maleimides can be polymerized by nanometer sized Na + /TiO 2
initiators. The temperature for the polymerization initiated by nanometer
sized Na + /TiO 2 is lower than that for the radical polymerization. An anionic
mechanism resulting from the catalysis by Na + /TiO 2 as the counter
ion is proposed.
92, 93
11.3.2.5 Diels-Alder Polymerization
A monomer suitable for Diels-Alder polymerization is shown in Figure
11.14. The reaction between α,α ′ -dibromo-m-xylene (DBMX) and
sodium 1,2,3,4,5-pentamethylcyclopenta-1,3-dienide gives the respective
pentamathylcyclopentadiene derivative, 25 as depicted in Figure 11.14.

Bismaleimide Resins 429
CH 3
CH 3
H 3 C
CH 3
H 3 C
CH 2
Br CH 2
Br
CH 3
CH 3 CH 3
CH 3
CH 3
H 3 C
CH 3
Na +
Na +
H 3 C CH 3 CH 2 CH
CH 3 2
H 3 C CH 3 H 3 C
CH 3
CH 3
Figure 11.14: Synthesis of Bis-1,3-methyl-1,2,3,4,5-pentamethylcyclopenta-
2,4-diene benzene
The Diels-Alder polymerization is shown in Figure 11.15. The reaction
must be performed in dimethylformamide at 140 to 150°C because
of the low solubility of the BMI.
11.3.3 Interpenetrating Networks
11.3.3.1 Polyurethane Bismaleimide
In polyurethane/poly(urethane-modified bismaleimide-bismaleimide) interpenetrating
polymer networks (PU/P(UBMI-BMI) IPNs) interpenetration
occurs at the hard segment domains of PU, which leads to an enhancement
of the phase separation of PU. The dispersing tendency of the dispersed
phase increases. 94
Poly(butylene adipate)-based polyurethane-crosslinked epoxy (BMI/
PU-EP IPN) and bismaleimide from interpenetrating networks are prepared
by using the simultaneous bulk polymerization technique. It was
demonstrated that the bismaleimide was dissolved primarily in the polyurethane
domains of the epoxy matrix to form a compatible system, thereby
increasing the mechanical strength of the BMI/PU-EP IPNs.
95, 96
An epoxy based on poly(propylene oxide) has a better grafting effect

430 Reactive Polymers Fundamentals and Applications
H 3 C
CH 3 CH 2
CH 3
CH
CH 3 2
O
O
H 3 C
CH 3
CH 3
H 3 C
N R N
CH 3 CH 3 O O
CH 3 CH 2 CH
CH 3 2
O
O
N
O
O
N
Figure 11.15: Diels-Alder Polymerization
due to higher compatibility between the BMI than poly(butylene adipate)
epoxies. 97
The incorporation of chain-extended BMI into polyurethane-modified
epoxy systems increases the thermal stability, and tensile and flexural
properties, but decreases the impact strength and the glass transition temperature.
98
11.3.3.2 Unsaturated Polyester Bismaleimide
A bismaleimide resin monomer can be readily dissolved in the uncured
polyester matrix up to a concentration of about 20%. 99 Spectroscopic investigation
during curing indicates that the crosslinking process is strongly
affected by the presence of the bismaleimide in the system. The maleimide
groups react preferentially with the styrene. The styrene radical reacts
with both the unsaturated polyester and the maleimide moieties so that a
crosslinked structure can emerge. When the maleimide groups are fully
consumed, the curing proceeds as in a neat resin. The bismaleimide effects
an increase of the crosslinking density of the final product. Further, the
bismaleimide increases the overall stiffness of the network.

Bismaleimide Resins 431
11.4 PROPERTIES
In comparison to epoxy resins, BMI resins exhibit a higher tensile strength
and modulus, excellent chemical and corrosion resistance, better dimensional
stability, and good performances at elevated temperature.
11.4.1 Thermal Properties
Among two high temperature adhesives, based on epoxy and bismaleimide,
the bismaleimide-based adhesive shows a better high temperature performance
and is more resistant to thermal aging than an epoxy based resin. 100
There are relationships between structure and thermal properties of polymers.
101
11.4.2 Water Sorption
In general, a disadvantage of thermoset resins is their tendency to absorb
significant amounts of water when exposed to humid environments. The
absorbed moisture has detrimental effects on material performance. The
temperature dependence of moisture content in equilibrium is controversial.
It has been reported that the equilibrium moisture content is independent
of temperature, 102 but also that it is dependent on the temperature.
103, 104
From the viewpoint of thermodynamics, the temperature dependence
of the solubility is governed by the enthalpy of dissolution
d lnc s
d1/T = −∆H s/R. (11.2)
During hydrothermal cycling experiments, the molecular network structure
of BMI appears to change. 105, 106 It was concluded that in the course
of water absorption at elevated temperatures, a chemical degradation can
occur. This is part of an aging mechanism. IR spectra obtained by the
reflection technique during water absorption show that the band at 1600
cm −1 increases. 107 This band is attributed to the N − H stretching of an
amine and also of an amide. The hydrolysis reaction is shown in Figure
11.16. It is assumed that the hydrolysis is similar to the reverse reaction of
formation of a bismaleimide. 107 When a BMI resin was stored in water at
temperatures of up to 70°C for a period of 18 months, blistering and severe
microcracking occurred, leading to severe weakening of the materials. 103

432 Reactive Polymers Fundamentals and Applications
O
O
N
H 2 O
O
O
OH
N
H
H 2 O
O
O
OH
H
OH N
H
Figure 11.16: Hydrolysis of a Cured Bismaleimide Resin
The presence of about 10 to 15% of alkenyl-substituted cyanate in
dicyanate and bismaleimide blends leads to a marked reduction in moisture
absorption in comparison with an unmodified bismaleimide/cyanate blend
containing a comparable amount of bismaleimide.
The modified samples display thermal stabilities that are indistinguishable
from cured resins that have not undergone immersion. 108 The
moisture transport can be correlated to the glass transition temperature and
the network properties. The network structure can be systematically varied
by the initial monomer composition and the conditions of curing. 109
11.4.2.1 Multivariate Analysis
An analysis of samples subjected to accelerated ageing tests shows that
simple near infrared spectroscopic measurements on virgin materials can
predict results otherwise obtained from dynamic mechanical thermal analysis,
and can provide correlations with thermogravimetric analysis.
Therefore, a rapid screening method for multivariate analysis has
been proposed, in conjunction with a combinatorial approach for the development
of advanced composites. 110

Bismaleimide Resins 433
11.4.3 Recycling
Various styrene copolymers containing comonomers with a pendant furan
ring were subjected to Diels-Alder reactions with a monomaleimide or a
bismaleimide. When the materials are heated in the presence of excess of
2-methylfuran, the retro Diels-Alder reaction is induced. The process is
rather a trans Diels-Alder reaction. The maleimides are released with the
furanic additive. Concomitantly the original copolymers can be recovered.
The reaction is of interest because of the possibility of recycling crosslinked
polymers by a simple thermal treatment. 111
11.5 APPLICATIONS AND USES
11.5.1 Biochemical Reagents
Bismaleimides are used as reagents in biochemical investigations. 112 Bismaleimide
is used as a crosslinking reagent for the synthesis of bifunctional
antibodies. The use of a solid-phase reactor in the preparation of the
bifunctional antibodies eliminates many time-consuming separation steps
between fragmentation and conjugation steps. 113
11.6 SPECIAL FORMULATIONS
11.6.1 Adhesives
For high-temperature usage, i.e., above 200°C, either bismaleimides or
polyimides are suitable. These are supplied as films, with or without a
carrier. Epoxies are not generally used at temperatures beyond 150°C, although
there are some modified epoxies that can be used up to 200°C. 114
11.6.1.1 Void Control
Polyimides have a higher service temperature than bismaleimides. However,
bismaleimides offer some advantages as they do not generate volatiles
during cure. When volatiles are created during curing a high void content
in the adhesive can develop. There are several methods to control the voids.
These include 114
• Vacuum release technique. The joint to be bonded is placed in
an oven under vacuum. The temperature is increased in order to

434 Reactive Polymers Fundamentals and Applications
reduce the viscosity of the adhesive. When the vacuum is released,
the voids collapse to a negligible volume.
• Another method uses an autoclave where hydrostatic pressure can
be applied. The hydrostatic pressure compresses the gas in a void
and reduces its volume.
11.6.1.2 Thermally Reversible Adhesives
A formulation of thermally reversible adhesives consists of a diepoxy compound
and aliphatic diamines. The diepoxy compound is formed by the
Diels-Alder reaction between epoxy-containing furans and a bismaleimide.
The epoxy resin is cured with aliphatic diamines. 115 At temperatures
above 90°C the retro Diels-Alder reaction occurs, which leads to a significant
loss in the shear modulus. The loss of the shear modulus is reversible
with temperature. Therefore, the formulation can act as a thermally reversible
adhesive. The adhesive bonds are easily broken at elevated temperature
where the modulus is low.
11.6.1.3 Adhesion Improvement
In order to improve the adhesion of Kevlar ∗ fibers to a 2,2-bis[4-(4-maleimido
phenoxy)phenyl]propane (BMPP) resin, the surface of the fibers can
be chlorosulfonated. The fibers are immersed in a solution of chlorosulfonic
acid in dichloromethane at −10°C. After the chlorosulfonation, the
surface concentration of carbon decreases. In the subsequent reaction with
ethylene diamine, allylamine, the O/N ratio again decreases. On the other
hand, the O/N ratio was increased by hydrolysis treatment.
The interfacial shear strength (IFSS) is determined by pull-out experiments
of the fiber from the matrix calculated by the relationship
τ = F dL . (11.3)
τ Interfacial shear strength
F Pull-out force
d Diameter of the fiber
L Embedded length of the resin
The interfacial shear strength (IFSS) between Kevlar fibers and the
BMPP resin increases slightly due to the chemical treatment.
116, 117
In
∗ Kevlar is a trademark of DuPont company

Bismaleimide Resins 435
graphite/bismaleimide composites, the treatment with ammonia has been
shown to be promising for the improvement of adhesion. 118
11.6.2 Phosphazene-triazine Polymers
Polyquinoline/bismaleimide blends are miscible thermosetting polymers.
Thermogravimetry shows a 5% weight loss between 450 and 535°C for
thin films at 5 to 60% of bismaleimide loading. The glass transition temperatures
are between 275 and 360°C. 119
11.6.3 Phosphazene-triazine Polymers
Phosphazene-triazine polymers can be obtained by curing a ternary blend
of tris(2-allylphenoxy)triphenoxy cyclotriphosphazene (TAP), tris(2-allylphenoxy)-s-triazine
(TAT) and bis(4-maleimidophenyl)methane (BMM).
The maleimide component increases the thermal stability. The tensile
strength decreases and the modulus increases with increasing maleimidecontent.
Tensile properties improve for an allyl/maleimide ratio of two. 120
11.6.4 Porous Networks
Network structures have been prepared by in-situ polymerization of a
mixture of N-phenylmaleimide and 1,1 ′ -(methylene di-4,1-phenylene)-
bismaleimide in 80% poly(vinylidene difluoride-co-hexafluoropropylene)
(PVDH). The maleimide monomers are forming thermoreversible gels
with PVDH.
After polymerization, porous networks are obtained by removing the
PVDH by solvent extraction. The poly(maleimide) networks are stable up
to 380°C in an inert atmosphere. It is suggested that these networks may
be used for thermally stable membranes. 121
11.6.5 Nonlinear Optical Systems
Thermally stable second-order nonlinear optical polymeric materials based
on bismaleimide contain chromophores with excellent thermal stability,
such as the N-maleimide of Disperse Orange 3. The synthesis of the monomer
is shown in Figure 11.17. A full interpenetrating polymer network
can be formed by the simultaneous reaction of bismaleimide and a solgel
process of the alkoxysilane dyes. The dynamic thermal and temporal

436 Reactive Polymers Fundamentals and Applications
O
O
+
H 2 N N N NO 2
O
O
N
N N NO 2
O
Figure 11.17: Synthesis of the Maleimide of Disperse Orange 3
stabilities of the interpenetrating network are much better than those of
comparable non-interpenetrating networks. 122
Azo chromophores with allyl groups at one or two ends of the
molecules can be thermally cured with bis(maleimidodiphenyl)methane to
give crosslinked and chromophore-modified bismaleimide resins. The resins
show no appreciable decomposition up to 300°C. By incorporating
a chromophore into the network of a BMI resin, an improvement of the
thermal stability of the materials is achieved. 123
Examples of azo chromophore allyl compounds include (4-(N,Ndiallyl)-4
′ -nitrophenyl)azoaniline, allyl-4-[(4-N-allyl-N-ethyl)aminophenylazo]-α-cyanocinnamate,
and allyl-4-[(4-N,N-diallyl)aminophenylazo]-
α-cyanocinnamate, c.f. Figure 11.18.

Bismaleimide Resins 437
CH 2 CH 2
CH CH
H
N CH 2 C 2
NO 2
CH 2
CH 3 CH
H 2 C
N CH 2
CH 2 CH 2
CH CH
H 2 C
N CH 2
N
N
N
N
N
N
CH
C CN
C O
O
CH 2
CH
CH 2
CH
C CN
C O
O
CH 2
CH
CH 2
Figure 11.18: Azo Chromophore Allyl Compounds: (4-(N,N-Diallyl)-4 ′ -nitrophenyl)azoaniline,
allyl-4-[(4-N-Allyl-N-ethyl)aminophenylazo]-α-cyanocinnamate,
allyl-4-[(4-N,N-Diallyl)amino-phenylazo]-α-cyanocinnamate

438 Reactive Polymers Fundamentals and Applications
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12
Terpene Resins
Terpenes are widespread in nature, mainly in plants as constituents of essential
oils. Some terpenes are pure hydrocarbons, but there are also terpenes
with hydroxyl functions and carbonyl functions. Terpenes provide
plants and flowers with fragrance.
12.1 HISTORY
Polyterpene resins were discovered in 1789 when turpentine was treated
with sulfuric acid to produce a crude resin. Turpentine is a semi-fluid resin
obtained from pines. Turpentine is used as a thinner, antiseptic, drug,
pesticide, insecticide, and raw material for the chemical industry.
Rouxeville observed that a great number of hydrocarbons may be
changed in their composition so that an artificial product that is formed is
distinguished by a new composition. This occurs by oxidation or polymerization.
He patented a process of polymerization by treatment with sulfuric
acid. 1, 2
12.2 MONOMERS
Terpenes and related monomers are relatively non-toxic liquids that may
be obtained from natural renewable nonpetroleum sources. The structure
of terpenes can be essentially derived from isoprene. This fact is known as
the isoprene rule. The terpene unit consists of two isoprene units. There-
447

448 Reactive Polymers Fundamentals and Applications
CH 3
CH 3
CH 3
CH 2
CH 3
CH 3
CH 3
α-Pinene
β-Pinene
Limonene
Figure 12.1: Terpenes
fore, terpenes have the general molecular formulas (C 5 H 8 ) 2n . According
to the number of isoprene units, terpenes are classified into monoterpenes
(2 isoprene units), sesquiterpenes (3 isoprene units), diterpenes (4 isoprene
units), triterpenes (6 isoprene units), and tetraterpenes (8 isoprene units).
Polyterpene resins are low molecular weight hydrocarbon polymers
prepared by cationic polymerization or copolymerization of monoterpenes
such as α-pinene and β-pinene or limonene. These types of terpenes are
bicyclic terpene hydrocarbons. The structures of some terpenes are shown
in Figure 12.1. α-Pinene and β-pinene and limonene are liquid at room
temperature. Naturally occurring terpene compounds are shown in Table
12.1. Natural rubber, or poly(isoprene), is a polyterpene which consists of
up of 1000 to 5000 isoprene units.
12.2.1 Resin
Crude resin is obtained by tapping living pine trees. It is a thick, sticky, but
still fluid material. Due to occluded moisture, the material is milky-gray
in color. The resin contains a certain amount of forest debris, such as pine
needles, insects, etc.
The separation of resin into its component parts, namely rosin and
turpentine, involves two basic operations: cleaning and distillation.
The approximate composition of crude resin, as it is received at the
plant for processing, is 70% rosin, 15% turpentine, and 15% debris and
water.
In the first stage of refinement, the resin is diluted with turpentine
and heated. During purification by filtering of the hot diluted resin, all
extraneous materials, both solid and soluble are removed. Filtration is usu-

Terpene Resins 449
Table 12.1: Naturally Occurring Terpene Compounds
Monoterpenes
α-Pinene In oil of turpentine
β-Pinene
Limonene In various vegetable oils
Camphene
Myrcene In various vegetable oils
Terpinene
Terpinolene
Phellandrene In eucalyptus oil
Chrysanthemol
Allo-ocimene
3
Carene
Dipentene
Sesquiterpenes
Longifolene
Carophyllene
Diterpenes
Retinol
Abietic acid
Pimaric acid
Triterpenes
Betulin
Lupeol
Squalene
Polyterpenes
Natural rubber
Guttapercha
From Himalaya pine
Rare, but its provitamin β-carotine is widespread
In rosin
A mixture of rosin acids. Components of pine rosin
In birch bark
In lupin seeds
In shark liver, and natural oils

450 Reactive Polymers Fundamentals and Applications
Table 12.2: Global Production Data (2000) of Terpenes and Derivatives 4
Terpene
Mill. Metric tons
Rosin 1.20
Rosin gum 0.72
Turpentine 0.33
Turpentine gum 0.10
ally followed by a washing step. The purified resin then undergoes a steam
distillation.
12.2.2 Turpentine
Turpentine is a clear, flammable liquid, with a pungent odor and a bitter
taste. It is immiscible with water and has a boiling point above 150°C.
Turpentine is a mixture of organic compounds, mainly terpenes, and
its composition can vary considerably according to the species of pine from
which it is derived. Fractional distillation of turpentine allows the isolation
of α-pinene and β-pinene.
12.2.3 Rosin
Rosin is the major product obtained from pine resin. It remains behind as
the non-volatile residue after distillation of the turpentine and is a brittle,
transparent, glassy solid.
It is insoluble in water but soluble in many organic solvents. 4 It
consists mainly of a mixture of abietic acids and pimaric acids. Most rosin
is used in a chemically modified form rather than in the raw state in which
it is obtained.
12.2.4 Production Data of Important Monomers
Global production data of the most important monomers used for unsaturated
polyester resins are shown in Table 12.2. Major producers are The
People’s Republic of China, Indonesia, Russia, Brazil, and Portugal.

Terpene Resins 451
H 3 C C + CH 3
CH 3
CH 3
H
CH 3
Figure 12.2: Cationic Initiation of the Polymerization of Terpenes
12.3 CURING
12.3.1 Homopolymers
Polymers are produced by the cationic polymerization of α-pinene, β-
pinene, or limonene. The initiation reaction is shown in Figure 12.2. The
initial stage is the same for α-pinene and β-pinene. However, the subsequent
propagation differs.
β-Pinene and limonene contain vinyl double bonds and vinylidene
double bonds that facilitate polymerization. α-Pinene does not contain
such double bonds. This makes the chain propagation more difficult for α-
pinene.
β-Pinene and limonene resins are manufactured by the reaction in
an aromatic solvent such as xylene or toluene by a Lewis acid, such as
anhydrous aluminum chloride as catalyst. Ethylaluminum dichloride is
also a suitable catalyst. 5
For α-pinene a co-catalyst is needed to reach a degree of polymerization
higher than dimer. Alkyl silicon halides and antimony chloride are
suitable co-catalysts. 6–8 The polymers are different in structure and molecular
weight, which has a direct effect on the areas of application.
The cationic polymerization is performed at 30 to 60°C, with 1 to
3% AlCl 3 in a solvent. The reaction is strongly exothermic. The reaction
is then quenched with water, dilute alkali, or acid.
The organic phase is washed with water to remove hydrochloric acid
and catalyst residues. Then the solvent and lower molecular weight dimer
oils are stripped until a material with the desired softening point is obtained.

452 Reactive Polymers Fundamentals and Applications
12.3.2 Copolymers
Copolymers of α-pinene, β-pinene, limonene, styrene, piperylene, cyclopentadiene,
and vinyl toluene can be prepared. The monomers are copolymerized
with Lewis acid catalysts.
The copolymerization of terpenes with other monomers such as styrene
extends their Hildebrand solubility parameter. Such copolymers are
compatible with poly(butadiene) rubbers. This copolymer is used in the
manufacture of disposable diapers.
12.3.3 Terpene Phenolic Resins
Terpene phenol resins are used in a variety of applications including adhesive
and ink formulations and in the manufacture of engineering thermoplastics.
Commercial terpene phenol resins are typically produced by
reacting a terpene with a phenol in a suitable solvent in the presence of a
catalyst. After the reaction is substantially complete, the catalyst is deactivated
with water or clay, and the resin is isolated from the reaction mass
product by distillation to remove the solvent and by-products.
In particular, a phenol-terpene-cyclic polyolefin resin can be synthesized
by reacting a phenol, a terpene or a low molecular weight propylene
polymer and a cyclic polyolefin in the presence of a Friedel-Crafts catalyst
in an aromatic, naphthenic, or paraffinic hydrocarbon solvent.
The monomer compounds can first be blended together, after which
the catalyst is added in small amounts with stirring. This method is particularly
suitable if relatively small amounts of phenol compound have to
be incorporated. The phenolic copolymer may also be prepared according
to a reverse cationic polymerization in a solvent. “Reverse” means that an
activated complex is first formed between the catalyst and the phenol compounds
and after that the remaining monomer units are added. This method
makes it possible to incorporate higher proportions of phenol compounds.
Both methods can be applied with or without a solvent. By using a solvent,
the reaction can proceed at lower temperatures. 9
12.3.3.1 Carene Resins
Carenes show a poor reactivity. Therefore, an improved procedure has
been identified. For preparation of carene-phenol resins a phenol with a
carene is reacted two steps. The first step comprises reacting the entire

Terpene Resins 453
CH 3
CH 3
CH 3
H
H
H
H 3 C
CH 3
H
H 3 C
CH 3
H
H 3 C
CH 3
H
(+)-2-Carene
(+)-3-Carene
(+)-4-Carene
Figure 12.3: Carenes
amount of phenol with about one-half the amount of carene in the presence
of a catalyst. Then the rest of the carene is reacted with the condensation
product obtained in the first step in the presence of the catalyst. The resulting
phenol-carene resin is then reacted with a reactive terpene to give an
improved resin. 10
Terpene-phenol-aldehyde resins based on α-pinene, phenol, and additional
formaldehyde have a high softening point, greater than 140°C. 11
Manufacturing of terpene-phenol resins with low softening points,
i.e., softening points in the range from about 80°C to about 110°C, is very
difficult. The traditional methods for producing such resins use one of two
approaches.
In the first approach, diluents such as mineral oil or polyolefin oligomers
are added to resins having higher softening points. This approach
usually results in reduced adhesive or ink formulation performance or excessive
amounts of volatiles in the resulting resin.
The second approach is to synthesize the low softening point resin
directly. Generally, the synthetic methods in current use produce base resins
that cannot be finished to softening points below 110 °C without leaving
substantial amounts of process solvents or phenol in the resin. Again,
this results in decreased adhesive or ink formulation performance. 12
A terpene phenol-based resin with a low softening point comprises
the reaction of a phenol dissolved in an organic solvent with terpene and
an acyclic monounsaturated olefin, such as a mixture of 1-diisobutylene
and 2-diisobutylene in the presence of a Lewis acid catalyst, such as boron
trifluoride. 13 Boron trifluoride is used as an acetic complex. 10
Cyclic polyolefins can produce products with unacceptable amounts

454 Reactive Polymers Fundamentals and Applications
of low molecular weight fractions. The low molecular weight fractions
tend to volatilize or cause smoking during the preparation and use of hot
melt adhesives. Therefore, the reaction product is washed and distilled to
remove the solvent and any unreacted phenol. Further, the product may
be sparged with an inert gas at a temperature up to 260°C to remove any
remaining low molecular weight terpene phenol alkylates and terpene-terpene
dimers. A high yield of relatively low softening point terpene phenol
resin is produced. It has softening point in the range from about 70°to
about 110°C.
Terpene phenol resins with low melting points are not suitable for
use in printing ink applications. For use in printing inks, the amount of
vinyl aromatic units should be less than 5%. The small fraction of resin
results in good solubility of the resin (in the ink) and an effective drying of
the ink. In these types of applications, dicyclopentadiene may be used. 9
Terpene phenolic resins are suitable for more polar adhesive resins.
They are made by the addition of a terpene to phenol.
12.3.4 Terpene Maleimide Resins
Resinous terpene maleimides are useful as tackifiers for elastomers. They
are prepared by reacting equimolar amounts of non-conjugated monocyclic
terpenes and maleic anhydride at temperatures between 140°C and 200°C.
Iodine in amounts of 0.05% to 0.15% is used as catalyst.
In the first step, maleic adducts with the terpene are formed, including
both mono adducts and a minor amount of di-adducts. This adduct
mixture is reacted with stoichiometric amounts of an aliphatic primary diamine,
such as ethylene diamine. A terpene maleimide resin having an
average molecular weight between about 500 Dalton and about 600 Dalton
is recovered. 14
A suitable terpene type is the terpene fraction containing about 90%
terpinolene with the remainder being monocyclic terpene hydrocarbons
and terpene alcohols.
A certain procedure 14 yields a product, which is a resinous terpene
maleimide, with properties as summarized in Table 12.3. The terpene
imide resins are soluble in aromatic hydrocarbons, chlorinated hydrocarbons,
esters, ketones, ethers, and alcohols, but insoluble in aliphatic
hydrocarbons. Due to their molecular weight and compatibility (as shown
by cloud point of 160°C), the resins find utility as tackifiers in chemically

Terpene Resins 455
Table 12.3: Properties of a Resinous Terpene Maleimide
Property
Unit
Softening point 88 [°C]
Acid number 1 [mgKOH/g]
Number-average molecular weight 533 [Dalton]
Cloud point 159 [°C]
polar formulations. The terpene imides prepared are compounded with
vinyl acetate-ethylene copolymers and a paraffin wax.
12.4 PROPERTIES
12.4.1 Solubility
Low molecular weight terpene resins have an excellent solubility in elastomers.
This makes them useful for adhesives.
12.4.1.1 Hildebrand Solubility Parameters
The Hildebrand solubility parameters δ can be predicted on the basis of
the solubility of polymers in solvents with known Hildebrand solubility
parameters.
The Hildebrand solubility is defined as the square root of the cohesive
energy density, which is a characteristic for the intermolecular interactions
in a pure liquid or solid. The solubility parameter is related to the
heat of mixing H m in Eq. 12.1.
∆H m = n s V s Φ p (δ s − δ p ) 2 (12.1)
H m Heat of mixing
n s Moles of solvent
V s Molar volume of solvent
Φ p Volume fraction of polymer
δ s Solubility parameter of solvent
δ p Solubility parameter of polymer
∆G m decreases as ∆G m decreases. Therefore, if the two Hildebrand
solubility parameters approach one another, the heat of mixing approaches
a minimum. The theory of solubility parameters was developed
by Scatchard in 1931 and further refined by Hildebrand. 15

456 Reactive Polymers Fundamentals and Applications
Terpene resins will be effective as solid solvents for an elastomer
when their Hildebrand solubility parameters are close to the Hildebrand
solubility parameters of the respective polymer. For example, from Table
12.4 it can be seen that pure polyterpene resins are suitable tackifiers
for poly(ethylene), natural rubber, and poly(butadiene) polymers. Further,
terpene phenol resins are suitable tackifiers for poly(vinyl acetate), poly-
(methyl methacrylate), and poly(ethylene terephthalate).
12.4.2 Adhesive Properties
12.4.2.1 Tackifiers
Low molecular weight polyterpene resins are addressed as tackifiers. They
act as solid solvents for adhesive backbone polymers and can modify the
ability of an adhesive formulation in wetting a surface. The resins impart a
tack, as they modify certain adhesion characteristics.
The adhesive properties are expressed in terms of shear adhesion,
peel adhesion, and quick stick. Quick stick is the resistance to separation
of the adhesive from substrate, bonded without pressure.
The addition of the rosin ester to ethylene/vinyl acetate (EVA) copolymers
produces a compatible mixture, whereas for a terpene resin a less
compatible mixture is obtained. The increase in the vinyl acetate amount
in the EVA decreases the crystallinity of EVA. Both the storage and the
loss moduli decrease, but the peel strength and the immediate adhesion increase.
The immediate adhesion of the EVA/tackifier blends is affected by
both the compatibility and the rheological properties of the blends. An increase
in the VA content increases the flexibility of the adhesives and thus
a decrease in peel strength is obtained. 16
The tackifying properties are used not only for adhesive purposes.
For example, the cover material of a golf ball can consist of an ionomer
resin with up to 50% of a tackifier such as terpene resins, or rosin ester
resins. 17
12.4.2.2 Cotackifiers
Polyterpene resins are compatible with paraffins. Therefore, they are also
compatible with petroleum hydrocarbon resins that are used as cotackifiers.
Other cotackifiers include rosins and coumarone-indene resins.

Terpene Resins 457
Table 12.4: Hildebrand Solubility Parameters δ of Solvents and Polymers
18, 19 Solvent δ
MPa 1/2 a
n-Pentane 14.4
n-Hexane 14.9
Diethyl ether 15.4
1,1,1-Trichloroethane 15.8
Turpentine 16.6
Cyclohexane 16.8
Xylene 18.2
Ethyl acetate 18.2
Benzene 18.7
Methylethylketone 19.3
Acetone 19.7
Pyridine 21.7
Ethanol 26.2
Dimethyl sulfoxide 26.4
n-Butanol 28.7
Methanol 36.2
Water 48.0
Polymer
δ
MPa 1/2
Poly(ethylene) 16–17
Poly(butadiene) 16–17
Poly(styrene) 17–20
Poly(vinyl acetate) 19
Poly(methyl methacrylate) 19–26
Poly(ethylene terephthalate) 19-22
Rosin esters 18
β-Pinene polyterpene 16
Terpene phenol polymers 19–21
a MPa 1/2 ∼ = 2.05× µm

458 Reactive Polymers Fundamentals and Applications
Table 12.5: Important Specifications of Terpene Resins
Parameter
Solubility
Cloud point
Softening point
Toluene insolubles
Color
Viscosity at compounding temperatures
Thermal stability
Compatibility
Remarks
Ring and ball method
Residues from catalyst
Gardner scale
12.4.3 Characterization
Some important specifications of terpene resins are shown in Table 12.5.
12.4.3.1 Rheological and Aging Characteristics
Polyterpene resins can modify the rheological and aging characteristics of
adhesive backbone polymers. In this way the polymers themselves become
usable as adhesives. It is possible to correlate rheological characteristics to
the tack, shear, and peel.
12.4.3.2 Cloud Point
Higher molecular weight resins will have a higher cloud point in polymerpolymer
combinations.
12.4.3.3 Softening Point
The softening point is related to the glass transition temperature and to the
melt viscosity. Polyterpene resins have cyclic and polycyclic structures
in the backbone. These provide high softening points at low molecular
weights and low viscosities, which is very useful. Terpene resins are available
in softening points from 25°C to 135°C. Most commercial resins have
softening points of 85°C to 115°C.
12.4.3.4 Color
The color of a resin is monitored in a 50% heptane solution and is given in
the Gardner scale.

Terpene Resins 459
12.4.3.5 Toluene Insolubles
The toluene insolubles is a measure of the amount of inorganic material in
the resin. The toluene insolubles consist mainly of catalyst residues.
12.4.4 Recycling
12.4.4.1 Pyrolysis of Poly(isoprene)
Controlled thermal depolymerization at 300 to 380°C of cis-1,4-poly(isoprene)
produces a liquid poly(isoprene) having a considerably lower molecular
weight in comparison to the starting cis-1,4-polymer. The product is
enriched in trans-1,4-units and 3,4-units together with vinylidene units.
FT-IR spectroscopy shows that the end groups of liquid poly(isoprene)
consist of diene, triene and tetraene moieties. Aldehyde groups conjugated
with dienes and trienes are also analyzed.
Pyrolysis opens a possible low cost source of raw materials, since the
pyrolysis of natural and synthetic cis-1,4-poly(isoprene) produces mainly
dipentene (DL-limonene) with small amounts of isoprene and other products.
A 3,4-poly(isoprene)-rich polymer produces mainly dipentene. The
residual of pyrolysis consists of 3,4-poly(isoprene). The crude dipentene
obtained from cis-1,4-poly(isoprene) pyrolysis can be converted into a terpene
resin usable in adhesive formulations and as thermoplastic rubber
tackifier. 20
12.4.4.2 Biodegradation
Films for packaging based on isotactic poly(propylene)-modified with natural
terpene resins are biodegradable. It was found that a certain microbial
community was able to erode the blend films but not the plain isotactic
poly(propylene) film. 21
12.5 APPLICATIONS AND USES
Only three terpenes, i.e., α-pinene, β-pinene, and limonene have found
commercial application in the manufacture of polyterpene resins. Polyterpene
resins are used as pressure-sensitive adhesives, hot-melt adhesives,
and sealants. Some polyterpene resins are used in chewing gum.

460 Reactive Polymers Fundamentals and Applications
12.5.1 Sealants
12.5.1.1 Moisture Barrier Films
Oriented poly(propylene) (OPP) is known for its inherent moisture barrier
properties. However, certain applications require even greater resistance to
water vapor transmission to increase the shelf life of the packed material.
The incorporation of terpene polymers at low levels in high crystallinity
poly(propylene) provides a product film having significantly improved
moisture barrier properties. The addition of a terpene polymer increases
the extent of amorphous orientation in the stretching of the poly-
(propylene), thereby restricting the diffusion of water molecules. 3 Terpene
polymers can also be added to poly(propylene) film materials to improve
the heat seal properties.
12.5.2 Pressure-sensitive Adhesives
Pressure-sensitive adhesives are used for adhesive tapes and labels. The
substrates include paper, polyvinyl chloride, polyester, poly(propylene), or
cellophane. 22
Pressure-sensitive adhesives (PSA) can be prepared via hot melts,
solvents, and waterborne systems. In solvent-containing systems, formulations
with a high content of solid material are possible, requiring a
minimum solvent recovery. Mixtures of polyterpene resins with different
molecular weights can be used to establish the desired adhesive properties.
12.5.2.1 Hot-melt Extrusion
The production of PSA via hot-melt extrusion methods is the preferred
route. The corresponding rubber is a styrene isoprene rubber or a styrene
butadiene rubber. These block copolymers are elastomers, but become
thermoplastic upon heating.
12.5.2.2 Waterborne Systems
For waterborne applied systems, the structural polymer and the tackifying
resin must be supplied as dispersion. No solvent recovery system is
necessary. For waterborne systems, the manufacture via rosin esters is easier
than the emulsification of polyterpene resins. For carboxylated styrene

Terpene Resins 461
butadiene rubber, pure polyterpenes are suitable. For neoprene and acrylic
rubbers, terpene phenol polymers are used.
12.5.2.3 Styrene-isoprene Block copolymers
Poly(styrene-b-isoprene-b-styrene) (SIS)/tackifier resin blends show a
lower critical solution temperature phase transition at around 150°C and an
upper critical solution temperature phase transition at around 200°C. The
properties of the pressure-sensitive adhesive in SIS/tackifier resin blends
change with the annealing temperature. 23
12.5.3 Polyacrylate Hot-melt Pressure-sensitive Adhesives
For industrial pressure-sensitive adhesive (PSA) tape applications it is very
common to use polyacrylate PSAs. Polyacrylates possess a variety of advantages
over other elastomers. They are highly stable toward UV light,
oxygen, and ozone. Synthetic and natural rubber adhesives normally contain
double bonds, which make these adhesives unstable to environmental
effects. Further advantages of polyacrylates include their transparency and
their serviceability within a relatively wide temperature range.
Polyacrylate PSAs are generally prepared in solution by free-radical
polymerization. A variety of polymerization methods are suitable for
preparing low molecular mass PSAs. Chain transfer agents, such as alcohols
or thiols, can be used. These chain transfer agents reduce the molecular
weight and broaden the molecular weight distribution.
Another controlled polymerization method is that of atom transfer
radical polymerization (ATRP). The initiators include monofunctional or
difunctional secondary or tertiary halides and, for abstracting the halides,
complexes of certain metals. However, the metal catalysts have the side
effect of adversely influencing the aging of the PSAs (gelling, transesterification).
Unfortunately, the majority of metal catalysts are toxic, discolor
the adhesive, and can be removed from the polymer only by means
of complicated precipitations. Another method is to use a nitroxide-controlled
polymerization process. It is possible to realize high conversions in
combination with high molecular weight and low polydispersity.
In order to increase the cohesion, the polymer is crosslinked. Curing
takes place thermally, by UV crosslinking, or by electron beam curing.
The polyacrylates are normally applied to the corresponding backing
material from solution using a coating bar, and then dried. However,

462 Reactive Polymers Fundamentals and Applications
it is difficult to produce PSA tapes with a high adhesive application rate,
without bubbles. One solution to overcome this disadvantage is the hotmelt
process. In this process, the PSA is applied to the backing material
from the melt.
Polyacrylate hot-melt pressure-sensitive adhesives with copolymerized
photoinitiators and with a narrow molecular weight distribution can
be processed very effectively in a melt process and can be crosslinked very
efficiently by UV crosslinking. 24 For the use of the polymers as pressure-sensitive
adhesives, they are optimized by blending with tackifying
resins. Tackifying resins include pinene resins, indene resins, and rosins,
and derivatives.
12.5.4 Hot-Melt Adhesives
Hot-melt adhesives are commonly used in bookbindery, for the manufacture
of packaging, for coatings, diapers, other sanitary products, and tapes.
Due to their properties, polyterpene resins are ideal materials for the formulation
of hot melt systems.
They are compatible with many structural polymers and they exhibit
a high softening point together with a low melt viscosity. Therefore,
upon melting, a low viscous mixture with the structural polymer is formed.
Therefore, polyterpene resins are considered as the best modifiers to improve
the tack and adhesion of elastomeric systems. Limonene polymers
have a good hot tack performance. Most commonly used hot-melt mixtures
are EVA (or block copolymers), resin tackifier, and wax blends.
Most commercially available hot melt adhesives require temperatures
of above 180°C to ensure complete melting of all the components
and also to achieve a satisfactory application viscosity. Adhesive formulations
that can be applied at temperatures below 120°C are prepared using
low molecular weight components or a high wax content, however, the
application viscosity and adhesive properties suffer.
Softer or more amorphous components may be added in order to
improve adhesion. However, these components reduce the effective heat
resistance.
Modified rosins and modified terpenes, having a molecular weightto-softening
point ratio of less than about 10, when used as tackifier alone
or in combination, in a hot melt provide adhesives that can be applied at
low temperature and exhibit high heat resistance and good cold resistance.

Terpene Resins 463
A modified rosin or terpene is a phenolic-modified resin. 25 The molecular
weight-to-softening point ratio is the molecular weight of the modified
rosin or modified terpene in Dalton divided by its softening point in °C.
12.5.5 Coatings
Thermoplastic resin compositions consisting of a poly(phenylene ether)
(PPE) and polyamide (PA) resin show outstanding properties that make
them well suited for inline coating. They also find extensive use in external
automobile components. They are used with paints such as acrylic
urethane paint, acrylic amino paint, and polyester polyol paint, but these
paints do not show sufficient adhesion to the PPE/PA resin composition,
and when they are used for direct coatings, peeling of the coating film may
occur. For this reason, the main method used is to first apply a coat of
primer to the molded product, followed by a finish coat. However, with
the tendency towards cutting costs, attitudes towards coatings tend to shift
toward the primerless approach, and there is a changeover toward thinner
coating films.
When a specified terpene phenol resin is added to a PPE/PA resin
composition, the coating film adhesion of the composition can be considerably
improved. 26
The terpene phenol resin must have a hydroxyl value of 50 or greater.
If the hydroxyl value is too low, the adhesion will be poor. For example,
a suitable terpene phenol resin is a copolymer of limonene and phenol or
copolymer of α-pinene and phenol. It has an average molecular weight of
700 Dalton, a softening point of 120 to 150°C, and a hydroxyl value of 50
to 130 mgKOH/g.
12.5.6 Sizing Agents
Sizing agents are used by the paper industry to give paper and paperboard
some degree of resistance to wetting and penetration by aqueous liquids.
There are two basic categories of sizing agents: acid and alkaline. Acid
sizing agents are intended for use in acid papermaking systems, traditionally
less than pH 5. Analogously, alkaline sizing agents are intended for
use in alkaline papermaking systems, typically at a pH greater than 6.5.
Most acid sizing agents are based on rosin. The development of
sizing with a rosin-based size is dependent upon its reaction with papermaker’s
alum, Al 2 (SO 4 ) 3 × 14 − 18H 2 O. Since aluminum species that ex-

464 Reactive Polymers Fundamentals and Applications
ist predominantly at a low pH (< pH 5) are required for the appropriate
interactions needed to effect sizing, rosin and alum have been used primarily
in acid papermaking systems.
It has been shown that, by proper selection of addition points in the
papermaking system. By using cationic dispersed rosin sizes, rosin-based
sizes can be used in papermaking systems up to about pH 7, thus extending
the range of acid sizes. However, due to the limitations imposed by alum
chemistry, the efficiency of rosin-based sizes decreases above about pH
5.5. 8
12.5.6.1 Alkaline Sizing
Sizing agents developed for papermaking systems above pH 6.5 are generally
based on alkylketene dimer (AKD) or alkenyl succinic anhydride
(ASA).
Alkylketene dimer. Sizes based on alkylketene dimer (AKD) form covalent
bonds with cellulose to give proper orientation and anchoring of the
hydrophobic alkyl chains. This covalent bond formation makes AKD sizing
very efficient and resistant to strong penetrants. However, AKD sizes
have some limitations: small changes in the amount of size added can lead
to large differences in sizing (steep sizing response curve), and there is a
slow rate of sizing development (cure).
Alkenyl succinic anhydride. The other major alkaline sizing agent is
based on ASA. As with AKD, the development of sizing with ASA sizes
is also dependent on the formation of covalent bonds with cellulose to give
proper orientation and anchoring. ASA is more reactive than AKD, resulting
in a greater sizing effect. However, the reaction rate with water is
also greater, producing a hydrolyzate that is an inefficient sizing agent in
alkaline systems. It also contributes to the formation of deposits on the
papermaking machine. To minimize the formation of hydrolyzate, ASA is
typically emulsified at the mill immediately before addition to the papermaking
system.
Cationic resins. Cationic resins have been used in the papermaking process.
8 Sizing of paper can be done with an aqueous emulsion of a partially
saponified terpene resin, 1 to 5% alum, and optionally a partially saponified

Terpene Resins 465
rosin. Sizing in the absence of alum is achieved with an aqueous dispersion
of fortified rosin, a hydrocarbon resin and a vinyl imidazoline polymer as a
retention aid. Another sizing composition for paper comprises an aqueous
dispersion of partially neutralized rosin, a terpene polymer, and 1 to 5%
aluminum sulfate.
The addition of a cationic polyamine resin is used to anchor the rosin
to the paper pulp. The cationic polyamine resin is of the type polyalkyleneamine-epihalohydrin
resin. 8 High levels of size or cationic resin cause
no significant reduction in the papers coefficient of friction.
12.5.7 Toner Compositions
Toner compositions containing copolymers based on styrene and myrcene
can be synthesized by an anionic polymerization process. The reaction
needs dried reagents. A resin was obtained with a T g of 60°C, with M n of
36 kDalton and M w of 64 kDalton. Charge additives are quaternary ammonium
bisulfates and distearyl methyl hydrogen ammonium bisulfate. 27
12.5.8 Chewing Gums
In general, chewing gums and bubble gums utilize as their gum base a combination
of natural or synthetic elastomers. Preferably, polymers of limonene
or other dipentenes with rosin-glycerol esters are used in the formulation
of chewing gums. The gum base that is selected provides the chewing
gum with its masticatory properties. A chewing gum base is normally admixed
with sugars or synthetic sweeteners, perfumes, flavors, plasticizers,
and fillers. Then it is milled and formed into sticks, sheets, or pellets.
Cottonseed oil is sometimes also added to give the gum softness.
Styrene butadiene rubber (SBR) is a synthetic elastomer that is widely used
as a gum base in chewing gums. However, SBR is not widely used in manufacturing
soft chew gums because it lacks the desired physical properties.
Poly(isobutylene) is widely used in manufacturing soft chew gums even
though it is much more expensive than SBR.
In any case, chewing gum compositions are typically comprised of
a water soluble bulk portion, a water insoluble chewing gum base portion
and typically water insoluble flavoring agents. The water soluble portion
dissipates with a portion of the flavoring agent over a period of time during
chewing. The gum base portion is retained in the mouth throughout the
chewing process.

466 Reactive Polymers Fundamentals and Applications
The gum base includes a number of ingredients that are subject to
deterioration through oxidation during storage. The insoluble gum base
is generally comprised of elastomers, elastomer plasticizers, waxes, fats,
oils, softeners, emulsifiers, fillers, texturizers and miscellaneous ingredients,
such as antioxidants, preservatives, colorants, and whiteners.
The compounds containing carbon-carbon double bonds, such as
fats, oils, unsaturated elastomers, and elastomer plasticizers are susceptible
to oxidation. The gum base commonly contains 15 to 35% by weight
of the chewing gum.
In chewing gum base natural or artificial antioxidants are utilized to
stabilize the rubbery polymer. For instance, β-carotenes, acidulants (e.g.,
Vitamin C), propyl gallate, BHA, and BHT are commonly used to stabilize
the rubber used in manufacturing chewing gum. Such antioxidants are
included in the chewing gum base as a stabilizer to inhibit oxidation.
Antioxidants are widely used in food products susceptible to degeneration,
in one form or another, due to oxidation. Commercial applications
include use in processed meat and poultry, salad dressings, seasonings,
snacks, nuts, soup bases, edible fats and oils, natural foods, pet foods, and
packaging. In addition to foods, antioxidants have been used to prevent
oxidation in various cosmetic and toiletry products and in pharmaceutical
preparations. The primary purpose in each of these applications is to
prevent deterioration of desirable product characteristics by inhibiting oxidation.
12.6 SPECIAL FORMULATIONS
12.6.1 Toughener for Novolaks
There is considerable technical interest in hydrophobically substituted, but
nevertheless crosslinkable and grindable novolaks, since they have considerably
better compatibility with hydrophobic substrates. In addition, it
is desirable to control the crosslinking rate of novolak/crosslinking agent
mixtures at a given temperature. It is furthermore desirable to reduce the
high brittleness of the crosslinking products of novolaks.
These difficulties can be overcome by means of modified novolaks
which contain, as modifying components, terpenes and unsaturated carboxylic
acids or derivatives of these compounds.
Phenols that have at least one free ring hydrogen atom in the orthoor
para-position can be substituted to the phenolic hydroxyl group with

Terpene Resins 467
terpenes in the presence of Lewis or protonic acids. This gives low-molecular-weight
synthetic resins which have a relatively high melting point, but
cannot be crosslinked. However, if a significant number of phenolic hydroxyl
groups is still present after the reaction, terpene modified resins can
be subjected to crosslinking reactions. 28
12.6.2 Fluoro Copolymers
A more uniform copolymer with a narrower molecular weight distribution
for improved flex life can be obtained by the copolymerization of tetrafluoroethylene
(TFE) and perfluoro (alkyl vinyl ether) (PAVE) in the presence
of a terpene in an aqueous polymerization medium.
This produces a melt-fabricable TFE/PAVE copolymer (PFA) having
a uniformly distributed PAVE. The small amount of terpene added to the
polymerization system does not decrease the rate of polymerization, but
is present in an amount that is effective for improving the uniformity of
the resin by narrowing the molecular weight distribution, i.e., in the ppm
range. 29
REFERENCES
1. É. A. L. Rouxeville. Treatment of hydrocarbons. US Patent 919 248, April
20 1909.
2. É. A. L. Creuzillet, Pauline Adrienneand Rouxeville. Procédé de polymérisation
de l’essence de térébenthine. FR Patent 639 726, June 28 1928.
3. M. T. Heffelfinger, J. K. Keung, and R. G. Peet. High moisture barrier opp
film containing high crystallinity polypropylene and terpene polymer. US
Patent 5 500 282, assigned to Mobil Oil Corporation (Fairfax, VA), March 19
1996.
4. J. J. W. Coppen and G. A. Hone. Gum Naval Stores. Turpentine and Rosin
from Pine Resin, volume 2 of Nonwood forest products. Food and Agriculture
Organization of the United Nations, Rome, 1995.
5. R. P. F. Guine and J. A. A. M. Castro. Polymerization of β-pinene with ethylaluminum
dichloride (C 2 H 5 AlCl 2 ). J. Appl. Polym. Sci., 82(10):2558–2565,
December 2001.
6. L. B. Barkley and A. B. Patellis. Polymerizing unsaturated cyclic hydrocarbons
using as catalysts AlCl 3 + R 3 SiX. US Patent 3 478 007, assigned to
Pennsilvania Industrial Chemical Corporation, November 11 1969.
7. I. B. Dicker. Catalyst for group transfer polymerization. US Patent 4 866 145,
assigned to E. I. Du Pont de Nemours and Company (Wilmington, DE),
September 12 1989.

468 Reactive Polymers Fundamentals and Applications
8. S. M. Ehrhardt and D. B. Evans. Rosin/hydrocarbon resin size for paper.
US Patent 6 273 997, assigned to Hercules Incorporated (Wilmington, DE),
August 14 2001.
9. J. Salvetat and R. Wind. Resinous copolymer comprising monomer units of
each of the groups of phenol compounds and olefinically unsaturated nonacidic
terpene compounds. US Patent 5 844 063, assigned to Arizona Chemical,
S.A. (Niort, FR), December 1 1998.
10. B. Lahourcade and G. Bonneau. Process for the preparation of terpenephenol
resins by three-stage reaction of phenol with carene using Friedel-
Crafts or Lewis acid catalyst. US Patent 4 056 513, assigned to Les Derives
Resiniques et Terpeniques (Dax, FR), November 1 1977.
11. S. F. Wang, T. Furuno, and Z. Cheng. Studies on the synthesis and properties
of terpene-phenol-aldehyde resin with a high softening point. J. Wood Sci.,
46(2):143–148, 2000.
12. R. P. Scharrer, K. L. Thompson, and J. M. Rosen. Low softening point
terpene-phenol resins. US Patent 5 457 175, assigned to Arizona Chemical
Company (Panama City, FL), October 10 1995.
13. K. L. Thompson and A. K. Deshpande. Method for making modified terpenephenol
resins. US Patent 6 160 083, assigned to Arizona Chemical Company
(Panama City, FL), December 12 2000.
14. R. W. Schluenz and C. B. Davis. Resinous terpene maleimide and process
for preparing the same. US Patent 4 080 320, assigned to Arizona Chemical
Company (Wayne, NJ), March 21 1978.
15. J. H. Hildebrand and R. L. Scott. The Solubility of Nonelectrolytes. Dover,
New York, 1964. Reprint of the 3rd (1950) edition published by Reinhold.
16. M. L. Barrueso-Martinez, T. P. Ferrandiz-Gomez, C. M. Cepeda-Jimenez,
J. Sepulcre-Guilabert, and J. M. Martin-Martinez. Influence of the vinyl acetate
content and the tackifier nature on the rheological, thermal, and adhesion
properties of EVA adhesives. J. Adhes. Sci. Technol., 15(2):243–263, 2001.
17. A. Kato, H. Hiraoka, M. Yokota, and S. Iwami. Golf ball. US Patent
6 608 127, assigned to Sumitomo Rubber Industries, Ltd. (Hyogo, JP), August
19 2003.
18. A. F. M. Barton. CRC Handbook of Solubility Parameters and Other Cohesion
Parameters. CRC Press, Boca Raton, FL, 2nd edition, 1991.
19. A. Barton. States of Matter, States of Mind. Inst. of Physics Publ., Bristol,
1997.
20. F. Cataldo. Thermal depolymerization and pyrolysis of cis-1,4-polyisoprene:
preparation of liquid polyisoprene and terpene resin. J. Anal. Appl. Pyrolysis,
44(2):121–130, January 1998.
21. S. Cimmino, E. D’ Alma, E. Ionata, F. La Cara, and C. Silvestre. Biodegradability
study on films for packaging based on isotactic polypropylene modified
with natural terpene resins. In H. Insam, N. Riddech, and S. Klam-

Terpene Resins 469
mer, editors, Microbiology of Composting, pages 265–272. Springer-Verlag,
Berlin, 2002.
22. D. Satas, editor. Handbook of Pressure Sensitive Adhesive Technology. Satas
& Associates, Warwick, RI, 3rd edition, 1999.
23. S. Akiyama, Y. Kobori, A. Sugisaki, T. Koyama, and I. Akiba. Phase behavior
and pressure sensitive adhesive properties in blends of poly(styreneb-isoprene-b-styrene)
with tackifier resin. Polymer, 41(11):4021–4027, May
2000.
24. M. Husemann and S. Zollner. UV-crosslinkable acrylic hotmelt PSAs with
narrow molecular weight distribution. US Patent 6 720 399, assigned to tesa
AG (Hamburg, DE), April 13 2004.
25. D. L. Haner, B. Carillo, and J. Mehaffy. Hot melt adhesive composition.
US Patent 6 593 407, assigned to National Starch and Chemical Investment
Holding Corporation (New Castle, DE), July 15 2003.
26. T. Ohtomo, K. Myojo, and H. Kubo. Compositions of polyphenylene ether
and polyamide resins containing terpene phenol resins. US Patent 5 554 693,
assigned to General Electric Company (Pittsfiled, MA), September 10 1996.
27. M. K. Georges, N. A. Listigovers, S. V. Drappel, M. V. McDougall, and
G. R. Allison. Toner compositions with styrene terpene resins. US Patent
5 364 723, assigned to Xerox Corporation (Stamford, CT), November 15
1994.
28. W. Hesse, E. Leicht, and R. Sattelmeyer. Modified novolak terpene products.
US Patent 5 096 996, assigned to Hoechst Aktiengesellschaft (DE), March 17
1992.
29. T. Iwasaki and M. Kino. Process for manufacture of a copolymer of tetrafluoroethylene
and perfluoro (alkyl vinyl ether). US Patent 6 586 546, assigned
to DuPont-Mitsui Fluorochemicals Co. Ltd. (Tokyo, JP), July 1 2003.

13
Cyanoacrylates
Cyanoacrylates were commercially introduced in 1950 by Tennesee Eastman
Company. Cyanoacrylate adhesives are monomeric adhesives. They
are generally quick-setting materials which cure to clear, hard glassy resins,
useful as sealants, coatings, and particularly adhesives for bonding
together a variety of substrates. 1 Polymers of alkyl 2-cyanoacrylates are
also known as superglues.
13.1 MONOMERS
13.1.1 Synthesis
In 1895 Auwers and Thorpe 2 attempted to synthesize diethyl-2,2-dicyanoglutarate
(Figure 13.1) by base-catalyzed condensation of aqueous formaldehyde
and ethyl cyanoacetate. They isolated a mixture of oily oligomers
and an amorphous polymer of higher molecular weight.
CH 2
CN
C
C O
O
R
R
H
O
CN
C CH 2
C
O
CN
C H
C O
O
R
Figure 13.1: 2,4-Dicyanoglutaric Acid Ester
471

472 Reactive Polymers Fundamentals and Applications
CH 2
O
+
H
CN
C H
C O
O
R
-H 2 O
CH 2
CN
C
C O
O
R
Figure 13.2: Synthesis of Cyanoacrylates: Knoevenagel Reaction
In fact ethyl 2-cyanoacrylate monomer was synthesized as an intermediate,
which underwent an immediate polymerization reaction. The
condensation of formaldehyde with cyanoacetate is still the most important
method for the commercial production of the monomers, c.f. Figure 13.2.
The reaction mechanism takes place as a base-catalyzed Knoevenagel condensation
of cyanoacetate and formaldehyde to give an intermediate 2-substituted
methylol derivative.
A. E. Ardis 3 at B.F. Goodrich (in 1947), found that the polymer-oligomer
mixture obtained in the formaldehyde-cyanoacetate condensation
reaction could be thermally depolymerized with acid catalysts. However,
the monomer prepared by utilizing these methods was unstable and the
yields were low. Later 4 it was realized that the water is responsible for
polymerization. Instead of aqueous formaldehyde, paraformaldehyde was
used with an organic solvent to remove the water by azeotropic distillation.
The stability of the monomer can be enhanced by the redistillation of
the crude monomer in the presence of small quantities of acidic stabilizers,
e.g., sulfur dioxide.
Several other methods for cyanoacrylate monomer production have
been described, including the pyrolysis of 3-alkoxy-2-cyanopropionates, 5
transesterification of ethyl 2-cyanoacrylate, 6 and displacement of cyanoacrylate
monomer from its anthracene Diels-Alder adduct by treatment
with maleic anhydride. This last method is used for the synthesis of monomers
that are not accessible or may be difficult to prepare by the retropolymerization
route, for example, difunctional cyanoacrylates, 7 thiocyanoacrylates,
8 and perfluorinated monomers.
13.1.2 Crosslinkers
To improve the cohesive strength, difunctional monomeric crosslinking
agents may be added to the monomer compositions. These include alkyl

Compound
Cyanoacrylates 473
Table 13.1: Commercially Available Cyanoacrylates
Remarks
Methyl cyanoacrylate Strongest bonding to metals, good stability
against solvents
Ethyl cyanoacrylate General purpose
Allyl cyanoacrylate > 100°C service temperature
n-Butyl cyanoacrylate Flexible, medical applications 9
Isobutyl cyanoacrylate Medical applications 9
2-Octyl cyanoacrylate Medical applications9, 10
2-Methoxyethyl cyanoacrylate
Weak odor
2-Ethoxyethyl cyanoacrylate Weak odor
2-Methoxy-1-methylethyl Weak odor
cyanoacrylate
CH 2
CN
C
C O
R
CH 2
CN
C
C O
R
n
O
O
Figure 13.3: Basic Structure of Cyanoacrylate Monomers and Polymers
bis(2-cyanoacrylates), triallyl isocyanurates, alkylene diacrylates, alkylene
dimethacrylates, 1,1,1-trimethylolpropane triacrylate, and alkyl bis-
(2-cyanoacrylates). 11
13.1.3 Commercial Products
Commercial products consist mainly of monofunctional monomers. Commonly
encountered monomers are shown in Table 13.1. The monomers
are usually low-viscosity liquids with excellent wetting properties. The
basic structure of cyanoacrylate monomers and polymers is shown in Figure
13.3. The syntheses of the monomers and the raw materials are shown
in Figures 13.4 and 13.5. Because of the high electronegativity of the
nitrile group and the carboxylate groups, they undergo rapid anionic polymerization
on contact with basic catalysts. The anionic polymerization is
facilitated by the possibility of resonance structures as shown in Figure
13.6. The polymers formed in this way exhibit high molecular weights,
usually more than 10 6 Dalton.

474 Reactive Polymers Fundamentals and Applications
CN
CH 2
O
H
C
H
+ +
C O R
N
O
H
-H2O
N
CN
CH 2 C H
C O R
O
CH 2
CN
C
C O
O
R
Figure 13.4: Synthesis of Cyanoacrylates: Mannich Reaction
Cl
C
H
Cl
C
Cl
H 2 O
Cl 2
CH 3
C
O
O
H
Cl
CH 2
C
O
H
O
Figure 13.5: Synthesis of Chloro acetic acid

Cyanoacrylates 475
Y - +
CH 2
CN
C
C O
O
R
Y
CH 2
C -
CN
C O
O
R
Y
CH 2
C
C
C
O -
N
O
R
Y
CH 2
C -
N
C
C O
O
R
Figure 13.6: Resonance Structures of the Growing Anions
13.2 SPECIAL ADDITIVES
13.2.1 Plasticizers
Adhesives based on cyanoacrylate esters are effective bonding agents for
a wide variety of materials, but do not give a permanent bond in joints involving
glass. A strong bond to glass is obtained initially but generally the
joint fails after a period of weeks or months at room temperature conditions.
The extremely rapid curing rate on glass caused by the basic nature
of the surface is responsible for high stresses that are generated in the bond
line immediately adjacent to the glass, at a molecular level. These stresses
make the polymer in the bond line uniquely susceptible to chemical or
physical degradation. 12
Cyanoacrylate adhesive bonds also tend to be relatively brittle; therefore,
the adhesive compositions are often plasticized. 13 Typical plasticisers
include various alkyl esters and diesters and alkyl and aromatic phosphates
and phosphonates, diallyl phthalates and aryl and diaryl ethers. Plasticisers
are summarized in Table 13.2
For glass bonding, dibutyl phthalate is a suitable plasticizer in n-
butyl cyanoacrylate. 12 The glass bonds were tested for durability by subjecting
them to a sequence of washing cycles in a domestic dishwasher.
The results shown in Table 13.3. suggest that the bond strength decreases
with increasing proportions of plasticizer. Levels greater than about 40%
result in bonds of reduced strength. The concentration of plasticizer needed

476 Reactive Polymers Fundamentals and Applications
Table 13.2: Plasticizers 11
Compound
Dioctyl phthalate
Dimethyl sebacate
Triethyl phosphate
Tri(2-ethylhexyl)phosphate
Tri(p-cresyl)phosphate
Glyceryl triacetate
Glyceryl tributyrate
Diethyl sebacate
Dioctyl adipate
Isopropyl myristate
Butyl stearate
Lauric acid
Dibutyl phthalate
Trioctyl trimellitate
Dioctyl glutarate
Table 13.3: Durability of Bonds to Glass with Various Amounts of Plasticizer
12 Dibutyl phthalate [%] Bond Strength N/mm 2 Durability a
0 2.70 5
10 3.20 3
20 3.20 5
25 1.94 5
30 2.46 50
40 1.86 90
50 0.80 90
60 0.32 20
70 0.08 10
a No. of Dishwasher Cycles

Cyanoacrylates 477
for good durability is about 30% to 50%.
13.2.2 Accelerators
The esters of 2-cyanoacrylic acid are also commonly called quick-set adhesives,
since they generally harden after a few seconds when used or the
joined parts exhibit at least a certain degree of initial strength. However,
in the case of some substrates, especially acidic substrates such as wood or
paper, the polymerization reaction may be very greatly delayed.
Acidic materials exhibit a pronounced tendency to draw the adhesive,
which is often highly liquid, out of the joint gap by capillary action
before hardening has taken place in the gap.
Even in cases in which, for reasons of geometry, the adhesive must
be applied in a relatively thick layer in the joint gap or in cases where
relatively large amounts of adhesive are applied and relatively large drops
of adhesive protrude from between the parts to be joined, rapid hardening
throughout may rarely be achieved. 14
Therefore, attempts have been made to accelerate the polymerization
for such applications by means of certain additives. The methods used may
roughly be divided into three categories:
• Addition of accelerators directly to the adhesive formulation. This
is possible to only a very limited extent, however, since substances
having a basic or nucleophilic action, which would normally
bring about a pronounced acceleration of the polymerization
of the cyanoacrylate adhesive, are generally used at the expense of
the storage stability of such compositions.
• The second common method is the addition of the accelerators
shortly before application of the adhesive in virtually a two-component
system. However, such method has the disadvantage that
the working life is limited after the activator has been mixed in. In
addition, with the small amounts of activator that are required, the
necessary accuracy of metering and homogeneity of mixing are
difficult to achieve.
• A third process is the use of activators in the form of a dilute solution.
The solution is either sprayed onto the parts before they
are bonded onto the places where the adhesive is still liquid after
the substrates have been joined. The solvents used for such dilute
solutions of activators are generally low-boiling organic solvents.

478 Reactive Polymers Fundamentals and Applications
R 1
(CH 2 CH 2 O)n Si O
R 2
n = 4..10
Figure 13.7: Silacrown ethers 15
Cure accelerators include crown ethers, calixarene compounds, silacrown
compounds, and amines.
13.2.2.1 Silacrown Compounds
Silacrown compounds as additives give substantially reduced fixture and
cure times on wood and other deactivating surfaces such as leather, ceramic,
plastics and metals with chromate treated or acidic oxide surfaces.
Silacrown accelerators have significantly lower reported acute toxicity
than the crown ether compounds. The lower observed toxicity of
silacrowns in comparison to crown-ethers may be related to the hydrolytic
instability of the Si-O-C linkage. Thus, while the silacrown ring is stable in
the cyanoacrylate composition, it will open up in biological environments,
reducing both acute and chronic risk. 16
Silacrowns are prepared by transesterification of alkoxysilanes with
poly(ethylene glycol)s, i.e., they are reaction products of silanes but are not
themselves silanes. Silacrown compounds are commercially available and
are reportedly readily synthesized in good yield. 15–18 Silacrown ethers are
shown in Figure 13.7.
13.2.2.2 Calixarenes
Cyanoacrylate adhesive compositions that employ calixarene compounds
as additives give substantially reduced fixture and cure times on wood and
other deactivating surfaces such as leather, ceramic, plastics and metals
with chromate-treated or ceramic oxide surfaces. 19–21

Cyanoacrylates 479
N
S
S
N
HOOC
N
S
S
N
COOH
N
N
S
S
N
N
Figure 13.8: 2,2 ′ -Dipyridyl disulfide, 6,6 ′ -Dithiodinicotinic acid and Bis(4-tertbutyl-1-isopropyl-2-imidazolyl)disulfide
13.2.2.3 Amines
Solutions of lower fatty amines, aromatic amines, and dimethylamine are
used that are sprayed on the surface before the cyanoacrylate is applied, or
at the same time. Examples are N,N-dimethylbenzylamine, N-methylmorpholine,
and N,N-diethyltoluidine.
N,N-Dimethyl-p-toluidine, when subsequently applied to the joined
parts, causes even relatively large amounts of adhesive to harden within
seconds. The poly(cyanoacrylate) so formed is completely free of turbidity.
Disadvantages are the very high volatility of the substance, which does
not permit long waiting times between the application of the accelerator
solution to the substrates to be bonded and the subsequent bonding process.
The compound is also toxic. 14
13.2.2.4 Disulfides
Examples of disulfides are dibenzodiazyl disulfide, 6,6 ′ -dithiodinicotinic
acid, 2,2 ′ -dipyridyl disulfide, or bis(4-tert-butyl-1-isopropyl-2-imidazolyl)disulfide,
14 c.f. Figure 13.8.The disulfides have a good accelerating
action, but they nevertheless permit a long waiting time between application
of the activator and application of the adhesive. In addition, they avoid
spontaneous, merely superficial hardening.

480 Reactive Polymers Fundamentals and Applications
Compound
Table 13.4: Thickeners
Reference
Fumed silica
16
Poly(cyanoacrylate)
11
Poly(lactic acid)
11
Poly(glycolic acid)
11
Lactic-glycolic acid copolymers
11
Poly(ε-caprolactone)
11
Poly(3-hydroxybutyric acid)
11
Polyorthoesters
11
Polyacrylates
11
Polymethacrylates
11
13.2.3 Thickeners
Thickeners are added to increase the viscosity of 2-cyanoacrylate adhesive
compositions. The 2-cyanoacrylate monomer generally has a low viscosity
of several centipoise, and, therefore, the adhesive penetrates into porous
materials such as wood and leather or adherents with a rough surface.
Thus, good adhesion bond strengths are difficult to achieve. Thickeners are
summarized in Table 13.4.
Various polymers can be used as thickeners, and examples include
poly(methyl methacrylate), methacrylate-type copolymers, acrylic rubbers,
cellulose derivatives, poly(vinyl acetate), and poly(2-cyanoacrylate). A
suitable amount of thickener is generally about 20% by weight or less
based on the total weight of the adhesive composition.
Fumed silica for use as thickener is treated with poly(dialkylsiloxane)
or trialkoxyalkylsilanes. 16 The purpose of the silane which is retained
on the surface of the silica is to maintain the fumed silica in a dispersion
within the composition.
13.2.4 Stabilizers
Stabilizers have to be added both for the production and for storage. The
stabilizer systems are added so that no polymerization would occur during
transportation and storage in sealed drums, even at elevated temperatures
and after long periods.
After application polymerization occurs immediately. Accordingly,
besides radical polymerization inhibitors, inhibitors against anionic poly-

Compound
Table 13.5: Stabilizers
Cyanoacrylates 481
Reference
Sulfur dioxide
11
6-Hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonic acid
11
Lactone
11
Boron trifluoride
11
Hydroquinone
11
Catechol
11
Pyrogallol
11
p-Benzoquinone
11
2-Hydroxybenzoquinone
11
p-Methoxyphenol
11
tert-Butyl catechol
11
Organic acid
11
Butylated hydroxy anisole
11
Butylated hydroxy toluene
11
tert-Butyl hydroquinone
11
Alkyl sulfate
11
Alkyl sulfite
11
3-Sulfolene
11
Alkylsulfone
11
Alkyl sulfoxide
11
Mercaptan
11
Alkyl sulfide
11
Dioxathiolanes
22
merization are generally added to cyanoacrylate adhesives. Stabilizers are
summarized in Table 13.5.
A typical stabilizer to prevent radical polymerization is hydroquinone.
Boron trifluoride prevents anionic polymerization.
13.2.4.1 Acidic Cation Exchanger
It has been proposed to add a strongly acidic cation exchanger as inhibitor.
Cation exchangers are based on crosslinked poly(styrene)-containing sulfonic
acid groups.
The disadvantage of this approach is that the ion exchanger added
can easily impede the outflow of the adhesive and that, as a solid, it does
not act throughout the entire volume of the adhesive.

482 Reactive Polymers Fundamentals and Applications
13.2.4.2 Acid Groups on Container Walls
It has been proposed to modify the surface of storage containers for cyanoacrylate
adhesives in such a way that they contain acid groups. 23 Although
this proposal can be successfully implemented, it is afflicted by the problem
that the inhibition occurs in the vicinity of the container wall.
13.2.4.3 Sulfur Compounds
Sulfur Dioxide. Another method of stabilizing cyanoacrylate adhesives
is to add sulfur dioxide as an inhibitor. Although this measure has been
successfully applied in practice, it is important to bear in mind that sulfur
dioxide is a gaseous substance and that uniform addition is difficult so that
quality variations can occur. In addition, sulfur dioxide can escape from
the adhesive containers by diffusion during storage.
Dioxathiolanes. Cyclic organic sulfates, sulfites, sulfoxides, sulfinates,
for example, 2-oxo-1,3,2-dioxathiolanes, act in raising the ceiling temperature
and hence to improve the thermal stability of the adhesives. 22
4,5-Dimethyl-2-oxo-1,3,2-dioxathiolane is a liquid with a boiling
point of 185°C. This is an inhibitor for the anionic polymerization and
should be effective throughout the entire volume of the adhesive. It could
be added more uniformly and more easily than gases. In addition, the discoloration
of the adhesive during storage is prevented. 24
13.2.5 Primers
It is well known in the adhesive field that there are plastic substrates made
from certain types of plastic materials which are extremely difficult to
bond. Such difficult-to-bond materials include low surface energy plastics
such as poly(ethylene) and poly(propylene) and highly crystalline materials
such as polyacetals and poly(butylene terephthalate). As a consequence
of the difficulty in bonding substrates made from these plastics materials
with adhesives, various surface treatments have been employed where such
materials require bonding. Examples of such surface treatments include
corona discharge exposure of the substrate surface, acid etching, plasma
treatment, etc. However, these methods are clearly not applicable to the
bonding of plastic substrates in the domestic or household areas. Alternatively,
various primer compositions have been developed which are de-

Compound
Table 13.6: Primers
Cyanoacrylates 483
Reference
n-Octylamine
25
1,5-Diazabicyclo[4.3.0]non-5-ene
26, 27
1,8-Diazabicyclo[5.4.0]undec-7-ene
26, 27
1,5,7-Triazabicyclo[4.4.0]dec-5-ene
26, 27
Tetra-n-butyl ammonium fluoride
28, 29
Tributylphosphine
30
N,N,N ′ ,N ′ -Tetramethylethylene diamine
31
N,N,N ′ ,N ′ -Tetraethylethylene diamine
32
N,N,N ′ ,N ′ -Tetramethyl-1,3-butane diamine
31
N,N-Dimethyl-N ′ ,N ′ -di(2-hydroxypropyl)-1,3-propane diamine
31
N-2-Aminoethyl-3-aminopropyl-tris(2-ethylhexoxy)silane
31
Imidazole derivatives
33
2-Phenyl-2-imidazoline
33
Organometallic compounds
34
Manganese(III)acetylacetonate
34
N
N
H
N
N
N
N
N
Figure 13.9: 1,5-Diazabicyclo[4.3.0]non-5-ene, 1,8-Diazabicyclo[5.4.0]undec-7-ene
and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene
signed to be applied to the plastic substrate to be bonded prior to application
of the adhesive. 31 Primers contain mostly aminic structures. Some
primers are listed in Table 13.6.
13.2.6 Diazabicyclo and Triazabicyclo Primers
1,5-Diazabicyclo[4.3.0]non-5-ene, 1,8-Diazabicyclo[5.4.0]undec-7-ene,
and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene are shown in Figure 13.9. It is
well known that solutions of amines and other organic and inorganic bases
will accelerate the curing of cyanoacrylate adhesives. Diazabicyclo and
triazabicyclo compounds also confer adhesion to nonpolar substrates.
26, 27
This primer acts in a two-component adhesive system comprising
2-cyanoacrylate adhesive and the azabicyclo primer. In poly(propylene)

484 Reactive Polymers Fundamentals and Applications
NH 2
CH 2
CH 2
H
+
N CH 2 CH 2 NH 2 O C (CH 2 ) 10 CH 3
CH 2
CH 2
NH 2
NH
C (CH 2 ) 10 CH 3
CH 2
CH 2
N CH 2 CH 2
CH 2
NH
C (CH 2 ) 10 CH 3
CH 2
NH
C
(CH 2 ) 10 CH 3
Figure 13.10: Condensation of Tris(2-aminoethyl)amine and Dodecyl aldehyde 35
the application of 1,8-Diazabicyclo[5.4.0]undec-7-ene, the tensile shear
bond strength raises to up to 74 kg/cm 2 in comparison to 7 kg/cm 2 without
primer.
13.2.7 Polyamine Dendrimers
Compounds with a variety of highly branched architectures are known,
including cascade, dendrimer, hyperbranched, and comb-like architectures.
The term multi-amine compounds refers to compounds with such branched
architectures in which branching occurs via tertiary amine groups.
For example, polyamine dendrimers are prepared by the condensation
of tris(2-aminoethyl)amine (TAA) and dodecyl aldehyde followed by
the reduction with tetra-n-butylammonium cyanoborohydride. 35 The reaction
is shown in Figure 13.10. The contact between the adhesive and
the multi-amine compound may be accomplished by mixing immediately
prior to bonding. Ordinarily, however, using the multi-amine compound in

Cyanoacrylates 485
a primer composition will provide the most practical and convenient application
to the substrate and will give effective bonding improvement on
polyolefin substrates.
13.3 CURING
Cyanoacrylates can be polymerized both by radical and by anionic mechanisms.
The polymerization of cyanoacrylates has been monitored by
Raman spectroscopy. 36 Cyanoacrylates polymerize comparatively slowly
with free-radical initiators. However, in the presence of catalytic amounts
of anionic bases and in the presence of covalent bases such as amines and
phosphines, they polymerize extremely rapidly.
The exceptionally fast rate of anionic polymerization of cyanoacrylates
in the presence of a base, including water, made this class of monomers
unique among all acrylic and vinyl monomers. Consequently, the anionic
polymerization is initiated by traces of moisture which are to be found on
almost all surfaces. Accordingly, cyanoacrylate adhesives set very quickly
when introduced between two surfaces stored under ambient conditions.
Of the alkyl cyanoacrylate family of monomers, the methyl- and ethyl-esters
are used extensively in industrial and consumer-type adhesives.
Consequently, most of the published work on the polymerization of cyanoacrylates
focuses on anionic polymerization.
13.3.1 Photo Curing
Although the predominant mechanism by which cyanoacrylate monomers
undergo polymerization is anionic, free-radical polymerization is also
known to occur. Radical polymerization of cyanoacrylate can be achieved
in the presence of a radical forming component and a photosensitizer. The
radical generating component can be dibenzoyl peroxide and the photoinitiator
component is 2,4,6-triphenylpyrylium tetrafluoroborate (TPT). 37
The chemical structures of these compounds are shown in Figure 13.11.
Some metallocene salts are capable of generating both a cationic species
and a free radical species upon exposure to radiation.
Ferrocene and DAROCUR 1173 (2-hydroxy-2-methyl-1-phenyl-
1-propane) are photo catalysts suitable for cyanoacrylates. 38 Radiation
times of 5 to 15 seconds are sufficient.

486 Reactive Polymers Fundamentals and Applications
C
O
O O C
O
O
BF 4
-
Figure 13.11: Dibenzoyl peroxide and 2,4,6-Triphenylpyrylium tetrafluoroborate
13.4 PROPERTIES
The particular advantage of cyanoacrylate adhesives in terms of adhesives
technology lies precisely in the high reactivity coupled with the high bond
strengths of the final materials, especially to polar substrates. Due to high
molar mass, good wetting properties, and polarity, poly(cyanoacrylate)s
exhibit excellent adhesive properties. In addition, they have been found
useful as polymeric binding agents in controlled drug delivery systems.
They are also useful for dry etching processes.
13.5 APPLICATIONS AND USES
Of the alkyl cyanoacrylate family of monomers, the methyl- and ethyl-esters
are used extensively in industrial and consumer-type adhesives.
13.5.1 Manicure Composition
Cyanoacrylate compositions are used as manicure compositions in treating
chapped nails. When nails are manicured, it is generally observed that the
moisture content in the nails becomes out of balance or lipids are eluted
out from the nails. As a result, nail chapping proceeds under the manicure
coating. Therefore, the nail chapping can be prevented by adding to manicure
compositions a substance capable of keeping nails in good health or
improving the nail health.
Cyanoacrylates are hardened so quickly that the hardening reaction
thereof is associated with heat generation. Therefore, when cyanoacrylates
are applied to nails, there arises heat irritation. Avocado oil and jojoba

Cyanoacrylates 487
oil can be added as plasticizer. In addition, these oils can suppress the
heat generation upon hardening without deteriorating the quick hardening
properties of cyanoacrylates or impairing its storage stability. Furthermore,
these natural oils may prevent nails from keratinization. 39
13.5.2 Tissue Adhesives
The isobutyl, n-butyl, and n-octyl cyanoacrylate esters are used clinically
as blocking agents, sealants, and tissue adhesives due to their much lower
toxicity as compared with their more reactive methyl and ethyl counterparts.
Cyanoacrylate ester compositions can be sterilized using visible light
irradiation at room temperature conditions. 9
There has been a great deal of interest in using tissue adhesives in
many surgical procedures in place of sutures and staples for a variety of
reasons, including 40
1. Ease of application and reduced clinician time,
2. Location of repairable site as in contoured locations,
3. Biomechanical properties as in weak organs, such as liver and pancreas,
and
4. Minimized hypertrophy and scar formation as in plastic surgery.
However, there have been a number of concerns associated with the
alkyl cyanoacrylates. These include
1. Their low viscosity and associated difficulties in precise delivery
at the application site in non-medical and medical applications,
2. Poor shear strength of the adhesive joint, particularly in aqueous
environments in both medical and non-medical applications,
3. High modulus or stiffness of cured polymers at soft tissue application
sites and associated mechanical incompatibility, which can
lead to adhesive joint failure and irritation of the surrounding tissue,
4. Excessive heat generation upon application of monomers to living
tissue due to exceptionally fast rate of curing resulting in necrosis,
and
5. Site infection, among other pathological complications, associated
with prolonged residence of the non-absorbable tissue adhesives.

488 Reactive Polymers Fundamentals and Applications
Problems with sterilization may arise. For example, poly(2-octyl
cyanoacrylate), degrades when exposed to a 160°C dry heat sterilization
cycle or 20 to 30 kGy (2 to 3 MRad) of electron beam radiation. 10
13.5.2.1 Bioabsorbable Polymers
Bioabsorbable polymers have been classified into three groups:
40, 41
• Soluble,
• Solubilizable, and
• Depolymerizable.
The most common materials used in bioabsorbable implants in orthopaedic
surgery 42 are polyglycolic acid (PGA), polylactic acid (PLA),
and polydioxanone (PDS).
Soluble polymers are water-soluble and have hydrogen-bonding polar
groups, the solubility being determined by the type and frequency of
the polar groups. Solubilizable polymers are usually insoluble salts, such
as calcium or magnesium salts of carboxylic or sulfonic acid-functional
materials which can dissolve by cation exchange with monovalent metal
salts. Depolymerizable systems have chains that dissociate to simple organic
compounds in vivo under the influence of enzymes or chemical catalysis.
Ester of Triethylene glycol. Bioabsorbable tissue adhesives 41, 43 are
based on a methoxypropyl cyanoacrylate as the precursor of an absorbable
tissue adhesive polymer and a polymeric, highly absorbable, liquid comprising
an oxalate ester of triethylene glycol as a modifier to modulate the
viscosity of the overall composition, lower the heat of polymerization, and
increase the compliance and absorption rate of the cured adhesive joint.
Copolymers of caprolactone, D,L-lactide, and glycolide also are considered
as bioabsorbable.
40, 44
Cyanoacrylate-capped Heterochain Polymers. Although the admixture
of a polymeric modifier has been shown to be effective in addressing most
of the medical and non-medical drawbacks of cyanoacrylate-based adhesives
represented by methoxypropyl cyanoacrylate, there remain technical
drawbacks in these systems, such as mutual immiscibility of two or more
polymers.

Cyanoacrylates 489
Cyanoacrylate-capped heterochain polymers having two or more
cyanoacrylate ester groups per chain have certain advantages. The heterochain
polymer used for capping can be one or more absorbable polymers
of the following types: polyester, polyester-carbonate, polyether-carbonate,
and polyether-ester. The capped polymer can also be derived from a
polyalkylene glycol such as poly(ethylene glycol), or a block copolymer of
poly(ethylene glycol) and poly(propylene) glycol.
The capping of the heterochain polymer can be achieved using an
alkyl cyanoacrylate, or an alkoxyalkyl cyanoacrylate such as ethyl cyanoacrylate
or methoxypropyl cyanoacrylate, respectively, in the presence of
phosphorus-based acids or precursors. In fact the capping takes place as
transesterification reaction. In the simplest case, a predried poly(ethylene
glycol) is mixed with ethyl cyanoacrylate in the presence of pyrophosphoric
acid under a dry nitrogen atmosphere. The reaction is allowed to
proceed by heating for 5 hours at 85°C. 40
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30. S. Fukushige et al. Primer for cyanoacrylate adhesive. JP Patent 2 120 378,
assigned to Koatsu Gas Kogyo Co Ltd, May 8 1990.
31. R. Grieves and K. G. M. Pratley. Adhesive primer. US Patent 5 837 092,
assigned to Pratley Investments (Proprietary) Limited (ZA), November 17
1998.
32. P. F. McDonnell, G. M. Wren, and E. K. Welch, II. Consumer polyolefin
primer. US Patent 5 314 562, assigned to Loctite Corporation (Hartford, CT),
March 24 1994.
33. H. C. Nicolaisen and A. Rehling. Primer for cyanoacrylate adhesives and
use thereof in a bonding method. US Patent 5 133 823, assigned to Henkel
Kommanditgesellschaft auf Aktien (Duesseldorf, DE), July 28 1992.
34. A. Hiraiwa, K. Ito, and K. Kimura. Primer composition. US Patent 5 292 364,
assigned to Toagosei Chemica Industry Co., Ltd. (Tokyo, JP), March 8 1994.
35. J. G. Woods and J. M. J. Frechet. Multi-amine compound primers for bonding
of polyolefins with cyanoacrylate adhesives. US Patent 6 673 192, assigned
to Loctite Corporation (Hartford, CT), January 6 2004.
36. E. Urlaub, J. Popp, V. E. Roman, W. Kiefer, M. Lankers, and G. Rossling. Raman
spectroscopic monitoring of the polymerization of cyanacrylate. Chem.
Phys. Lett., 298(1-3):177–182, December 1998.
37. H. R. Misiak. Radiation-curable, cyanoacrylate-containing compositions. US
Patent 6 734 221, assigned to Loctite (R&D) Limited (Dublin, IE), May 11
2004.
38. S. Wojciak and S. Attarwala. Radiation-curable, cyanoacrylate-containing
compositions. US Patent 6 726 795, April 27 2004.

492 Reactive Polymers Fundamentals and Applications
39. K. Kishita and N. Ohsawa. Manicure composition for nail. US Patent
6 703 003, assigned to Three Bond Co., Ltd. (Tokyo, JP); Three Bond International
Inc. (West Chester, OH), March 9 2004.
40. S. W. Shalaby. Cyanoacrylate-capped heterochain polymers and tissue adhesives
and sealants therefrom. US Patent 6 699 940, assigned to Poly Med,
Inc. (Anderson, SC), March 2 2004.
41. S. W. Shalaby. Biabsorbable polymers. In J. Swarbrick and J. C. Boylan,
editors, Absorption of Drugs to Bioavailability of Drugs and Bioequivalence,
volume 1 of Encyclopedia of Pharmaceutical Technology, pages 465–476.
Marcel Dekker, Inc., New York and Basel, 1988.
42. P. B. Maurus and C. C. Kaeding. Bioabsorbable implant material review.
Operative Techniques in Sports Medicine, 12(3):158–160, July 2004.
43. C. L. Linden and S. W. Shalaby. Absorbable tissue adhesives. US Patent
5 350 798, assigned to The United States of America as represented by the
Secretary of the Army (Washington, DC), September 27 1994.
44. S. W. Shalaby. Polyester/cyanoacrylate tissue adhesive formulations. US
Patent 6 299 631, assigned to Poly-Med, Inc. (Pendleton, SC), October 9
2001.

14
Benzocyclobutene Resins
Benzocyclobutene (BCB) or bicyclo[4.2.0]octa-1,3,5-triene is also called
cardene, cyclobutabenzene and cyclobutarene. Benzocyclobutene was first
synthesized by Finkelstein in 1909 by the 1,4-elimination of bromine from
α,α,α ′ ,α ′ -tetrabromo-o-xylene, 1 as shown in Figure 14.1. Finkelstein’s
thesis was rejected for publication and was accidentally discovered more
than 40 years later. 1,5-Hexadiyne trimerizes to give 1,2-bis(benzocyclobutenyl)ethane
(BCBE). Various other methods of synthesis of benzocyclobutene
derivatives have been reported. 2 Suitable monomers are summarized
in Table 14.1.
The four-membered ring in benzocyclobutene (BCB) imparts a ring
strain. Therefore, this class of molecules is especially reactive. Benzocy-
Compound
Table 14.1: Benzocyclobutene Derivatives
Benzocyclobutene (BCB)
Benzocyclobutene-maleimide
1,2-Dihydrocyclobutabenzene-3,6-dicarboxylic acid
2,6-Bis-4-benzocyclobutene benzo[1,2-d:5,4-d ′ ]bisoxazole
Isophthaloyl bis-4-benzocyclobutene
1-Methoxypoly(oxyethylene)benzocyclobutene
3
1-Benzocyclobutenyl vinyl ether
4
2,6-Bis(4-benzocyclobutenyloxy)benzonitrile
5
4-Trimethylsiloxybenzocyclobutene
5
Reference
493

494 Reactive Polymers Fundamentals and Applications
(a)
CHBr Br
2
NaJ NaJ, H 2
CHBr 2 Br
(b)
O
O
(c)
+
O
O
O
O
(d)
+ +
Figure 14.1: a) Synthesis of Benzocyclobutene, (b) Isomerization, (c) Diels-
Alder Reaction with Maleic anhydride, (d) Cyclotrimerization of 1,5-Hexadiyne

Benzocyclobutene Resins 495
∆
Figure 14.2: Thermal Polymerization of o-Xylylene
clobutene derivatives serve as important building blocks for natural product
syntheses and for polymers and advanced materials.
In the presence of dienophiles the o-xylylene unit undergoes a Diels-Alder
reaction. However, in the absence of a dienophile the o-xylylene
unit polymerizes as shown in Figure 14.2. The BCB four-membered ring
opens thermally around 200°C to produce o-quinodimethane (QDM), also
known as o-xylylene. 2, 6 o-Xylylene readily undergoes Diels-Alder reactions
with available dienophiles or, in the absence of a dienophile, it reacts
to give a dimer, 1,2,5,6-dibenzocyclooctadiene. The dimerization reaction
is thermodynamically preferred over a Diels-Alder reaction. However, the
Diels-Alder reaction is kinetically favored.
Benzocyclobutene-maleimide monomers (c.f. Figure 14.3) polymerize
to yield exceptionally tough resins with high glass transition temperatures.
Upon heating at above 200°C, the benzocyclobutene ring opens
to form o-xylylene, which then undergoes a cycloaddition or dimerization
reaction. The cyclobutene structure in 1,2-Dihydrocyclobutabenzene-
3,6-dicarboxylic acid can act as a crosslinking site when incorporated in a
polymer.
Poly(benzo[1,2-d4,5-d ′ ]bisthiazole-2,6-diyl)-1,4-phenylene (PBT) is
a rod-like monomer. A thermal crosslinking occurs, when benzocyclobutene
substructures are imbedded in PBT. 7 The mechanism is shown in Figure
14.4.
1-Methoxypoly(oxyethylene)benzocyclobutene has been prepared by
reacting 1-benzocyclobutenyl-1-hydroxyethyl ether with the mesylate of
methoxypoly(oxyethylene). The Diels-Alder reactions of 1-methoxypoly-
(oxyethylene)benzocyclobutene with maleic anhydride and N-phenylmaleimide
runs to 100% conversion. 3 1-Benzocyclobutenyl vinyl ether has been
prepared by the elimination of hydrogen bromide from 1-benzocyclobutenyl-1-bromoethyl
ether. This compound was obtained from 1-bromobenzocyclobutene
and ethylene glycol. 1-Benzocyclobutenyl vinyl ether can be
polymerized by a cationic mechanism. 4

496 Reactive Polymers Fundamentals and Applications
O
C
O
COOH
N
(1)
O
COOH
(2)
O
N
(3)
O
N
O
C
O
C
(4)
Figure 14.3: Benzocyclobutene-maleimide monomer (1),
1,2-Dihydrocyclobutabenzene-3,6-dicarboxylic acid (2)
2,6-Bis-4-benzocyclobutene benzo[1,2-d:5,4-d ′ ]bisoxazole (3),
Isophthaloyl bis-4-benzocyclobutene (4)

Benzocyclobutene Resins 497
ClOC
COCl
+
H 2 N
SH
ClOC
COCl
HS NH 2
Polyphosphoric acid
N
S
S
N
∆
N
S
S
N
Crosslinking
Figure 14.4: Crosslinking of Poly(benzo[1,2-d4,5-d ′ ]bisthiazole-2,6-diyl)-
1,4-phenylene Modified with Benzocyclobutene Structures

498 Reactive Polymers Fundamentals and Applications
The microwave curing of benzocyclobutene has been described. 8
Microwave curing may speed up the manufacture of parts used in microelectronics.
14.1 MODIFIED POLYMERS
14.1.1 Thermotropic Copolymers
Thermotropic polymers are polymers that are forming liquid crystalline
phases in the melt. Thermotropic copolymers composed of hydroxybenzoic
acid (HBA), hydroxynaphthoic acid (HNA), and systematically varying
amounts of hydroquinone (HQ) and crosslinkable terephthalic acid have
been described. 9 Also, the chain extension is possible if a BCB functionality
is on one or both ends of a polymer chain. 2
14.1.2 BCB-modified Aromatic Polyamides
The compressive strength of high modulus fibers such as Kevlar can be
improved by the use of a latently crosslinkable monomer, such as 1,2-dihydrocyclobutabenzene-3,6-dicarboxylic
acid. BCB modified aromatic polyamides
as shown in Figure 14.5 can be synthesized by the condensation of
terephthaloyl dichloride and 3,5-diaminophenyl-4-benzocyclobutenylketone.
10 The polymers can be crosslinked by the application of heat. These
polymers exhibited broad cure exotherms with onset temperatures in the
range of 238°C, reaching maximum at 275°C. The polymers are useful as
crosslinkable, thermoplastic matrix materials for rigid rod-like composites.
Such composites include composites with poly(p-phenylene benzobisthiazole)
(PBZT), as well as with other benzobisazole polymers. 10
14.1.3 BCB End-capped Polyimides
Benzocyclobutene-terminated polyimide oligomers are useful for high performance
adhesive applications. They are more processable than conventional
polyimide systems, yet form polymers that are thermally stable
at temperatures above 200°C. For example, imide oligomers can be prepared
from 4,4 ′ -[1,3-phenylene(1-methyl ethylidene)]bisaniline (Bis-M),
and 4-amino-benzocyclobutene as chain stopper and 4,4 ′ -oxydiphthalic anhydride
(ODPA) to arrive at a structure as shown in Figure 14.6. Benzo-

Benzocyclobutene Resins 499
H 2 N
NH 2
O
C
+
Cl
O
C
O
C
Cl
O
O
C
HN
NH
C
O
C
Figure 14.5: BCB-modified Aromatic Polyamides

500 Reactive Polymers Fundamentals and Applications
H 2 N
O
CH 3 CH 3
C C
NH 2
CH 3 CH 3
Bis-M
O
+
O
O
O
+
H 2 N
O
ODPA
O
4-amino-BCB
Ar
N
O
O
O
N
O
O
Figure 14.6: BCB end-capped Polyimides Prepared from 4,4 ′ -[1,3-Phenylene(1-methyl
ethylidene)]bisaniline (Bis-M), 4-Amino-benzocyclobutene, and
4,4 ′ -Oxydiphthalic anhydride (ODPA) 11

Benzocyclobutene Resins 501
cyclobutene-terminated polyimides can be cured to form polymers that exhibit
high adhesive strength. 11 The adhesives have been shown to withstand
exposure to hot wet environment. For example, lap shear samples
immersed in boiling water for three days and tested at room temperature
are found to retain over 80% of their strength.
14.1.4 Flame Resistant Formulations
Benzocyclobutene polymers are known as thermosetting polymers having
high thermal stability, but they are flammable. Both the flammability and
brittleness of BCB resins can be reduced by adding a brominated acrylate,
such as pentabromobenzyl acrylate (PBA) monomer to the BCB resins and
causing them to react to form a resulting flame retardant thermoset material.
The PBA reduces the brittleness of the cured material by reducing the
crosslinking density. PBA is advantageous because it reacts with the BCB
to create a homogeneous system. 12
14.2 CROSSLINKERS
14.2.1 Modified Poly(ethylene terephthalate)
Thermally crosslinkable polyester copolymers can be synthesized by the
incorporation of a benzocyclobutene-containing terephthalic acid derivative
into poly(ethylene terephthalate) (PET). The cyclobutene moiety on
the chain allows the reactive crosslinking at temperatures at ca. 350°C.
No catalyst is needed and no volatile products are formed. Crosslinking
occurs above the melting temperature of 250°C but below the
degradation temperature of 400°C. Therefore, the material can be melt processed.
The degradation temperature and the melting temperature decrease
slightly with increased cyclobutene content. The recrystallization and glass
transition temperature are insensitive to the cyclobutene content. The limiting
oxygen index (LOI) increases with cyclobutene content. 13
14.3 APPLICATIONS AND USES
Polymer films from BCB formulations exhibit many desirable properties
for microelectronic applications. 14 In particular, they have a low dielectric
constant and dissipation factor, low moisture absorption, rapid curing and

502 Reactive Polymers Fundamentals and Applications
E-BCB
DVB-BCB
CH 3 CH 3
Si O Si
CH 3 CH 3
DVS-BCB
Figure 14.7: 1,2-Bis(4-benzocyclobutenyl)ethylene (E-BCB), Bis(benzocyclobutenyl)-m-divinylbenzene
(DVB-BCB), and Bis(benzocyclobutenyl)divinyltetramethylsiloxane
(DVS-BCB)
low temperature cure without generating by-products, minimum shrinkage
in curing process, and no Cu migration issues. 15
Due to these properties, applications have been found in bumping/
wafer level packaging, optical wave guides, 16, 17 and flat panel display.
14.3.1 Applications in Microelectronics
Several BCB-containing polymers have been investigated for their use in
coating applications. Suitable monomers are analogues to trans-stilbene,
e.g., 1,2-bis(4-benzocyclobutenyl)ethylene (E-BCB), bis(benzocyclobutenyl)-m-divinylbenzene
(DVB-BCB), and bis(benzocyclobutenyl)divinyltetramethylsiloxane
(DVS-BCB).
The structures of the monomers are shown in Figure 14.7.

Benzocyclobutene Resins 503
+
CH 3
Si
CH 3
H 3 C
H 3 C
Si
O
Si
CH 3
CH 3
H 3 C
Si
CH 3
Figure 14.8: Basic Curing Reaction and the Structure of the Polymer of DVS-
BCB 2
14.3.1.1 Siloxane-modified Benzocyclobutene
For microelectronics applications, the polymer from DVS-BCB is commonly
used, because it results in a polymer with a high glass transition
temperature of greater than 350°C, a low dielectric constant, a low dissipation
factor, low water absorption, and good adhesive properties. 2 The basic
curing reaction and the structure of the polymer are shown in Figure 14.8.
With a siloxane bisbenzocyclobutene, high quality spin-on gate dielectric
layers as thin as 50 nm have been fabricated over the semiconductor
layer for polymer field-effect transistors by a solution process. 18 It is
desirable to get materials with low refractive index, and thus low dielectric
constant. This can be achieved when the curing reaction is stopped before
vitrification is reached. 19
The treatment with ultraviolet light in the presence of ozone modifies
the chemical properties of BCB, as the polymeric structure of BCB is
degraded and becomes soluble in acetone. This behavior may be useful for
BCB reworking after polymerization. 20

504 Reactive Polymers Fundamentals and Applications
+
Br
OH
O
OH
O
Figure 14.9: Synthesis of BCB-acrylic acid 21
14.3.1.2 Acid Functional Benzocyclobutenes
Acid functional polymers based on benzocyclobutene display excellent
qualities of toughness, adhesion, dielectric constant, and low stress. 21 The
synthesis of BCB-acrylic acid is shown in Figure 14.9.
14.3.2 Optical Applications
Diffractive gratings made from benzocyclobutene can withstand temperatures
up to 300°C with only small optical and topographical changes after
45 min., whereas conventional photoresist gratings change drastically
within a few minutes under these conditions. 22
The fabrication of Bragg reflector mirrors for GaInAsP/InP lasers
has been described. 23 The process involves multiple sequential steps of
CH 4 /H 2 reactive ion etching (RIE) and O 2 plasma etching.
REFERENCES
1. G. Mehta and S. Kotha. Recent chemistry of benzocyclobutenes. Tetrahedron,
57(4):625–659, January 2001.
2. M. F. Farona. Benzocyclobutenes in polymer chemistry. Prog. Polym. Sci.,
21(3):505–555, 1996.
3. R. S. Herati. Synthesis of 1-methoxypoly(oxyethylene)benzocyclobutene
and its Diels-Alder reactions. J. Polym. Sci. Pol. Chem., 42(8):1934–1938,
April 2004.
4. K. Chino, T. Takata, and T. Endo. Synthesis of a poly(vinyl ether) containing
a benzocyclobutene moiety and its reaction with dienophiles. J. Polym. Sci.
Pol. Chem., 37(1):59–67, January 1999.
5. L. S. Tan, N. Venkatasubramanian, P. T. Mather, M. D. Houtz, and C. L. Benner.
Synthesis and thermal properties of thermosetting bis-benzocyclobutene-terminated
arylene ether monomers. J. Polym. Sci. Pol. Chem., 36(14):
2637–2651, October 1998.

Benzocyclobutene Resins 505
6. R. A. Kirchhoff and K. J. Bruza. Benzocyclobutenes in polymer synthesis.
Prog. Polym. Sci., 18(1):85–185, 1993.
7. Y.-H. So. Rigid-rod polymers with enhanced lateral interactions. Prog.
Polym. Sci., 25(1):137–157, February 2000.
8. R. V. Tanikella, S. A. B. Allen, and P. A. Kohl. Variable-frequency microwave
curing of benzocyclobutene. J. Appl. Polym. Sci., 83(14):3055–3067, April
2002.
9. P. T. Mather, K. P. Chaffee, A. Romo-Uribe, G. E. Spilman, T. Jiang, and
D. C. Martin. Thermally crosslinkable thermotropic copolyesters: synthesis,
characterization, and processing. Polymer, 38(24):6009–6022, November
1997.
10. L.-S. Tan and N. Venkatasubramaian. Aromatic polyamides containing keto-benzocyclobutene
pendants. US Patent 5 514 769, assigned to The United
States of America as represented by the Secretary of the Air (Washington,
DC), May 7 1996.
11. E. S. Moyer and D. J. D. Moyer. Benzocyclobutene-terminated polymides.
US Patent 5 464 925, assigned to The Dow Chemical Company (Midland,
MI), November 7 1995.
12. M. W. Wagaman and T. F. McCarthy. Flame retardant benzocyclobutene
resin with reduced brittleness. US Patent 6 342 572, assigned to Honeywell
International Inc. (Morris Township, NJ), January 29 2002.
13. E. Pingel, L. J. Markoski, G. E. Spilman, B. J. Foran, T. Jiang, and D. C.
Martin. Thermally crosslinkable thermoplastic PET-co-XTA copolyesters.
Polymer, 40(1):53–64, January 1999.
14. Y. H. So, P. Garrou, J. H. Im, and D. M. Scheck. Benzocyclobutene-based
polymers for microelectronics. Chem. Innov., 31(12):40–47, December 2001.
15. K. Ohba. Overview of photo-definable benzocyclobutene polymer. J. Photopolym.
Sci. Technol., 15(2):177–182, 2002.
16. C. W. Hsu, H. L. Chen, W. C. Chao, and W. S. Wang. Characterization
of benzocyclobutene optical waveguides fabricated by electron-beam direct
writing. Microw. Opt. Technol. Lett., 42(3):208–210, August 2004.
17. W. S. Sul, S. D. Kim, S. D. Lee, T. S. Kang, D. An, Y. H. Chun, I. S. Hwang,
J. K. Rhee, and K. H. Ryu. Low-characteristic-impedance transmission line
of a benzocyclobutene-based 3-dimensional structure at millimeter-wave frequencies.
J. Korean Phys. Soc., 43(6):1076–1080, December 2003.
18. L. L. Chua, P. K. H. Ho, H. Sirringhaus, and R. H. Friend. High-stability
ultrathin spin-on benzocyclobutene gate dielectric for polymer field-effect
transistors. Appl. Phys. Lett., 84(17):3400–3402, April 2004.
19. K. C. Chan, M. Teo, and Z. W. Zhong. Characterization of low-k benzocyclobutene
dielectric thin film. Microelectron. Int., 20(3):11–22, 2003.
20. B. Viallet, E. Daran, and L. Malaquin. Effects of ultraviolet/ozone treatment
on benzocyclobutene films. J. Vac. Sci. Technol., A, 21(3):766–771,
May–June 2003.

506 Reactive Polymers Fundamentals and Applications
21. Y. H. So, R. A. DeVries, M. G. Dibbs, R. L. McGee, E. O. Shaffer, II, M. J.
Radler, and R. DeCaire. Acid functional polymers based on benzocyclobutene.
US Patent 6 361 926, assigned to The Dow Chemical Company (Midland,
MI), March 26 2002.
22. A. Straat and F. Nikolajeff. Study of benzocyclobutene as an optical material
at elevated temperatures. Appl. Optics, 40(29):5147–5152, October 2001.
23. M. M. Raj, J. Wiedmann, S. Toyoshima, Y. Saka, K. Ebihara, and S. Arai.
High-reflectivity semiconductor/benzocyclobutene Bragg reflector mirrors
for GaInAsP/InP lasers. Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes
Rev. Pap., 40(4A):2269–2277, April 2001.

15
Reactive Extrusion
Reactive extrusion is an attractive route for polymer processing in order to
carry out various reactions including polymerization, grafting, branching,
and functionalization. There are monographs on reactive extrusion. 1, 2
In this chapter, we deal mainly with the formation of polymers by
reactive extrusion, i.e., reactive extrusion polymerization. Aspects of reactive
extrusion are covered in other chapters: this includes grafting, compatibilization,
and controlled rheology. Reactive extrusion polymerization
involves polymerizing a liquid or solid monomer or a prepolymer during
the residence time in the extruder to form a high molecular weight melt.
Low-cost production and processing methods for biodegradable
plastics are of great importance, since they enhance the commercial viability
and cost-competitiveness of these materials. Reactive extrusion is an
attractive route for the polymerization of cyclic ester monomers, without
solvents, to produce high molecular weight biodegradable plastics.
Extruders can be used for bulk polymerization of monomers, like
methyl methacrylate, styrene, lactam, and lactide. From a mechanistic
peerspective, nearly all kinds of polymerization have been performed in
an extruder. These include radical polymerization, ionic polymerization,
metathesis polymerization, 3 and ring opening polymerization. The techniques
of characterization and experimental setup for reactive extrusion
can be found in the literature. 4, 5 The technique is also attractive for melt
spinning. 6, 7
The economics of using an extruder as a bulk polymerization reactor
are favorable when high throughputs and control of molecular weight
507

508 Reactive Polymers Fundamentals and Applications
V
R
H
H
∆T
∆T
Figure 15.1: Balance of an Extruder
are realized. The limitation arises due to the residence time required to
complete the polymerization, which ideally should be less than 5 minutes.
There are significant kinetic, heat transfer, and diffusion-related issues
in a bulk polymerization process that make it difficult to develop and
design processing methods that result in high molecular weight polymer at
high throughputs with a high conversion of the monomer. However, extruders
are ideal process vehicles for this purpose as they can be tailored to
give various flow patterns, residence time distributions and shear effects,
each of which affect the polymerization and polymer quality.
15.1 EXTRUDER
In this section the reactive extruder depicted in Figure 15.1 is modelled
mathematically. There is an input of monomer on the left side with a volume
rate of ˙V . The average residence time t r is then
t r = , (15.1)
V˙V
when the volume of the extruder is V . The reaction rate in the extruder is Ṙ.
Let us assume for simplicity sake that the rate of reaction is not dependent
on the conversion. The conversion C, as a fraction is then
C = t r Ṙ. (15.2)
To obain full conversion, i.e., C = 1, the residence time should be t r > 1/Ṙ.
The rate of reaction heat generation is calculated by means of Eq. 15.3.
Ḣ = ṘH 0 V (15.3)

Ḣ
H 0
Ṙ
V
Rate of heat released in the whole extruder
Heat released for full conversion in the unit volume
Rate of reaction
Volume of extruder
Reactive Extrusion 509
The heat released in the extruder must be conducted through the
walls. Here we neglect that some of the heat is transported away with the
melt. We also neglect that additional heat is generated by friction forces
through kneading. The heat that can be transported though the walls of the
extruder is given by the heat flow equation Eq. 15.4.
Ḣ = kA∆T. (15.4)
Here k is the overall heat transfer coefficient ([Js −1 K −1 m −2 ] (different
from the conductivity coefficient). The area A relates to the volume of
the extruder with a geometry factor g.
V = gA (15.5)
In the case of a cylinder, V = r 2 πh = g2rπh. Let us assume that the heat is
transferred through the envelope of the cylinder. Combining Eq. 15.3 and
Eq. 15.4, yields Eq. 15.6
∆T = ˙V H 0 g
V k . (15.6)
We have previously implied the condition of full conversion. Eq. 15.6
states that a temperature gradient will be created by the reaction in the
extruder. We are restricted by the temperature difference by the cooling
facilities. For example, the outer temperature is usually not set below the
room temperature for economic reasons. On the other hand, the temperature
inside the extruder cannot get too high. Otherwise the material will
pyrolyze. The temperature gradient is limited. Now the temperature difference
will be affected by the throughput. The throughput will be pushed to
a maximum for economic reasons. The heat of reaction for a given process
cannot be changed. However, if there are alternative processes found that
achieve a material with identical properties, the process with a low heat
of conversion should be selected. The geometry factor can be influenced
by the design of the extruder. Clearly, a smaller diameter is advantageous.
This will lead to a design of a longer machine, if a large volume is desired.
The length of a machine is restricted by the mechanical properties of
a screw. The situation is simpler in a chemical plant. There are bent loop
reactors in which the material can freely flow.

510 Reactive Polymers Fundamentals and Applications
The model described is a very simple, because the temperature gradient
in the melt, the residence time distribution, and many other parameters
have not been taken into account. It does provide a basic insight into
important parameters of the device.
More sophisticated models are available in the literature. The reactive
extrusion process in a single-screw extruder has been assessed by
power law fluids undergoing isothermal homogeneous and heterogeneous
reactions. The reaction was reported to be first-order. The equation of
conservation of component species was transformed into an eigenvalue
problem. Analytical solutions were developed for the concentration distribution
in the extruder. Expressions for the conversion of the reactant and
Sherwood number were given. 8
Sometimes severe fluctuations in product quality have been observed.
These fluctuations can be caused by thermal, hydrodynamic, or chemical
instabilities. 9 Some of these instabilities are dependent on the scale of
the equipment. The experimental design is thus important when a reactive
extrusion process is developed in the laboratory for scale up to larger
machines.
15.1.1 Heat of Polymerization
The performance of a reactive extrusion polymerization depends on the
heat of polymerization itself. Table 15.1 summarizes heat and entropy of
polymerization for selected compounds.
A review of the data in Table 15.1 reveals that vinyl polymers, such
as propene, styrene, and acrylics have a high enthalpy of polymerization.
Polymers that are formed by ring opening polymerization have a relatively
lower enthalpy of polymerization. From the point of view of heat transfer
it is desirable to use monomers that have a lower polymerization heat, because
the heat must be removed through the walls of the reactor which has
a limited surface area. Only a low polymerization heat guarantees a high
throughput.
15.1.2 Ceiling Temperature
On the other hand, low polymerization heat implies low thermal stability
from the view point of thermodynamics. The free enthalpy of polymerization
is given by Eq. 15.7.

Reactive Extrusion 511
Table 15.1: Heats and Entropies of Polymerization 10
Compound State a −∆H −∆S Temperature
[kJ/mol] [J/mol/K] [°C]
Propene lc 84 116 25
Acrylic acid lc 67 75
Acrylonitrile lc 77 109 75
Methyl methacrylate lc 56 117 130
Styrene lc 70 149 25
Maleic anhydride ls 59 — 75
1,3-Dioxolan lc 24 76 100
Tetrahydrofuran lc 19 16 25
γ-Butyrolacton lc -5 30 25
Caprolacton lc 17 4 25
D,L-Lactide lc 27 13 127
a lc: from liquid to crystalline
ls: from liquid to solid
∆G
∆H
∆S
Free enthalpy of polymerization
Enthalpy of polymerization
Entropy of polymerization
∆G = ∆H − T ∆S. (15.7)
If ∆G turns negative, then the polymer is no longer stable with respect
to the monomer. Assuming an equilibrium is established, then the
ceiling temperature T c can be calculated by equating Eq. 15.7 to zero.
T c = ∆H
T ∆S
(15.8)
The ceiling temperature yields reasonable results for vinyl monomers,
but in the case of polymers formed by ring opening polymerization,
unreasonable values are obtained.
15.1.3 Strategy of Reactive Extrusion
As pointed out above, it is desirable to use materials with a low polymerization
heat in reactive extrusion. Only then can a high throughput be obtained.
On the other hand, it is possible to use a mixture of a polymer and
monomer. The latter is then polymerized in the extruder. This concept can

512 Reactive Polymers Fundamentals and Applications
Table 15.2: Polymers Obtained by Reactive Extrusion
Polymer
Radical Polymerization
Reference
Poly(styrene)
11
Poly(butyl methacrylate)
12
Ring opening Polymerization
Poly(lactide)
13
Anionic Polymerization
Poly(styrene)
Styrene-butadiene copolymer
14
Polyamide 12
15
Metathesis Polymerization
Poly(octenylene)
3
reduce the amount of heat to be transferred. In compatibilization, a modified
polymer is used, with only one chemically reactive group in the chain.
In this case the heat of polymerization with respect to volume is reduced
drastically.
On the other hand, in injection molding of small articles with a
high surface-to-volume ratio, the viscous melt often must be driven though
small channels, before the melt is placed in the form. In the case of small
articles only small amounts of material are needed. Therefore, the cost of
the material used is less influential in the choice of the process.
The cycle time can be reduced, if the form filling can be reduced.
This can be done by selecting a material that is less viscous. In the case
of small articles, the heat of polymerization is reduced. Therefore, reactive
extrusion is possibly attractive, in the manufacture of small articles.
15.2 COMPOSITIONS OF INDUSTRIAL POLYMERS
Before going into detail, we summarize the polymers that have been obtained
by reactive extrusion according to the mechanism of reaction in Table
15.2.

Reactive Extrusion 513
15.2.1 Poly(styrene)
Styrene was polymerized in a twin-screw extruder. The polymerization
reaction mainly occurred in the zone between 400 and 1000 mm along
the screw axis in the extruder, corresponding to the residence time of the
reactants ranging from 1 to 4 min in the extruder. Based on dimensionless
analysis, a model of the residence time was established. A kinetic model of
the polymerization was set up under the assumption that the screw extruder
can be treated as an ideal plug flow reactor. 11
A styrene-butadiene multiblock copolymer was synthesized by anionic
polymerization in a twin-screw extruder. The polymerized materials
exhibit a nanometer size styrene and butadiene multiblock structure. Further,
they show an ultrahigh elongation at break, which differs considerably
from conventional polymers made by traditional solution polymerizing
methods. 14
Poly(styrene) could be modified by reactive extrusion with trimethylolpropane
triacrylate (TMPTA) and dicumyl peroxide (DCP). 16 The
TMPTA increased the molecular weight of PS by a coupling reaction. The
coupling was enhanced in the presence of DCP at a high ratio of TMPTA
to DCP.
15.2.2 Poly(tetramethylene ether) and Poly(caprolactam)
A polyetheramide, composed of poly(tetramethylene ether) (PTMEG) as
soft segment and poly(caprolactam) as the hard segment, is synthesized in
a one-step, solvent-free process. No volatile by-product is formed during
the process. An isocyanate-terminated telechelic PTMEG was premixed
with caprolactam, and this mixture was allowed to react in the twin-screw
extruder to form the polyetheramide triblock copolymer. 17
15.2.3 Polyamide 12
Polyamide 12 was prepared in a reactive extrusion process by the anionic
polymerization of lauryllactam. 15 Sodium hydride was used as initiator
and N,N ′ -ethylene-bisstearamide (EBS) was used as activator. The reaction
was complete to 99.5% in less than 2 min at 270°C and could be performed
in an internal mixer and a twin-screw extruder with co-rotating intermeshing
screws. Rubber-toughened polyamide 12 blends were obtained when
poly(ethylene-co-butyl acrylate) was dissolved in lauryllactam. 1,3-Phen-

514 Reactive Polymers Fundamentals and Applications
ylene-bis(2-oxazoline) is a suitable chain extender. 18 It reacts with the
terminal carboxyl groups of the polyamide. During the extrusion process,
the residence time distribution (RTD) has been measured by the addition
of ultraviolet and ultrasonic detectable tracers.
19, 20
15.2.4 Poly(butyl methacrylate)
Telomers of butyl methacrylate were obtained by reactive extrusion with
1-octadecanethiol as chain transfer agent. The transfer constant to 1-octadecanethiol
was measured. It was shown that the use of relatively high
ratio of chain transfer agent to monomer had no perceptible effect on the
kinetics of telomerization. 12
15.2.5 Poly(carbonate)
Poly(carbonate)s, such as bisphenol A poly(carbonate), are typically prepared
either by interfacial or melt polymerization methods.
The reaction of a bisphenol such as bisphenol A with phosgene in
the presence of water, a solvent such as methylene chloride, an acid acceptor
such as sodium hydroxide, and a phase transfer catalyst such as
triethylamine is typical of the interfacial methodology.
The interfacial method for making poly(carbonate) has several inherent
disadvantages. The process requires phosgene which is highly poisonous.
Further, the process requires large amounts of organic solvent.
The reaction of bisphenol A with diphenyl carbonate at high temperature
in the presence of sodium hydroxide as a catalyst is typical for
the melt polymerization method. The melt method, although obviating the
need for phosgene or a solvent, such as methylene chloride, requires high
temperatures and relatively long reaction times. As a result, by-products
may be formed at high temperature, such as the products arising by Fries
rearrangement of carbonate units along the growing polymer chains. Fries
rearrangement gives rise to undesired and uncontrolled polymer branching
which may negatively impact the polymer’s flow properties and performance.
The melt method further requires the use of complex processing
equipment capable of operation at high temperature and low pressure, and
capable of efficient agitation of the highly viscous polymer melt during the
relatively long reaction times required to achieve high molecular weight.
On the other hand, poly(carbonate) can be formed under relatively
mild conditions by reacting a bisphenol A with a diaryl carbonate formed

Reactive Extrusion 515
O C R
HO
C
R
O
O
Figure 15.2: Fries Rearrangement
by the reaction of phosgene with methyl salicylate. Early procedures used
relatively high levels of transesterification catalysts such as lithium stearate
in order to achieve the desired high molecular weight poly(carbonate).
15.2.5.1 Linear Poly(carbonate)
Poly(carbonate) is prepared by introducing an ester substituted diaryl carbonate,
such as bis(methyl salicyl)carbonate, a bisphenol A, and a transesterification
catalyst, e.g., tetrabutylphosphonium acetate (TBPA) into an
extruder. 21 Within the extruder, a molten mixture is formed in which the
reaction between carbonate groups and hydroxyl groups occurs, giving rise
to a poly(carbonate) product and an ester-substituted phenol by-product.
The extruder may be equipped with vacuum vents which serve to
remove the ester-substituted phenol by-product and thus drive the polymerization
reaction toward completion. The molecular weight of the poly-
(carbonate) may be controlled by controlling, among other factors, the feed
rate of the reactants, the type of extruder, the extruder screw design and
configuration, the residence time in the extruder, the reaction temperature,
the number of vents present in the extruder, and the (vacuum) pressure.
The poly(carbonate) reaches a weight-average molecular weight of greater
than 20,000 Dalton.
In a special experimental design, the extruder included 14 segmented
barrels, each barrel having a ratio of length to diameter of about 4, and six
vent ports for the removal of the by-product methyl salicylate. Two vents
were configured for the operation at atmospheric pressure and four vents
were configured for operation under vacuum. The methyl salicylate formed
as the polymerization reaction took place was collected by means of two
condensers.
The poly(carbonate)s have extremely low levels of Fries rearrangement
products and possess a high level of endcapping. Contrary to this is a
bisphenol A poly(carbonate) prepared by a melt reaction method in which
the Fries reaction occurs. The Fries rearrangement is shown in Figure 15.2.

516 Reactive Polymers Fundamentals and Applications
15.2.5.2 Branched Poly(carbonate)s
Branched poly(carbonate) resins differ from most thermoplastic polymers
used for molding in their melt rheology behavior. Most thermoplastic polymers
exhibit non-Newtonian flow characteristics over essentially all melt
processing conditions. However, in contrast to most thermoplastic polymers,
certain branched poly(carbonate)s prepared from dihydric phenols
exhibit Newtonian flow at normal processing temperatures and shear rates
below 300 s −1 .
Copolyester-carbonate resins are prepared analogous to the preparation
of poly(carbonate), but a difunctional carboxylic acid is added. Usually
the carboxylic acid is aromatic and used as halide, i.e., isophthaloyl
dichloride and terephthaloyl dichloride. Aliphatic diacid components yield
soft segment co-poly(carbonate)s.
Poly(carbonate) and copolyester-carbonate resins can be branched
by reaction with tetraphenolic compounds during synthesis. On the other
hand, a poly(carbonate) resin possessing a certain degree of branching and
molecular weight can be produced via reactive extrusion. This is achieved
by melt extruding a linear poly(carbonate) resin with a specific branching
agent and an appropriate catalyst system. 22 The resulting molecular weight
increases with branching, but can also decrease if conditions are chosen
that favor degradation.
Branching agents useful to branch linear poly(carbonate)s are polyacrylates
and polymethacrylates, in particular pentaerythritol triacrylate
(PETA). Organic peroxides include 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane
(DHBP) and 2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne
(DYBP).
Upon melt extrusion, branching and crosslinking occurs in the poly-
(carbonate) resin melt. The material is compounded on a melt extruder,
a co-rotating twin-screw extruder under reduced pressure of 0.5 atmospheres,
at a temperature profile of 200 to 300°C.
The assumed mechanism of branching consists of thermal decomposition
of a radical initiator which attacks the methyl groups of the BPA
units in order to create poly(carbonate) macroradicals. The macroradicals
can be recombined by a radical branching agent (compound containing
at least two double bonds) to generate a branched structure. The key to
the process will be the lifetime of the radicals and the sensitivity of the
poly(carbonate) backbone versus radicals. A copolyester-poly(carbonate)-
containing long chain aliphatic diacid moieties, such as dodecyl diacid,

Table 15.3: Biodegradable Compositions
Compounds
Reactive Extrusion 517
Reference
Poly(lactide)s
23, 23
Poly(ε-caprolactone)
Poly(ε-caprolactone)-grafted starch
24, 25
Poly(propylene) wood flour composites
26
Poly(ε-caprolactone), wood flour or lignin
27
Starch and poly(acrylamide)
28
Protein and polyester
29
Poly(styrene)-grafted starch
30
is more sensitive to radical attack. Branched poly(carbonate) resins produced
by reactive extrusion are useful blow-moldable resins exhibiting an
enhanced melt strength and melt elasticity. The branched poly(carbonate)
products are useful in applications such as 22
• Profile extrusion: of wire and cable insulation, extruded bars, pipes,
fiber optic buffer tubes, and sheets;
• Blowmolding: of containers and cans, gas tanks, automotive exterior
applications such as bumpers, aerodams, spoilers and ground
effects packages; and
• Thermoforming: of automotive exterior applications and food packaging.
15.3 BIODEGRADABLE COMPOSITIONS
Many biodegradable compositions have been synthesized and investigated.
These are summarized in Table 15.3.
Poly(β-hydroxybutyrate-co-valerate), poly(butylene succinate), poly-
(ethylene succinate) and poly(ε-caprolactone) are biodegradable polymers
which are thermally processable. Poly(β-hydroxybutyrate-co-β-hydroxyvalerate)
(PHBV) can be made by both the fermentation process of carbohydrate
and an organic acid by a microorganism, e.g., Alcaligenes Eutrophus,
and by the use of transgenic plants.
Polyalkylene succinate (PAS) is produced by the reaction between
aliphatic dicarboxylic acids and ethylene glycol or butylene glycol. Poly(εcaprolactone)
(PCL) is produced by the ring-opening polymerization of ε-
caprolactone.

518 Reactive Polymers Fundamentals and Applications
By grafting polar monomers onto poly(β-hydroxybutyrate-co-valerate),
poly(butylene succinate), or poly(ε-caprolactone), the resulting modified
polymer is more compatible with polar polymers and other polar substrates.
Useful polar monomers, oligomers, or polymers include ethylenically
unsaturated monomers containing a polar functional group, such
as 2-hydroxyethyl methacrylate (HEMA) and poly(ethylene glycol)methacrylate
(PEG-MA).
The grafted biodegradable polymer may contain 1.5 to 20% of
grafted polar monomers. Other reactive ingredients which may be added
to the compositions include free-radical initiators, such as Lupersol 101.
The amount of free-radical initiator ranges from 0.1 to 1.5%. A low
dosage of free-radical initiator cannot initiate the grafting reaction. On the
other hand, if the amount of free-radical initiator is too high, it will create
undesirable crosslinking of the polymer composition. Crosslinked polymers
are undesirable, because they cannot be processed into films, fibers
or other products.
The grafting reaction can be performed by a reactive-extrusion process.
31 A particularly useful reaction device is a co-rotating twin-screw
extruder having one or more ports. Such an extruder allows multiple feeding
and venting ports and provides high intensity distributive and dispersive
mixing. The grafting may be achieved in several ways.
1. All of the ingredients, including a biodegradable polymer, a freeradical
initiator, and the polar monomer are added simultaneously
to a melt mixing device or an extruder.
2. The biodegradable polymer may be fed to a feeding section of a
twin-screw extruder and subsequently melted, and a mixture of a
free-radical initiator and the polar monomer is injected into the
biodegradable polymer melt under pressure. The resulting melt
mixture is then allowed to react.
3. The biodegradable polymer is fed to the feeding section of a twinscrew
extruder, then the free-radical initiator and the polar monomer
are fed separately into the twin-screw extruder at different
points along the length of the extruder. The heated extrusion is
performed under high shear and intensive dispersive and distributive
mixing resulting in a grafted biodegradable polymer of high
uniformity.
The modified polymer compositions have a greater compatibility

Reactive Extrusion 519
with water-soluble polymers, such as polyvinyl alcohol and poly(ethylene
oxide), than the unmodified biodegradable polymers.
The compatibility of modified polymer compositions with a polar
material can be controlled by the selection of the monomer, the level of
grafting and the blending process conditions. Tailoring the compatibility of
blends with modified polymer compositions leads to better processability
and improved physical properties of the resulting blend.
The compositions are biodegradable so that the articles made from
them could be degraded in aeration tanks by aerobic degradation, and by
anaerobic degradation in wastewater treatment plants.
PHBV allows only a low cooling rate, such that commercial use of
this material is impractical. On the other hand, polylactic acid (PLA) is
brittle. However, a blend of PLA and PHBV allows to the PHBV cool
at an acceptable rate and also makes PLA more flexible such that these
materials can be used.
15.3.1 Poly(lactide)s
It is generally known that lactide polymers are unstable. The concept of
instability has both advantages and disadvantages. The advantage is the
biodegradation or other forms of degradation that occur when lactide polymers
or articles manufactured from lactide polymers are discarded or composted
after completing their useful life. A negative aspect of such instability
is the degradation of lactide polymers during processing at elevated
temperatures as, for example, during melt processing by end user.
Thus, the same properties that make lactide polymers desirable as
replacements for non-degradable petrochemical polymers also create undesirable
effects during production of lactide polymer resins and processing
of these resins. In general, poly(lactide) is a relatively brittle polymer
with low impact resistance. Articles made of poly(lactide) may be brittle
and prone to shatter under use conditions.
For example, if poly(lactide) is made into articles such as razor holders,
shampoo bottles, and plastic caps, these articles may be prone to undesirable
shatter in use. 23 However, compositions with modified physical
properties can avoid these drawbacks.

520 Reactive Polymers Fundamentals and Applications
O
H 3 C
O
O
CH 3
O
HO
O
CH
CH 3
C
O
n
Figure 15.3: Ring Opening Polymerization of a Lactide
15.3.1.1 Ring Opening Polymerization of Lactide
The ring opening polymerization of a lactide using an equimolar complex
of 2-ethylhexanoic acid tin(II) salt Sn(Oct) 2 and triphenylphosphine PΦ 3
as catalyst exhibits a high reactivity to polymerization that is too high to
allow a continuous single-step reactive extrusion process for bulk polymerization.
The catalyst also delays the occurrence of undesirable backbiting
reactions. The ring opening polymerization is shown in Figure 15.3. A sophisticated
screw design is required to ensure further enhancement of the
polymerization reaction by using mixing elements and by the introduction
of shear into the melt. It is possible to design a single stage process using
reactive extrusion to polymerize the lactide into a poly(lactide) that can be
fabricated by most any known polymer processing techniques. 13 Possible
uses of such polymers include food packaging for meat and soft drinks,
films for agro-industry, and non-wovens in hygienic products. 32
15.3.1.2 Functionalized Poly(lactide)s
A functionalized poly(lactide) is a polymer which has been modified to
contain groups capable of bonding to an elastomer or which have a preferential
solubility in the elastomer. Only a portion of the poly(lactide)
needs to be functionalized in order to gain the benefit of improved impact
strength, however, uniform distribution of the functionalization throughout
the poly(lactide)-based polymer is preferred. The functionalized poly(lactide)
can be created during the lactide polymerization process, for example,
by copolymerizing a compound containing both an epoxide ring and
an unsaturated bond. The functionalized poly(lactide) polymer, containing
unsaturated bonds, can be blended and linked via free radical reactions to
an elastomer which contains unsaturated bonds. The functionalized polymer
can also be prepared subsequent to polymerization reaction, for ex-

Reactive Extrusion 521
ample, by grafting a reactive group, such as maleic anhydride (MA), to
the poly(lactide)-based polymer using peroxides. 23 Typically, the resulting
polymer compositions have an impact resistance of at least 0.7 ft − lb/in
(120 kgs −2 ). and an impact resistance of at least about 1 ft − lb/in (180
kgs −2 ).
A poly(lactide) can be also functionalized by radical grafting of
maleic anhydride onto it.
33, 34
A concentration of 2% MA in the presence
of 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane suffices to reach up
to 0.7% MA grafted onto the poly(lactide). Increasing the initiator concentration
results in an increase in the grafting of MA, but also in a decrease
in the molecular weight of the polymer. Without initiator, extensive degradation
was observed.
15.3.2 Biodegradable Fibers
One of the most promising biodegradable polymers is poly(lactide) (PLA),
in particular, from the viewpoint of environmental protection. PLA is of
great interest due to its mechanical property profile, its thermoplastic processability,
and its biodegradability. Further advantages of PLA compared
to other biodegradable polymers are its renewable origin and low price.
PLA is synthesized by the polycondensation of lactic acid or by the
ring-opening polymerization of the lactide. In both cases, lactic acid is the
starting monomer. Lactic acid is commercially produced by means of bacterial
fermentation. Fibers from PLA can obtained in a high-speed melt
spinning and spin drawing process. 35 A copolymer of L-lactide and 8%
meso-lactide is used that can be obtained by reactive extrusion polymerization.
15.3.3 Poly(ε-caprolactone)
Bulk polymerization of ε-caprolactone in an extruder in the presence of
starch to give a compatibilized blend of poly(ε-caprolactone), starch and
grafted starch-g-poly(ε-caprolactone) is described in the literature. A suitable
catalyst is aluminum isopropoxide. Aluminum isopropoxide can be
generated in-situ by using tri ethyl aluminum or diisobutyl aluminum hydride.
The lactone should contain less than 100 ppm water and should have
an acid value less than 0.5 mgKOH/g. The presence of water and free
acid in the reactant mixture is especially significant in the synthesis of high

522 Reactive Polymers Fundamentals and Applications
molecular weight poly(ε-caprolactone) polymer by reactive extrusion polymerization
since it has a deleterious effect on the kinetics and ultimately
leads to lower conversion of monomer to polymer. The impurities interact
with the polymerization catalyst or the propagating species and lower
the overall rate of polymerization. In cases where the monomer contains
greater than 100 ppm water, the desired water content may be achieved by
drying it using molecular sieves or calcium hydride (chemical method).
The ring-opening polymerization of ε-caprolactone in the presence
of starch leads to a poly(ε-caprolactone)-grafted starch. The reactant mixture
is extruded at a temperature of 80 to 240°C with residence times up to
12 minutes. 24
15.3.3.1 Blends with Starch
Films produced from poly(ε-caprolactone) and its copolymers which have
low melting points, are tacky, as extruded, and noisy to the touch and have
a low melt strength over 130°C. Due to the low crystallization rate of such
polymers, the crystallization process proceeds for a long time after the production
of the finished articles, followed by an undesirable change of properties
with time.
However, the blending of pre-blended starch with other polymers,
such lactone polymers, improves their processability without impairing the
mechanical properties and biodegradability properties. 36 The improvement
is particularly effective with polymers having low melting point temperatures
from 40°C to 100°C.
The pre-blends are obtainable by blending a starch-based component
and a synthetic thermoplastic component, such as an ethylene-vinyl
alcohol copolymer in the presence of a plasticizer. Suitable plasticizers are
glycerol, sorbitol, and sorbitol monoethoxylate. Urea as additive can destroy
hydrogen bonds of the starch. The addition of urea is advantageous
for the production of blends for film-blowing. By means of extrusion, thermoplastic
blends are obtained wherein the starch-based component and the
synthetic thermoplastic component form an interpenetrating structure.
In a first step, starch and an ethylene-vinyl alcohol copolymer (1:1)
with minor amounts of plasticizer, and other additives such as urea are melt
blended in a twin-screw extruder. This extrudate is pelletized. In a second
step the extrudate from the first step is blended with poly(ε-caprolactone).

Reactive Extrusion 523
15.3.3.2 Blends with Wood Flour and Lignin
Poly(ε-caprolactone) was compounded in twin-screw extruder together
with wood flour and lignin. 27 Maleic anhydride-grafted poly(ε-caprolactone)
(PCL-g-MA) was used as a compatibilizer. The grafting of maleic
anhydride onto PCL was achieved with 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane.
Low contents of grafted maleic anhydride and PCL-g-MA
were required to improve both mechanical properties and interfacial adhesion.
The addition of lignin retarded the biodegradation.
15.3.4 Cationically Modified Starch
Cationic wheat starch has been prepared by reactive extrusion in a twinscrew
extruder. The modifiers are 2,3-epoxypropyltrimethylammonium
chloride and 3-chloro 2-hydroxypropyltrimethylammonium in aqueous
sodium hydroxide (NaOH). 37 A high reaction efficiency can be reached
if a low degree of substitution is adjusted.
15.3.5 Blends of Starch and Poly(acrylamide)
Starch-poly(acrylamide) copolymers have been prepared by reactive extrusion
with ammonium persulfate as initiator. The extrusion temperature had
no significant impact on acrylamide conversion. 28
15.3.6 Blends of Protein and Polyester
Blends of soy protein and biodegradable polyester could be prepared with
glycerol as compatibilizer. 29 Miscibility was only achieved when the soy
protein was processed with glycerol applying high shear at elevated temperatures
in an extruder. There, a partial denaturation of the soy protein
occurred. Extruder screws with large kneading blocks were preferred.
Thermoplastic blends were obtained with high elongation and high tensile
strength. When the concentration of protein was increased, a lower degree
of crystallinity and a lower melting point was obtained. It is possible to
use a soy protein concentrate instead of a more expensive soy protein with
higher purity.

524 Reactive Polymers Fundamentals and Applications
15.4 CHAIN EXTENDERS
15.4.1 Recycling of Poly(ethylene-terephthalate)
Chain extenders are low molecular weight compounds that can be used
to increase the molecular weight of polymers. Pyromellitic dianhydride
(PMDA) is a suitable chain extender to increase the molecular weight of
poly(ethylene terephthalate) (PET) industrial scraps with low intrinsic viscosity.
Industrial scraps coming from PET processing plants are in many
cases uncontaminated. However, their viscosity is lowered by the first extrusion.
PMDA has a melting point (283°C) close to that of PET and it reacts
within a few minutes under the processing conditions of PET. PMDA is a
tetrafunctional compound, therefore, branching can occur. The PET end
groups consist of carboxyl and hydroxyl groups. The chain extension occurs
by a polyaddition between the hydroxyl groups and the pyromellitic
dianhydride.
The crucial parameters of the process are the concentration of the
chain extender, the residence time of the polymer in the extruder, and the
working temperatures. Dry blends of PET chips and PMDA powder were
prepared with different amounts of PMDA (0.25, 0.50, 0.75, and 1.00%
by weight). These were vacuum dried for 12 h at 110°C and extruded at
280°C. The average residence time is approximately 150 s. An amount
of PMDA from 0.50 to 0.75% is sufficient to result in an increase of M w ,
a broadening of M w /M n , and branching phenomena. The recycled polymer
from PET scraps is then suitable for film blowing and blow molding
processes. 38
15.4.2 Modified Poly(ethylene terephthalate)
Multifunctional epoxy based modifiers, such as a tetraglycidyl diaminodiphenylmethane
(TGDDM) resin, can be used to increase the melt strength
of PET. The progress conversion with time can be measured by the change
of torque in an internal mixer. With a stoichiometric concentration of
TGDDM, the molecular weight distribution of modified PET shows an
eight-fold increase of the z-average molecular weight (M z ) and the presence
of branched molecules of very large mass. 39
Further, a tetrafunctional epoxy based additive can be used to extrude
PET in order to produce PET foams. The molecular structure ana-

Reactive Extrusion 525
lysis and shear and elongation rheological characterization indicates that
branched PET is obtained for small amounts, up to 0.4% of a tetrafunctional
epoxy additive. Gel permeation chromatography (GPC) studies suggest
that a randomly branched structure is obtained, the structure being
independent of the modifier concentration. 40 An increase in the degree of
branching and the M w and the broadening of the molecular weight distribution
causes an increase in the Newtonian viscosity, the relaxation time,
flow activation energy, and the transient extensional viscosity. On the other
hand, the shear thinning onset and the Hencky strain at the fiber break decrease
markedly.
15.4.3 Poly(butylene terephthalate)
The chain extension reaction in poly(butylene terephthalate) (PBT) can be
achieved by a diglycidyl tetrahydrophthalate with high-reactivity. 41 The
chain extender reacts with the hydroxyl and carboxyl end groups of PBT
very fast and also at a comparatively high temperature. The chain extension
reaction is complete within 2 to 3 min at temperatures above 250°C. The
chain-extended PBT is thermally more stable than the original polymer.
In order to obtain PBT resins with a high molecular weight, the reactive
extrusion process is simpler and cheaper than the post-polycondensation
method.
15.5 RELATED APPLICATIONS
15.5.1 Transesterification
The transesterification is a different concept from polymerization. Transesterification
of mixtures of polyesters and oligoesters allows synthesizing
new types of polymers. Block copolyesters have been synthesized from
poly(neopentyl isophthalate) and poly(ethylene terephthalate). 42 The esterification
of poly(neopentyl isophthalate) is somehow resistant to transesterification.
Therefore, blocks instead of alternating polyesters will be
obtained. Poly(neopentyl isophthalate) is expected to exhibit high barrier
properties. Therefore, such materials are of interest in the field of beverage
containers.
Similarly, block co-polyesters of PET and poly(ε-caprolactone) have
been synthesized by reactive extrusion. In the presence of stannous octoate,
the ring-opening polymerization of ε-caprolactone can be initiated due

526 Reactive Polymers Fundamentals and Applications
to the hydroxyl end groups of molten PET to form poly(ε-caprolactone)
blocks. 43 A block copolymer with a minimal degree of transesterification
can be obtained under conditions of a fast distributive mixing of the
ε-caprolactone into the high viscous PET.
15.5.2 Hydrolysis and Alcoholysis
The continuous hydrolytic depolymerization of a poly(ethylene terephthalate)
was carried out in a twin-screw extruder. The hydrolysis was achieved
by the injection of saturated steam at high pressure. Low molecular weight
products were obtained even at low residence times in the extruder. Therefore,
high depolymerization rates should occur under the conditions selected.
44
α,ω-Diols have been obtained by the alcoholysis of PET through
reactive extrusion. The alcoholysis of PET with diols in the presence of
dibutyltin oxide was carried out in a twin-screw extruder with residence
times of ca. 1 min. Scissions of PET chains are taking place and oligoester
α,ω-diols are formed with a number-average of around 1 kDalton. 45 The
study revealed that oligoesters synthesized by reactive extrusion are quite
similar to oligoesters synthesized by batch processes which last many
hours.
15.5.3 Flame Retardant Master Batch
A master batch of an intumescent flame retardant was prepared by reactive
extrusion of melamine phosphate and pentaerythritol with a poly(propylene)
carrier in a twin-screw extruder. 46
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528 Reactive Polymers Fundamentals and Applications
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530 Reactive Polymers Fundamentals and Applications
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Int., 53(4):439–448, April 2004.

16
Compatibilization
There are innumerable binary, ternary, and multiple alloys known in metallurgy.
Metals easily form mutual alloys. The situation is completely
different in polymer chemistry, as is pointed out in the literature. 1 Most
of the organic polymers are not mutually miscible. Methods have been
reported for compatibilization of immiscible blends of polymers by reactive
mixing, in which functionalized versions of the polymeric components
react in-situ to form a block copolymer compatibilizer. The fundamental
requirements for a compatibilizer as additive and in reactive processing
include the following: 2, 3
• The interfacial tension must be optimized.
• There must be sufficient mixing to achieve the desired fineness of
morphological texture.
• Some of the polymer molecules must contain chemical functional
groups which can react to form primary bonds during the mixing/-
mastication process. The functional groups must be of sufficient
reactivity for reactions to occur across melt phase boundaries.
• The reactions must occur rapidly enough to be completed during
processing in the extruder or mixer within a reasonable time.
• The bonds formed as a result of reactive blending must be stable
enough to survive subsequent processing.
• The adhesion between the phases in the solid state should be enhanced.
• The compatibilization reactions should be fast and irreversible.
531

532 Reactive Polymers Fundamentals and Applications
Many new products can be manufactured by melt blending of polymers
to achieve improved properties that are not available in any single
polymeric material, e.g., toughness, chemical resistance, ease of fabrication,
etc.
The use of blends and alloys of immiscible polymers has increased
because it is generally less expensive to develop a new blend composition
than to develop new polymers based upon new monomers to meet the need
for specialized polymers.
16.1 EQUIPMENT
Compatibilization reactions are normally performed in an extruder. Also
blenders have been used for discontinuous work. Ultrasonic assisted extrusion
in the molten state has been described in extruders. 4, 5 Ultrasonic
horns placed at the exit of the extruder that are vibrating in the direction
perpendicular to the flow direction introduce longitudinal ultrasonic waves
into the polymer melt. The mechanical performance of polymer blends
subjected was significantly enhanced by ultrasonic treatment in comparison
to the performance of blends not subjected to ultrasonic treatment
with a similar phase morphology.
Ultrasonically assisted melt mixers also have been described. 6 Poly-
(propylene)/poly(styrene)/clay nanocomposites and poly(methyl methacrylate)/clay
nanocomposites were prepared by in-situ polymerization
and ultrasonic assisted melt mixing.
16.2 BASIC TERMS
16.2.1 Thermodynamic Compatibility
Compatibilizing methods and agents are required for such blends, since
most polymers are mutually immiscible and have poor interfacial adhesion.
Compatibilizers generally are believed to act at interfaces to improve
interfacial interactions between immiscible polymeric species. It is recognized
that miscibility between polymers is determined by a balance of
enthalpic and entropic contributions to the free energy of mixing. While
for small molecules the energy is high enough to ensure miscibility, for
polymers the entropy is almost zero, causing enthalpy to be decisive in determining
miscibility. The change in free energy of mixing (∆G) is written

Compatibilization 533
as
∆G = ∆H − T ∆S (16.1)
where H is enthalpy, S is entropy, and T is temperature. For spontaneous
mixing, ∆G must be negative, and so
∆H − T ∆S < 0. (16.2)
This implies that exothermic mixtures (∆H < 0) will mix spontaneously,
whereas for endothermic mixtures miscibility will only occur at high temperatures.
2
16.2.2 Thermodynamic Models
Flory’s solution theory was modified by Hamada. 7 This modified theory
was used to predict the miscibility of blends of poly(ethylene oxide) with
poly(methyl methacrylate) (PEO-a-PMMA) and with poly(vinyl acetate)
(PEO-PVAc). 8
The interaction parameters of a PEO-a-PMMA blend with the weight
ratio of PEO/aPMMA = 50/50 at the temperature range of 393 to 433 K
and PEO-PVAc blends with different compositions and temperatures were
calculated from the parameters of the equation of state. The interaction
parameters of the PEO-a-PMMA blend turned out to be negative. The interaction
parameters and excess volumes of PEO-PVAc blends are negative
and increase with enhancing the content of PEO and the temperature.
The miscibility of blends of poly(methyl methacrylate) (PMMA)
and poly(ethylene oxide) (PEO) oligomers was studied by temperaturemodulated
DSC. The miscibility domain is larger for the atactic and syndiotactic
PMMA than for the isotactic isomer. The Flory-Huggins interaction
parameter χ 1,2 decreases with the increase of the PEO molecular
weight as well as with the syndiotacticity of the PMMA and is lower for
the PEO with alkyl modified chain ends. 9
16.2.3 Particle Size
Wu 10 proposed Eq. 16.3 to predict the particle size for polyamide and
polyester blends containing 15% ethylene/propylene rubber as a dispersed
phase.
d ¯= 4γη±0.84 r
(16.3)
Gη m

534 Reactive Polymers Fundamentals and Applications
d¯
Average diameter of the droplet
G
Shear rate
γ
Interfacial tension
η r = η d /η m Viscosity ratio
η m Viscosity of the matrix
η d
Viscosity of the dispersed phase
The positive exponent is for η r > 1; the negative exponent is for η r < 1.
16.2.4 Interfacial Slip
The viscosity of uncompatibilized polymer blends often exhibits a negative
deviation from a log-additivity rule at shear rates relevant to processing.
This deviation is attributed to the interfacial slip. The interfacial slip
arises from the loss of entanglements at the interface. The effect of reactive
compatibilization on the interfacial slip has been studied in blends
from ethylene/propylene rubber and polyamide 6. It has been demonstrated
that the interfacial slip can be important in uncompatibilized systems
whereas it is suppressed in compatibilized blends. 11
16.2.5 Interpolymer Radical Coupling
By using a solid-state shear pulverization technique in order to blend polymers,
an interpolymer radical coupling reaction has been discovered.
12, 13
This reaction leads to the formation of block copolymers. Pulverization
leads to an intimate mixing, creating a large interfacial area between blend
components, and to chain scission reactions, resulting in polymer radicals.
These radicals can cause interpolymer coupling in the solid state. The
interpolymer reaction was proved in a PMMA/PS blend using a pyrenelabelled
PS. The blends were characterized by gel permeation chromatography
with a fluorescence detector. The change in elution times was noted
and taken as proof that the interpolymer radical coupling happened at mixing.
16.2.6 Technological Compatibility
However, thermodynamic compatibility need not be attained. Technological
compatibility, where the blend has useful properties, normally is sufficient.
Mechanical or chemical techniques can be used to attain technological
compatibility. Technological compatibility of immiscible polymers
can be produced by

Compatibilization 535
• The addition of a compatibilizer before or during the mixing/blending
process,
• Adjustment of viscosity ratios to favor rapid formation of the desired
phase morphology during mixing,
• In-situ formation of a compatibilizer during the mixing/blending
process, and
• Introduction of crosslinks in one of the phases.
The objective of technological compatibilization is to produce compositions
which exhibit good ultimate properties, e.g., strength, elongation,
fatigue life, etc. Compatibilized polymer blends exhibit at least some of
the following differences from uncompatibilized polymer blends: reduced
morphological dimensions (smaller domain sizes, thus smaller potential
flaws); improved bonding or adhesion between phases; and reduced tendencies
to form highly shaped domains during flow in processing, molding,
etc.
One approach to technological compatibilization is the addition of
a compatibilizer before or during the mixing or blending process, respectively.
Such compatibilizers are frequently a block copolymer. To be efficient,
the compatibilizing block copolymer must possess segments with
chemical structures or solubility parameters, which are similar to or the
same as those of the polymers being blended. A sufficient amount of the
compatibilizing polymer must be located at the interface of the polymer
phases. Usually in this type of compatibilization, one block, A, is chemically
similar to one of the polymer components of the blend and the other
block, B, is chemically similar to the other blend component. This method
is usually extremely successful in stabilizing the polymer blend. Nevertheless,
this method is rarely used in commercial applications because of the
high expense usually involved in synthesizing the block copolymer.
Another method of promoting the presence of a compatibilizing block
copolymer at the interfacial region is to use reactive mixing techniques,
whereby the compatibilizing copolymer forms at the interface. In such cases,
polymer molecules of one phase contain functional groups which chemically
interact with molecules of a polymer in an adjacent phase, so that a
compatibilizer could form in the interfacial regions where it is needed.
In other words, reactive compatibilization involves the formation of
a block or graft copolymer via a coupling reaction between the reactive
functional groups of two additives. 2 In Table 16.1 and Table 16.2, compatibilizers
for various polymer blends are listed.

536 Reactive Polymers Fundamentals and Applications
Blends
Table 16.1: Compounds for Compatibilization of Polyolefines
Compatibilizer
LDPE/PA6 Diethylsuccinate, 14 glycidyl methacrylate, 15 ethylene and
acrylic acid copolymer, 16 poly(ethylene) grafted with
maleic anhydride
LDPE/PET Ethylene-propylene copolymer-g-methacryloyl carbamate 17
LDPE/Starch Poly(ethylene-co-glycidyl methacrylate) 18
HDPE/HIPS Styrene/ethylene-butylene/styrene block copolymer 19
HDPE/PA12 Maleic anhydride 20
HDPE/PET Poly(ethylene-co-glycidyl methacrylate)
21, 22
PP/PS Styrene-butadiene triblock copolymer, 23, 24 styrene-ethylene/propylene
diblock copolymer (SEP) 25
PP/PA6 ε-Caprolactam and maleic anhydride grafted poly(propylene),
26 isocyanate-modified PP, 27, 28 poly(styrene-b-(ethylene-co-butylene)-b-styrene)
grafted with maleic anhydride
29
EPDM/PTT Grafted ethylene/propylene rubber (EPM-g-MA) 30
Polyolefins Triallyl isocyanurate
Abbreviations
EPDM Ethylene propylene diene rubber
HDPE High density poly(ethylene)
HIPS High impact poly(styrene)
LCP Liquid crystalline polymers
LDPE Low density poly(ethylene)
PA6 Polyamide 6
PA12 Polyamide 12
PE Poly(ethylene)
PET Poly(ethylene terephthalate)
PP Poly(propylene)
PS Poly(styrene)
PTT Poly(trimethylene terephthalate)

Compatibilization 537
Blends
Table 16.2: Compounds for Compatibilization
Compatibilizer
PA6/PPO Styrene/maleic anhydride copolymer,
31, 32
poly(ethylene 1-octene), 33
PA6/PS Styrene/glycidyl methacrylate (SG) copolymers, 34 EPDM
grafted with maleic anhydride, 35 styrene-ethylene-butadiene-styrene
block copolymer grafted with maleic anhydride
35
PA66/PBT Bisphenol A-type epoxy resins 36
PA66/PS Styrene-maleic anhydride copolymer 37
PBT/EVA Maleic anhydride
PBT/EVA/PA6 Maleic anhydride 38
PBT/PEO Poly(ethylene-co-glycidyl methacrylate) 39–41
PC/PVDF Copolymer of methyl methacrylate and acrylic acid 42
PE/Fillers Functionalized ethylene copolymers with n-butyl acrylate,
maleic anhydride, epoxy, and acrylic acid 43
PE/Wood flour Maleated and acrylic acid grafted polyethylenes 44
PET Glycidyl methacrylate grafted rubber 45
PET/LCP Multifunctional epoxies
ABS/PA6
36, 46
poly(methyl methacrylate-co-maleic anhydride)
copolymers 47
PET/PA6 Acrylic modified polyolefin-type ionomer 48
PS
Poly(styrene)-b-poly(ethylene-co-butylene) poly(styrene)
triblock copolymer 49
PS/EPR Interphase modifiers 50
SBR/XNBR Surfactants 51
Abbreviations
Abbreviations
ABS Acrylonitrile-butadiene-styrene PA6 Polyamide 6
EPR Ethylene/propylene rubber PA12 Polyamide 12
EVA Ethylene/vinyl acetate copolymer PA66 Polyamide 6,6
LCP Liquid crystalline polymers PC Poly(carbonate)
PBT Poly(butylene terephthalate) PE Poly(ethylene)
PEO Poly(ethylene-octene) PP Poly(propylene)
PET Poly(ethylene terephthalate) PS Poly(styrene)
PMMA Poly(methyl methacrylate) PVDF Poly(vinylidene
PPO Poly(2,6-dimethyl-1,4- fluoride)
phenylene oxide) SBR Styrene butadiene
XNBR Carboxylated nitrile rubber blend rubber

538 Reactive Polymers Fundamentals and Applications
16.3 COMPATIBILIZATION BY ADDITIVES
The next topic is compatibilization by additives and reactive compatibilization.
This classification is somewhat arbitrary. In fact, additives react
chemically with some ingredients of a blend to increase the compatibility
of their constituents. Section 16.4 discusses reactive compatibilization
issues where the compatibilizer is essentially formed during the blending.
16.3.1 Poly(ethylene) Blended with Inorganic Fillers
Aluminum hydroxide and magnesium hydroxide blends with poly(ethylene)
composites can be compatibilized with functionalized polyethylenes.
Suitable compatibilizers are hydroxyl or carboxylic acid functionalized
ethylene copolymers prepared with metallocene catalysts.
Compatibilizer precursors are n-butyl acrylate, maleic anhydride,
epoxy, and acrylic acid. 43 These polymeric compatibilizers improve adhesion.
The improved adhesion is reflected in the mechanical properties,
such as stiffness and toughness. The flame retardancy imparted by the inorganic
hydroxides does not deteriorate upon addition of compatibilizers.
16.3.2 Filler Materials without Chemical Compatibilizers
Filler materials modify the melt elasticity and viscosity of a dispersed
phase of a lower viscosity material sufficiently to result in a reduction of
the efficiency of dispersed phase particle collisions in a higher viscosity
matrix. Since the efficiency of such collisions is inversely related to the
modulus of the dispersed phase, for instance, more elastic, higher modulus
dispersed phase particles have a lower probability of coalescing upon collision.
This reduces the coalescence of the dispersed phase under conditions
of high shear experienced, for example, during injection molding.
Selective precompounding or extrusion of polymer components with
fillers can change the viscosity and/or elasticity of the dispersed phase
polymer prior to forming the blend, so that a customized viscosity/elasticity
ratio of the blend components may be achieved, obviating the need
for added compatibilizers. 52
Matrix phase polymers include a wide range of polymers. The volume
of the matrix phase polymer is greater than about 65%. There is a
wide range of suitable materials that may be used as filler material, such
as carbon black, hydrated amorphous silica, fumed silica, fumed titanium

Compatibilization 539
dioxide, fumed aluminum oxide, diatomaceous earth, talc, and calcium
carbonate.
In general, blends may be formed by dispersing the filler material
within the dispersed phase polymer to form a modified dispersed phase
polymer, then dispersing the modified material within the matrix phase
polymer.
The first step is a melt blending of the filler with the dispersed phase
polymer. The goal of the first step is to ensure that the filler is completely
wetted by the polymer, and to take advantage of the strong interaction of
the dispersed phase polymer and the filler surface. If the interactions are
not sufficiently favorable, it may be desirable to pretreat the filler to ensure
strong interactions between the filler and the dispersed phase so that the
filler stays confined in the dispersed phase.
The modified dispersed phase polymer is then mixed with the matrix
phase polymer. Typically, this mixing occurs at a temperature which
is less than the melting point of the matrix phase polymeric component.
In the subsequent mixing step the components are well mixed in a melt
mixing process. However, due to the strong interaction between the filler
and the dispersed phase polymer, the filler stays substantially confined in
the dispersed phase.
16.3.3 Modified Inorganic Fillers
16.3.3.1 Magnesium Hydroxide
For high molecular weight medium density poly(ethylene) (MDPE) compounds,
the magnesium hydroxide filler can be surface-treated by fatty acid
coatings. The surface treatment modifies the yield stress and modulus.
Maxima are observed close to the monolayer coverage of the acid
modifier. Acid-group terminated poly(ethylene) (ATPE) coatings produce
the highest yield stress, as a result of physical interaction with the matrix
polymer. The thermomechanical history during processing also modifies
physical properties of MDPE/Mg(OH)(2) composites to some extent.
Anisotropic effects include molecular orientation and filler particle
alignment induced by shear stress during the injection molding process.
The use of organo-acid coatings reduces polymer-particle surface interaction
and thermodynamic work of adhesion, leading to an improved dispersion
and enhanced mechanical properties.

540 Reactive Polymers Fundamentals and Applications
16.3.3.2 Fumed Silica
The compatibility of PP/PS blends can be improved by the addition of
nano-silica particles. Fumed SiO 2 particles with a size of 10 to 30 nm
are treated with octamethylcyclotetraoxysilane. 53 Possible explanations
for the compatibilization effect caused by the nano-silica particles have
been pointed out:
1. The enhanced compatibility is caused by the adsorption of both PP
and PS molecules onto the surface of the silica.
2. By the introduction of the particles, the viscosity changes. This
causes a retardation of the coalescence of the dispersed PS particles.
It seems that the compatibilization in PP/PS blends by fumed silica
particles is controlled by the kinetics rather than by thermodynamics.
16.3.4 Clay Nanocomposites
Maleic anhydride grafted poly(ethylene) (maleated poly(ethylene))/ clay
nanocomposites can be prepared by simple melt compounding. The exfoliation
and intercalation behaviors depend on the hydrophilicity of poly-
(ethylene) grafted with maleic anhydride and the chain length of organic
modifier in the clay. When the number of methylene groups in the alkylamine
acting as organic modifier is more than 16, an exfoliated nanocomposite
is formed. Unmodified LLDPE shows only an intercalation, which does
not depend on the initial spacing between clay layers. 54 In a similar study
another group used octadecylamine-modified montmorillonite clay. 55
16.3.5 Thermoplastic Elastomers
Thermoplastic elastomers with 50% poly(ethylene terephthalate) (PET),
30% compatibilizer, i.e., glycidyl methacrylate grafted rubber or glycidyl
methacrylate-containing copolymer and 20% other rubbers, can be produced
by melt blending with and without dicumyl peroxide initiated curing.
The compatibility of the blend with PET is strongly improved when a
nitrile rubber (NBR) with a high content of acrylonitrile and an ethylene/-
glycidylmethacrylate copolymer (EGMA) or an ethylene/propylene rubber
grafted with GMA (EPR-g-GMA), are used as rubber and compatibilizer
respectively. 45

Compatibilization 541
The reactive compatibilization of poly(butylene terephthalate) (PBT)
with an epoxide-containing rubber is influenced by the concentration of the
reactive groups. The interfacial reaction is slow and not controlled by diffusion.
The kinetics of the interfacial grafting only depends on the concentration
of the reactive functions in the vicinity of the interface. The final
particle size correlates to the amount of copolymer formed in-situ at the
blend interface. 56
Reactive compatibilization of a poly(butylene terephthalate) (PBT)
and ethylene/vinyl acetate copolymer (EVA) can be achieved by maleic
anhydride (MA).
The graft copolymerization of EVA with MA is done, using dicumyl
peroxide (DCP) as an initiator, by melt-free radical grafting. PBT is then
blended with the EVA-g-MA obtained in the first step. The impact strength
of PBT/EVA-g-MA (80/20) blend showed about threefold increase in comparison
with a comparable PBT/EVA blend without compatibilizer. 57
16.3.6 Polyamide 6,6 and Poly(butylene terephthalate)
A bisphenol A-type solid epoxy resin is a low cost and efficient compatibilizer
for immiscible and incompatible blends of polyamide 6,6 (PA66)
and poly(butylene terephthalate) (PBT). 36 The epoxy resin is able to form
in-situ a PBT-co-Epoxy-co-PA66 mixed copolymer at the interface. This
mixed copolymer with both segments structurally identical to both base
polymers will anchor along the interface, and functions as an effective
compatibilizer for the PA66/PBT blends.
16.3.7 Poly(ethylene)/Wood Flour Composites
Functionalized polyolefins such as maleated and acrylic acid grafted polyethylenes,
maleated poly(propylene) (PP-g-MA), and styrene-ethylene/-
butylene-styrene triblock copolymer (SEBS-g-MA) have been tested to reduce
the interfacial tension between a poly(ethylene) matrix and the wood
filler.
Among these compounds, maleated linear low density poly(ethylene)
shows a maximum tensile and impact strength of the composites. This
is effected by the improved compatibility with the HDPE matrix. 44

542 Reactive Polymers Fundamentals and Applications
16.3.8 Recycled Polyolefins
Post-consumer high density poly(ethylene) (HDPE) has been investigated
for use in recycling in large-scale injection moldings. Blends with recycled
high density poly(ethylene) (re-HDPE) and low density poly(ethylene)
(LDPE) or linear low density poly(ethylene) (LLDPE) are considered
to improve the mechanical properties. 58
The mechanical and rheological data show that LDPE is a better
modifier for re-HDPE than LLDPE. The mechanical properties of re-HD-
PE/LLDPE blends are lower than the additive properties, i.e. they exhibit
a negative synergism. This demonstrates the lack of compatibility between
the blend components in the solid state. The mechanical properties of
blends of recycled HDPE and LDPE are equal to or higher than calculated
from linear additivity.
16.3.9 Block Copolymers
Poly(styrene) (s-PS)/ethylene/propylene rubber (EPR) blends have been
compatibilized with triblock copolymers such as poly(styrene)-b-poly(ethylene-co-butylene)
poly(styrene) (SEBS). 49 The size of the dispersed EPR
phase in s-PS/EPR/SEBS blends decreases and the particle size distribution
becomes narrower with increasing amounts of SEBS in the blends. Low
molecular weight SEBS is more effective in increasing the impact strength
of s-PS/EPR blend than a high molecular weight SEBS. This correlates
with the fact that s-PS/EPR blends compatibilized by the low molecular
weight SEBS have good adhesion between the s-PS matrix and dispersed
EPR particles, whereas the s-PS/EPR blends compatibilized by the high
molecular weight SEBS exhibit poor adhesion between phases. It is suggested
that the blocks in the low molecular weight SEBS penetrate into
the corresponding phase more easily than the blocks in the high molecular
weight SEBS.
The functionalization of a styrene-b-(ethylene-co-1-butene)-b-styrene
triblock copolymer (SEBS) and styrene-co-butadiene (SBR) random
copolymer takes place in the melt with diethyl maleate (DEM) and dicumyl
peroxide (DCP) as initiator. Under these conditions, the functionalization
proceeds with a large preference at the aliphatic carbons of the polyolefin
block. 59 The situation is similar, when maleic anhydride is used. 60
Triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene]
(SEBS) or poly(styrene-b-(ethylene-co-butylene)) (SEB) can be used

Compatibilization 543
to compatibilize high density poly(ethylene) and syndiotactic poly(styrene)
blends. The phase size of the dispersed s-PS particles is significantly reduced
by the addition of all these copolymers, and the interfacial adhesion
between the two phases is dramatically enhanced. The mechanical performance
of the modified blends is dependent not only on the interfacial
activity of the copolymers but also on the mechanical properties of the copolymers,
in particular at a high copolymer concentration. The addition of
compatibilizers to HDPE/s-PS blends results in a significant reduction in
crystallinity of both HDPE and s-PS. The Vicat temperature of the blends
indicates an improved heat resistance of the HDPE by addition of incorporation
of 20% s-PS. 61
The lack of adequate characterization techniques has been a hindrance
to the effective exploitation and study of co-continuous morphologies
in polymer blends. Blends of high density poly(ethylene) and poly-
(styrene) blends have been compatibilized with a triblock copolymer interfacial
modifier. The influence of the triblock copolymer interfacial modifier,
hydrogenated styrene-ethylene-butadiene-styrene, has been investigated
by the measurement of the surface area and the pore dimensions of
the blends after solvent extraction of one of the phases. The Brunauer Emmett
Teller (BET) nitrogen adsorption technique and mercury porosimetry,
respectively, have been used. Mercury porosimetry can lead to erroneous
information, while the BET method appears to be both rapid and consistent
with SEM observation. The specific surface area of the compatibilized
co-continuous blend system is five-fold higher than that of its non-compatibilized
counterpart, while the pore diameter of the extracted compatibilized
blend is reduced five-fold. Using the BET technique, it is possible to generate
an emulsification curve in the continuous region, demonstrating the
efficiency of the interfacial modifier. 62
The Brunauer Emmett Teller equation 63 can be used to determine the
surface area of solids. It takes into account a multiple layer absorption, in
contrast to the earlier derived Langmuir adsorption isotherm. The volume
of gas absorbed at the surface V is related to the pressure p applied by Eq.
16.4.
p
V(p − p 0 ) = 1
V m C + C − 1
V m C
p
p 0
(16.4)
V m
p 0
C
Volume of a monomolecular layer
Saturation pressure
Constant related to activation energy of absorption and desorption

544 Reactive Polymers Fundamentals and Applications
16.3.10 Impact Modification of Waste PET
The impact properties of waste poly(ethylene terephthalate) can be improved
by melt blending with a polyolefinic elastomer, in a co-rotating
twin-screw extruder. The compositions have an elastomer content up to
10%. Poly(ethylene-co-acrylic acid) is a suitable compatibilizer for this
system. 64 The incorporation of polyolefinic elastomer improves the impact
properties of PET significantly.
16.3.11 Starch
Starch is a carbohydrate that is produced by many plants to store chemical
energy. It is a polymer built from glucose. The main components are amylose
which is a linear polymer and amylopectin which is branched.The ratio
of amylose to amylopectin varies with origin. Most common are potato
starch, maize starch, soybean starch, and rice starch.
Sago is manufactured from the tree trunks of an Indian pomp tree.
In grain form it is exported to Europe and America where it is used in the
food industries. 65
Cassava is also known as manioc, manihot, yucca, mandioca, sweet
potato tree, and tapioca. It originates from tropical regions of America and
is now cultivated in Africa and East Asia. It has a particular high starch
content. The starch is collected from its tuberous roots. Tapioca starch is
an important carbohydrate in tropical countries. When gelatinized it results
in a highly cohesive paste.
16.3.11.1 Sago Starch
Sago starch is a possible filler for polyolefins. Sago starch can be chemically
modified through esterification using 2-dodecen-1-yl succinic anhydride
and propionic anhydride in solvents, such as N,N-dimethylformamide,
triethylamine, or toluene. Evidence of anhydride modification was
indicated by a weight gain of the material and was further confirmed by
infrared spectroscopy. Starch modified with 2-dodecen-1-yl succinic anhydride
and propionic anhydride can be used for the preparation of composites.
66 In unmodified blends of starch and LLDPE, the tensile modulus
and water absorption increase with increasing starch content.
However, the tensile strength and the elongation at break show a
decrease with increasing starch content. Modified starch shows improved

Compatibilization 545
mechanical properties and water absorption properties in comparison to
unmodified starch.
16.3.11.2 Cassava and Tapioca Starch
Cassava starch can be chemically modified by radiation induced grafting
with acrylic acid to obtain a cassava starch graft poly(acrylic acid). This
product is further modified by esterification and etherification with poly-
(ethylene glycol) and propylene oxide, respectively. The chemical modifications
of cassava starch cause it to become partially hydrophobic. It can
be used for blending with LDPE. 67
A functionalized epoxy resin, poly(ethylene-co-glycidyl methacrylate),
can be used as a compatibilizer for blends of low density poly(ethylene)
(LDPE) and tapioca starch. The mechanical properties are significantly
improved by the addition of the epoxy compatibilizer, approaching
values close to those of virgin LDPE. Scanning electron micrographs of
the compatibilized blends show a ductile failure structure, which obviously
contributes to the enhanced mechanical properties. 18
16.3.12 Blends of Cellulose and Chitosan
Blends of the naturally occurring polysaccharides, cellulose and chitosan,
can be obtained in the solid phase by the combined action of high pressure
and shear deformation. A diepoxide can act as a crosslinking agent,
even when cellulose reacts with chitosan without the compatibilizer. The
crosslinking agent reacts predominantly at the amino groups of chitosan,
forming a three-dimensional network. The cellulose macromolecules are
located within and partially bound with this network by the crosslinks. The
formation of the network results in the insolubility of cellulose-chitosan
compositions in acidic and alkaline aqueous media. 68
16.4 REACTIVE COMPATIBILIZATION
It is a common practice to blend existing polymers to obtain new materials,
instead of searching for new monomers, which is often more costly and
time-consuming.
Addition of block copolymers or the use of functionalized homopolymers
which can react to form copolymers in-situ is an effective method

546 Reactive Polymers Fundamentals and Applications
CH 3
C CH 2
CH 3
C
NCO
H 3 C
TMI
Figure 16.1: 3-Isopropenyl-α,α-dimethylbenzene isocyanate (TMI)
for compatibilization of two immiscible phases in a polymer blend and prevention
of coalescence.
The role of compatibilization is to stabilize the morphology and
modify the interfacial properties of the blend. This is achieved by adding
or creating in-situ, during the blending process, a third component, often
called an interfacial agent, emulsifier or compatibilizer. 69
Reactive compatibilization allows generating the compatibilizer insitu
at the interfaces directly during blending. The presence of a copolymer
also accelerates the melting of polymer blends.
70, 71
In the case of poly(propylene)/polyamide 6 (PA6), a graft copolymer
can be formed easily during blending, if a fraction of the poly(propylene)
chains are functionalized with a functional vinyl monomer such as maleic
anhydride. The anhydride then reacts with the terminal amine groups of
polyamide 6. Since the compatibilizer is formed in-situ at the interfaces,
placing it at the interfaces is straightforward.
In general, the functional groups must be stable enough under
the process conditions, to withstand high temperature and exposure
to air and humidity. Poly(propylene) can also be functionalized
with 3-isopropenyl-α,α-dimethylbenzene isocyanate, 69, 72 c.f. Figure
16.1. 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane (DHBP) is a suitable
free-radical initiator for the functionalization of poly(propylene) with
3-isopropenyl-α,α-dimethylbenzene isocyanate (TMI). The free radical
grafting is performed at 200°C.
In the second step, an in-situ polymerization of ε-caprolactam in the
presence of poly(propylene) and an in-situ compatibilization of the functional
poly(propylene) with the PA6 occurs. Activator and catalyst for the

Compatibilization 547
polymerization of ε-caprolactam are sodium chloride and ε-caprolactam
blocked hexamethylene diisocyanate.
The compatibilizing efficiency is very high compared with that of the
classical compatibilization method starting with a premade PP, PA6 and a
maleic anhydride modified PP. In the classical compatibilization method,
a copolymer of PP and PA6 is formed by an interfacial reaction between
maleic anhydride functionalized PP and the terminal amine group of PA6.
Thus, the amount of copolymer formation depends very much on the interfacial
volume available in the system. This is usually very small for
immiscible polymer pairs. On the other hand, when one polymer component
is formed in-situ, the amount of the copolymer formation is no longer
limited by the interfacial. 69
Another type of reactive compatibilizer is 4,4 ′ -diphenylmethane
carbodiimide (OCDI), 4,4 ′ -diphenylmethane bismaleimide (BMI), and
2,2 ′ -(1,4-phenylene)bisoxazoline (BOX). OCDI and BOX are chain extenders
and react with the carbonyl groups of PA6. On the other hand, BMI
has a lower reactivity. Grafting of BMI to PP chains improves the compatibility
in a PA6/PP blend and increases PP adhesion to glass fiber. 73
The functionalization of a propylene moiety with a bismaleimide is
shown in Figure 16.2. Among acrylic acid (AA), bismaleimide (BMI) and
maleic anhydride as compatibilizing agent for an isotactic poly(propylene)
(IPP)/polyamide 6 blend, the effectiveness increases in the following order:
IPP-AA < IPP-BMI

548 Reactive Polymers Fundamentals and Applications
O
O
N
CH 2
N
O
O
CH CH 3
CH 2
+
CH CH 3
CH 2
O
O
O
N
CH 2
N
O
C CH 3
CH 2
CH CH 3
H
CH 2
Figure 16.2: Functionalization of a Propylene Moiety with a Bismaleimide 78
of BMI. A possible mechanism of compatibilization has been proposed.
The shear forces during melt mixing cause the rupture of chemical bonds
in the polymers, which form macroradicals of PET, LDPE, or EPDM.
Subsequently, the macroradicals react with BMI to form copolymers
of the respective constituents. These copolymers act as compatibilizers. 79
16.4.1 Coupling Agents for Compatibilization
Coupling agents can be used to form chemical bonds between a polyolefin
and a second polymer. Blends of polyolefins and other polymers can be
coupled by a peroxide, such as dicumyl peroxide and triallyl isocyanurate
as coupling agent. A hexafunctional coupling agent for polyolefins is
hexa(allylamino)cyclotriphosphonitrile (HAP). 80
For the coupling of polyamides, triallyl isocyanurate, maleic anhydride
and undecenal have been described.

Compatibilization 549
16.4.1.1 Diamines
Diamines are suitable to couple poly(acrylic acid-co-ethylene) and poly-
(maleic anhydride-co-styrene). 81 Melt blends of maleic anhydride grafted
poly(styrene) with amino-methacrylate-grafted poly(ethylene) display a
somewhat finer morphology and improved mechanical properties.
4,4 ′ -Diaminodiphenylmethane was used as coupling agent in blends
of maleated poly(propylene) and maleated styrene-butadiene-styrene triblock
copolymers.
82, 83
16.4.1.2 Epoxy Monomers
Multifunctional epoxy compounds are universal coupling agents for compatibilization
of polymers such as poly(ethylene terephthalate) (PET) and
liquid crystalline polymers (LCP).
36, 46
16.4.1.3 Styrene/maleic anhydride Copolymer
A commercially available styrene/maleic anhydride copolymer (SMA)
with 8% MA is a highly effective compatibilizer for polymer blends of
polyamide 6 (PA6) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO).
SMA is miscible with PPO and tends to be dissolved in the PPO phase
during the early stages of melt blending. The dissolved SMA can make
reactive contacts of PA6 at the interface to form the desirable SMA-g-PA6
copolymer. 31
16.4.2 Vector Fluids
To enhance the formation of the graft copolymer in compatibilization, vector
fluids are introduced. A vector fluid is immiscible with both polymeric
components of the two-phase blend. In the extruder it forms a thin and
low viscous film at the interphase of the immiscible polymers. It may have
dissolved the peroxide. 84
16.4.3 Poly(ethylene) and Polyamide 6
16.4.3.1 Maleic anhydride Grafted Polyethylenes
Various grades of poly(ethylene) grafted with maleic anhydride (PE-g-MA)
and ethylene/acrylic acid copolymers (EAA) were used as compatibilizer

550 Reactive Polymers Fundamentals and Applications
precursors for the reactive blending of low density PE (LDPE) with polyamide
6 (PA6). Binary and ternary blends of compatibilizer, LDPE, and
polyamide were prepared in a Brabender mixer and were characterized by
DSC, SEM, and solvent fractionation. PE-g-MA copolymers react more
rapidly with PA than the EAA copolymers. The effectiveness depends critically
on the microstructure and the molar mass of their PE backbones.
Compatibilizers produced by the functionalization of LDPE are miscible
with the LDPE component and scarcely available at the interface
where reaction with PA is expected to occur. On the other hand, compatibilizers
prepared from HDPE grades were immiscible with LDPE and
showed a better performance. The concentration of the carboxyl groups
and the concentration of the succinic anhydride groups of the PE-g-MA
compatibilizer play a minor role, in contrast to EAA copolymers.
85, 86
A low-viscosity maleated poly(ethylene) is ineffective in toughening
nylon 6. This arises because of the propensity of poly(ethylene) to become
continuous even when nylon 6 is the majority component. Higher viscosity
maleated polyethylenes produce blends with high impact strength
and excellent low temperature toughness over a range of compositions.
Even poly(ethylene) materials with a low degree of anhydride functionality
can generate blends with excellent impact properties. In ternary blends
of nylon 6, maleated poly(ethylene), and nonmaleated poly(ethylene), the
impact properties improve as the molecular weight of nylon 6 increases
and the ratio of maleated poly(ethylene) to nonmaleated poly(ethylene) increases.
87
16.4.3.2 Epoxies
In an ethylene-glycidylmethacrylate copolymer, the epoxy groups of the
compatibilizer react quite easily during melt blending. Both the amine
and the carboxyl end groups of PA react to result in CP-g-PA copolymers.
These copolymers may be partially crosslinked. The efficiency of these
compatibilizers is comparable to that of the ethylene-acrylic acid copolymers,
but lower than that of a maleic anhydride-functionalized poly(ethylene).
85, 86
16.4.3.3 Diethylsuccinate
Linear low density poly(ethylene) or ethylene propylene copolymer and
poly(ε-caprolactam) (PA6) can be compatibilized by reactive extrusion in

Compatibilization 551
a Brabender mixer. The formation of a polyolefin-nylon grafted copolymer
has been shown by selective solvent extraction of the product. The
formation of the grafted copolymer has a substantial effect on the compatibilization
of the two polymers.
Differential scanning calorimetry shows a decrease of crystallization
temperature and the enthalpy of PA6 crystallization. Scanning electron
microscopy (SEM) micrographs show the size reduction of PA6 domains. 14
16.4.3.4 Acrylic Acid
Blends of polyamide 6 and polyolefins functionalized with acrylic acid,
such as poly(ethylene)-PE-AA and poly(propylene)-PP-AA, exhibit changes
in the crystallization behavior. Thermal analysis showed that in the case
of blends, with functionalized polyolefin as a matrix, the following occurs:
The crystallization of the polyamide 6 is spread and dramatically
shifted toward lower temperatures, approaching that of the polyolefin component
125 to 132°C. The major phase present is a polymorph γ-crystal of
polyamide 6. When polyamide 6 is dispersed in the functionalized polyolefin
matrix, the weight content of polyamide 6 γ-crystals increases up to
three times relative to the analogous, non-compatibilized blends and up to
approximately 16 times relative to the polyamide 6 homopolymer. These
phenomena are explained by the reduction of the size of polyamide 6 dispersed
particles, caused by the interactions between the functional groups
of polyolefin and the polar groups in polyamide chain. The nucleation
mechanism is changed due to the lack of heterogeneous nuclei in most
small polyamide 6 droplets, which results in the enhanced γ-crystal formation.
88
16.4.4 Poly(ethylene-octene) and Poly(butylene terephthalate)
Toughened poly(butylene terephthalate) (PBT) materials can be obtained
by melt blending with poly(ethylene-octene) copolymer (PEO) and maleic
anhydride grafted PEO (g-PEO) in a twin-screw extruder followed by injection
molding at either 7 cm 3 /s or 17 cm 3 /s injection speed.
The presence of either PEO or g-PEO did not influence either the
nature of the PBT phase or the crystallization of PBT. Low injection speeds
(7 cm 3 /s) and g-PEO provided the best mechanical response. Increasing
levels of maleic anhydride in g-PEO led to a continuous overall decrease
in the particle size.

552 Reactive Polymers Fundamentals and Applications
Super-tough poly(butylene terephthalate) (PBT)/ poly(ethyleneoctene)
blends with an impact strength more than twenty-fold that of PBT
are obtained using 2% poly(ethylene-co-glycidyl methacrylate) (EGMA)
as a compatibilizer by extrusion or injection molding. Two percent EGMA
is the minimum content required to reach maximum super-toughness that
also corresponds to the maximum ductility. Partially reacted EGMA dissolves
completely, mainly in the PBT-rich phase, up to 4% EGMA, at
which point a crystalline EGMA phase appears. The blends consist of
an amorphous PBT-rich phase with some mixed EGMA, a pure poly(ethylene-octene)
amorphous phase, and a crystalline PBT phase. The blends
show a fine particle size up to 20% poly(ethylene-octene) content. The
inter-particle distance controls toughness in these PBT/PEO blends. The
maximum toughness is very high, greater than 700 J/m, and was attained
with 20% poly(ethylene-octene).
39, 40, 89–91
16.4.5 Poly(ethylene-octene) and Polyamide 6
A maleated ethylene-octene copolymer promotes the toughness efficiency
of PA6 remarkably. A blend with 20% ethylene-octene copolymer grafted
with 1% MA reached a 20 times higher impact strength, i.e., 1000 J/m,
than pure PA6 with 55 J/m impact strength. 92 The dispersed particle size
was drastically reduced.
16.4.6 Ethylene Acrylic Acid Copolymers and Polyamide 6
In blends with polyamide 6 and ethylene acrylic acid copolymers, acrylic
acid causes a compatibilizing effect between poly(ethylene) and polyamide
components. The morphology of the blends and mechanical behavior thus
changes. These effects are enhanced with increasing acrylic acid content in
the copolymer and are attributed to interactions of hydrogen bonds between
the acrylic acid group and the functional groups of the polyamide. Blends
with a higher concentration of the terminal amino group in the polyamide
suggest that these functional groups interact better with acrylic groups of
the copolymer than the carboxylic groups. 93
16.4.7 Sisal Fibers
Sisal fibers show high strength and are obtained from the leaves of the
sisal plant (agave sisalana). The leaves reach a length of 2 m. The plant

Compatibilization 553
originates from central America and is now cultivated in East Africa and
East Asia.
Acetylation of the sisal fiber improves the adhesion of the fiber to
the polyolefin matrix. Acetylation of the sisal fiber enhances the tensile
strength and modulus of the resulting composites, except in some cases.
When the acetylated fiber is mixed with polyolefins, greater interactions
with polyolefin and fiber takes place. These interactions enhance the stability
of the composites. The thermal properties indicate mixing and molding
temperatures between 160 and 230°C. 94
16.4.8 Thermotropic Liquid Crystalline Polyesters
Liquid crystalline polymers are polymers which in melt state lie between
the boundaries of solid substances and liquids. The liquid crystalline structure
is called a mesomorphic phase or an anisotropic phase because macroscopically
in the melt state the liquid crystalline polymers are fluids. Microscopically
they have a regular structure similar to that of crystals. The
liquid crystalline polymers are called thermotropic (TLCP) if their anisotropy
depends only on the temperature. The strength and stiffness of many
thermoplastics can be substantially improved by blending them with thermotropic,
main-chain liquid crystalline polymers. This is because the liquid
crystalline polymers form fibers which orientate in the flow direction
of the thermoplastic matrix melt. As a result there is an improvement of
the mechanical properties, such as tensile strength and modulus of elasticity,
of the thermoplastic in this direction. Often, the addition of the liquid
crystalline polymer improves the heat resistance and dimensional stability
of the thermoplastics and makes it easier to process them. 95
The major limitation to the use of blends of TLCP in other polymers
is the poor interfacial adhesion between the TLCP and matrix polymer.
16.4.8.1 Physical Compatibilizer
A physical compatibilizer for TLCP blends is the zinc salt of a sulfonated
poly(styrene) ionomer. This ionomer can compatibilize blends of a
hydroxybenzoate/hydroxynaphthonate liquid crystalline copolyester with
poly(styrene), nylon 66 (PA66), bisphenol A, and poly(carbonate). 96–98

554 Reactive Polymers Fundamentals and Applications
16.4.8.2 Transesterification
Transesterification reactions have been used to improve the compatibility
of a TLCP with polyesters or poly(carbonate)s. Maleated poly(propylene)
can be used to improve the interfacial adhesion and mechanical properties
of blends of a TLCP with polyolefins or polyamides
16.4.8.3 Blends of Polyolefin and LCP
A polymer blend of a polyolefin or a polyester polymer matrix and an
aromatic main-chain liquid crystalline polymer can be compatibilized by
a styrene-ethylene/butylene-styrene triblock copolymer that is functionalized
with maleic anhydride. Olefin polymers functionalized with glycidyl
methacrylate are suitable compatibilizers. 95
By adding about 1 to 15% of a liquid crystalline polymer to the matrix
polymer, e.g., poly(propylene), a decrease of the viscosity is obtained
which enhances the processing. An example of a liquid crystalline polymer
is a copolymer of hydroxynaphthoic acid and hydroxybenzoic acid. The
compatibilizer is an ethylene-terpolymer containing glycidyl methacrylate.
16.4.9 Ionomers and Ionomeric Compatibilizers
16.4.9.1 Synthesis
Ionomers formed by copolymerization of ethylene and methacrylic acid,
either in the acid form or partially neutralized with zinc and sodium, have
been blended with poly(3-hydroxybutyrate). The blending was achieved in
an internal mixer and in a twin-screw extruder. During processing of the
mixture of poly(3-hydroxybutyrate) and the sodium neutralized ionomer,
a degradation accompanied with gas evolution took place. The best impact
resistance was noticed in blends containing 30% of zinc neutralized
ionomer, showing an increase of 53%. There is a strong indication that
exchange reactions occur during the mixing process. 99
16.4.9.2 Poly(ethylene terephthalate) and Polyamide 6
An acrylic modified polyolefin-type ionomer with Zn 2+ is suitable to compatibilize
blends of poly(ethylene terephthalate) (PET) and polyamide 6
(PA6). Compatibilization is achieved with Zn 2+ levels higher than 10%.
Good tensile and impact properties are obtained in quenched blends, while

Compatibilization 555
in annealed samples the crystallization of the main components reduces the
ductility. 48
16.4.9.3 Poly(ethylene-co-vinyl alcohol) and Polyester
Polymeric alloys of poly(ethylene-co-vinyl alcohol) (EVOH) with an amorphous
copolyester (PETG) can be prepared using the sodium or the zinc
ionomer of acrylic modified polyolefin ionomers. The sodium neutralized
ionomer is a more efficient compatibilizer than the zinc salt. 100
16.4.9.4 Poly(styrene) and Polyamide 6
Poly(styrene-co-sodium acrylate) can be synthesized via emulsion polymerization.
It is used as compatibilizer for poly(styrene) polyamide 6 mixtures.
101
16.4.9.5 Aromatic Polyester Blends
Graft copolymers of wholly aromatic TLCP and ethylene-co-acrylic acid
(EAA) ionomers can be produced using reactive processing. In particular,
a wholly aromatic copolyester of 73% hydroxybenzoate (HBA) and 27%
hydroxynaphthanoate (HNA) (Vectra A) and a wholly aromatic polyester
from the foregoing compounds with the addition of terephthalic acid
and hydroquinone was used. 102
Blends of the ionomers with Vectra A were prepared by melt mixing
in a Brabender Plasti-Corder EPL-5501 mixer at 300°C, likely due to an
acidolysis reaction.
Liquid crystalline polymer reinforced plastics are compounded from
a mixture of poly(p-hydroxybenzoate) (PHB), poly(ethylene terephthalate)
(PET) and poly(ethylene 2,6-naphthalate) (PEN). A fibrillar PHB structure
is formed in-situ in the PEN/PET matrix under a high elongational flow
field during melt spinning of the composite fibers.
The PHB microfibril reinforced PEN/PET composite fibers exhibit
a very low tensile modulus that can be explained by the assumption of a
very large number of PHB microfibrils, by the Takayanagi model. 103
16.4.9.6 Aromatic Polyether Blends
Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(2,6-dichloro-
1,4-phenylene oxide) (PDClPO) can be compatibilized with sulfonated

556 Reactive Polymers Fundamentals and Applications
poly(styrene). 104 Neutralized sulfonated poly(styrene) has a high miscibility
with both PPO and PDClPO.
16.4.10 Poly(styrene)
16.4.10.1 Poly(styrene) and Polyamide 6,6
Poly(styrene)s and nylons have been produced commercially by polymerization
in an extruder.
Blends of polyamide and poly(styrene) are attractive because the incorporation
of various functional groups such as maleic anhydride, glycidyl
methacrylate, and acrylic acid into poly(styrene) is comparatively
simple. Functionalized poly(styrene) can be used as compatibilizer for
PA/poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blends, because it is
miscible with PPO. Phthalic anhydride-terminated poly(styrene) (PS-PAH)
and styrene-maleic anhydride copolymer (SMA) is a compatibilizer at low
loadings of smaller than 10% in blends of 70%polyamide 66 (PA66) and
30% poly(styrene) (PS). 37
16.4.10.2 Poly(styrene/acrylonitrile) and Polyamide 6
Blends of polyamide 6 (PA6) and a copolymer of styrene/acrylonitrile
(SAN) can be compatibilized by an imidized acrylic polymer (IA) or a
styrene/acrylonitrile/maleic anhydride terpolymer (SANMA). 105
The addition of IA causes the phase inversion composition to shift
to a higher nylon 6 volume fraction. Without any compatibilizer, the phase
inversion occurs at a volume fraction of about 0.48 of polyamide 6. By the
addition of IA, the phase inversion composition shifts to a higher polyamide
6 volume fraction.
For uncompatibilized blends, the relationship between particle size
and composition is symmetric about the phase inversion composition,
whereas, blends compatibilized with IA show an intense asymmetric behavior,
i.e., SAN dispersed particles in a nylon 6 matrix are quite small,
while nylon 6 particles in a SAN matrix are much larger and are elongated.
106 Using Wu’s equation, predicting the dispersed phase particle size,
it is suggested that the viscosity increase of a nylon 6 phase due to the
formation of graft polymers may affect the asymmetric behavior. However,
the predicted asymmetry was less pronounced than the experimentally
observed asymmetry.

Compatibilization 557
IA also results in a significant increase of the nylon 6 phase viscosity
due to the in-situ formation of graft polymers during the melt processing.
The significant change in the ratios of the phase viscosity is to the formation
of a PA/IA graft polymer. The formation of the graft polymer may be
partially responsible for the shift of the phase inversion composition observed,
when IA is added. IA does not stabilize the morphology near the
phase inversion composition, however, it is effective at compositions where
either of the components would form a clearly defined dispersed phase.
The addition of SANMA only slightly changes the phase inversion
composition to a lower nylon 6 volume fraction. The phase viscosity nylon
6 is only slightly increased. The addition of IA or SANMA does not
increase the viscosity of the SAN phase. 105
16.4.10.3 Poly(styrene) and Ethylene/propylene Rubber
Blends of poly(styrene) (PS) andethylene/propylene rubber (EPR) can be
compatibilized by various block copolymer interfacial modifiers by melt
processing. 50
16.4.10.4 SAN and Poly(carbonate)
The nitrile groups in SAN can be converted by 1,3-aminoethylpropanediol
or by o-aminophenol into oxazoline groups. Dibutyltin oxide is an effective
catalyst. Thus, ethyl hydroxymethyl oxazoline (EHMOXA) and benzoxazole
(BenzOXA), respectively, were introduced in the polymer. 107, 108 The
modified SAN was reacted with poly(carbonate). The SAN modified with
reacted EHMOXA exhibited crosslinked structures when reacted with PC,
whereas the BenzOXA-modified SAN showed a compatibilization without
crosslinking.
16.4.10.5 SAN and EPDM
Free-radical initiators such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,
2,5-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, α,α ′ -di(tert-butylperoxy)diisopropylbenzene,
and 2,2 ′ -azobis(2-acetoxy)propane were used
for the reactive blending of styrene/acrylonitrile copolymer (SAN) and ethylene-propylene-diene
terpolymer (EPDM). 109 A dominant grafting reaction
was observed in blends using α,α ′ -di(tert-butylperoxy)diisopropylbenzene
as initiator.

558 Reactive Polymers Fundamentals and Applications
16.4.11 Polyolefins/Poly(ethylene oxide)
Personal care products, such as baby diapers, sanitary napkins, adult diapers,
etc., are generally constructed from a number of different components
and materials. Such articles typically have some portion, usually the backing
layer, that is composed of a film constructed from a liquid repellent
material.
This repellent material is appropriately constructed to minimize or
prevent the exuding of the absorbed liquid from the article and to obtain
greater utilization of the absorbent capacity of the product. The liquid
repellent film commonly used includes plastic materials such as poly(ethylene)
films.
Polymer blends of polyolefins and poly(ethylene oxide) are melt
processable but exhibit very poor mechanical compatibility. This poor mechanical
compatibility is particularly manifested in blends having greater
than 50% of polyolefin. Generally the film is not affected by water since
typically the majority phase, i.e., polyolefin, will surround and encapsulate
the minority phase, i.e., the poly(ethylene oxide).
The encapsulation of the poly(ethylene oxide) effectively prevents
any degradability and/or flushability advantage that would be acquired by
using poly(ethylene oxide). An inverse phase composition, characterized
by a continuous phase of poly(ethylene oxide) and a dispersed phase of
polyolefin, can be produced by reactive extrusion.
The components, the polyolefin, poly(ethylene oxide), poly(ethylene
glycol)methacrylate or 2-hydroxyethyl methacrylate and the initiator
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, i.e., Lupersol 101 or Interox
DHBP can be premixed before heating, and blending to produce
an inverse phase composition. Alternatively, the components may be added
simultaneously or separately to a reaction vessel for melting and blending.
Ideally, the polyolefin and poly(ethylene oxide) should be melt blended before
adding monomer or initiator. The monomer and initiator may be added
to the molten polymers separately or combined in a solution comprised of
the monomer and the initiator.
In a reactive extrusion process, it is desirable to feed the polyolefin
and poly(ethylene oxide) into an extruder before adding monomer further
down the extruder and adding initiator even further down the extruder. This
sequence facilitates mixing of the monomer or mixture of monomers into
the polymers before the initiator is added and radicals are created. 110

Compatibilization 559
16.4.12 Poly(phenylene sulfide)/Liquid Crystalline Polymers
The in-situ compatibilization of poly(phenylene sulfide) (PPS) with aromatic
thermotropic liquid crystalline polymers occurs via a transesterification
reaction between the carboxyl groups of a modified poly(phenylene
sulfide) and the ester linkages of the liquid crystalline polymer. 111
16.4.13 LDPE/Thermoplastic Starch
Thermoplastic starch (TPS), in contrast to dry starch, is capable of flow.
When thermoplastic starch is mixed with other synthetic polymers, these
blends behave in a manner similar to conventional polymer blends. A onestep
combined twin-screw/single-screw extrusion setup is suitable for the
melt-melt mixing of LDPE and thermoplastic starch.
Glycerol is used as a plasticizer for starch in the content range of 29
to 40%. It is possible to manufacture a continuous TPS (highly interconnected)
and co-continuous polymer/TPS blend extruded ribbon. This ribbon
has excellent mechanical properties in the absence of any interfacial
modifier and despite the high levels of immiscibility in the polar-nonpolar
TPS-PE system. A high degree of transparency is maintained over the entire
concentration range due to the similar refractive indices of PE and TPS
and the virtual absence of interfacial microvoiding.
This material also has the benefit of containing large quantities of a
renewable resource and hence represents a more sustainable alternative to
pure synthetic polymers. 112
16.4.14 PE and EVA
Saponified ethylene-vinyl acetate copolymers in general have good oxygen
barrier properties, mechanical strength, etc. and, as such, have found
application in many uses such as film, sheet, container material, and textile
fiber. However, this saponified copolymer gives rise to a variation in
product thickness in the molding process for manufacture of film or sheet,
with the consequent decrease in the marketability of the product. Because
of the deficiency in stretchability and flexibility, it gives rise to uneven
stretching in deep-drawing and other processes involving a stretching force
or pinholes in use of the product, thus imposing serious limitations on its
application as a packaging raw material.

560 Reactive Polymers Fundamentals and Applications
Blends of saponified ethylene-vinyl acetate copolymer and an ethylene
copolymer, such as low density poly(ethylene), linear low density
poly(ethylene), ethylene-vinyl acetate copolymer, or an ethylene-acrylic
ester copolymer show improved properties, however they need a compatibilizer.
The compatibilizer can consist of a graft polymer, obtainable by
grafting an ethylenically unsaturated carboxylic acid such as acrylic acid,
or methacrylic acid, to a polyolefin resin and reacting this carboxylic acid
or derivative thereof with a polyamide oligomer or polyamide. The compatibilizer
is added in amounts of 0.5 to 10%. 113
The compatibility of the blend is markedly improved and the material
shows an excellent oxygen barrier property and improvements in
stretchability, film thickness, and flexibility which are deficient in the saponified
ethylene-vinyl acetate copolymer alone.
16.4.15 SBR and EVA
Poly(chloroprene)/EVA blends are miscible in all proportions. However,
other EVA/rubber blends are incompatible because of the strong differences
in chemical structure, polarity, etc. EVA copolymers are potential
interesting partners for blends with unsaturated elastomers because of their
excellent ozone resistance, weather resistance, and mechanical properties.
Blends of a styrene/butadiene copolymer and an ethylene/vinyl acetate
copolymer (SBR/EVA) can be compatibilized with a mercapto-modified
EVA (EVALSH). This polymer promotes the bonding between the SBR
phase and the EVALSH through a chemical reaction between the mercapto
groups of the reactive compatibilizing agent and the double bond of the
unsaturated rubber. 114, 115 Blends of SBR and EVA find important applications
in the footwear industry
16.4.16 NBR and EPDM
The reactive compatibilization of NBR/EPDM blends can be achieved by
the combination of mercapto and oxazoline groups. 116, 117 Mercapto-modified
EPDM copolymers are blended with oxazoline-functionalized NBR.
Insoluble material was found in non-vulcanized blends which suggested
a reactive compatibilization mechanism. Namely, the mercapto groups are
able to react with the carbon-carbon double bonds of the high diene rubber.
This results in a good interaction between the phases. A functionalization
of the nitrile rubber with epoxy groups also increases performance. 118–120

Compatibilization 561
16.4.17 NBR and PA6
The compatibilization of blends of polyamide 6 with a nitrile butadiene
rubber consists of two steps: 121
1. Modification of the nitrile groups of the rubber into oxazoline in
the melt through condensation of ethanolamine with loss of ammonia.
2. Melt mixing the modified rubber with the polyamide.
16.4.18 Poly(carbonate)–Poly(vinylidene fluoride) Blends
Immiscible PC/PVDF blends can be compatibilized by the addition of
poly(methyl methacrylate) (PMMA). PMMA is miscible with PVDF and
is compatible to PC. When PVDF is premixed with 40% PMMA, the interfacial
tension with PC is substantially decreased and the interfacial adhesion
is increased. Actually, the original PVDF/PC interface is replaced
by the more favorable PMMA/PC. 122 The PMMA content in PVDF can be
decreased further, by enhancing the PMMA/PC interactions.
When the PMMA contains acid groups, the carbonate bonds of PC
can be acidolyzed according to the mechanism of Figure 16.3. However,
the acidolysis reaction does not proceed, significantly, below 240°C. The
neutralization of the carboxylic acid groups by metal cation could contribute
to the catalysis of the acidolysis reaction. Zinc cations are known for
coordinative interaction with electron donating heteroatoms and are active
in catalyzing the acidolysis grafting reaction. For this reason, a tailor-made
compatibilizer has been designed that includes the desired issues.
Poly(carbonate) and Poly(vinylidene fluoride) (PVDF) are melt
blended with a random copolymer of methyl methacrylate and 6 mol-%
of acrylic acid [poly(MMA-co-AA)] as compatibilizer. The copolymer is
neutralized by Zn 2+ . Poly(carbonate) reacts in solution at 240°C with the
compatibilizer. The reaction leads to the grafting of PC onto the copolymer
whether it is neutralized or not neutralized. In the melt at 235°C, the
grafting reaction occurs only when the copolymer is at least partly neutralized.
42
16.4.19 Bisphenol A-poly(carbonate) and ABS Copolymers
An amine-functional styrene/acrylonitrile (SAN/amine) polymer is a reactive
compatibilizer for blends of bisphenol A-poly(carbonate) and acryl-

562 Reactive Polymers Fundamentals and Applications
CH 3
CH 2 C
C
O OH
+
O C
O
O
O
CH 3
C
C
O
CH 2
CO 2
OH
Figure 16.3: Acidolysis of a Poly(carbonate) by a Pendent Polymeric Acid Group

Compatibilization 563
onitrile/butadiene/styrene (PC/ABS) copolymers. Amine groups react
rapidly with poly(carbonate).
Secondary-amine-functional SAN polymers can be synthesized by
the derivatization of an SAN/MA terpolymer with a difunctional amine,
such as 1-(2-aminoethyl)piperazine (AEP). The anhydride forms with the
amine the amic acid intermediate. A thermally or chemically mediated
dehydration yields the imide. The compatibilization reaction occurs by
the reaction of the secondary amine group attached to this SAN backbone
with the poly(carbonate). The poly(carbonate) grafts are attached to the
SAN backbone by a urethane linkage. 123
Most polyurethanes are not stable at processing temperatures above
200°C. However, urethanes resulting from piperazine or other secondary
amines do not undergo the dissociation reaction because they lack a labile
hydrogen.
16.4.20 Kevlar
Poly(p-phenylene terephthalamide) (Kevlar) is used as reinforcing material
in composite systems with a polyolefin-based thermoplastic elastomer.
With increasing amounts of Kevlar in the composite, the low-strain modulus
and tensile strength increases, while the elongation at break decreases
sharply. To improve mechanical properties of the composite, a hydrolysis
of the Kevlar surface can be employed. Further, maleic anhydridegrafted-poly(propylene)
(MA-g-PP) is used as a reactive compatibilizer.
The treated Kevlar greatly improves the low-strain modulus, the tensile
strength, and elongation at break of the composite.
In such a composite the interfacial adhesion of the fiber and the matrix
might increase, as well as the effective volume fraction of the fiber,
thereby resulting in a better distribution of the stress along the reinforcing
fiber. 124
16.4.21 Polyamides
The amino group of polyamides easily undergoes reactions with anhydrides,
acids, esters, and oxazolines. The rate of these reactions is sufficient
for applications in reactive extrusion. The polyolefins used are modified
with maleic anhydride, glycidylmethacrylate and acrylic acid and acrylic
esters.

564 Reactive Polymers Fundamentals and Applications
The amide linkage in polyamide is substantially less reactive than
the terminal primary amino group. On the other hand, the concentration
of amide linkages is much higher than amino end groups. The reaction of
an amide with an anhydride results in cleavage of the polyamide chain. It
was shown that the reaction of the amine with the anhydride is dominant
for graft formation of polyamide with polyolefins. 125–127
A copolymer of ethylene and acrylic acid (EAA) is an effective compatibilizer
precursor for PA/LDPE blends. However, the in-situ formation
of copolymers of PA grafted onto EAA is slow. A bis-oxazoline compound,
such as 2,2 ′ -(1,3-phenylene)bis(2-oxazoline) (PBO) is a promoter
for the formation of PA-g-EAA copolymers. The oxazoline rings of PBO
react under the conditions of preparation of the blends in bridging reactions.
Further, the addition of the bis-oxazoline causes some reduction of
the degree of crystallinity of the PA phase of these blends. 16
In order to compatibilize polyamide 12,12 with polyamide 6, a maleated
triblock copolymer of styrene-(ethylene-co-butene)-styrene (SEBSg-MA)
was successful. At a ratio of polyamide 12,12 to polyamide 6
of 30/70, supertoughness was achieved by the addition of 15% SEBSg-MA.
128
16.4.21.1 Ethylene/propylene Elastomers
In melt blending of nylon 6 and ethylene/propylene rubber grafted with
maleic anhydride (EPR-g-MA), for certain compositions, nylon 6 forms
finely dispersed particles due to the reaction of the polyamide amine end
groups with the grafted maleic anhydride. Under these circumstances, the
polyamide has the potential to reinforce the elastomer matrix. Further,
the addition of magnesium oxide causes significant improvement in tensile
properties of these blends. 129
16.4.22 Polyethers
Poly(phenylene ether)s (PPE) constitute a family of high performance engineering
thermoplastics possessing outstanding properties, such as relatively
high melt viscosities and softening points, which make them useful
for many commercial applications.
However, high temperatures are required to soften poly(phenylene
ether)s which cause instability and changes in the polymer structure. Further,
PPE polymers tend to degrade and to grow dark during melt process-

Compatibilization 565
ing. In order to improve molding properties and impact strength, blends of
poly(phenylene ether)s with styrene resins have been employed. 130
Polyethers will have hydroxy end groups, if they are not derivatized.
Polyethers with amino end groups and carboxyl end groups and various
nonreactive chain groups are commercially available.
Blends based on poly(2,6-dimethyl-1,4-phenylene ether) (PPE) and
poly(butylene terephthalate) (PBT) are mutually incompatible. The phase
morphologies obtained during blending of these polymers are generally
unstable. When PPE is functionalized selectively, in-situ compatibilization
during processing is possible. PPE with hydroxyalkyl, carboxylic acid,
methyl ester, amino and tert-BOC protected amino end groups are active as
compatibilizers. These reactive groups are positioned either in the middle
of the chain or as end groups. PPEs with carboxylic acid end groups are
most efficient in compatibilizing the blends with PBT. Promoters, which
catalyze or take part in the coupling between PBT and/or functionalized
PPEs, are triphenyl phosphite (TPP), sodium stearate, titanium (IV) isopropoxide,
and epoxy resins. 131
Polyolefins, particularly poly(ethylene) (PE), even when added in
small amounts, can noticeably change some characteristics of the PPE,
such as impact strength and solvent resistance. PE acts as a plasticizer for
PPE, and the resulting blends are endowed with enhanced workability and
better surface properties.
In order to increase the amount of compatible PE in PPE-PE blends,
styrene (co)polymers or block copolymers of styrene and a conjugated
diene as compatibilizers can be added. Another possibility is the use of
PPE-PE copolymers. These copolymers serve as compatibilizers for PPE
and PE.
Poly(phenylene ether)-grafted polyolefin can be obtained by reacting
a glycidylated PPE with a polyolefin having anhydride groups or by
reacting a poly(phenylene ether) having anhydride groups with a glycidylated
polyolefin, respectively. 132
In particular, PPE can be end-capped with epoxychlorotriazine.
PPE-PE graft copolymers can also be obtained by melt kneading a poly-
(phenylene ether), modified with maleic anhydride and a polyolefin, modified
with maleic anhydride in the presence of a binder such as phenylene
diamine. 133
Further, poly(phenylene ether)-poly(ethylene) copolymer blends can
be prepared by reactive melt blending of poly(phenylene ether) or an ester

566 Reactive Polymers Fundamentals and Applications
end-capped poly(phenylene ether) with an ethylene/acrylic acid copolymer.
130 End-capped PPE is generally prepared by the reaction of a poly-
(phenylene ether) with carboxylic anhydride in the presence of a catalyst.
16.4.23 Polyurethane and Poly(ethylene terephthalate)
The compatibility behavior of polyurethane (PU)/poly(ethylene terephthalate)
(PET) is of interest because of the following considerations: 134
1. PET is a widely used thermoplastic with a poor impact resistance
when it is injection molded. The combination with PU promises
to raise its impact strength.
2. The polymer pair may be compatible since the carbonyl groups of
the polyester may interact with the hydrogens of NH groups of the
polyurethane.
Polymeric alloys with good mechanical properties over the complete
composition range are obtained by melt blending a polyester polyurethane
(PU) and poly(ethylene terephthalate) (PET). During the mixing, ester-amide
reactions take place which cause an in-situ reactive compatibilization
without a catalyst. 134
16.5 FUNCTIONALIZATION OF END GROUPS
16.5.1 Mechanisms
16.5.1.1 Anionic Polymerization
Poly(styrene) with hydroxyl end groups can be prepared by anionic polymerization.
After the propagation reaction, the living polystyryl anions are
reacted with ethylene oxide by a ring opening reaction. A poly(styrene)
with hydroxyl end groups can be reacted with polyolefins that are modified
with maleic anhydride.
The process can be conducted either in solution or by the extrusion
of a mixture of the two modified polymers in a single-screw extruder. A
high yield of graft copolymer is obtained.
Poly(ethylene-co-methyl acrylate) can be transesterified with hydroxy-terminated
poly(styrene) in a batch mixer. The final conversion and
the rate of the reaction are strongly dependent on the molecular weight of
the poly(styrene). 135

Compatibilization 567
The transesterification of ethylene and alkyl acrylate copolymers
with 3-phenyl-1-propanol (PPOH) as a model substance was studied in
1,2,4-trichlorobenzene solution and in the melt. Among various catalysts,
dibutyltin dilaurate (DBTDL) and dibutyltin oxide (DBTO) show the highest
activities. In the melt, in a semi-open batch mixer at temperatures between
170 and 190°C, the equilibrium is totally shifted to the product side
due to effective removal of the lighter alcohols generated from the reaction.
136
16.5.1.2 Living Free-Radical Polymerization
Free-radical polymerization has not been regarded as a useful technique
in the synthesis of end-functional polymers, however, the advent of living
radical polymerization has changed the situation. End-functional polymers
can now be produced with this technique. 137–139
Living free-radical polymerization is a comparatively recent method
for controlled free-radical polymerization. It combines the advantages of
conventional free-radical polymerization (simple production process, low
cost, and a wide range of monomers) with those of living polymerization
(polymers of a defined structure, molecular weight, molecular weight distribution,
and end group functionality).
Precise control of the free-radical polymerization is achieved by reversible
chain termination/blocking (endcapping) after each growth stage.
The equilibrium concentration of the actively polymerizing chain ends at
this point is so low in comparison with the equilibrium concentration of the
blocked (dormant) chain ends that termination and transfer reactions are
largely suppressed in comparison with the growth reaction. Since endcapping
is a reversible reaction, all the chain ends remain living providing that
no terminating reagent is present. This allows the control of the molecular
weight, a narrow molecular weight distribution, and purposeful functionalization
of the chain end by terminating reagents. Various techniques of
living free-radical polymerization are known: 140
• Iniferter Method
• Reversible Chain Termination
• Atom Transfer Radical Polymerization.
Iniferter Method. The iniferter method uses a class of free radical initiators
which can enter into initiation, transfer, and reversible termination re-

568 Reactive Polymers Fundamentals and Applications
actions, e.g., tetraalkylthiuram disulfides which are photolytically cleaved
and activated. In this manner, it is possible to produce polymers having
dithiocarbamate end groups that may be reactivated by irradiation.
Poly(isoprene-butyl acrylate) block copolymers have been prepared
by the iniferter method. These block copolymers were used as compatibilizers
in blends of natural rubber and acrylic rubber. 141
Reversible Chain Termination. The principle of reversible chain termination
uses free radicals based in linear or cyclic nitroxides such as
tetramethyl-1-piperidinyloxy (TEMPO). If this nitroxide is reacted with
a reactive carbon radical capable of initiating a free radical vinyl polymerization
reaction, a reversibly cleavable C–O bond is formed which, when
subjected to moderate heating, is capable of bringing about polymerization
by insertion of vinyl monomers between the nitroxide and carbon radical.
After each monomer addition, the newly formed radical is scavenged
by the nitroxide. This reversibly blocked chain end may then insert further
monomer molecules. Reversible termination with nitroxide may use, for
example, a combination of dibenzoyl peroxide (BPO) and TEMPO.
Atom Transfer Radical Polymerization. Another approach is atom
transfer radical polymerization (ATRP). Here, a transition metal complex
compound ML x abstracts a transferable atom or group of atoms X, for
example, Cl and Br, from an organic compound RX to form an oxidized
complex compound ML x X and an organic radical R·, which undergoes an
addition reaction with a vinyl monomer Y to form the carbon radical RY ·.
This radical is capable of reacting with the oxidized complex compound,
transferring X to RYX and regenerating ML x , which can initiate a new
ATRP reaction and thus a further growth stage. The actively polymerizing
species RY· is thus reversibly blocked by the abstractable group X with
the assistance of the transition metal compound, which makes the redox
process possible. 140
Telechelic Polymers. Telechelic substances are generally defined as linear
oligomers or low molecular weight linear polymers having functional
groups on both chain ends. Living free-radical polymerization is a suitable
method to produce such telechelic polymers. For example, telechelic
polyacrylates can participate in crosslinking, chain extension or coupling
reactions conventionally used in lacquer chemistry. Therefore, they are of

Compatibilization 569
great interest for use in the lacquer industry. Telechelic polymers can be
produced by atom transfer radical polymerization with a suitable functionalizing
reagent that has a polymerizable double bond. 140 Examples for the
production of telechelic polymers are given in Table 16.3.
16.5.1.3 Friedel-Crafts Alkylation of Poly(styrene) and Polyolefin
Poly(styrene) is subject to a Friedel-Crafts alkylation with AlCl 3 as catalyst.
A PP macrocarbocation is chemically bonded to the PS benzene ring
by aromatic electrophilic substitution. 142
In-situ compatibilization of polyolefin and poly(styrene) is achieved
by Friedel-Crafts alkylation through a reactive extrusion process. Styrene
monomer is used as co-catalyst . A two-step procedure gives better results
than a one-step procedure. The method has the potential to recycle mixed
wastes from polyolefins and poly(styrene). 143 In the case of blends of PS
and LLDPE it was proven that the LLDPE segments were grafted onto the
para position of the benzene rings of PS. 144
16.5.2 Amino-terminated Nitrile Rubber
Amino-terminated nitrile rubber reacts with maleic anhydride grafted poly-
(propylene).
16.5.3 Functionalization of Olefinic End Groups of Poly(propylene)
Various end groups, such as anhydride, carboxylic acid, alcohol, thiol, silane,
and borane can be introduced into the terminal unsaturations of poly-
(propylene) with a metallocene catalyst. 145
16.5.3.1 Maleated Poly(propylene)
Maleated poly(propylene) is not a copolymer of maleic anhydride and
propylene, such that the maleic anhydride moiety is predominantly in the
backbone of the copolymer. Suitable monomers for preparing functionalized
poly(propylene) are
• Olefinically unsaturated monocarboxylic acids, e.g., acrylic acid
or methacrylic acid, and the corresponding tert-butyl esters, e.g.,
tert-butyl acrylate or tert-butyl methacrylate,

570 Reactive Polymers Fundamentals and Applications
Table 16.3: Production of Telechelic Polymers 140
Example No. 1 2 3 4 5 6
Composition
CuCl/CuBr 49 25 25 20 9 30
Bipyridin 234 117 117 94 43 140
Methyl methacrylate 939 500 196 400 187 100
n-Butyl acrylate 894 128
2-Ethylhexyl acrylate 184
Allyl alcohol 582 135 171
AMPC 175 112 153 344
HCPA 246 61
NHCPA 50
BIAE
α,α-Dichlorotoluene 32 15 48
Butyl acetate 710 440 440 440 180 440
Reaction time [h] 60 20 21 24 22 21
Reaction temp. [°C] 130 130 130 130 130 130
M n (GPC) 1900 6300 2500 3000 3100 2000
M w /M n (GPC) 1,25 1,14 1,39 1,43 1,25 1,43
Functionality a 1,8 1,9 1,97 1,95 >1.6 >1,8
AMPC Allyl-N-(4-methyl-phenyl)carbamate
HCPA 4-Hydroxybutyl-2-chloro-2-phenylacetate
NHCPA N-(2-Hydroxyethyl)-2-chloro-2-phenylacetamide
BIAE 2-Bromoisobutyric acid ethylester
a
with respect to end groups
Example 1:
Initiator + end capping with allyl alcohol
Examples 2 and 3: OH-functional initiator + end capping with
the phenylurethane derivative of allyl alcohol
Examples 4 and 6: Double end capping with the phenylurethane
derivative of allyl alcohol
Example 5:
Double end capping with allyl alcohol.

Compatibilization 571
• Olefinically unsaturated dicarboxylic acids, e.g., fumaric acid,
maleic acid, and itaconic acid and the corresponding di-tert-butyl
esters, e.g., mono or di-tert-butyl fumarate and mono or di-tertbutyl
maleate,
• Olefinically unsaturated dicarboxylic anhydrides, e.g., maleic
anhydride, sulfo- or sulfonyl-containing olefinically unsaturated
monomers, e.g., p-styrenesulfonic acid, 2-methacrylamide-
2-methylpropenesulfonic acid or 2-sulfonyl(meth)acrylate,
• Oxazolinyl-containing olefinically unsaturated monomers, e.g.,
vinyloxazolines and vinyloxazoline derivatives, and
• Epoxy-containing olefinically unsaturated monomers, e.g., glycidyl
(meth)acrylate or allyl glycidyl ether.
The most common monomer for preparing functionalized poly(propylene)
is maleic anhydride. Maleated poly(propylene) is commercially
available.
16.5.3.2 Amine Functions in Poly(propylene)
A polyether monoamine containing ethylene oxide (EO) units and propylene
oxide (PO) units is useful as a reactant with maleated poly(propylene)
to form a reaction product that can be blended with poly(propylene). 146
Generally, the polyether amines are made by aminating a polyol, such as
a polyether polyol with ammonia in the presence of a catalyst such as the
nickel-containing catalyst Ni/Cu/Cr.
The mixing of the maleated poly(propylene) and polyetheramine
may be carried out in a customary mixing apparatus including batch mixers,
continuous mixers, kneaders, and extruders. For most applications,
the preferred customary mixing apparatus is an extruder in which the polyetheramine
is grafted onto the maleated poly(propylene). The residence
time varies from about 25 to 300 seconds. The preferred temperature range
is from about 190 to 260°C.
Blends of poly(propylene), maleated poly(propylene), and Jeffamine
M-2070 produced in an extruder exhibit the characteristics as shown
in Table 16.4.
Maleated poly(propylene) and polyether amine show improved
paintability, improved impact resistance, and excellent mold flowability
over blends of poly(propylene) and maleated poly(propylene).

572 Reactive Polymers Fundamentals and Applications
Table 16.4: Properties of Poly(propylene) Blends with Poly(propylene)
Modified Polyether Amines 146
Example 1 2 3 4 5 6
% MAL-PP 20 20 20 30 30 30
% M2070 0 2 4 0 2 4
FM,[kpsi] 284 255 226 289 256 201
StY, [psi] 8660 7980 7030 8750 7830 6170
TE,% 8 16 10 4 13 5
TSt [psi] 4990 4770 4280 5000 4630 3720
NI [ft lb/in] 0.161 0.220 0.386 0.123 0.139 0.220
UnI [ft lb/in] 12 14 10 10 14 5
%MAL-PP % Maleated poly(propylene)
% M2070 % Jeffamine 2070
Rest filled with poly(propylene) to 100%
FM Flexural modulus
StY Stress at yield
TE
Tensile elongation
TSt Tensile strength
NI
Notched Izod impact
UnI Unnotched Izod impact
16.5.3.3 Amidoamine Functions in Poly(propylene)
Amidoamines can be obtained by reacting caprolactam, laurolactam or another
cyclic lactam with a polyetheramine. The molar ratio of lactam to
amine may vary in wide ranges. Water may be used to control the speed of
the reaction and the molecular weight of the amidoamine product.
The polyetheramines used to make the amidoamines are prepared
from ethylene oxide and propylene oxide. Any combination of ethylene
oxide and propylene oxide will work, however, the ratio of ethylene oxide
to propylene oxide may be tailored to control the water absorption. The
amount of ethylene oxide should be greater than about 90%. Maleated
poly(propylene) is used for reaction of the amidoamines. 147
The reaction takes place in an extruder in which the amidoamine reacts
with the maleated poly(propylene) to form a reaction product at about
240°C to about 260°C. Blends of poly(propylene), maleated poly(propylene),
and amidoamine can be produced in a single-screw extruder.

Compatibilization 573
16.5.4 Muconic Acid Grafted Polyolefin Compatibilizers
Muconic acid is also known as 2,4-hexadienedioic acid. cis,cis-muconic
acid and cis,trans-muconic acid are commercially available. Due to its
double bonds and diacid functionality, muconic acid can undergo a wide
variety of reactions. Many muconic acid derivatives are known, including
lactones, sulfones, polyamides, polyesters, thioesters, addition polymers,
and other compounds. Such compounds have a wide variety of uses, including
use as surfactants, flame retardants, UV light stabilizers, thermoset
plastics, thermoplastics, and coatings. Muconic acid units grafted onto a
polyolefin backbone are compatibilizers. The muconic acid group itself
may have special advantages in the reactive compatibilization of certain
polymers due to its particular chemical properties compared to other functional
groups. 148
To manufacture the compatibilizer, the polyolefin is melt extruded
with muconic acid at a temperature in the range of about 180°C to 220°C. A
suitable initiator is Lupersol 130, an organic peroxide free-radical initiator
containing 2,4-dimethyl-2,5-di(tert-butylperoxy)-3-hexyne. When the
polyolefin and muconic acid are mixed and free radical addition is initiated
a hydrogen atom on a polyolefin carbon atom (either on the main chain or
on a side group) is replaced by a muconic acid side group; the muconic
acid loses one of its double bonds as one of its carbon atoms bonds to the
polyolefin carbon atom in place of the lost hydrogen and the muconic acid
side group picks up another hydrogen atom. Only little polymer degradation
during muconic acid grafting compared to the known degradation
produced by grafting acrylic acid and other units onto polyolefins is observed.
Muconic acid graft copolymers exhibit a greater intrinsic viscosity
retention than acrylic acid graft copolymers. Muconic acid graft copolymers
are also far more ductile.
16.5.5 Polyfunctional Polymers and Modified Polyolefin
By the reaction of a polyfunctional polymer with a modified polyolefin,
crosslinked products may be formed. A copolymer of vinyloxazoline or
2-isopropenyl-2-oxazoline (IPO) and styrene produced by Dow, containing
ca. 1% oxazoline, has been used for the reaction with carboxylic acid
functional polyolefins. 149, 150 A copolymer of styrene and 2-isopropenyl-
2-oxazoline (SIPO) and a copolymer of ethylene and acrylic acid have been
melt blended at 280°C in an extruder. 151

574 Reactive Polymers Fundamentals and Applications
N
C
O
CH 2
CH 2
+
HO
O
C
O
C
N
H
O
CH 2 CH 2 O C
Figure 16.4: Reaction of Oxazoline and Carboxylic Acid 152
Other suitable polymers, being reactive with the oxazoline group,
include those which contain amine, carboxylic acid, hydroxyl, epoxy, mercaptan,
and anhydride in the polymer chain or as end groups. Examples
are SIPO and a high density poly(ethylene)/maleic anhydride graft copolymer
(HDPE/MA), a styrene/acrylonitrile/IPO terpolymer (SANIPO), and
a propylene/acrylic acid copolymer (PAA) with /6acrylic acid, 75% SIPO,
and 25% of a carboxylated polyester resin, sold as Vitel VPE6434, SIPO
and a vinylidene chloride/methacrylic acid copolymer with 1% methacrylic
acid. 153 The reaction of the oxazoline group with a carboxylic acid group
is shown in Figure 16.4.
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17
Rheology Control
17.1 MELT FLOW RATE
The technical terms melt flow index (MFI), melt flow rate (MFR), and
melt flow number (MFN) are used synonymously. Throughout the text we
prefer to use melt flow rate.
The melt flow rate is the measure of a polymer’s ability to flow under
certain conditions. It measures a melt flow rate, which is the amount of
polymer that flows over a period of time under specified conditions. Typical
melt flow units of measurement are dg/min. Melt flow provides an
indication of the resin’s processability, such as in extrusion or molding,
where it is necessary to soften or melt the polymer. 1
17.2 RHEOLOGY CONTROL TECHNIQUES
High melt flow rate poly(propylene) can be produced directly in a polymerization
reactor, but its production is often limited by the solubility of
hydrogen in the reaction. Hydrogen is the most effective chain transfer
agent for propylene polymerization reactions, whether the reaction takes
place in solution or in the bulk monomer. 2
Another method for producing high melt flow rate poly(propylene)
is to degrade low melt flow rate poly(propylene) using controlled rheology.
Controlled rheology treatments are often employed as alternative
techniques for producing high melt flow rate poly(propylene) because these
treatments do not depend on hydrogen solubility.
587

588 Reactive Polymers Fundamentals and Applications
Controlled rheology treatments can also be used to increase production
efficiency by converting the low melt flow rate polymers into high
melt flow rate polymers without changing the reactors operating conditions.
Thus, many manufacturers prefer controlled rheology treatments to
produce high melt flow rate polymers.
Poly(α-olefins), particularly poly(propylene), may have its weightaverage
molecular weight decreased substantially, or its melt flow rate substantially
increased, by controlled degradation of the polymer. This may
be accomplished by
1. Reaction of the polymer with free radicals or free radical-producing
agents such as peroxides,
2. Heat treatment, and
3. Subjecting the polymer to high shear, 3
or combinations of these methods. The effect attained is that the polymer
molecule scission occurs, resulting in an overall lowered molecular weight
or elevated MFR.
Early techniques have been developed to degrade and to narrow the
molecular weight using high shear gradients at temperatures between the
melting point and the temperature at which purely thermal degradation of
the polyolefin occurs. 3
The degradation of the polyolefin can be achieved by a metal salt
catalyst. 4 A crystalline polyolefin is mixed with a metal salt of a carboxylic
acid, and the resultant mixture is heated in an atmosphere which is
substantially free of oxygen to a temperature of 275 to 450°C. Also an organic
anhydride catalyst is suitable for degradation of polyolefins at 200 to
400°C. 5 The controlled oxidative degradation of propylene polymers has
been further proposed by injecting oxygen or an oxygen-containing gas
and an organic or inorganic peroxide. Next the melt is subjected to a high
shear. An essentially odor-free propylene polymer can be recovered with a
melt flow rate higher than that of the feed polymer. 6
The addition and reaction of a peroxide with polymer is well known
in the industry and is known generally as vis-breaking or peroxide degradation.
7 Polymer resins produced with a low melt flow may need to be further
modified after their initial polymerization to improve their processability.
This is typically done through controlled rheology (CR) techniques

Rheology Control 589
wherein the molecular weight of the polymer is lowered, usually by the addition
of peroxide, to improve its flowability. This secondary processing,
however, adds additional processing steps and increases the cost of manufacturing.
Controlled rheology processing may also degrade the polymer
and leave peroxide residue so that its use may be limited in certain applications.
17.2.1 Pelletizing
While vis-breaking is useful to the finishing of the polymer, it creates a
need for an extra process step and adds expense to the process in equipment
and process requirements.
Provision of vis-breaking or controlled rheology (CR) process initiators
prior to or during pelletization is a complex operation.
Typical pelletizing equipment operates at shear rates or temperatures
sufficient to trigger molecular degradation. However, molecular degradation
should not take place during pelletizing. Instead, it is desirable that
vis-breaking is the last process step prior to the final polymer transformation
into its desired product. If vis-breaking already occurs in a preprocess,
the material would result in a low-viscosity, sticky mass rather than discreet
easily to handle pellets.
This problem can be solved if the preparation of the pellets starts
with a lower initial molecular weight polymer, or higher melt flow rate
polymer. Such a material will generate less frictional heat in compounding
into pellets. This means that the viscous dissipation of the heat will cause
less peroxide activation and allow pelletizing at generally lower temperatures
or at longer exposure periods.
Using lower weight-average molecular weight M w , or higher melt
flow rate, the starting material requires less of the vis-breaking agent, such
as peroxide, to reach the desired very high or ultra-high melt flow rates.
A further benefit is the formation of less of the undesirable by-products of
peroxide degradation.
Poly(propylene) with 30 to 33 g/min MFR and with xylene solubles
of about 2 to 6% material is compounded with peroxides and 0.025% calcium
stearate. To obtain a polymer with MFR in the range of 120 to 150
g/min, about 1,800 to 2,000 ppm of peroxide will be added.
The inclusion of other additives can be accomplished in a continuous
blender in a separate step. The dry-blended material plus additive

590 Reactive Polymers Fundamentals and Applications
is further compounded and pelletized under time and conditions where the
peroxide would not react to decompose the polymer significantly. By keeping
the residence time short and the temperature low to prevent significant
molecular scission or degradation, the polymer can be neatly and cleanly
pelletized. Thus, a useful, easily handled, and convenient pelletized product
is created. 7
17.3 PEROXIDES FOR RHEOLOGY CONTROL
The technique for controlling the rheology of homopolymers and copolymers
of poly(propylene) consists of peroxide degradation of these polymers.
It is used to develop fluid products in an efficient way without having
a detrimental effect in terms of production flow rates by reducing the
number of basic polymerization powders.
It is also possible to melt a propylene homopolymer or copolymer
powder and to incorporate in it a peroxide before the extrusion followed by
granulation.
Peroxide radicals can cause chain scission resulting in shorter polymer
chains, which increases the melt flow rate of the polymer. Such modification
also causes a decrease in the flexural modulus versus non-degraded
polymer of similar final melt flow rate.
The drawback of this process is the fact that these products have
mechanical properties, strength and shock resistance that are weaker than
those of a product that is obtained directly after polymerization, extrusion
and granulation, or a powder that has been extruded and pelletized for a
second time.
Actually, a poly(propylene) resin that is degraded by a peroxide may
contain peroxide radicals, thus runs the risk of modifying the viscosity of
the resin when it is processed at elevated temperatures. During this transformation,
the peroxide again degrades the resin to reduce its viscosity.
Now, during storage, the peroxide has the tendency to migrate and
therefore to leave the resin. Thus, during the storage period, the resin may
have a different behavior and show a viscosity that is different during or
after processing, depending on whether there is a little or a lot of peroxide. 8
17.3.1 Hydroperoxides
Hydroperoxides for rheology control are shown in Table 17.1.

Rheology Control 591
Table 17.1: Hydroperoxides for Controlled Rheology 8
Hydroperoxide
tert-Butyl hydroperoxide
tert-Amyl hydroperoxide
Pinane hydroperoxide
Cumene hydroperoxide
2,5-Dimethyl-2,5-di(hydroperoxy)hexane
Diisopropylbenzene mono hydroperoxide
Remarks
Most common
Common
17.3.2 Peroxides
Peroxides for rheology control are shown in Table 17.2.
17.3.2.1 4-(tert-Amylperoxy)-4-methyl-2-pentanol
4-(tert-Amylperoxy)-4-methyl-2-pentanol has over the years found utility
as a reactant or a reaction catalyst which made use of its hydroxy functionality
for various purposes. 9
17.3.2.2 DHBP
Over time, because of its safety in handling and decomposition temperature,
one specific peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane
(DHBP) also known as LUPEROX 101, Trigonox 101, and Interox,
has become the industry standard for poly(propylene) modification. 9
DHBP is a liquid, so the dosage and admixture are more comfortably
compared to solid peroxides. Its half-life time is 5.9 s at 200°C. Typical
decomposition side products of DHBP are considered to be acceptable for
using it as an additive for food packages.
17.3.2.3 Di-tert-butyl peroxide
Di-tert-butyl peroxide (DTBP) has a particularly simple structure and from
the commercial point of view is the most advantageous of these peroxides.
However, it has high volatility and its use is therefore restricted. DTBP is
only added in low concentrations, in the form of a master batch with a solid
carrier. In addition, its ignition point is between 48 and 55°C, even under
nitrogen. Safety issues in its use are therefore problematic. DTBP can be
fed as a liquid via metering pumps to the extruder.

592 Reactive Polymers Fundamentals and Applications
Peroxide
Table 17.2: Peroxides for Controlled Rheology 8
Remarks
Dibenzoyl peroxide
p-Chlorobenzoyl peroxide
Lauroyl peroxide (Dodecanoyl peroxide)
Decanoyl peroxide
3,5,5-Trimethylhexanoyl peroxide
Acetyl peroxide
2,5-Dimethyl-2,5-di(benzoylperoxy)hexane
2,5-Dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane
2,2-Di(tert-butylperoxy)butane
2,2-Di(tert-amyl)peroxypropane
10
4-(tert-Amylperoxy)-4-methyl-2-pentanol
9
1,1-Di(tert-butylperoxy)cyclohexane
1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane
1,1-Di(tert-amylperoxy)cyclohexane
2,2-Bis(4,4-di-tert-butylperoxycyclohexyl)propane
2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne Lupersol 130
Di-tert-butyl peroxide
Di-tert-amyl peroxide
1,4-Di(tert-butylperoxyisopropyl)benzene
2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane Trigonox 101
1,1,4,4,7,7-Hexamethylcyclo-4,7-diperoxynonane
3,3,6,6,9,9-Hexamethylcyclo-1,2,4,5-tetraoxanonane
3,6,6,9,9-Pentamethyl-3-n-propyl-1,2,4,5-tetraoxacyclononane
10
3,6,6,9,9-Pentamethyl-3-(ethyl acetate)-
USP-138
1,2,4,5-tetraoxacyclononane
3-Phenyl-3-tert-butylperoxyphthalide

Rheology Control 593
However, when the peroxide is added as a liquid to the extruder,
disadvantages are often encountered in relation to polymer properties, in
particular the film properties of degraded propylene polymers. There is
the danger of explosion within the extruder. Gaseous DTBP is capable of
exploding even in an inert gas atmosphere. If a gas explosion of this type
extends to involve liquid peroxide, wherever it is present it can damage the
extruder. 11
Other compounds of this type which are more expensive but easier
to handle are frequently used in industrial applications.
17.3.3 Diacyl Peroxides
Diacyl peroxides and hydroperoxides often exhibit an induced decomposition.
Acyl peroxides decompose into acyloxy radicals. These radicals
undergo β-scission very fast to give the corresponding alkyl radical or aryl
radical and eject carbon dioxide. Therefore, the acyloxy group is not observed
in the decomposition products.
17.3.4 Ketone Peroxides
Methylethylketone peroxide and methylisobutylketone peroxide are known
to be mixtures of several different ketone peroxide compounds, among
which the noncyclic ketone peroxides predominate. However, these ketone
peroxides do contain some small quantities of cyclic ketone peroxides
which result from side reactions during the preparation of the methylethyl
and methylisobutylketone peroxides. For example, in commercially available
methylethylketone peroxides about 1 to 4% of the total active oxygen
content is attributable to cyclic ketone peroxides.
17.3.4.1 Cyclic Ketone Peroxides
The cyclic ketone peroxides are exceptionally well suited for use in the
modification of polymers. In general, the cyclic ketone peroxide trimers
are less volatile and more reactive than the corresponding dimers.
Cyclic peroxides can be made by reacting a ketone with hydrogen
peroxide. Suitable ketones for use in the synthesis of the cyclic peroxides
include methylethylketone, methylisobutylketone, diethylketone,
and methylisopropylketone. Therefore, examples for cyclic peroxides are

594 Reactive Polymers Fundamentals and Applications
H 3 C
CH 3 CH 3
CH 3 CH 3
C O O C CH 2 CH 2 C O O C CH 3
CH 3 CH 3 CH 3 CH 3
2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane
H
H 5 C 2
CH 3
O O
C C C
H 3 C C 2 H 5
H 3 C
O O
2 5
O
C
O
3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane
Figure 17.1: 2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane and
3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane
cyclic methylethylketone peroxide, cyclic methylisobutylketone peroxide,
cyclic diethylketone peroxide, and cyclic methylisopropylketone peroxide.
Cyclic ketone peroxides are composed of at least two ketone peroxide
entities which may be the same or different. Thus, cyclic ketone peroxides
may exist in the form of dimers, trimers, etc. When cyclic ketone
peroxides are prepared, a mixture usually is formed which predominantly
exists of the dimeric and trimeric forms. The ratio between the various
forms mainly depends on the reaction conditions during the preparation.
The peroxides can be prepared, transported, stored, and applied as
such or in the form of powders, granules, pellets, pastilles, flakes, slabs,
pastes, and solutions. These formulations may optionally be phlegmatized,
as necessary, depending on the particular peroxide and its concentration in
the formulation .
Other examples for cyclic ketone peroxides, are, 12 e.g., 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane,
and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,
c.f. Figure 17.1. Cyclic ketone peroxides give a much
higher degree of poly(propylene) degradation than their non-cyclic ketone
peroxide counterparts. The degradation of polyolefins with cyclic ketone
peroxides results in less yellowing than comparable processes employing
their non-cyclic ketone peroxides. The principal advantage of these prod-

Rheology Control 595
ucts is that they do not produce tert-butanol as a decomposition by-product.
17.3.5 Masterbatches of Peroxides
Masterbatching can be used to facilitate the process mixing the peroxide
with the polyolefin. Masterbatching refers to a process of adding a small
amount of poly(propylene), which has an organic peroxide and/or other
additives within it, to a larger amount of poly(propylene) and subsequently
blending and extruding in order to achieve the desired poly(propylene)
characteristics.
A problem in masterbatching is the melt blending of large amounts
of peroxide into poly(propylene). This is difficult because the peroxide
tends to decompose during the melt blending step. While some of the peroxide
can survive the melt blending step, at least some degrades the poly-
(propylene). Another problem with mixing solid poly(propylene) pellets,
flakes, or powder with a liquid organic peroxide is that the poly(propylene)
does not usually form a homogeneous, free-flowing phase with the liquid
organic peroxide.
Usually, an absorbent, such as silica, is added to the poly(propylene)
in order to facilitate the addition of organic peroxide in the masterbatching
process. However, an absorbent which is added to the poly(propylene) can
interfere with the processing of the poly(propylene) material. Therefore,
poly(propylene) which could absorb liquid organic peroxide without the
necessity of using other absorbents, such as silica, is of great economic
and scientific value.
A free-flowing material typically contains 80 to 90% of poly(propylene)
and 10 to 20% of liquid organic peroxide. The organic peroxide used
can be any liquid organic peroxide, for example: 2,5-dimethyl-2,5-di(tertbutylperoxy)-3-hexyne,
dicumylperoxide or 2,5-dimethyl-2,5-di-tert-butylperoxyhexane.
13
17.3.6 Peresters
Peresters for controlled rheology are shown in Table 17.3. Peresters decompose
into acyloxy and alkoxy radicals.
17.3.7 Properties of Peroxides
Peroxides used in industrial applications are shown in Table 17.4.

596 Reactive Polymers Fundamentals and Applications
Table 17.3: Peresters for Controlled Rheology 8
Peresters
tert-Butylperoxybenzoate
tert-Butylperoxyacetate
tert-Butylperoxy-3,5,5-trimethylhexanoate
O,O-tert-Butyl-O-isopropyl monoperoxy carbonate
O,O-tert-Butyl-O-(2-ethylhexyl)monoperoxy carbonate
O,O-tert-Amyl-O-(2-ethylhexyl)monoperoxy carbonate
tert-Butylperoxyisobutyrate
tert-Butylperoxy-2-ethylhexanoate
tert-Amylperoxy-2-ethylhexanoate
tert-Butylperoxypivalate
tert-Amylperoxypivalate
tert-Butylperoxyneodecanoate
tert-Butylperoxyisononanoate
2,5-Dimethylhexene-2,5-diperoxyisononanoate
tert-Amylperoxyneodecanoate
α-Cumylperoxyneodecanoate
3-Hydroxy-1,1-dimethylbutylperoxyneodecanoate
tert-Butylperoxymaleate
Ethyl-3,3-di(tert-butylperoxy)butyrate
Ethyl-3,3-di(tert-amylperoxy)butyrate
n-Butyl-4,4-di(tert-butylperoxy)valerate
Di(2-ethylhexyl)peroxydicarbonate
Dicyclohexylperoxydicarbonate

Rheology Control 597
Table 17.4: Industrial Used Peroxides for Controlled Rheology and Crosslinking
14
Peroxide
Remarks
2,5-Dimethyl-2,5-di(tert-butylperoxy)- Lupersol 130,
3-hexyne
Mackine 201
2,5-di(tert-Butylperoxy)hexyne
DYBP
Di(2-tert-butylperoxyisopropyl)benzene Perkadox 14-40
Dicumyl hydroperoxide
Perkadox BC-FF
tert-Butyl hydroperoxide
1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane
Varox 231-XL
α,α ′ -Bis(tert-butylperoxy)diisopropyl benzene
or crosslinking of
Varox VC-R vulcanization
elastomers
Peroxide for Other Uses
Remarks
Dibenzoyl peroxide
Curing
MEK peroxide
Curing
Dicumyl peroxide
Vulcanizing agent
tert-Butylperoxybenzoate Esperox 10
Lauroyl peroxide (Dodecanoyl peroxide)
1,3-Di(2-tert-butylperoxyisopropyl)benzene
Methylisobutylketone peroxide
Methylethylketone peroxide
Laurox W-25 Polymerization
initiator
Trigonox HM curing of unsaturated
polyester resins
Curing of unsaturated polyester
resins

598 Reactive Polymers Fundamentals and Applications
CH 3 CH 3
C O O C
CH 3 CH 3
CH 3 CH 3
C O* *O C
CH 3 CH 3
2
O
C
CH 3
*CH 3
Figure 17.2: Decomposition of Dicumylperoxide 15
Some peroxides suffer from excessively long half-lifes. However,
the half-life of the initiator should be shorter than the residence time of
the resin in the extruder. A long half-life is undesirable because it will
lead to product quality problems due to residual peroxide in resin, or lower
productivity or higher resin color depending on the amount of undecomposed
peroxide in the resin. These include longer residence times or higher
temperatures in the extruder. 9
Often the use of safety diluent is required. Diluents are undesirable
in at least some poly(propylene) grades because they may produce smoking
or dripping in an end user’s extruder. It has been reported that diluents
are also undesirable for fiber or film grades where, for example, they may
adversely affect the feel of the surface.
17.3.7.1 Mechanism of Decomposition
Peroxides decompose in a rather complicated way in a multistep reaction.
The mechanism of decomposition of dicumylperoxide is shown in Figure
17.2. The mechanism of decomposition of dicumylperoxide is shown in
Figure 17.3.

Rheology Control 599
CH 3 CH 3 CH 3 CH 3
CH 3 C O O C
C O O C CH 3
CH 3 CH 3 CH 3 CH 3
4 * CH 3
2 H 3 C
O
C
CH 3
O
C
O
C
CH 3
CH 3
Figure 17.3: Decomposition of 1,4-Di(tert-butylperoxyisopropyl)benzene 15
17.3.7.2 Kinetics of Decomposition
Most studies on the decomposition of peroxides have been done in dilute
solutions at low temperatures at which only small concentrations of radicals
occur at low pressures. The conditions under which grafting occurs in
the extruder are different in these aspects:
• High temperatures,
• High pressures,
• High viscous environment.
For these reasons there is not much knowledge concerning the radical
reaction in the extruder. However there are some qualitative statements.
High temperatures decrease the selectivity of radical reactions. High pressures
reduce the tendency of chain scission. In high viscous media, diffusion
controlled reactions are significantly slower than in low viscous
solutions.
From kinetic constants it may be concluded that tert-alkoxy radicals
favor the abstraction of hydrogen atoms rather than the addition on vinyl
groups. This tendency is enhanced at higher temperatures.
16, 17
17.3.7.3 Half-life of Peroxides
The half-life of peroxides listed is shown in Table 17.5. If the residence
time is in the range of five half-life times, then the decomposition of the
peroxide will reach more than 97%. If the half-life time is very short in

600 Reactive Polymers Fundamentals and Applications
Table 17.5: Half-life of Peroxides 10
Peroxide °C a,b °C a,c
LUPEROX 101 140 145
2,2-Di(tert-amylperoxy)propane 128 –
Di-tert-amyl peroxide 143 –
MEK cyclic trimer – 158
4-(tert-amylperoxy)-4-methyl-2-pentanol 141 –
a One hour half-life time at the temperature specified
b in dodecane
c in poly(propylene)
Table 17.6: Flash Points of Peroxides 10
Peroxide Flash point [°C a ]
LUPEROX 101 (92% assay) 49
LUPEROX 101 (95% assay) 78
Di-tert-amyl peroxide
25 a
4-(tert-Amylperoxy)-4-methyl-2-pentanol >60
a Performed with ASTM D3278
b Depending on preparation
comparison to the residence time, then the peroxide decomposes to a great
extent in the initial stage of the process. This results in high concentrations
of radicals, and secondary radicals in the polymer backbone, which may
result in an enhanced crosslinking.
The majority of today’s production processes require that the peroxide
be mixed with solid poly(propylene) in a blender. Under such conditions,
it is crucial that the peroxide has a high flash point for safety. Flash
points can be determined using the small scale closed cup method (ASTM
D3278). Flash points of commercially available peroxides are shown in
Table 17.6
17.3.8 Azo Compounds
Azo compounds are shown in Table 17.7. Azo compounds are advantageous
over peroxides in that they show no or much less induced decomposition.
However, the most common azonitriles, e.g., AIBN decompose too
quickly at the required temperatures. In addition, the cyanoalkyl radicals

Rheology Control 601
Table 17.7: Azo Compounds for Controlled Rheology 8
Azo Compounds
2,2 ′ -Azobis(2-acetoxy)propane
2,2 ′ -Azobis(isobutyronitrile) (AIBN)
2,2 ′ -Azobis(2,4-dimethylvaleronitrile)
2,2 ′ -Azobis(cyclohexanenitrile)
2,2 ′ -Azobis(2-methylbutyronitrile)
2,2 ′ -Azobis(2,4-dimethyl-4-methoxyvaleronitrile)
are comparatively unreactive to abstract hydrogen from a polyolefin.
17.4 SCAVENGERS
17.4.1 Stable Nitroxyl Radicals
Incorporation of stable radicals that are always present after extrusion provides
a better thermal stability to the products that are obtained, improves
the UV resistance of the latter and reduces their tendency to depolymerize.
In the case where a peroxide is also incorporated into the resin, the
latter has a more stable viscosity over time because of comprising a reservoir
of heat-reacting counter-radicals.
However, the resin contains a reservoir of stable free radicals that
have the tendency to neutralize the peroxide as soon as the latter is breaks
down, thus reducing its degradation effects, regardless of whether its concentration
is high or low. The storage time thus no longer has as much
effect on the viscosity of the transformed resin. 8
Stable nitroxyl radicals are shown in Table 17.8 and in Figure 17.4.
The properties of stable nitroxyl radicals are described in the literature. 18
17.5 MECHANISM OF DEGRADATION
The degradation of poly(propylene) with peroxides is believed to occur via
a series of free radical reactions involving steps such as initiation, scission,
transfer and termination. The mechanism of degradation of a poly(propylene)
by a peroxide is shown in Figure 17.5. First, the peroxide decomposes
by a homolytic scission into two radicals. The tertiary carbon atom would
yield most stable radicals and therefore is preferably attacked. The peroxide
is deactivated by hydrogen transfer. In the next step, a scission of

602 Reactive Polymers Fundamentals and Applications
Table 17.8: Stable Nitroxyl Radicals for Controlled Rheology 8
Nitroxyl Radicals
2,2,5,5-Tetramethyl-1-pyrrolidinyloxy a
3-Carboxy-2,2,5,5-tetramethyl-pyrrolidinyloxy b
2,2,6,6-Tetramethyl-1-piperidinyloxy c
4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy d
4-Methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy e
4-Oxo-2,2,6,6-tetramethyl-1-piperidinyloxy f
Bis(1-oxyl-2,2,6,6-tetramethylpiperidine4-yl)sebacate g
2,2,6,6-Tetramethyl-4-hydroxypiperidine-1-oxyl monophosphonate
N-tert-Butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide h
N-tert-Butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide
N-tert-Butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl nitroxide
N-tert-Butyl[(1-diethylphosphono)-2-methyl-propyl]nitroxide
N-(1-Methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide
N-(1-Phenylbenzyl)-((1-diethylphosphono)-1-methyl ethyl)nitroxide
N-Phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide
N-Phenyl-1-diethylphosphono-1-methyl ethyl nitroxide
N-(1-Phenyl-2-methylpropyl)-1-diethylphosphono-1-methyl ethyl nitroxide
N-tert-Butyl-1-phenyl-2-methylpropyl nitroxide
N-tert-Butyl-1-(2-naphthyl)-2-methylpropyl nitroxide
a PROXYL
b 3-carboxy PROXYL
c TEMPO
d 4-hydroxy-TEMPO
e 4-methoxy-TEMPO
f
4-oxo-TEMPO
g CXA 5415
h DEPN

Rheology Control 603
H 3 C
H 3 C
N
O -
CH 3
CH 3
H 3 C
H 3 C
CH 3
N
CH
O - 3
PROXYL TM
TEMPO TM
H 3 C CH 3
C H
CH 3
H 3 C C C CH 3
P N
H
O CH
2 C O 3
O O -
CH 3
CH 2
CH 3
DEPN TM
H 3 C
H 3 C
- O N
H 3 C
H 3 C
O
C
O
(CH 2 ) 3
C
O
O
CH 3
CH 3
N
O -
CH 3
CH 3
CXA 5415 TM
Figure 17.4: Stable Nitroxyl Radicals: 2,2,5,5-Tetramethyl-1-pyrrolidinyloxy
(PROXYL), 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), N-tert-butyl-1-diethylphosphono-2,2-dimethylpropyl
nitroxide (DEPN), Bis(1-oxyl-2,2,6,6-tetramethylpiperidine4-yl)sebacate
(CXA 5415)

604 Reactive Polymers Fundamentals and Applications
R O O R R O* *O R
R O*
H H H
CH 2 C CH 2 C CH 2 C
CH 3 CH 3 CH 3
R O H
H
H
CH 2 C CH 2 C* CH 2 C
CH 3 CH 3 CH 3
H H
CH 2 C CH 2 C*
CH 3 CH 3
CH 2
C
CH 3
H H
CH 2 C CH 2 C*
CH 3 CH 3
*C
CH 3
CH 2
H H
CH 2 C CH C H
CH 3
CH 3
H
C
CH 3
CH 2
Figure 17.5: Mechanism of Degradation of a Poly(propylene) Chain

Rheology Control 605
the main chain takes place. The radicals migrate to find another radical.
Finally two radicals terminate by a disproportionation. A termination by
recombination would be unfavorable in this case. In addition to the peroxide
induced degradation, other models include the thermal decomposition
of peroxides.
17.6 ULTRA HIGH MELT FLOW POLY(PROPYLENE)
Ultra high melt flow (UHMF) poly(propylene) generally has a melt flow
of greater than about 30 g/min. The production of UHMF polymers can
be achieved during their initial polymerization, without the need for secondary
processing. This usually involves the addition of hydrogen during
the polymerization reaction. Increasing the hydrogen concentration in the
polymerization reactor, however, can result in the production of excessive
xylene solubles, which is often undesirable. Equipment or process limitations
may also limit the amount of hydrogen that can be used during the
polymerization reaction. 1
17.7 IRREGULAR FLOW IMPROVEMENT
Molded parts made from typical controlled rheology-treated poly(propylene)
tend to have inferior appearance and surface characteristics, and are
often marred by flow marks such as tiger marks. Controlled rheology poly-
(propylene) has a narrow molecular weight distribution which results from
the selective loss of longer molecular chains due to the action of the organic
peroxides. This narrow molecular weight distribution does not permit
good surface molding of the molded article due to the irregular flow of
the molten polymer in the mold. This irregular flow will lead to the surface
flaws. Therefore, the use of controlled rheology poly(propylene) in
injection molding has been limited to applications that do not require good
surface characteristics.
The addition of a high molecular weight component to the controlled
rheology materials will improve the irregular flow in the mold. It is believed
that this improvement occurs because of the broadened molecular
weight distribution. However, the addition of the high molecular weight
component sacrifices the high MFR properties gained in controlled rheology
treatment.

606 Reactive Polymers Fundamentals and Applications
Thus, there is a need in the art for controlled rheology propylene
polymers which have a high MFR and good surface characteristics when
in injection molding.
Poly(tetrafluoroethylene) (with a molecular weight above 1,000,000
Dalton or even above about 5,000,000 Dalton) can be dispersed by mechanically
blending with propylene polymers in the same extruder which
is used for a simultaneous or subsequent controlled rheology treatment.
Poly(tetrafluoroethylene) preferably can be dispersed simultaneously with
the controlled rheology treatment in the extruder. A surface-modified poly-
(tetrafluoroethylene) is particularly useful. This is an acrylic modified
poly(tetrafluoroethylene), commercially available as Metablen. 2
17.8 HETEROPHASIC COPOLYMERS
Poly(propylene) heterophasic copolymers are typically made up of three
components. These include a poly(propylene) homopolymer, a rubbery
ethylene propylene copolymer, and a crystalline ethylene-rich ethylene
propylene copolymer. The typical heterophasic morphology of these polymers
consists of the rubbery ethylene propylene copolymer being dispersed
as generally spherical domains within the semi-crystalline poly(propylene)
homopolymer matrix.
Poly(propylene) copolymers can be modified to improve their impact
strength. This can be done through the use of elastomeric modifiers
or with peroxides. When using elastomeric modifiers, the elastomeric
modifiers are melt blended with the poly(propylene) copolymer,
with the increased elastomer content typically contributing to a higher impact
strength. Examples of elastomeric modifiers include ethylene/propylene
rubber (EPR) and ethylene propylene diene monomer (EPDM) rubber.
In poly(propylene) heterophasic copolymers modified with peroxides
during the controlled rheology process, performance improvements
can be achieved by adjusting the conditions under which the controlled
rheology is carried out. By slowing deactivation of the peroxide, impact
copolymers with higher impact strength and lower stiffness values can be
attained, while achieving the desired final melt flow characteristics.
A slower decomposition of the peroxide during controlled rheology
polymer modification also slows down the vis-breaking reactions. This allows
the polymer fluff to remain at a higher viscosity for longer periods of
time during the extrusion. It is believed that by maintaining the polymer

Rheology Control 607
viscosity at higher levels during extrusion, the rubber phase of the poly-
(propylene) copolymer is more uniformly dispersed, which in turn results
in higher impact strength for the same polymer modified with peroxide
having shorter decomposition times.
Linear peroxides having at least two peroxide groups, such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane,
are particularly suitable for delayed
decomposition. Other suitable peroxides are the cyclic ketone peroxides,
such as those disclosed in the literature, 12 e.g., 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane,
c.f. Figure 17.1.
Improvements in impact strength for poly(propylene) heterophasic
copolymers have been observed by slowing the decomposition or increasing
the half-life of the peroxide during degradation. This is accomplished
through a reduction in extrusion temperatures.
Alternatively, a peroxide with a longer half-life than would otherwise
be selected may also be employed if required by the extrusion conditions.
Normal extrusion temperatures for most controlled rheology of
heterophasic copolymers are usually from about 230°C to about 290°C.,
but may be hotter depending upon the product being processed. By significantly
reducing these temperatures, improvements in impact strength can
be achieved.
To achieve slower decomposition, the poly(propylene) heterophasic
copolymer is extruded at temperatures sufficient to maintain the material
in a molten state, but reduced from those used in conventional controlled
rheology processes. Thus, extrusion temperatures may range anywhere
from the minimum temperature to maintain the copolymer in a molten state
up to about 215 °C. When such temperatures are employed, at least
some amount of the peroxide will usually remain unconsumed within the
extruded copolymer.
In heterophasic poly(propylene) (PP), both the degradation and the
functionalization mainly occur in the ethylene rich phase. A preferential
attack of the free radicals at single tertiary hydrogens between ethylene
units, or at the ends of a PP block adjacent to one or multiple ethylene
units, results in a selective functionalization of the ethylene rich copolymers,
regardless of the solubility parameter or decomposition rate of the
peroxides.
These tertiary hydrogen atoms are not sterically protected by adjacent
methyl groups, and are therefore more accessible to the generated free
radicals and the bulky maleic anhydride. 19

608 Reactive Polymers Fundamentals and Applications
17.9 POLY(PROPYLENE)
Commercial poly(propylene) resins commonly are polymerized by conventional
Ziegler-Natta catalyst systems and have a high molecular weight
and a broad molecular weight distribution (MWD). The chemical structure
of poly(propylene) is generally influenced by the kind of polymerization
system used during its production. Because the MWD largely determines
the rheological properties of poly(propylene) melts, this parameter must
be controlled to improve the material response during processing and to
achieve the diversity in polymer grades suitable for the different applications
of poly(propylene).
Establishing of a broad molecular weight distribution of the poly-
(propylene) in conventional reactors is difficult because it requires the addition
of chain terminators and transfer agents. These operations decrease
output of the reactor and are often uneconomical.
The most important characteristic of peroxides is that the half-life
time at 130°C must be higher than 1 hour and smaller than 10 hours. Examples
of peroxides industrially accepted for this degradation reaction are
given in Table 17.4.
17.9.1 Long Chain Branched Poly(propylene)
Poly(propylene) with long chain branches can be obtained by reactive extrusion
of a poly(propylene) in the presence of a peroxide, a polyfunctional
acrylate monomer and thiuram disulfide as co-reactant.
The thiuram disulfide gives two dithiocarbamate radicals by thermal
decomposition. These radicals react with the PP radicals in a reversible
reaction. Therefore, a decrease in the instantaneous concentration of free
radicals is achieved, which favors the branching reaction. In this way the
β-scission is reduced. 20
17.9.2 Effect of MFR on Temperature and Residence Time
The initiator decomposition rate and residence time distribution in the extruder
increase with increasing temperature. The change of the screw speed
affects mixing and residence time distribution. So the MFR should increase
with increasing residence time. However, if the process is performed at a
sufficient long residence time to allow all degradation reactions to complete,
a further increase in residence time will not change the MFR.

Rheology Control 609
Is has been demonstrated with dicumyl peroxide (DCP) as radical
generator, the melt flow rate increases with increasing amount of peroxide.
Generally, the crystalline fraction of samples increases with increasing peroxide
concentration. 14
REFERENCES
1. K. P. Blackmon, L. P. Barthel-Rosa, S. A. Malbari, D. J. Rauscher, and M. M.
Daumerie. Production of ultra high melt flow polypropylene resins. US
Patent 6 657 025, assigned to Fina Technology, Inc. (Houston, TX), December
2 2003.
2. M. Fujii and S. Kim. Polypropylene materials with high melt flow rate and
good molding characteristics and methods of making. US Patent 6 599 985,
assigned to Sunoco Inc. (R&M) (Philadelphia, PA), July 29 2003.
3. G. Schmidtthomee, C. Alt, R. Herbeck, H. Moeller, and H. G. Trieschmann.
Narrowing the molecular weight distribution of polyolefins. GB Patent
1 042 178, assigned to BASF AG, September 14 1966.
4. J. J. Baron, Jr. and J. P. Rakus. Thermal degradation of polyolefins in the
presence of a metal salt carboxylic acid catalyst. US Patent 3 332 926, assigned
to Allied Chem, July 25 1967.
5. R. L. McConnell and D. A. Weemes. Method for making polyolefin waxes by
thermal degradation of higher molecular weight polyolefins in the presence
of organic acids and anhydrides. US Patent 3 519 609, assigned to Eastman
Kodak Co, July 7 1970.
6. E. G. Castagna, A. Schrage, and M. Repiscak. Process for controlled degradation
of propylene polymers. US Patent 3 940 379, assigned to Dart Industries,
Inc. (Los Angeles, CA), February 24 1976.
7. M. W. Musgrave. Pelletized polyolefin having ultra-high melt flow and its
articles of manufacture. US Patent 6 423 800, assigned to Fina Technology,
Inc. (Houston, TX), July 23 2002.
8. D. Bertin and P. Robert. Method for the production of a controlled rheological
polypropylene resin. US Patent 6 620 892, assigned to Atofina (Puteaux, FR),
September 16 2003.
9. L. Kasehagen, R. Kazmierczak, R. Cordova, and T. Myers. Safe, efficient,
low t-butanol forming organic peroxide for polypropylene modification. US
Patent 6 599 990, assigned to Atofina Chemicals, Inc. (Philadelphia, PA), July
29 2003.
10. R. J. Ehrig and R. C. Weil. Controlled-rheology polypropylene. US
Patent 4 707 524, assigned to Aristech Chemical Corporation (Pittsburgh,
PA), November 17 1987.

610 Reactive Polymers Fundamentals and Applications
11. K. Huber, J. Schwind, K. Lehr, H. Elser, H. Klassen, and K.-H. Kagerbauer.
Peroxidic treatment of olefin polymers. US Patent 6 313 228, assigned to
Basell Polyolefine GmbH (Ludwigshafen, DE), November 6 2001.
12. J. Meijer, A. H. Hogt, G. Bekendam, and L. A. Stigter. Modification of (co)
polymers with cyclic ketone peroxides. US Patent 5 932 660, assigned to
Akzo Nobel NV (Arnhem, NL), August 3 1999.
13. J. D. Adams, R. H. Dorn, M. J. King, J. L. Kulasa, N. J. Motto, L. J.
Ostanek, and D. Petticord. High organic peroxide content polypropylene.
US Patent 5 198 506, assigned to Phillips Petroleum Company (Bartlesville,
OK), March 30 1993.
14. H. Azizi and I. Ghasemi. Reactive extrusion of polypropylene: production
of controlled-rheology polypropylene (CRPP) by peroxide-promoted degradation.
Polymer Testing, 23(2):137–143, April 2004.
15. T. Bremner and A. Rudin. Peroxide modification of linear low density polyethylene:
A comparison of dialkyl peroxides. J. Appl. Polym. Sci., 49:
785–798, 1993.
16. G. Moad. The synthesis of polyolefin graft copolymers by reactive extrusion.
Prog. Polym. Sci., 24(1):81–142, April 1999.
17. G. Moad. Corrigendum to “the synthesis of polyolefin graft copolymers
by reactive extrusion”[progress in polymer science 1999;24:81-142]. Prog.
Polym. Sci., 24(10):1527–1528, December 1999.
18. L. B. Volodarsky, V. A. Reznikov, and V. I. Ovcharenko. Synthetic Chemistry
of Stable Nitroxides. CRC Press, Boca Raton, FL, 1994.
19. T. Kamfjord and A. Stori. Selective functionalization of the ethylene rich
phase of a heterophasic polypropylene. Polymer, 42(7):2767–2775, March
2001.
20. D. Graebling. Synthesis of branched polypropylene by a reactive extrusion
process. Macromolecules, 35(12):4602–4610, June 2002.

18
Grafting
Pros and cons of grafting copolymers by reactive extrusion in comparison
to other methods are: 1, 2
+ essentially no solvents,
− intimate mixing of reactants compulsory,
− the high reaction temperatures needed,
+ fast preparation,
− side reactions, e.g., degradation, crosslinking or discoloration,
+ simple product isolation,
+ extrusion is a continuous process.
Grafting takes place mostly by a radical reaction mechanism 3 and is
also called free radical grafting. However, there are other techniques for introducing
functional groups into polymers, e.g., according to the Alder-ene
reaction. 4
18.1 THE TECHNIQUES IN GRAFTING
18.1.1 Parameters that Influence Grafting
18.1.1.1 Mixing
Efficient mixing of the individual components is of critical importance for
the success of a graft process. The mixing efficiency is dependent on the
screw geometry, the melt temperature, the pressure, the rheological prop-
611

612 Reactive Polymers Fundamentals and Applications
erties of the polymer, and the solubilities of the monomer and the initiator,
respectively, in the polyolefin.
18.1.1.2 Grafting Efficiency
In order to obtain a high grafting efficiency together with an effective suppression
of the side reactions, it is necessary to transform the macroradicals
on the backbone as far as possible into graft sites. In general, within
reasonable limits, higher reaction temperatures, higher initiator levels, and
lower throughput rates result in higher grafting efficiency.
Peroxide Concentration. The grafting efficiency of maleic anhydride on
low density poly(ethylene) (LDPE) increases as the concentration of the
peroxide increases. Further, the grafting efficiency depends on the means
of reactive processing. In a comparative study with varying experimental
setup, the lowest efficiency was found for extrusion using a typical shaping
extrusion head, a higher efficiency was found with a static mixer and the
highest efficiency was found with a dynamic mixer. The dynamic mixer
is a cavity transfer mixer that provides shear rates of the moving melt of
about 100 s −1 .
Propene Content. In a series of polyolefins with different ethene/propene,
the efficiency of grafting of maleic anhydride (MA) both in the melt
and in solution was studied. The maleic anhydride graft content is low for
polyolefins with high propene content, increases as the propene content decreases,
and reaches a plateau at propene levels below 50%. Branching and
crosslinking occurs for polyolefins with low propene content, while degradation
is the main side reaction for polyolefins with high propene content. 5
Mechanochemistry. Shear stresses in the dynamic mixer cause a formation
of radicals even in the absence of any peroxide. Therefore, grafting
of maleic anhydride on LDPE even without the action of peroxide initiator
is observed. The dynamic mixer helps to obtain a high grafting efficiency
on LDPE using a small concentration of peroxide initiator. Under these
conditions, grafting is not accompanied by a crosslinking reaction of the
poly(ethylene) chains. 6

Grafting 613
18.1.1.3 Screw Geometry
Reactive extruders usually have a modular construction. This allows flexible
arrangements of the screw elements and barrel sections as needed.
18.1.1.4 Processing Temperature
The processing temperature is of critical importance. Too high processing
temperatures will cause degradation reaction, and the initiator may decompose
too quickly to be effective.
18.1.1.5 Processing Pressure
In contrast to temperature, a high processing pressure can improve the solubility
of the monomer to be grafted and the solubility of the initiator in
the polymer.
18.1.1.6 Residence Time
The residence time is governed by the overall throughput which can be
adjusted by the screw speed, the screw design, and the geometry of the
extruder.
18.1.1.7 Removal of By-Products
The unreacted monomers and decomposition products from the initiator,
etc., are removed by the application of vacuum to the melt.
18.1.1.8 Consistency
Experiments of grafting maleic anhydride onto poly(propylene) by melt
extrusion with dicumyl peroxide, where the poly(propylene) was fed either
as powder or in granular form, showed that consistency plays a role
on the degree of grafting. 7 The grafting efficiency of powdered poly(propylene)
was higher than that obtained for the granular form of poly(propylene).
It is believed that the grafting of powder is more successful because
a better initial mixing and less diffusional resistance during the grafting is
provided.

614 Reactive Polymers Fundamentals and Applications
Table 18.1: Reaction Temperatures for Coupling of Stable Radicals 8
Polymer Abbreviation Temperature [°C]
Low density poly(ethylene) LDPE 170–260
High density poly(ethylene) HDPE 180–270
Poly(propylene) PP 180–280
Poly(styrene) PS 190–280
Styrene-block copolymers SB(S) 180–260
Ethylene-propylene-diene modified EPDM 180–260
Ethylene/propylene rubber EPR 180–260
18.1.2 Free Radical Induced Grafting
The most commonly used grafting method is free radical induced grafting.
However, the efficiency of grafting cannot simply be increased by increasing
only the concentration of the radical initiator. More important for the
grafting efficiency are proper mixing and a sophisticated choice of proper
comonomers.
Grafting without radical initiator is also possible. In this case, the
macroradicals are formed by a shear induced chain scission. Of course,
this process is accompanied by degradation or crosslinking reactions.
18.1.3 Grafting Using Stable Radicals
The technique of grafting using stable radicals involves two steps. 8
1. A stable nitroxyl radical is grafted onto a polymer, which involves
the heating of a polymer and a stable nitroxyl radical.
2. The grafted polymer of the first step is then heated in the presence
of a vinyl monomer or oligomer to a temperature at which cleavage
of the nitroxyl-polymer bond occurs and polymerization of the
vinyl monomer is initiated at the polymer radical.
The temperature applied in the first reaction step depends on the
polymer and is for example, 50°C to 150°C above the glass transition temperature
(T g ) for amorphous polymers and 20°C to 180°C above the melting
temperature (T m ) for semi-crystalline polymers. Typical temperatures
are summarized in Table 18.1.
Stable nitroxyl radicals are collected in Table 18.2. The first step of
the process is performed conveniently in an extruder or a kneading appa-

Compound
Table 18.2: Stable Nitroxyl Radicals
Grafting 615
Benzoic acid 2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl ester
4-Hydroxy-2,2,6,6-tetramethyl-piperidin-1-oxyl
4-Propoxy-2,2,6,6-tetramethyl-piperidin-1-oxyl
Decanedioic acid bis(2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl)
ratus. In the extruder, a reduced pressure of less than 200 mbar is applied
during extrusion. Volatile by-products may be removed thereby. Typical
reaction times are from 2 min to 20 min.
For the monomer grafting reactions, unsaturated monomers are selected
from styrene, dodecyl acrylate, and other compounds. The second
reaction step may be performed immediately after the first step, however it
is also possible to store the intermediate polymeric radical initiator at room
temperature for some time.
Because the graft polymerization is a living polymerization, it can be
started and stopped practically at will. The intermediate polymeric radical
initiator is stable at room temperature and no loss of activity occurs up to
several months.
The reaction step may also be performed in a mixer or extruder.
However, it is also possible to dissolve or disperse the polymer and to add
the monomer to the solution. If the second reaction step is performed in a
melt, a reaction time of 2 to 20 min is adequate.
The grafted polymers are useful in many applications such as compatibilizers
in polymer blends or alloys, adhesion promoters between two
different substrates, surface modification agents, nucleating agents, coupling
agents between filler and polymer matrix, or dispersing agents. The
process is particularly useful for the preparation of grafted block copolymers.
Grafted block copolymers of poly(styrene) and polyacrylate are useful
as adhesives or as compatibilizers for polymer blends or as polymer
toughening agents. Poly(methyl methacrylate-co-acrylate) diblock graft
copolymers or poly(methyl acrylate-co-acrylate-co-methacrylate) triblock
graft copolymers are useful as dispersing agents for coating systems, as
coating additives or as resin components in coatings. Graft block copolymers
of styrene, (meth)acrylates, or acrylonitrile are useful for plastics,
elastomers, and adhesives.

616 Reactive Polymers Fundamentals and Applications
Table 18.3: Monomers for grafting onto Polyolefins 1
Vinyl Monomer
Remarks/References
Maleic anhydride
Most common
Maleate esters
9
Styrene Auxiliary monomer 10
Maleimide derivatives
11
Methacrylate esters
12
Acetoacetoxy methyl methacrylate
11
Glycidyl methacrylate
13, 14
Acrylate esters
15
Ricinoloxazoline maleate
16
Vinylsilanes
17
18.2 POLYOLEFINS
The synthesis of polyolefin graft copolymers by reactive extrusion has been
reviewed by Moad. 1, 2 The methods of modification can be classified as
1. Free radical induced grafting of unsaturated monomers onto polyolefins,
2. End-functional polyolefins by the ‘ene’ reaction,
3. Hydrosilylation,
4. Carbene insertion, and
5. Transformation of pending functional groups on polyolefins, e.g.,
by transesterification, alcoholysis.
18.2.1 Monomers for Grafting onto Polyolefins
Monomers for grafting onto polyolefins are listed in Table 18.3.
18.2.1.1 Macromonomers
Polymeric or oligomeric vinyl compounds are addressed as macromonomers
in the field of reactive extrusion. Examples for macromonomers
are higher molecular acrylate esters, methacrylate esters, and maleimides.
Macromonomers are less likely to undergo homopolymerization than low
molecular vinyl compounds. This property arises due to steric effects.
Thus they may not form longer pendent chains on the grafting sites consisting
of homopolymers. A disadvantage of macromonomers is their low

Grafting 617
HC CH
O C C O
OH OH
CH 3
C O
CH 3 O
C CH
C C O
OH OH
CH 3
C O C 6 H 12 CH
CH 3 O
C CH 2
C C O
OH OH
Figure 18.1: Structure of Low Molecular Weight Fraction of Extrudates of Poly-
(propylene) with Maleic anhydride and Dicumyl peroxide
volatility. For this reason, an unreacted or excess compound may not easily
be removed by vacuum treatment in the extrusion device.
18.2.2 Mechanism of Melt Grafting
Functionalized poly(propylene) (PP) has been used extensively for compatibilization
of immiscible poly(propylene)/polyamide and poly(propylene)/polyester
blends. Also, the interfacial adhesion of PP with glass and
carbon fibers can be improved. Further, functionalized PP is a processing
aid for degradable plastics.
18, 19
It is generally accepted that chain scission occurs during the peroxide
initiated functionalization of PP. 20 Maleic anhydride (MA) is appended
to a tertiary carbon atom along the PP backbone as a single ring or as a
short pendant chain due to the homopolymerization of MA. 21 On the other
hand, according to the ceiling temperature, there is no possibility for the
homopolymerization of MA under the melt grafting process conditions at
190°C. 22
Chemical analysis of the low molecular weight fraction of extrudates
of poly(propylene) with maleic anhydride and dicumyl peroxide by
mass spectrometry indicated the products shown in Figure 18.1. No MA
oligomers or MA homopolymers are found in the low molecular weight
fraction. The MA radicals always contain double bonds after termination.
Peroxide residues are attached to MA molecules. A reduction of the
molecular weight occurs when the degree of grafting increases. From the

618 Reactive Polymers Fundamentals and Applications
inspection of the chemical structure of the low molecular weight residue, it
can be concluded that the maleic anhydride is attached as a single moiety
on the tertiary carbon atoms of the poly(propylene) backbone. From these
experimental findings a mechanism of grafting has been proposed 23 that is
given in Figure 18.2. Furthermore, the grafting of maleic anhydride onto
poly(propylene) has been studied by a Monte Carlo simulation method. 24
The results presented in this study are in agreement with the experiments.
The grafting efficiency of methyl methacrylate is similar to that of maleic
anhydride. 12
18.2.3 Side Reactions
Side reactions accompany the grafting reaction of polyolefins. These include
1, 2
1. Radical induced crosslinking of the polyolefin substrate,
2. Radical induced chain scission of the polyolefin substrate,
3. Shear induced degradation of the polyolefin substrate,
4. Homopolymerization of the monomer, and
5. Side reactions which lead to a coloration of the product.
The extent of the side reactions depends on the type of polyolefin.
Some poly(ethylene) types are sensitive to branching and crosslinking.
This is due to the recombination of the macroradicals. 25
Poly(propylene) and linear low density poly(ethylene) copolymers
undergo degradation rather than crosslinking, although crosslinking may
occur. Degradation is often favored to synthesize controlled rheology
types.
18.2.4 Viscosity
The formation of products with higher molecular weight is indicated by an
increase of the apparent viscosity. On the other hand, by the introduction
of polar groups during grafting, an increase of the viscosity is observed
because of physical crosslinks of the individual molecules.
Maleic anhydride has been grafted onto poly(propylene) in the presence
of supercritical carbon dioxide. Supercritical carbon dioxide was used
in order to reduce the viscosity of the poly(propylene) melt phase. A reduced
viscosity should promote a better mixing of the reactants. The characterization
of the products showed that the use of supercritical carbon

Grafting 619
O
O
O
CH 3 CH 3 CH 3 CH 3 CH 3
CH 3 CH 3 CH 3 CH 3 CH 3
CH 3 CH 3 CH 3 CH 3 CH 3
O
O
O
CH 3 CH 3 CH 3 CH 3 CH 3
Figure 18.2: Mechanism of Grafting of Maleic anhydride onto Poly(propylene) 23
(abbreviated)

620 Reactive Polymers Fundamentals and Applications
Table 18.4: Ceiling Temperatures for Important Monomers in Reactive
Extrusion Grafting1, 26
Monomer
Ceiling Temperature [°C]
Maleic anhydride 400
Methacrylate esters
∼200
Acrylate esters >400
dioxide in fact resulted in improved grafting when high levels of maleic
anhydride were used. No evidence of an improvement in the homogeneity
of the product was observed. However, melt flow rate showed a reduction
in the degradation of poly(propylene) during the grafting reaction when
low levels of maleic anhydride were used. 27
18.2.5 Ceiling Temperature
The ceiling temperature is an important parameter for the ability of polymerization
itself. We are dealing here with homopolymerization. The
concept of the ceiling temperature is not restricted to a polymerization
mechanism, because it deals with the thermodynamic equilibrium. Ceiling
temperatures for important monomers in reactive extrusion grafting onto
polyolefins are given in Table 18.4.
The ceiling temperatures given in Table 18.4 could be important for
the grafting of maleic anhydride and maleic esters.
28, 29
The ceiling temperatures depend on the pressure and on the concentration
of the monomer. They are usually calculated from the heats and
the entropies of polymerization that are usually given at one atmosphere.
In fact, the homopolymerization of maleic anhydride was observed at a
higher temperature than 150°C, even when the ceiling temperature would
not predict a polymerization reaction.
18.2.6 Effect of Initiator Solubility
Experiments of grafting of itaconic acid (IA) onto a low density poly(ethylene)
(LDPE) with various initiators in the course of the reactive extrusion
revealed that the solubility of the peroxide initiator in the molten polymer
is the most important parameter in the IA grafting onto LDPE. The kinetics
of decomposition is an important parameter for the efficiency of grafting.

Peroxide
Table 18.5: Solubility Parameters of Peroxides 30
Grafting 621
δ [Jcm −3 ] 1/2 a
Dicumyl peroxide 17.4
2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane 11.3
Di-tert-butyl peroxide 15.3
2,2-Di(tert-butylperoxy)-5,5,6-trimethyl bicyclo[2.2.1]heptane 16.1
2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne 19.1
a calculated for 25°C
The solubility parameters of various peroxides are collected in Table 18.5.
The solubility parameters δ in Table 18.5 are calculated from group contributions
31 according to Eq. 18.1.
√
∑
δ = i ∆E i
(18.1)
N a ∑ i ∆V i
∆E i Contribution of every atom and type of the intermolecular interaction
in the molar cohesion energy
∆V i van der Waals volume of a group constituting the molecule
N a Avogadro number
The temperature dependence of δ can be expressed by Eq. 18.2:
logδ(T) = logδ(298K) − αk(T − 298) (18.2)
k is a coefficient. For the polyolefin k = 1 and for the peroxides and
the monomer k = 1.25. α is the linear thermal expansion coefficient. The
cohesion energy density δ calculated from Eq. 18.1 correlates well with the
values obtained from the heat of vaporization of the respective substances.
Substances are thermodynamically miscible in the absence of strong
specific interactions between them, if their solubility parameters differ by
less than 2 (Jcm −3 ) 1/2 . The solubility parameters of IA and LDPE are 24.6
(Jcm −3 ) 1/2 and 16.1 (Jcm −3 ) 1/2 , respectively. Therefore, IA and LDPE
form a heterogeneous system in the melt. On the other hand, it is expected
that some of the peroxides listed in Table 18.5 would dissolve in LDPE.
It is assumed that radicals formed during peroxide decomposition interact
first with LDPE macromolecules, then the formed macroradicals initiate
the grafting reactions with IA. Peroxides, which are easily dissolved
in LDPE, are most efficient in initiating the grafting reactions. 30
It was found that neutralizing agents introduced into the initial reaction
mixture increase the yield of LDPE-g-IA, when the carboxyl groups

622 Reactive Polymers Fundamentals and Applications
were neutralized partially or totally. As neutralizing agents, zinc oxides
and hydroxides as well as magnesium oxides and hydroxides can be used. 32
18.2.7 Distribution of the Grafted Groups
There is a lot of research presented in the literature, and there is still a
controversy concerning the mechanism and the distribution and the structure
of the grafted portions on the backbone. This is reviewed in detail by
Moad. 1
18.2.8 Effect of Stabilizers on Grafting
The grafting of maleic anhydride onto poly(ethylene) is fully inhibited by
adding a phenolic stabilizer to the reactive blend. 33
In a system consisting of itaconic acid, linear low density poly(ethylene)
and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane with Irganox
1010 (Ciba Geigy, Switzerland), i.e. the ester of 3,5-di-tert-butyl-4-hydroxyphenyl-propanoic
acid and pentaerythritol, the grafting efficiency decreases
slightly.
However, at concentrations of the stabilizer greater than 0.3% some
improvement in the grafting efficiency occurs and the melt viscosity is
much lower. 30 The efficiency of stabilizers on the grafting and on the
crosslinking also depends on their solubility in the polymer and the monomer.
For example, 1,4-dihydroxybenzene has an increased affinity toward
the monomer and both reduces the yield of grafting and inhibits crosslinking.
34
18.2.9 Radical Grafting of Polyolefins with Diethyl Maleate
The use of maleate esters such as diethyl maleate or dibutyl maleate has
been suggested because of their lower volatility and lower toxicity in comparison
to maleic anhydride. However, maleate esters are less reactive towards
free radical addition than maleic anhydride.
Grafting polyolefins with diethyl maleate can be carried out in solution.
However, the use of extruders as reactors has several economic advantages.
The extruder screw is advantageously configured with different
mixing elements after an additional feed zone downstream from the initial
feed port for peroxide and diethyl maleate. Further there are no mixing
elements beyond the vent port. Turbine mixing elements are used for the

Grafting 623
improved blending of the low-viscosity initiator and the diethyl maleate
into the high-viscosity poly(ethylene). A vacuum vent port is used to eliminate
the unreacted monomer. In the extruder, dicumyl peroxide (DCP), is
used as initiator. 35
The kinetics of the free radical grafting of diethyl maleate (DEM)
onto linear poly(ethylene) initiated by dicumyl peroxide has been studied
by differential scanning calorimetry (DSC). The activation energy E a and
the order of the reaction n depend on the conditions and vary with the feed
composition. The values of E a and n increase with increasing DCP/DEM
ratio because of secondary reactions, such as chain extension and degradation.
The data can be described by a mathematical model which can
be used to select feed composition and process parameters to obtain the
desired products. 36
18.2.10 Inhibitors for the Homopolymerization of Maleic anhydride
In a series of papers, Gaylord showed that various additives are effective
in reducing both the amount of crosslinking and chain scission. 37, 38 These
additives include amides, such as N,N-dimethylacetamide, N,N-dimethylformamide,
caprolactam, stearamide, sulfoxides such as dimethyl sulfoxide,
and phosphites, such as hexamethylphosphoramide, triethyl phosphite.
The action has been attributed to the electron donating properties of these
compounds. It was shown that these compounds also act as inhibitors of
the homopolymerization of maleic anhydride, thus reducing its grafting
efficiency. However, it seems that these compounds are not effective in
general at least, there was some controversy. 1
18.2.11 Inhibitors for Crosslinking
p-Benzoquinone, triphenyl phosphite and tetrachloromethane were found
to be good inhibitors for the crosslinking reaction of LDPE. 39
In the melt grafting of maleic anhydride onto an elastomeric ethylene-octene
copolymer, N,N-dimethylformamide was used as an inhibitor
to reduce the crosslinking reaction. Further N,N-dimethylformamide is a
solvent for peroxide initiator. The melt grafting was carried out in a twinscrew
extruder, in the presence of dicumyl peroxide as an initiator. However,
increasing the initiator concentration increased the degree of grafting,
and at the same time, increased the extent of crosslinking. 40

624 Reactive Polymers Fundamentals and Applications
Compound
Table 18.6: Functionalized Peroxides 41
1,1-Dimethyl-3-hydroxybutyl-6-(hydroxy)peroxyhexanoate
1,1-Dimethyl-3-hydroxybutyl-2-(carboxy)perbenzoate
1,1-Dimethyl-3-hydroxybutyl-2-(carboxy)peroxycyclohexanecarboxylate
1,1-Dimethyl-3-hydroxypropyl-3-(carboxy)peroxypropanoate
1,1-Dimethyl-3-hydroxybutyl-3-(carboxy)-5-norbornene-2-ylperoxycarboxylate
18.2.12 Special Initiators
18.2.12.1 Bisperoxy Compounds
The decomposition of the two peroxy groups in bisperoxy compounds is
not concerted. The two peroxy groups decompose independently to yield
a variety of alkoxy and alkyl radicals.
18.2.12.2 Functionalized Peroxides
To optimize the chemical compatibility or solubility of the peroxides in a
wide variety of polymeric systems, the organic character of these peroxides
may be tailored by introducing suitable groups.
Functionalized peroxides may be used as crosslinking, grafting and
curing agents, initiators for polymerization reactions and as monomers for
condensation polymerizations to form peroxy-containing polymers, which
in turn can be used to prepare block and graft copolymers. Some functionalized
peroxides are shown in Figure 18.3 and collected in Table 18.6.
The half-life times of the peroxides at 180°C are ca. 0.27 min for
LUPEROX PMA and LUPEROX TA-PMA and 0.31 min for Luperco
212-P75 and Lupersol 512. The peroxides are assumed to result
in acrylic carboxyl groups and propionic carboxyl groups on the tertiary
carbon atoms of poly(propylene) on recombination with the tertiary radicals
formed previously. The highest acidity on the polymer backbone is
obtained with LUPEROX PMA. With respect to the functional radicals,
the peroxides which yield radicals that bear double bonds have a higher
grafting efficiency. It is assumed that the alkenyl radicals have a higher
reactivity with respect to alkyl radicals. Further, the increased grafting efficiency
may arise since macroradicals can add across the double bond of
the alkenyl groups. 42

Grafting 625
CH 3
O
H 3 C C O O C
CH 3
O
CH CH C
OH
Luperox TM PMA
CH 3
O
H 3 C C O O C
CH 3
O
CH 2 CH 2 C
OH
Luperco TM 212-P75
CH 3
CH 2
CH 3
O
C O O C
CH 3
O
CH CH C
OH
Luperox TM TA-PMA
CH 2
CH 3
O
C O O C
CH 3
O
CH 2 CH 2 C
OH
CH 3
Lupersol TM 512
Figure 18.3: Functionalized Peroxides, manufactured by Elf Atochem North
America

626 Reactive Polymers Fundamentals and Applications
O
CH 3
O
+
OH
CH
O
CH 2
CH 3
C O O H
+
O
O
CH 3
O
O
HO
O
O
CH 3
O C
CH 3 CH CH 2
CH 3
HO
O
O
Figure 18.4: Reaction of 1,1-Dimethyl-3-hydroxybutyl hydroperoxide with
Maleic anhydride
O
Preparation of Functionalized Peroxides. There are several routes to
preparing functionalized peroxides. 1,1-Dimethyl-3-hydroxybutyl hydroperoxide
reacts with two units of glutaric anhydride or maleic anhydride
in ring opening of the anhydride 43 as shown in Figure 18.4. Similarly,
1,1-dimethyl-3-hydroxybutyl-2-(carboxy)perbenzoate can be prepared
from phthalic anhydride by adding 1,1-dimethyl-3-hydroxybutyl hydroperoxide
in equimolar quantities.
Peroxyketals. The chemical modification of molten poly(ethylene) by
thermolysis of peroxyketals involves the decomposition of three cyclic or
acyclic peroxyketals. An ester function by coupling of an alkyl radical
bearing such a function, arising from the peroxyketals, a polymer radical,
generated from the poly(ethylene), were identified as grafting products. 44
18.2.12.3 Induced Decomposition of Peroxides
Peroxides show an induced decomposition with amino-functional monomers
such as diethylaminoethyl acrylate (DEAEMA) and diethylamino-

Grafting 627
Br
Br
Br
Br
H 3 C
H C
C H
CH 3
Br
Br
Br
Br
2,3-Dimethyl-2,3-diphenylbutane
Hexabromocyclododecane
Figure 18.5: Dicumyl and Hexabromocyclododecane
ethyl acrylate (TBAEMA). Instead of a peroxide an azo compound can be
used as an radical initiator.
18.2.12.4 Grafting to Poly(ethylene) with Bicumene
Bicumene, i.e., dicumyl or 2,3-dimethyl-2,3-diphenylbutane, can serve as
a radical initiator as an alternative to a peroxide. Compounds of the bicumene-type
also serve as synergists for flame retardants polyolefin by using
them in combination with a known flame-retardant for polyolefin such as
hexabromocyclododecane (c.f. Figure 18.5) and 2,3-tris(dibromopropylene)phosphate.
When a peroxide is employed as the reaction initiator, the peroxide
serves as a graft polymerization initiator, but at the same time a portion of
the peroxide induces a crosslinking reaction and a decomposition reaction
of the polyolefin. Because of the crosslinking reaction or the decomposition
reaction, the inherent physical properties of polyolefin deteriorate and
the resulting modified product is unable to maintain the properties of the
polyolefin.
In addition, when the peroxide decomposes as the reaction proceeds,
the decomposition products (e.g., butanol or other decomposition products)
stain the modified product. For example, the modified product yields odor
originating from the decomposition product, or turns to yellow because of
the action of the decomposition product.
The graft polymerization reaction starts more moderately and proceeds
more selectively, in comparison to a conventional reaction using peroxide.
Also, the crosslinking reaction or decomposition reaction of poly-

628 Reactive Polymers Fundamentals and Applications
olefin is less, and the resulting modified polyolefin has the excellent physical
properties of the unmodified polyolefin. For instance, when a linear
low density poly(ethylene) is employed, the modified product thereof has
a high mechanical strength at low temperatures. 45
The bicumene-initiated modification of high density poly(ethylene)
at 290°C provides no benefits in terms of selectivity when compared to
a standard peroxide-based process operating at 180°C. However, the selectivity
of linear low density poly(ethylene) modification is influenced by
chain scission, which counteracted the molecular weight effects of macroradical
combination. 46
As compared with the case of using peroxide, the variation of melt
index caused by the modification is smaller, and the modified product obtained
shows a melt index only slightly different from that of the polyolefin
employed as a starting material.
Maleic anhydride is generally employed in the amount of 10 −3 to
10 −5 mol/g of polyolefin. When the amount of maleic anhydride exceeds
10 −3 mol/g, the graft efficiency of maleic acid sometimes decreases, and
unreacted maleic anhydride remains in a large amount. This results in
an unfavorable effect on the physical properties of the resulting modified
product. When the amount of maleic anhydride is less than 10 −6 mol/g,
the modification with the maleic anhydride is unsatisfactory, and accordingly
the resulting modified product does not have sufficiently improved
adhesive properties. 45
The graft polymerization reaction is performed by heating a mixture
of the polyolefin, maleic anhydride and the initiator under kneading.
18.2.12.5 Ultrasonic Initiation
The grafting of maleic anhydride onto high density poly(ethylene) also can
be performed through ultrasonic initiation. Obviously, the ultrasonic waves
can decrease the molecular weight of the grafted product and increase the
amount of grafted maleic anhydride.
In comparison to the initiation with peroxide, ultrasonic initiation
can prevent the crosslinking reaction by adjusting the ultrasonic intensity.
The mechanical properties of the improved HDPE glass fiber composite
produced by ultrasonic initiatives are higher than in those produced by
peroxide initiatives. 47

Grafting 629
Table 18.7: Use of Maleic anhydride-grafted Linear low density poly(ethylene)
as Compatibilizer
System
Reference
Poly(propylene)/organoclay nanocomposites
48
Low density poly(ethylene)/ethylenevinyl alcohol
49
Poly(propylene)/Poly(styrene)
50
Low density poly(ethylene)/rice starch
51
18.2.13 Maleic anhydride
Maleic anhydride is most frequently used for grafting and functionalization
of polyolefins. Many of the features are described in the general sections,
e.g., Section 18.2.2.
Systematic and quantitative studies of the graft copolymerization
in batch and continuous mixers and kinetic data for poly(propylene) and
maleic anhydride are available. 52 In the melt grafting of maleic anhydride
onto low density poly(ethylene)/poly(propylene) blends, in the presence of
dicumyl peroxide (DCP), the blend had lower viscosity in comparison to
exclusively pure poly(ethylene) under comparable conditions. However,
the grafting degree of the MA grafted LDPE/PP (90/10) blend was almost
the same as or a little higher than that of the MA grafted LDPE. 53
Maleic anhydride can be grafted onto poly(propylene) using benzophenone
(BP) as the photoinitiator. 54 In comparison to thermally initiated
grafting with peroxide initiators, photoinitiated grafting has a higher grafting
efficiency. Maleic anhydride-grafted linear low density poly(ethylene)
(LDPE-g-MA) is widely used as compatibilizer for various applications,
as shown in Table 18.7.
18.2.14 Polyolefins Grafted with Itaconic Acid Derivatives
18.2.14.1 Poly(ethylene) Polyamide 6 Blends
Two-phase blends of polyamide 6 (PA6) and low density poly(ethylene)
(LDPE) have been prepared. Here in the course of reactive extrusion, an
in-situ grafting of itaconic acid (IA) on the LDPE takes place. The performance
of blending was tested with neutralization and without neutralization
of the acid groups of itaconic acid. 55 The maximum increase with
regard to the mechanical properties was achieved when magnesium hydroxide
was used as a neutralizing agent.

630 Reactive Polymers Fundamentals and Applications
18.2.14.2 Poly(propylene)
Functionalized poly(propylene) (PP) by radical melt grafting with monomethyl
itaconate or dimethyl itaconate is a compatibilizer in PP/poly(ethylene
terephthalate) (PET) blends. Blends with compositions 15/85 and
30/70 by weight of PP and PET, prepared in a single-screw extruder, revealed
a very fine and uniform dispersion of the PP phase compared to the
respective non-compatibilized blends.
An improved adhesion between the two phases is shown. Dimethyl
itaconate as compatibilizer derived agent exhibits only a small activity to
increase the impact resistance of PET in PP/PET blend. However, monomethyl
itaconate is active in this respect. This finding is attributed to the
hydrophilic nature of monomethyl itaconate. The tensile strength of PET
in non-compatibilized blends gradually decreases with increasing content
of PP. Blends containing functionalized PP exhibit, in general, higher values.
56
18.2.15 Imidized Maleic Groups
The chemical modification of swollen HDPE particles in near critical propane
seems to be much more effective in avoiding crosslinking than the conventional
modification in the melt phase.
High density poly(ethylene) grafted with 0.17% maleic anhydride
(PE-g-MA) can be additionally modified with 1,4-diaminobutane (DAB).
After formation of amic acid groups, the excess of diaminobutane is extracted
with a near critical propane-ethanol mixture.
Finally, the obtained PE-g-MA-DAB is imidized to the corresponding
imide (PE-g-MI) in the melt. The obtained PE-g-MI shows no increased
gel content with respect to the initial PE-g-MA. It appears that
PE-g-MI samples react with the anhydride groups of a styrene/maleic anhydride
copolymer (SMA) during melt blending of SMA with PE-g-MI,
while the PE-g-MA do not react. 57
18.2.16 Oxazoline-modified Polyolefins
The free radical induced grafting of 2-isopropenyl-2-oxazoline (IPO) onto
PP has been reported. 58

18.2.17 Modification of Polyolefins with Vinylsilanes
Grafting 631
Vinylsilanes, e.g., vinyltrimethoxysilane (VTMS) do not readily homopolymerize.
The modification of polyolefins with vinylsilanes, such as vinyltrimethylsilane,
vinyltriethylsilane, or 3-(trimethoxysilyl)propyl methacrylate
aims to the preparation of a moisture curable crosslinked polyolefins.
For example, the silane grafting of a metallocene ethylene-octene
copolymer is carried out in a twin-screw extruder, in the presence of vinyltrimethoxysilane
and dicumyl peroxide. 17 These materials are used in the
manufacture of electrical cables.
18.2.17.1 Vinyltriethoxysilane
Bicumene initiates the grafting of vinyltriethoxysilane (VTEOS) to poly-
(ethylene) efficiently over an uncommonly large range of operating temperatures.
The analysis of kinetics of bicumene decomposition suggests
that the initiation occurs via an autoxidation mechanism that is facilitated
by the interaction of cumyl radicals with oxygen. 46
The analysis of poly(ethylene-g-vinyltrimethoxysilane) by differential
scanning calorimetry-successive self-nucleation and annealing
(DSC-SSA) indicated that the distribution of pendant alkoxysilane grafts
amongst polymer chains is not uniform. Fractionation and characterization
of a graft-modified model compound, tetradecane-g-VTMS, showed that
the composition distributions were influenced strongly by intramolecular
hydrogen atom abstraction. It yields multiple grafts per chain as single
pendant units and oligomeric grafts. The chain transfer to the methoxy
substituent of VTMS grafts contributes significantly to the product distribution.
59
The selectivity for the ratio of grafting to crosslinking shows a considerable
scope for optimization through variation of monomer and peroxide
loadings in the case of VTEOS as modifier, in contrast to maleic
anhydride. 60
18.2.18 Ethyl Diazoacetate-modified Polyolefins
Ethyl diazoacetate and chloroethyl diazoacetate is inserted by a carbene
insertion mechanism at 210°C. No radical initiator is needed, however the
grafting efficiency is small.
61, 62

632 Reactive Polymers Fundamentals and Applications
H 3 C
C
H 3 C
CH 3
HO
H 3 C
C
H 3 C CH 3
CH 2 O CH CH 2
DBBA
O
CH 2
CH C
O
O
CH 2
CH 2
CH C O CH 2
C CH 2 CH 3
CH 2
CH C O CH 2
O
TRIS
Figure 18.6: 3,5-Di-tert-butyl-4-hydroxybenzyl acrylate (DBBA) and 1,1,1-Trimethylolpropane
triacrylate (TRIS)
18.2.19 Grafting Antioxidants
Routes for grafting antioxidants onto polyolefins with high grafting yields
have been reported. The antioxidant 3,5-di-tert-butyl-4-hydroxybenzyl
acrylate (DBBA) reacts with the trifunctional coagent 1,1,1-trimethylolpropane
triacrylate (TRIS), c.f. Figure 18.6, in the presence of a small
concentration of a free-radical initiator in a poly(propylene) melt during
processing.
The major reaction is a homopolymerization of the antioxidant in
the absence of TRIS. This results in low grafting levels. However, in the
presence of TRIS, more than 90% grafting efficiency of DBBA on the polymer
is monitored, 6% of DBBA is used. The mechanism of the grafting
reaction could be established with decalin, used as a hydrocarbon model
compound. 15 The decalin adds with the hydrogen atom on the bridge to
the double bond of DBBA.
Quinoneimines containing an N-p-hydroxyphenyl and an N-p-aminophenyl
substituent have a high antioxidant efficiency when added to
isoprene rubber (IR), styrene butadiene rubber (SBR), ethylene/propylene
rubber (EPR), and ethylene propylene diene monomer (EPDM) rubbers,

Grafting 633
H 3 C
C
H 3 C
CH 3
R
O
O
+
H 2 N
R’
H 3 C
C
H 3 C
CH 3
H 3 C
C
H 3 C
CH 3
R
O
N
R’
H 3 C
C
H 3 C
CH 3
Figure 18.7: Synthesis of Quinoneimines
because they add to the allylic −CH of the polymer giving active adducts.
The synthesis of the quinoneimines is shown in Figure 18.7. The retention
of the protective activity after extraction of the material indicates the
grafting of these compounds during the thermal or mechanical processing
of the rubbers. 63
18.2.20 Comonomer Assisted Free Radical Grafting
The idea of using styrene as a comonomer originated from a detailed analysis
of the mechanism of free radical grafting. To obtain high graft efficiency,
together with a reduced degradation of polymer, it is essential that
the macroradicals in the backbone react with the grafting monomers before
they undergo chain scission of the backbone. If the primary monomer
is not sufficiently reactive towards the macroradicals, it is helpful to add
another monomer that reacts with the macroradicals faster than primary
monomer. A further requirement is that the resulting pendent free radicals
of the secondary monomer copolymerize readily with the primary monomer.
It was shown that the addition of styrene can improve the graft efficiency
of monomers such as hydroxyethyl methacrylate (HEMA) and

634 Reactive Polymers Fundamentals and Applications
N
C
O
CH 2
CH 2
+
HO
O
C
O
C
N
H
O
CH 2 CH 2 O C
Figure 18.8: Ring Opening of a Pendant Oxazoline Group
methyl methacrylate (MMA), glycidyl methacrylate (GMA), but not vinyl
acetate (VAc) and ricinoloxazoline maleate (OXA). This is due to the fact
that styrene copolymerizes readily with HEMA, MMA, and GMA, but not
with VAc and OXA. The ring opening of a pendant oxazoline group is
shown in Figure 18.8.
Ricinoloxazoline maleate is a bifunctional compatibilizer agent. It
can be grafted with the vinyl function of the maleate unit onto a poly-
(propylene) site by usual radical grafting, thus becoming oxazoline groups
attached to the poly(propylene) chain. The oxazoline group can be reacted
with the carboxyl groups of poly(butylene terephthalate). 16
18.2.20.1 Styrene-assisted Grafting
Maleic anhydride. The low reactivity of MA with respect to free-radical
polymerization is inherently due to its structural symmetry and the deficiency
of the electron density around the double bond.
It is clear that the addition of a monomer capable of donating electrons,
i.e., an electron-rich comonomer, would activate an electron deficient
monomer like MA by changing the electron density of the π-bond.
The addition of styrene to a melt grafting system as a comonomer
of maleic anhydride can significantly enhance the graft degree onto poly-
(propylene). The maximum graft degree is obtained when the molar ratio
of maleic anhydride to styrene is approximately 1:1.
Styrene improves the grafting reactivity of maleic anhydride and
also reacts with maleic anhydride to form a styrene/maleic anhydride co-

Grafting 635
polymer (SMA) before grafting onto the poly(propylene) backbone.
When the concentration of maleic anhydride is higher than that of
styrene, some maleic anhydride monomer reacts with styrene to form
SMA, but others can directly graft onto macroradicals on the poly(propylene)
chain. When the amount of styrene added is higher than that of
maleic anhydride, a part of the styrene monomer may preferentially react
with the macroradicals to form macroradicals with styryl ends, while
others copolymerize with maleic anhydride to yield SMA. 10
On the other hand, styrene is ineffective as comonomer for maleate
esters grafting onto PP. 64 This arises from the low affinity of the styryl
radical towards the maleate ester species. This could be predicted from the
critical inspection of the monomer reactivity ratios of styrene and maleic
esters.
Glycidyl Methacrylate. The reactivity of glycidyl methacrylate (GMA)
in free radical grafting onto poly(propylene) (PP) is low. However, adding
styrene as a comonomer for glycidyl methacrylate increases both the rate
and grafting efficiency. Further the degradation of PP is reduced. It is believed
that when styrene is added to such a grafting system, styrene reacts
first with PP macroradicals to form pendent styryl radicals. These styryl
radicals are the starting point for a copolymerization with GMA to form a
grafted PP. 13
Poly(propylene) functionalized with glycidyl methacrylate has been
used for the compatibilization of poly(propylene) and poly(butylene terephthalate)
blends. 65 Similar studies have been done for the grafting of
glycidyl methacrylate onto linear low density poly(ethylene) (LLDPE). 14
18.2.20.2 Increasing the Grafting Efficiency with Comonomers
The mechanisms that result in higher grafting yields by the addition of
comonomers can be attributed to 1
• Longer chain grafts,
• More grafting sites,
• Use of polyvinyl monomers.
Longer chain grafts appear to be the favored alternating copolymerization
of electron donor-electron acceptor forming monomer pairs. Examples are
styrene, and maleic anhydride. More grafting sites emerge by a more efficient
addition of the macroradicals on the backbone by the addition of

636 Reactive Polymers Fundamentals and Applications
Table 18.8: Experimental Techniques for the Characterization of Modified
Polyolefins
Method
Remarks
Titration
Maleic anhydride, glycidyl units
FTIR spectroscopy Most widely used method
NMR spectroscopy Chemical shifts are very sensitive to the
chemical environment
13 C NMR spectroscopy Poor sensitivity
a comonomer. Polyfunctional monomers effect presumptive branching or
crosslinking sites when once grafted onto the backbone. In this way a star
shaped or comb shaped grafting center may emerge. An example for this
concept is the use of a triacrylate monomer as comonomer. 66
18.2.21 Radiation Induced Grafting in Solution
A suitable solvent for the radiation induced graft copolymerization of styrene
and maleic anhydride (Sty/MA) binary monomers onto high density
poly(ethylene) (HDPE) is acetone. Untreated and treated grafted HDPE
membranes have potential applications in dialysis. 67
The hydrophilicity of the membrane, the degree of grafting and the
molecular weight and chemical structure of the metabolites, such as urea,
creatinine, uric acid, glucose, and phosphate salts, have a great influence
on the transport properties of the membrane. The permeability increases
with the degree of grafting. Basic metabolites show higher permeation
rates through the modified membrane as acidic metabolites, in particular
phosphate salts. The permeabilities of high molecular weight compounds
are low.
18.2.22 Characterization of Polyolefin Graft Copolymers
The characterization of the grafted functionality in modified polyolefins is
difficult because the small number of modified units are overwhelmed by
the normal polyolefin repeat units.
The content of modified units is typically only about one to five
modified units per molecule in a polymer of typical molecular weight of 20
to 40 kDalton. 1, 2 Some experimental techniques to characterize modified
polyolefins are summarized in Table 18.8.

Table 18.9: Polymers Used for Grafting
Grafting 637
Polymer Grafting Agent Reference
Poly(styrene) Maleic anhydride
68
Poly(vinyl chloride) n-Butyl methacrylate
69
Poly(alkylene terephthalate) Nadic anhydride
70
Starch Vinyl acetate
71
Starch Methyl acrylate
72
18.2.23 PVC/LDPE Melt Blends
In blends of a low density poly(ethylene) (LDPE) with polyvinyl chloride
(PVC) during melt blending, chemical reactions take place. 73 This is indicated
by changes in the molecular weight, M n and M w number-average
molecular weight, the polyene and the carbonyl indices, color changes,
and the changes of the glass transition and decomposition temperatures.
By mixing of LDPE to PVC and melt blending, short-chain LDPE grafted
PVC (s-LDPE-g-PVC) copolymers are formed. On the other hand, the
dehydrochlorination reaction of PVC was suppressed.
18.3 OTHER POLYMERS
Table 18.9 summarizes polymer types other than polyolefins that have been
used for grafting other units.
18.3.1 Poly(styrene) Functionalized with Maleic anhydride
Maleic anhydride (MA) can be grafted to poly(styrene) (PS) by reactive
extrusion in the presence of a free-radical initiator, namely 1,3-Bis(tertbutylperoxyisopropyl)benzene.
Its half-life is about 2.5 min at 180°C. The
introduction of the maleic anhydride units in PS proved to be very effective
for controlling the morphology of blends of PA6 with modified PS. The
rheological properties of the blends indicate the formation of long branching
between the amine end groups of PA6 and the maleic anhydride unit of
maleic anhydride grafted poly(styrene) (MPS) during melt mixing. 68
18.3.2 Multifunctional Monomers for PP/PS Blends
Polyolefins, do not have reactive functionalities. There are two commonly
used approaches for compatibilization in reactive extrusion. 74

638 Reactive Polymers Fundamentals and Applications
1. In the two-step process, polymers are functionalized selectively
in the first step, and then blended in an extruder in the second
step. The grafting reaction should occur between the functionalized
groups during blending, and graft co-polymers are formed
in-situ.
2. In the one-step process, low molecular weight compounds are
added into the melted blends to initiate grafting and coupling reactions
at the phase interface to form graft or block copolymers
during the extrusion process.
Peroxides cause serious chain scission of the PP backbone, which
affects the properties of the alloys. Multifunctional monomers, such as glycol
trilinoleate (GTL), trimethylolpropane triacrylate (TMPTA), diethylene
glycol diacrylate (DEGDA) or tripropylene glycol diacrylate (TPGDA) in
combination with dicumyl peroxide (DCP) can suppress the PP degradation
efficiently, and promote the grafting reaction to some extent at the
same time. GTL is prepared by the esterification of glycerol with linoleic
acid. 74
18.3.3 Poly(ethylene-co-methyl acrylate)
Maleic anhydride can be melt-grafted onto poly(ethylene-co-methyl acrylate).
The grafting is enhanced with a comonomer, i.e., divinylbenzene or
vinyl-4-tert-butylbenzoate. A suitable radical initiator is 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane
(LUPERSOL 231). The processing
temperature of the internal batch mixer is at 140°C. It was observed
that styrene and vinyl-4-tert-butylbenzoate can significantly increase the
amount of anhydride grafted. The styrene comonomer system is most efficient.
75 The use of 1-dodecene in this system showed primarily a plasticizer
effect.
18.3.4 n-Butyl methacrylate Grafted onto Poly(vinyl chloride)
Melt grafting of n-butyl methacrylate onto poly(vinyl chloride) was
achieved by a melt mixing process with a free-radical initiator. 69 A maximum
of 14% graft was obtained. The graft copolymer showed significant
improvement in processability and both thermal and mechanical properties.

Grafting 639
18.3.5 Starch Esterification
Starch esters with low degrees of substitution are prepared in aqueous media
by batch methods. 76 Extrusion is not used widely for modification of
starch, however, it has great potential. Extruders have been used to manufacture
carboxymethylated and cationic potato starch, starch phosphates,
anionic starch, and oxidized starches. 77–80
Starch esters can be synthesized by extruding 70% amylose starch
with fatty anhydrides and sodium hydroxide as catalyst in a single-screw
extruder. The sodium hydroxide neutralizes the organic acids formed in the
course of the reaction. Acetic anhydride, propionic anhydride, heptanoic
anhydride, and palmitic anhydride have been used. 81 The degrees of substitution
of esterified starch can be determined by hydrolyzing substituted
groups with NaOH and then titrating back with acid. The degree of substitution
coincides with the expected value from the monomer feeds. Some
molecular weight reduction of the amylopectin fraction was detected in the
esterified products from cornstarch with a 70% amylose content. Lower
molecular weights and higher levels of anhydride resulted in the greatest
reduction in starch molecular weight.
The acid esters decrease the hydrophilic character of the starch. The
introduction of heptanoic anhydride and palmitic anhydride result in a
higher water absorption index. This is explained by the disruption of the
crystalline structure of the starch. By disrupting the crystalline structure of
the starch, the opportunity for hydrogen-bonding between starch and water
is increased. Clearly, the heptanoic and palmitic acid residues provide a
more significant steric hindrance for the formation of starch crystals than
the smaller acetic and propionic acid residues.
Another approach for the acetylation of starch is the use of vinyl
acetate and sodium hydroxide. 71 The acetylation reaction is accompanied
by the hydrolysis of vinyl acetate and a consecutive hydrolysis reaction of
the acetylated starch. The degree of substitution could be varied from 0.05
to 0.2.
18.3.6 Starch Grafted Acrylics
Starch graft poly(methyl acrylate) (S-g-PMA) could be prepared from an
aqueous cornstarch slurry and methyl acrylate by the initiation with ceric
ions. At the end of the reaction, an additional small amount of ceric ion solution
was added. After this addition no unreacted methyl acrylate mono-

640 Reactive Polymers Fundamentals and Applications
mer remained. 72 The grafted starch is intended for the use as loose-fill
foam. This type of loose-fill foam has a better moisture and water resistance
than other starch-based materials.
Graft copolymers of starch and poly(acrylamide) could be prepared
by reactive extrusion with ammonium persulfate as initiator. 82
18.3.7 Thermoplastic Phenol/Formaldehyde Polymers
Phenol/formaldehyde resins with high viscosity are needed in reactive extrusion
with poly(propylene) to establish a favorable viscosity ratio. Most
commercially available phenol/formaldehyde resins have a molar mass of
0.5 to 1 kDalton. Only thermoplastic phenol/formaldehyde polymers of
the novolak type meet the requirement of avoiding crosslinking in the extruder.
High molecular weight novolak-type resins can be obtained by adjusting
the ratio of formaldehyde to the phenol near unity. 83
18.3.8 Polyesters and Polyurethanes
A number of techniques for polymerizing radical polymerizable monomers
with polyester resins and polyurethane resins to obtain graft or block reaction
products have been published. The graft or block reaction products
have been studied to improve, for example, the impact resistance of
molding compounds by using them as a compatibilizer, the adhesiveness
of paints and adhesives to substrates, the curing property of the paints and
adhesives, and the dispersibility of pigments. 84
The modification of high molecular weight polyesters introduces
polymerizable unsaturated double bonds into the main chain or into the
molecular terminal groups. The double bonds can be polymerized with
radical polymerizable monomers by graft or block polymerization. Similarly,
graft or block modifications for polyurethane can be achieved.
When a high molecular weight polyester or polyurethane is grafted
for the modification, crosslinking between the polyester molecules or the
polyurethane molecules is more likely.
18.3.8.1 Polyesters
In the case of polyesters, the sum of polymerizable unsaturated double
bonds is desirably up to 20 mol-% of the total acid components and diol

Grafting 641
components. When the sum exceeds 20 mol-%, various properties of the
base resin itself are largely reduced.
18.3.8.2 Polyester Polyurethanes
The polyester polyurethanes should contain up to 30 polymerizable unsaturated
double bonds in one molecule.
18.3.8.3 Radical Polymerizable Monomers
Radical polymerizable monomers are a mixture of an electron accepting
monomer and an electron donor monomer. This combination allows controlling
the gelation, even if the resin has a very large amount of unsaturated
bonds. Electron donor monomers are styrene, α-methyl styrene, tertbutyl
styrene, and N-vinyl pyrrolidone. 85 Electron accepting monomers
are fumaric acid, monoesters, and diesters of fumaric acid.
Basically gelation can be avoided by a dilution of the polymeric
vinyl groups by monomeric vinyl groups that are more prone to copolymerize.
18.3.8.4 Grafting Reaction
This technique is a graft polymerization of the polymerizable unsaturated
double bond existing in the base resin, i.e., the main chain with the radical
polymerizable monomers. The graft polymerization reaction is performed
by reacting the base resin, which is dissolved in an organic solvent, with a
mixture of the radical polymerizable monomers and a radical initiator.
Suitable radical initiators are organic peroxides and organic azo compounds.
The organic peroxides include dibenzoyl peroxide and tert-butylperoxypivalate
and the organic azo compounds include 2,2 ′ -azobis(isobutyronitrile)
and 2,2 ′ -azobis(2,4-dimethylvaleronitrile). A chain transfer
agent such as octyl mercaptane, dodecyl mercaptane, 2-mercaptoethanol,
and α-methyl styrene dimer may be used to control the grafted chain
length.
The solvents that can be utilized include methylethylketone, methylisobutylketone,
cyclohexanone, toluene, xylene, ethyl acetate, and butyl
acetate. The solvent itself should neither decompose the radical initiator by
induced decomposition nor create a combination with the initiator which

642 Reactive Polymers Fundamentals and Applications
O
O
+
O
O
H
O
enophil
H
O
ene
Figure 18.9: Basic Mechanism of the Ene Reaction
causes a danger of explosion that has been reported between specific organic
peroxides and specific ketones. Furthermore, it is important that the
solvent has a suitably lower chain transfer constant as a reaction solvent
for the radical polymerization. 84
18.3.9 Polyacrylic Hot-melt Pressure-sensitive Adhesive
A polyacrylic hot-melt pressure-sensitive adhesive is prepared as follows.
A copolymer consisting of acrylic acid, tert-butyl acrylamide, maleic anhydride,
2-ethylhexyl acrylate, n-butyl acrylate is manufactured in acetone/-
isopropanol solution, with 2,2 ′ -azobis(2-ethylpropionitrile) as initiator in a
batch reactor.
This polymer contains anhydride groups that are useful for coupling.
The polymer is then degassed from the solvent in an extruder. In the next
step, the acrylic hot-melt is compounded with 2-hydroxypropyl acrylate.
Pendent acrylate groups are formed in this way. This offers the advantage
of very gentle crosslinking methods, since crosslinking can be carried out
directly by way of the installed acrylate groups. The hot-melt exhibits
viscoelastic behavior at room temperature. 86
18.4 TERMINAL FUNCTIONALIZATION
18.4.1 Ene Reaction with Poly(propylene)
Polyolefins prepared with Ziegler-Natta processes or metallocene catalysts
may carry olefinic end groups. Olefinic end groups are also introduced by
melt degradation.
A poly(propylene) functionalized at the end groups with anhydride
can be obtained via the Alder-ene reaction from a low molecular weight

Grafting 643
amorphous poly(propylene) by reactive extrusion. The Alder-ene reaction
is a pericyclic reaction with a 6-center intermediate. It involves the reaction
of an ene and a enophil. The ene moiety in the Alder-ene reaction is a
double bond with an allylic hydrogen. The basic mechanism is shown in
Figure 18.9.
The ene reaction is reversible. 87 However, the reverse reaction seems
to be not a simple retro-ene process. The rate of the Alder-ene reaction depends
on the acidity and basicity of ene and enophile, respectively. Lewis
acids, like SnCl 4 ,TiCl 4 , and AlCl 3 develop fumes of hydrochloric acid during
reaction. However, a less reactive Lewis acid, SnCl 2·2 H 2 O, can also
catalyze the reaction without the drawback of developing HCl.
The reaction is complete at 230°C within 5 min in the presence of
a stable radical, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO),
which acts as a free radical scavenger. This prevents the maleic anhydride
from being grafted onto the backbone of the poly(propylene).
4, 88
The maleation of polypropylene by reactive extrusion via the Alderene
reaction produces a terminal functionality of the polymer without significant
chain scission.
18.4.2 Styrene-butadiene Rubber
The end capping of living anions of poly(styrene-butadiene) can be done
with polymeric terminator molecules. A polar functional terminator is
a block copolymer of poly(ethylene glycol) and poly(dimethylsiloxane)
(PEG-PDMS) containing a chlorosilyl moiety at one chain end. This polymer
is synthesized by two-step hydrosilylation reaction. 89 The PEG-PDMS
end groups behave as polar functional groups, showing an increase of the
glass transition temperature and storage modulus in a composite of endcapped
SBR with silica particles.
18.4.3 Diels-Alder Reaction
A benzocyclobutene (BCB) capped polymer can be used to react in a Diels-Alder
reaction with another polymer bearing a dienophile. 90 4-(3-iodopropyl)benzocyclobutene
was used to terminate an anionic polymerization
of styrene to give a poly(styrene) end-capped with BCB.
A copolymer of 1-hexene and 7-methyl-1,6-octadiene was prepared
by Ziegler-Natta polymerization, with the pendant double bonds intended
as the grafting sites. The reaction is illustrated in Figure 18.10.

644 Reactive Polymers Fundamentals and Applications
CH
CH 2
CH 2
CH 2
CH
+
C
H 3 C CH 3
H
H 3 C
CH
CH 2
CH 2
CH 2
C
C
CH 3
Figure 18.10: Grafting of an Isomerized Benzocyclobutene Unit to a Polyolefin
Dienophile 90
18.5 GRAFTING ONTO SURFACES
18.5.1 Grafting onto Poly(ethylene)
18.5.1.1 Sulfonic Acid Groups
In order to introduce sulfonic acid groups on poly(ethylene), poly(ethylene)
samples are irradiated with UV light in a gas atmosphere containing
SO 2 and air to achieve a photosulfonation of the surface. The surface modification
is carried out under atmospheric pressure and is considered to be
an inexpensive alternative to plasma modification techniques.
The hydrophilicity of the PE surface increases considerably compared
to unreacted PE. The depth of photomodification reached several µ.
Because of the large depth of modification, the process may also be useful
for the modification of membranes. In combination with projection lithography
the process could be suitable for the manufacture of gratings in
thin polymer films, as required for holographic recordings and distributed
feedback lasers. 91
18.5.1.2 Sulfate Groups
Sulfate groups at the surface of poly(ethylene) are introduced by immobilizing
a precoated layer of either sodium 10-undecenyl sulfate (SUS) or
sodium dodecyl sulfate (SDS) on the polymeric surface by means of an
argon plasma treatment. SUS is synthesized by sulfating 10-undecene-
1-ol with the pyridine-SO 3 complex. The presence of sulfate groups at the
polymeric surfaces was confirmed by X-ray photoelectron spectroscopy

Grafting 645
(XPS). The presence of an unsaturated bond in the alkyl chain of the surfactant
improved the efficiency of the immobilization process. About 25%
of the initial amount of sulfate groups in the precoated layer was retained
at the PE surface for SUS, but only 6% for SDS. 92
18.5.1.3 Photochemical Bromination
The gas phase bromination of poly(ethylene), poly(propylene) and poly-
(styrene) film surfaces by a free-radical photochemical mechanism occurs
with high regioselectivity. The surface bromination is accompanied by a
simultaneous dehydrobromination. This results in the formation of long
sequences of conjugated double bonds. Thus, the brominated polyolefin
surface contains bromide moieties in different chemical environments. 93
In contrast, the gas phase free radical photochemical chlorination of
polyolefin films proceeds in a rather random way and is also accompanied
by simultaneous dehydrochlorination.
18.5.1.4 Poly(thiophene)
Poly(thiophene) (PT) can be grafted on a PE film using three reaction steps.
1. PE films are brominated in the gas phase, yielding PE-Br.
2. A substitution reaction of PE-Br with 2-thiophene thiolate anion
gives the thiophene-functionalized PE.
3. PT is grafted on the PE surface using chemical oxidative polymerization
to give PE-PT.
The polymerization is performed in a suspension solution of anhydrous
FeCl 3 in CHCl 3 , yielding a reddish PE-PT film after dedoping with
ethanol. Infrared spectroscopy reveals that the PT is grafted on PE in the
2,5-position.
SEM imaging shows islands of PT on the PE film. The thickness of
the islands is in the range of 120 to 145 nm. The conductivity of these thin
films is in the range of 10 −6 Scm −1 , which is a significant increase from
the value of 10 −14 Scm −1 measured for an ungrafted PE film. 94
18.5.1.5 Acrylics
Ion beam-modified poly(ethylene) was exposed to the solutions of acrylic
acid, acrylonitrile, and bromine. 95 The chemical and structural changes

646 Reactive Polymers Fundamentals and Applications
were examined using spectroscopic techniques, electronparamagnetic resonance,
and Rutherford back-scattering techniques.
Acrylic acid, acrylonitrile, and bromine react with radicals and conjugated
double bonds created by the ion irradiation in the poly(ethylene).
The reactions in the ion beam-modified surface layer may lead to the creation
of a grafted surface layer with a thickness of up to 150 nm.
Surface photo grafting of high density poly(ethylene) (HDPE) powder
can be achieved with a pretreated HDPE surface by benzophenone
(BP). Onto such a surface, acrylic acid can be graft copolymerized by
photo grafting in the vapor phase. 96 The most suitable reaction temperature
is 90°C. The grafting degree can reach a comparable high value of
10%.
18.5.1.6 Siloxane
The dyeing properties on high-strength and high modulus poly(ethylene)
fibers are improved by building up a layer of a polysiloxane network. The
grafting of siloxane onto poly(ethylene) proceeds first via a treatment with
peroxide. Hydrogen peroxide in o-xylene emulsion is emulsified by sonication.
The emulsion is effective for introduction of hydroxide groups onto
the poly(ethylene) fiber surface. The treatment does not influence the tensile
strength of the fiber. A polysiloxane network can be built up on the
fiber surface by treating the surface with a (3-aminopropyl)triethoxysilane
(APS) solution. 97 In fact, this method can be used to dye a poly(ethylene)
fiber surface.
18.5.1.7 Silicone
The surface graft copolymerization of hydrogen silicone fluid onto a low
density poly(ethylene) (LDPE) film through corona discharge shows an
improved hydrophobicity of the grafted LDPE films. However, the mechanical
properties decrease slightly. Thus there is evidence that HSF can
be graft copolymerized onto an LDPE film surface through corona discharge.
98
18.5.1.8 Surface Crosslinking
Ultra-high molecular weight poly(ethylene) (UHMWPE) can be crosslinked
at the surface by irradiation with electron beams. 99 Attenuated total

Grafting 647
reflectance Fourier transform infrared spectroscopy (ATR-FTIR) infrared
techniques suggest that the irradiation in air atmosphere introduced hydroperoxide
groups into the polymer without formation of any other oxygencontaining
groups.
The generated hydroperoxides could be decomposed further by subsequent
heat treatment of the irradiated polymer, resulting in crosslinking
of UHMWPE chains in the region of the material near the surface. As
a result of this surface modification, the surface hardness of UHMWPE
substantially increases.
18.5.2 Grafting onto Poly(tetrafluoroethylene)
18.5.2.1 Diazonium Salts
Functionalization of poly(tetrafluoroethylene) (PTFE) surfaces can be
achieved by diazonium salts. Reduced PTFE can be grafted by nitro and
bromophenyldiazonium tetrafluoroborate salts in a manner similar to that
used for carbon, except that no application of a reductive potential during
grafting is required. The grafting is evidenced by cyclic voltametry, X-
ray fluorescence or time of flight single ion monitoring mass spectroscopy
(TOF-SIMS). 100–102
18.5.2.2 Epoxide-containing Monomers
A pretreated PTFE film with argon plasma can be further modified by
a graft copolymerization with hydrophilic and epoxide-containing monomers.
The grafting is initiated by UV light. Functional monomers for
grafting include acrylic acid (AA), sodium salt of p-styrenesulfonic acid,
N,N-dimethylacrylamide (DMAA), and glycidyl methacrylate (GMA).
A stratified surface microstructure with a significantly higher ratio
of substrate to grafted chains in the top surface layer than in the subsurface
layer is always obtained. The grafted PTFE films show a number of new
issues. These include: 103
• Covalent immobilization of an enzyme, such as trypsin, for AA
graft copolymerized surface,
• Change transfer included coating of an electroactive polymer, such
as polyaniline, for AA and styrenesulfonic acid graft copolymerized
surfaces,

648 Reactive Polymers Fundamentals and Applications
• Adhesive-free adhesion between two PTFE surfaces, for AA, styrenesulfonic
acid and DMAA graft copolymerized surfaces,
• Improved adhesive bonding via interfacial crosslinking of the
grafted chains, for GMA graft copolymerized surfaces.
18.5.2.3 2-Hydroxyethyl acrylate
Surface modifications of Ar plasma pretreated poly(tetrafluoroethylene)
(PTFE) film via graft copolymerization improve the adhesion of copper.
The PTFE film surface is initially modified by graft copolymerization
with a monomer, such as 2-hydroxyethyl acrylate and acrylamide.
These monomers contain the functional groups for epoxide groups. The
modified PTFE surface is subsequently again exposed to an Ar plasma and
subjected to UV induced graft copolymerization with glycidyl methacrylate.
104
18.5.2.4 Glycidyl Methacrylate
The surface modification of a PTFE film is done by the deposition of glycidyl
methacrylate (GMA) in the presence of H 2 plasma activation of the
PTFE substrates. The H 2 plasma treatment results in an effective defluorination
and hydrogenation of the PTFE surface. This enhances the adhesion
of Cu vapor onto the PTFE surface.
In addition, a plasma polymerization with glycidyl methacrylate is
performed. High adhesion strength for the Cu on such a surface is obtained
only in the presence of H 2 plasma activation of the PTFE substrates prior
to the plasma polymerization and deposition of GMA. In the absence of
H 2 plasma pre-activation, the deposited pp-GMA layer on the PTFE surface
can be readily removed by acetone extraction. The enhancement of
the adhesion of the Cu on the surface is attributed to the covalent bonding
of the pp-GMA layer with the PTFE surface, the preservation of the epoxide
functional groups in the pp-GMA layer, and the strong interaction of
evaporated Cu atoms with the epoxide and carboxyl groups of the GMA
chains. 105
18.5.2.5 Oxygen and Ammonia Plasmas
PTFE can be treated in oxygen or ammonia plasmas in order to introduce
oxygen-containing or nitrogen-containing groups, respectively. These

Grafting 649
groups increase the surface free energy and allow the adsorption of polyelectrolytes
via electrostatic interactions. 106 The effects of such a modification
can be evaluated by means of contact angle measurements.
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19
Acrylic Dental Fillers
Polymers in dental applications are used as restorative materials, cements,
adhesives, cavity liners, and as protective sealants for pits and fissures. The
use of composite resins is recommended for amalgam replacement.
Polymers are further used as denture base materials, denture relines,
crown and bridge resins, dental impressions, and duplicating materials.
There are monographs on the topic. 1–5
Polymeric materials used in dental applications must meet certain
physical, chemical, biological, and aesthetic requirements. These requirements
include
• Adequate strength
• Resilience,
• Abrasion resistance,
• Dimensional stability,
• Color stability,
• Resistance to body fluids,
• Tissue tolerance, low allergenicity, toxicity, mutagenicity, carcinogenic
responses.
Further, the materials should be easy to use and should not be expensive.
657

658 Reactive Polymers Fundamentals and Applications
19.1 HISTORY
The first polymeric materials used in dental applications were guttapercha,
celluloid, phenol/formaldehyde, and acrylic resins. Polymers such
as acrylics, poly(styrene)s, poly(carbonate)s, and polysulfones can be injection-molded
to yield dentures with outstanding toughness, high fatigue
strength, and low water absorption. Most common are acrylic-based resins.
However, other classes also gain importance, such as spiro orthocarbonates,
cycloaliphatic epoxy compounds, cyclic ketene acetals and 2-vinylcyclopropanes,
5, 6 because of the demand for low shrinkage materials. Often
these monomers are in combination with acrylic-based resins. We will
mention these classes briefly here.
Acrylic resins have been used in the construction of denture bases
since 1930. 4 Multifunctional acrylates and methacrylates can be polymerized
to crosslinked polymers to be used as restorative materials. A
polymerization involving cold curing is carried out with redox initiators at
ambient temperature.
Bisphenol A diglycidyl ether dimethacrylate with a ceramic filler
opened a new area in the state of the art. A silane coupling agent between
ceramics and organic polymer increases the adhesion strength.
The principle of photopolymerization for dental resins was introduced
around 1975. Also, a polyurethane resin, based on polyurethane
dimethacrylate and similar monomers was developed 7 that can be cured
with visible light.
19.2 POLYMERIC COMPOSITE FILLING MATERIALS
An overview of the ingredients in a dental composite is given in Table 19.1.
Dental polymeric composite filling materials consist of di- and trifunctional
monomer systems that undergo crosslinking in the course of
polymerization. Reinforcing fillers are silanized quartz, glass, and ceramics.
The polymerization must be initialized effectively under oral conditions.
Various additives may increase the chemical stability of the cured
materials. Dental sealants mostly are not filled with reinforcing fillers.
Dental composites may be used as two-component formulations or as a
one-component formulation.

Acrylic Dental Fillers 659
Table 19.1: Constituents in a Dental Composite
Compound Type
Organic resin
Initiator systems
Polymerization inhibitors
Fillers
Pigments
Coloring or tint agents
Caries inhibiting agents
Fluoride release agents
UV-absorbers
Stabilizers
Surfactants
Thickening agents
19.3 MONOMERS
Common monomers are shown in Table 19.2. Some acrylics and methacrylics
are shown in Figure 19.1.
19.3.1 Acrylics and Methacrylics
Most common thermosets are methacrylate based, for example, 2,2-bis[p-
(2-hydroxy-3-methacryloxypropoxy)phenyl]propane, i.e., the bisphenol A
adduct of glycidylmethacrylate (Bis-GMA) and triethylene glycol dimethacrylate
(TEGDMA), c.f. Figure 19.1.
19.3.1.1 Urethane-modified Acrylics
The reaction product of 1,6-hexamethylenediisocyanate and ethylene glycoldimethacrylate
or other glycol esters is also a suitable monomer. Other
urethane dimethacrylates are 1,6-bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane
(UDMA). Further polyurethane dimethacrylate
(PUDMA) is commonly used as a principal polymer in dental restoratives
of this type.
Urethane derivatives of Bis-GMA exhibit lower viscosities and are
more hydrophobic than Bis-GMA. In general, the viscosities of these
monomers decrease with increasing chain length of the alkyl urethane substituent.
Since Bis-GMA, PUDMA, and others are still highly viscous at

660 Reactive Polymers Fundamentals and Applications
Vinyl Monomer
Table 19.2: Monomers for Dental Polymers
Reference
2,2-Bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane
(Bis-GMA)
Bisphenol A dimethacrylate (Bis-A-Dima)
Ethoxylated Bis-A-Dima
Triethylene glycol dimethacrylate (TEGDMA)
Ethoxylated bisphenol A dimethacrylate (EBPDMA)
Hydroxyethyl methacrylate (HEMA)
Hydroxyethyl methacrylate maleic anhydride adduct (HEMAN)
8
1,1,1-Trimethylolpropane trimethacrylate (TMPTMA)
Tetrahydrofurfuryl cyclohexene dimethacrylate (TCDM)
Hexafunctional methacrylate ester (HME)
1,6-Hexanediol dimethacrylate (HDDMA)
9
2-Isocyanatoethyl methacrylate (IEM)
10
Di-2-methacryloxyethyl-2,2,4-trimethylhexamethylene
dicarbamate (UDMA)
Polyurethane dimethacrylate (PUDMA) esters
Tetrahydrofurfuryl methacrylate (THFMA)
Glycidyl methacrylate (GMA)
Methacryloyl-β-alanine (MBA)
11
Methacryloyl glutamic acid
11
Acryloyl-β-alanine
11
Acryloyl glutamic acid
11
Poly(carbonate)dimethacrylate (PCDMA)
12
Cyclic Monomers
Reference
α-Methylene-γ-butyrolactone
13
Epoxy Monomers
Reference
Cycloaliphatic diepoxide
14
Epoxylated vinyl ether
14

Acrylic Dental Fillers 661
OH
CH 3
OH
CH CH 2
C
CH 2 CH
CH 2 CH 3 CH 2
O
C
C
O
CH 3
O
H 3 C
CH 2 CH 2
CH 2
CH2
O
O
CH 2
CH2
Bis-GMA
CH 2
O
CH2
O
TEGDMA
O
C
C
O
CH 3
CH 2 C
C CH 2
CH 3
O
C
C
CH 2
CH 3
C C
O
O CH 2 CH 2 OH
HEMA
CH 2
CH 3
C C
O
O CH 2
O
THFMA
CH 2
CH 3
C C
O
O CH 2 CH 2 N C O
IEM
CH 2
CH 3
C C
O
O CH 2 CH 2
O
GMA
Figure 19.1: 2,2-Bis[p-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane
(Bis-GMA), Triethylene glycol dimethacrylate (TEGDMA), Hydroxyethyl methacrylate
(HEMA), Tetrahydrofurfuryl methacrylate (THFMA), 2-Isocyanatoethyl
methacrylate (IEM), Glycidyl methacrylate (GMA)

662 Reactive Polymers Fundamentals and Applications
Table 19.3: Example for a Resin Matrix 9
Monomers %
Ethoxylated bisphenol A dimethacrylate 30
Polyurethane dimethacrylate ester 50
1,6-Hexanediol dimethacrylate 20
Initiator System
phr
Camphorquinone 0.1
Ethyl-4-dimethylamino benzoate 0.3
2,4,6-Trimethylbenzoyldiphenylphosphine oxide 0.2
room temperature, they are generally diluted with an acrylate or methacrylate
monomer having a lower viscosity, such as trimethylolpropyl trimethacrylate,
1,6-hexanediol dimethacrylate, or 1,3-butanediol dimethacrylate.
Other dimethacrylate monomers, such as ethylene glycol dimethacrylate,
diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, poly-
(ethylene glycol)dimethacrylate (PEGDMA) and tetraethylene glycol dimethacrylate,
are also in general use as diluents. 7
The photopolymerization of these monomers shows high degrees
of conversion of the vinyl groups in comparison to Bis-GMA. Polymers
with lower polymerization shrinkages at equivalent degrees of vinyl conversion
than Bis-GMA are obtained. The refractive indices of the urethane
derivatives were similar to Bis-GMA. However the flexural strengths of
the polymers are lower than that of the Bis-GMA homopolymer. The flexural
strengths decrease with increasing chain length of the alkyl urethane
substituent. 15 An example for a resin matrix is shown in Table 19.3.
19.3.1.2 Isocyanatomethacrylates
The potential utility of isocyanatomethacrylates in dental adhesives arises
from the possibility of dual modes of reaction, i.e., free-radical polymerization
via the methacrylate double bonds, and the reaction via the NCO
group with active hydrogens in a suitable compound to be admixed. 10
19.3.1.3 Nematic Acrylics
Zero polymerization shrinkage is one of the most necessary features of a
dental restorative so that accumulated stresses do not debond the dentinrestorative
interface or fracture the tooth or restorative which can result in

Acrylic Dental Fillers 663
marginal leakage and microbial attack. This feature is also important in
bone repair and in accurate reproduction of photolithographic imprints and
optical elements.
Attempts have been made to reduce polymerization shrinkage by utilizing
nematic liquid crystal monomers. The expected low polymerization
shrinkage for such compounds originates from the high packing efficiency
that already exists in the nematic state, thus minimizing the entropy reduction
that occurs during polymerization. Liquid crystal monomers or
prepolymers have another advantage in that the viscosity is lower than that
of an isotropic material of the same molecular weight. 16
An example for a liquid crystalline methacrylate is shown in Figure
19.2, i.e. 4,4 ′ -Bis(2-hydroxy-3-methacryloylpropoxy)biphenyl esterified
with 4 ′ -cyano-4-biphenyloxyvaleric acid. The liquid crystalline di(meth)-
acrylate is synthesized by the reaction of 2,3-epoxypropoxy methacrylate
with 4,4 ′ -dihydroxybiphenyl to form a methacrylate-terminated macromonomer
having hydroxyl groups. The macromonomer hydroxyl groups
are then esterified with 4 ′ -cyano-4-biphenyloxyvaleric acid. The (meth)-
acrylate polymerizes quantitatively and with very low volume shrinkage of
less than 2.5%. 17
19.3.1.4 Amino Acid Derivatives of Acrylics
It is known that unreacted 2-hydroxyethyl methacrylate (HEMA) in current
resin-modified glass ionomer cements (RMGICs) shows potential cytotoxicity
to pulp and surrounding tissues. 18 Amino acid acrylate and methacrylate
derivatives were found to be suitable in light curable glass-ionomer cements
(LCGIC). Methacryloyl and acryloyl derivatives of the amino acids
can be synthesized via the Schotten-Baumann reaction.
Among several derivatives, methacryloyl-β-alanine (MBA) has a
particularly low solution viscosity and a high compressive strength. The
LCGIC system based on amino acid derivatives is free from HEMA.
This system may eliminate a potential cytotoxicity in LCGICs caused by
leached HEMA. Optimal MBA-modified cements are higher in certain mechanical
properties in comparison to conventional cements. 11
19.3.1.5 Phosphoric Esters
Phosphoric acid esters with pendant acrylate or methacrylate functions
serve as adhesion promoters to fillers such as surface active glasses. Ex-

664 Reactive Polymers Fundamentals and Applications
CH 2 CH 2
CH CH 3
H 3 C
C O O
O
CH
C
O
CH 2
HC H 2 C
O
C O
O O CH 2
O
CH 2
CH
O
C
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2 CH 2
O
O
C
N
C
N
Figure 19.2: Nematic Monomer, 4,4 ′ -Bis(2-hydroxy-3-methacryloylpropoxy)biphenyl
esterified with 4 ′ -cyano-4-biphenyloxyvaleric acid17, 19

Acrylic Dental Fillers 665
amples are 2-(methacryloyloxy)ethyl phosphate, bis[2-(methacryloyloxy)-
ethyl]phosphate 7 or pentaerythritol trimethacrylate monophosphate. They
added up to 5% with respect to the organic curable composition.
19.3.1.6 Hydrophobic-Modified Acrylics
Hydrophobic composites stronger than methacrylate prepolymers, are the
corresponding analogues where most of the hydrogens are replaced by fluorine.
19.3.2 Cyclic Monomers
Cyclic monomers generally exhibit less shrinkage in the course of polymerization
as the polymerization process occurs by a ring opening reaction,
in contrast to vinyl monomer that is basically the ring opening of a
two membered ring, i.e., the double bond.
α-Methylene-γ-butyrolactone (MBL) is an expanding monomer and
does not cause shrinkage of the material during polymerization. It can
be described as the cyclic analog of methyl methacrylate, and it exhibits
greater reactivity in free-radical polymerization than conventional methacrylate
monomers. 13
19.3.2.1 Spiroorthocarbonates
Spiroorthocarbonates (SOC), spiroorthoesters (SOE) and bicyclic orthoesters
are attractive because they show a very low shrinkage or even expansion
during polymerization. 20, 21 Spiroorthocarbonates with polymerizable
double bonds have been investigated; some of them are shown in Figure
19.3. A few are bearing methacrylic substructures. 21
Spiroorthocarbonates with seven membered rings show a high tendency
of ring opening when they undergo a radical polymerization. This is
favorable for low shrinkage. Spiroorthocarbonate compounds that include
epoxy groups as a substituent have been described. 22
The synthesis of 7,26-Dioxatrispirobicyclo[4.1.0]heptane-4,5 ′ -1,3-dioxane-2
′ ,2 ′′ -1,3-dioxane-5 ′′ ,4 ′′ -bicyclo[4.1.0]heptane (DCHE) is shown
in Figure 19.4. It has been concluded that although the polymerization
shrinkage has been one of the main shortcomings of resin-based composites,
the ring-opening polymerization of cyclic monomers has not been successfully
achieved for commercial dental filling materials. 5

666 Reactive Polymers Fundamentals and Applications
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O O
O
O
Figure 19.3: Spiroorthocarbonates with Polymerizable Double Bonds 21
19.3.3 Epoxy Monomers
Acrylate based compositions have the disadvantage of shrinking strongly
at hardening. Epoxy compounds containing compositions are known; they
can undergo cationic polymerization with low shrinkage. In this case, it is
necessary to use a high energy light source for such a polymerization, e.g.,
a mercury vapor lamp, which cannot be used in medical practices because
of the danger of combustion. Certain compositions are not completely
cured and do not fulfill the requirements of adhesiveness and abrasiveness.
To achieve a complete hardening, it is necessary to apply a thermic aftertreatment,
which is not practicable in the mouth of a patient. 14
However, a composition obtained by the combination of a cyclic
diepoxide, tetrahydrofuran, diphenyliodoniumhexafluorantimonate and
camphorquinone by means of accelerators, e.g., 4-dimethylaminobenzaldehyde,
4-dimethylaminophenethanol, dihydroxyethyl-p-toluidine, ethyl-
4-dimethylamino benzoate can be cured at wavelengths of 400 to 1000
nm. These materials can be used in dental applications. 23
N,N-bis-hydroxyalkyl-p-aminobenzoic acid alkyl esters have an excellent
efficiency as accelerators of the light induced hardening of a composition
based on epoxy compounds. 14

Acrylic Dental Fillers 667
OH
+
OH
O
Bu
Sn
Bu
S
Cl
C
Cl
+
HO
HO
O Bu
Sn
O Bu
+
S
O
O
O
O
O
O
O
O
O
O
O
O
Figure 19.4: Synthesis of 7,26-Dioxatrispirobicyclo[4.1.0]heptane-4,5 ′ -1,3-dioxane-2
′ ,2 ′′ -1,3-dioxane-5 ′′ ,4 ′′ -bicyclo[4.1.0]heptane (DCHE) 22

668 Reactive Polymers Fundamentals and Applications
Catalyst
Table 19.4: Chemical Curing Systems24, 25
Dibenzoyl peroxide
Organic peroxides
Hydroperoxides
Peroxides
Barbituric acid
Aryl borate
Tri-n-butylborane
Promoter
Tertiary aromatic amines
4-(N,N-Dimethylamino)phenethyl alcohol 26
Cobalt salt
Thioureas
Ascorbic acid
Cu 2+ Cl-compound
Acid
Oxygen
19.3.4 Highly Loaded Composite
In general, a highly loaded composite looks very dry and is hard to handle.
Suitable monofunctional monomers may be used to act as a diluent
to control or reduce the viscosity of the resin as well as to provide fewer
polymerization sites, both of which assist in formulating the composition.
The addition of a viscosity controlling monofunctional monomer makes
the composition and composites easier to handle.
19.4 RADICAL POLYMERIZATION
Initiators for methacrylics generally fall within one of three categories:
1. Cold curing chemical systems that initiate polymerization upon
admixing two or more compounds,
2. light initiated initiator systems,
3. heat initiated initiator systems.
19.4.1 Chemical Curing Systems
Cold curing chemical systems include traditional free-radical polymerization
initiators normally used with polymerizable ethylenically unsaturated
materials and resins.
A variety of catalysts for chemical polymerization have been proposed.
The types of chemical curing systems are summarized in Table 19.4.

Acrylic Dental Fillers 669
19.4.1.1 Peroxide Amine Systems
For example, organic peroxide initiators and amine accelerations may be
used. The initiators are admixed with the monomers shortly before application
to the tooth or dental appliance. 25 The kinetics of curing of several
dimethacrylate monomers initiated by a dibenzoyl peroxide amine system
has been studied using differential scanning calorimetry. 26 A mathematical
model was developed to describe the rate of polymerization.
Here tertiary amines are aromatic tertiary amines, for example,
ethyl-4-dimethylamino benzoate (EDMAB), 2-[4-(dimethylamino)phenyl]
ethanol, N,N-dimethyl-p-toluidine (DMPT), bis(hydroxyethyl)-p-toluidine,
and triethanolamine. Such accelerators are generally present in the
range from about 0.5 to about 4.0% of the resin composition. 9
The combination of the organic peroxide and the tertiary amine involves
problems such as tinting the cured product due to oxidation of the
amine compound and discoloration, and impairing the polymerization due
to oxygen and acidic components. An acidic component would produce a
quaternary salt which does not exhibit reducing ability upon reacting with
the tertiary amine.
The problem of tinting or discoloration causes the color tone to differ
from that of a natural tooth when the catalyst is used for a dental restorative
as represented by a composite resin, and deteriorates the aesthetic value.
Impairing the polymerization means that the catalyst cannot be used for the
dental adhesive that uses an acid group-containing polymerizable monomer
as an essential component. 24
19.4.1.2 Hydroperoxides Thiourea Systems
Other redox initiators are hydroperoxides with thioureas, and peroxides
with ascorbic acid. A two-part system may be built up as follows: One part
contains an initiator. The second part comprises filler and the co-initiator.
The two parts are spatuled (mixed) to form a cement prior to placement on
tooth.
19.4.1.3 Barbituric Acid-based Initiators
Catalyst systems based on barbituric acid are most generally used in the
field of dental materials because of relatively low harmful effect on the
body and ready availability. 1-benzyl-5-phenylbarbituric acid can be used

670 Reactive Polymers Fundamentals and Applications
Bu
B
Bu
O 2
Bu
O
O
B
Bu
Bu
Bu
Bu
Bu
B
Bu O
Bu
O
Bu
B
Bu
*O
Bu
Bu
B
Bu
Bu
B O* Bu
Bu
Bu = CH 3 CH 2 CH 2 CH 2
Bu
O
Bu
B
Bu
Bu*
Figure 19.5: Radical Generating Mechanisms of Alkylboranes 27
in combination with peroxide and with a heavy metal accelerator in a second
component. 28 However, a barbituric acid-type catalyst can cause problems,
such as the difficulty in controlling the curing time and poor preservation
stability.
24, 29
19.4.1.4 Borane and Borate-based Initiators
Triethylborane initiates a very fast polymerization of methyl methacrylate.
Since some radical inhibitors are active in the inhibition, the type of
polymerization was identified as a radical polymerization. In a series of experiments,
high molecular weight polymers were produced in the presence
of p-benzoquinone. Consequently a speculative mechanism was postulated
that an adduct of quinone and borane should be responsible for the
initiation. 30 The basic radical generating mechanism of borane systems is
shown in Figure 19.5. Trialkylborane or the partial oxide thereof is an excellent
promoter for chemical polymerization and is very active, but it is
chemically unstable. Therefore, this catalyst must be packaged separately
from other components, must be picked up in suitable amounts just before

Acrylic Dental Fillers 671
it is used and must be mixed with other monomer components, requiring
cumbersome operation, which is a drawback.
Aryl borate as catalyst is easy to handle, does not cause the cured
product to be tinted or discolored, and exhibits excellent preservation stability
without, however, exhibiting sufficient activity for polymerization.
The activity for polymerization is greatly enhanced when an aryl
borate compound and an acidic compound are used in combination with a
particular oxidizing agent.
Suitable peroxides are methylethylketone peroxide, cumene hydroperoxide
or tert-hexyl hydroperoxide. A mixture of 2-methacryloyloxyethyldihydrogen
phosphate and bis(2-methacryloyloxyethyl)hydrogen phosphate
is used as acidic compound. Optional metal compounds are ferric
acetylacetonate and copper(II)acetylacetonate.
The catalyst is easy to handle, exhibits high activity for polymerization
even in the presence of oxygen or an acidic compound, and imparts
a suitable degree of surplus operation time. Catalysts that contain a metal
compound for promoting the decomposition of the organic peroxide exhibit
a particularly high polymerizing efficiency.
If the polymerizable monomer is an acidic compound, e.g., 11-methacryloyloxy-1,1-undecanedicarboxylic
acid (MAC-10), then there is no
need to add any other acidic compound, and no acidic compound elutes
out from the obtained cured product when it is used. The mechanism of
initiation of polymerization is proposed as follows: The aryl borate compound
is decomposed due to the acid compound. Thereby an aryl borane
compound is formed which is then oxidized with oxygen present in the
atmosphere to form polymerizable radicals. It is further oxidized with an
organic peroxide to form more radicals in the composition containing less
oxygen. Thereby it serves as a highly active catalyst for chemical polymerization.
The metal compound promotes the decomposition of the organic
peroxide. Oxidation of the aryl borane compound with the organic peroxide
is promoted lending the catalyst itself for use as a more active catalyst
for chemical polymerization. The polymerization proceeds at ambient
temperature even in a dark place to give an excellently cured product. 24
Several techniques have been reported for increasing the work-life,
e.g., slowing the cure rate of the polymerizable system by reducing the
amount of initiators, adding inhibitors, or adding comonomers to decelerate
the cure rate of the free radical composition. 31 Examples for work-life
extenders are allylsuccinic anhydride, 2-octen-1-ylsuccinic anhydride, iso-

672 Reactive Polymers Fundamentals and Applications
Table 19.5: Two Component Formulation 32
Base paste %
Pyrogenic silicic acid (particle size < 0.05 µ) 5.00
Glass powder, silanized (average particle size 10 µ) 32.50
2,2-Bis(4-(oligo(ethoxy))phenyl)propanedimethacrylate 61.48
N,N-Dimethyl-p-toluidine 0.50
Hydroquinone monomethyl ether 0.02
Tributylborane 0.50
Catalyst paste %
Glass powder, silanized (average particle size 10 µ) 32.00
2,2-Bis(4-(oligo(ethoxy))phenyl)propane diacetate 65.50
Dibenzoyl peroxide 2.50
butenylsuccinic anhydride, and itaconic anhydride.
19.4.1.5 Hybrid Initiator Systems
A hybrid initiator system acts on a mixture of epoxide monomers and
acrylic group-containing monomers. The epoxide monomers are cured by
a cationic reaction mechanism. The acrylic group-containing monomers
are cured by a radical mechanism.
Two initiator systems are needed to ensure polymerization. 32 The
first initiator system is comprised of boranes and hydrazones and releases
species that initiate a curing reaction upon contact with oxygen. The second
initiator system is comprised of iodonium compounds capable of radical
fission.
An oxygen-sensitive compound is used that, when brought into contact
with oxygen, can form radicals that in turn can release acid from a
saline initiator by means of another reaction sequence. The acid so formed
can initiate a polymerization reaction, in particular a cationic polymerization
reaction.
This saline initiator is an iodonium compound, which, when activated
by means of free radicals, can decompose into acids. Thus, there
are two initiator systems which react with each other to control the course
of the polymerization reaction. A two component material for temporary
crowns and bridges, which is mixed in a ratio of 10/1 (base/catalyst) and
cured without any smear layer, is shown in Table 19.5. One special advantage
of the preparations and processing techniques lies in the fact that the

Table 19.6: Photoinitiators for acrylics
Compound
Acrylic Dental Fillers 673
Reference
Benzil
Camphorquinone
8, 33
Benzoin methyl ether
Isopropoxybenzoin
Benzoin phenyl ether
Benzoin isobutyl ether
Eosine
33
Titanocene
33, 34
range of the activation time and the processing time is determined by the
composition of the dental materials. The processor can influence, within
specific limits, the requisite processing time by means of the intensity with
which the materials are brought into contact with oxygen or air.
19.4.2 Photo Curing
Light or photo curing or photosensitive polymerization initiation and curing
systems are activated to harden and cure the composition by irradiation
with visible or UV light. Visible light of a wavelength of about 400 to 500
nm initiates rapid and efficient curing within a few minutes.
Preferably, the photoinitiator systems should be sensitive to light in
a range of wavelength that is not harmful to the patient who is undergoing
a dental procedure. 25 Photoinitiators for acrylics are summarized in
Table 19.6.
Initiation by photo curing is achieved with α-diketone light-sensitive
initiator compounds such as benzophenone or a derivative, or a 1,2-diketone
such as benzil or camphorquinone (CQ) and derivatives. Certain
tertiary aromatic amines act as accelerator compounds. Some compounds
that may be suitable are ultraviolet light-sensitive initiators, like 1,2-diketones,
benzophenones, substituted benzophenones, benzoin methyl ether,
isopropoxybenzoin, benzoin phenyl ether, and benzoin isobutyl ether, as
shown in Figure 19.6. An example for an effective photoinitiator system is
camphorquinone (CQ) and ethyl-4-dimethylamino benzoate (EDMAB) or
cyanoethylmethylaniline. 8
The crosslinking density of the final product is dependent on the way
the radiation energy is offered to the curing system. 35

674 Reactive Polymers Fundamentals and Applications
H 3 C
CH 3
CH 3
O
O
C
O
C
O
Camphorquinone
Benzil
H 3 C
N
H 3 C
O
C
O CH 2 CH 3
Ethyl 4-(dimethylamino)benzoate
F
N
Ti
F
F
F
N
Titanocene
Figure 19.6: Photoinitiators

Acrylic Dental Fillers 675
The photopolymerization or a Bis-GMA/TEGDMA resin was examined
with light sources with extremely different intensities, i.e., 200 and
1800 mW/cm 2 ). In general, the polymers irradiated using the high light
intensity source showed a greater conversion.
However, an increased light intensity also increased the maximum
temperature reached during polymerization. Therefore, the greater conversion
results form both a photopolymerization and a thermal polymerization.
Extreme differences in the initiation rate do not significantly alter the
mechanical properties of the polymer matrix as long as the conversions are
similar. 36
The kinetics of the photopolymerization of dental composites has
been monitored in-situ by a modified Fourier Transform infrared spectrometer
with attenuated total reflection. The experimental setup could reveal
the kinetic stages of the photopolymerization of dental composites. The
spectroscopic results correlate with the Vickers micro-hardness. 37 Under
comparable conditions, UDMA resins are significantly more reactive than
Bis-GMA and EBADMA resins. 38
In urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate
(TEGDMA)-based dental resins, differential scanning calorimetry
(DSC) showed that the light-cured specimens contain residual living
groups entrapped by the fast reaction, which lead to further reaction during
postcure heat treatment.
After an additional heating to 175°C above the exothermic peak,
most of the residual groups in the light-cured specimen were found to have
reacted. A single decrease in modulus and a single peak in the tanδ curve,
was observed and no exotherm in the DSC curve. 39
19.4.2.1 Tertiary Amine Reductants
In visible light curable compositions, the tertiary amines are most profitably
acrylate derivatives such as dimethylaminoethyl methacrylate and,
particularly, diethylaminoethyl methacrylate (DEAEMA) in amounts ranging
from about 0.05 to about 0.5% of the resin composition. 9
Other suitable tertiary amine reductants are tributylamine, tripropylamine,
N-methyldiethanolamine, N-propyldiethanolamine, N-ethyldiisopropanolamine,
triethanolamine and triisopropanolamine. One of the
preferred tertiary amine reductants is ethyl-4-dimethylamino benzoate
(EDMAB). 25

676 Reactive Polymers Fundamentals and Applications
19.4.3 Curing Techniques
Various techniques of curing are in use. Soft-start cure of a resin composite
may give rise to a reduced contraction because of a possible flow before
gelling. Soft-start cure may be achieved by a pulse-delay cure technique,
where the polymerization is initiated by a short flash of light followed by
a waiting time of several minutes before the final curing is performed.
40, 41
Another soft-start technique is characterized by step-curing. Here a reduced
intensity of curing light is used during the first part of the polymerization
period. Next the intensity is increased. 42 The use of a soft-start
polymerization mode, from low to high, offers some modest advantages
in curing effects, especially the delay in the original shrinkage-strain. In
general, a higher conversion is accompanied by a higher shrinkage. Some
reductions in the problems of shrinkage may be achieved by an acceptable
reduction in degree of conversion.
The pulse-cure method may give rise to a different structure of the
polymer although the degree of conversion and the hardness in the final
state are not affected by the curing method.
43, 44
An initially slow cure may favor the formation of a relatively linear
polymer. A slow start of the polymerization could be associated with
relatively few centers of polymer growth, resulting in a more linear polymer
structure with relatively few crosslinks. The differences in structure
can be examined by studies of the Wallace hardness of cured swollen samples.
The Wallace hardness measures the depth of penetration of a Vickers
diamond under a predetermined load. The Wallace hardness is in fact a
measure of softness, in that the higher the Wallace hardness, the softer is
the material. A lower degree of conversion is associated with softer polymers
after storage in ethanol. Polymers with the same degree of conversion
respond differently to the softening action by ethanol swelling, dependent
on the history of light exposure. 45
In a series of experiments using microwave curing of acrylic resins
with different cure cycles, it was shown that the porosity of the cured resin
was not affected by the manner of curing. 46
19.4.4 Dual Initiator Systems
Initiator systems employing two or more initiators, i.e., light and self-curing
or light and heat initiated systems, can also be formulated.
Such multi-initiator systems may have utility in that they may in-

Acrylic Dental Fillers 677
clude a rapid cure initiator, and light or heat cure to impart significant polymerization
in the dental office or dental laboratory. A light cure system in
combination with a longer time self-cure initiator continues to cause further
polymerization after the patient leaves the office and further secures
the restorative to the tooth structure. 25
Such dual cure light/heat systems, as well as their respective single
initiator systems, are also desirable in that they may be formulated and
packaged in one container or syringe, thereby avoiding the need for mixing
by the dental professional before application. For example, such one-component
systems exhibit good shelf life of more than a year when stored
away from light at room temperature.
If self-curing compositions are desired, the self-curing initiator may
be packaged in one of two containers separately from the polymerizable
components of the composition, with the contents of both containers being
admixed shortly before use in the dental office.
19.5 INHIBITORS
Polymerization inhibitors are mainly substituted phenols, for example,
hydroquinone monomethyl ether (MEHQ) or 2,6-di-tert-butyl-4-methylphenol
(BHT)
19.6 ADDITIVES
19.6.1 Fillers and Reinforcing Materials
Fillers are summarized in Table 19.7. Filler particles can be silanized
aluminum oxide, zirconium oxide, silicon oxide, barium glass, strontium
glass, and silicate glasses. Spherical particles in the compositions improve
the handling characteristics, such as bulk and consistency, and improve
the filler packing for better restoration placement in cavity preparations by
minimizing the flow and the slump of the composition. In most composites,
fillers have a higher refractive index than the resin. Typical levels
of filler are from about 50 to 80%. If a more finely particulated filler is
used, the amounts of filler may be decreased due to the relative increase
in surface area which attends the smaller sizes of particles. Particle size
distributions may range from 0.02 to 50 µ.
Both the chemical structure of the polymer matrix and the type of

678 Reactive Polymers Fundamentals and Applications
Table 19.7: Fillers for Dental Composites
Material
Reference
Calcium hydroxy apatite
Silanized aluminum oxide
Zirconium oxide
Siliconedioxide
Barium glass
Strontium glass
Strontium fluoroaluminosilicate cement
17
Silicate glass
Functionalized metal oxide nanoparticles
Silsesquioxane
9
Polyamide 6 nanofibers
47
filler system can have significant effects on the strength and water sorption
of dental composites. 48
19.6.1.1 Sub-micron Size Fillers
Sub-micron size fillers are preferred to minimize surface wear and plucking
of filler components from the restorative surface, as well as imparting a
surface which may be easily polished by the dental professional. Filler
particles have an average size of about 0.04 to 0.08 µm. 25
19.6.1.2 Glass Fibers
Glass fibers increase filler packing and improve filler self-orientation for
high filler loadings. 25
19.6.1.3 Functionalized Metal Oxide Nanoparticles
There have been efforts to generate functionalized metal oxide nanoparticles
to make highly uniform composite materials. For example, aluminum
tri-sec-butylate is dissolved in toluene, reacted with one allyl acetoacetate,
49 c.f. Figure 19.7. The dispersed, individual metal oxide particles can
be prepared by partially replacing the organic radical by a functional one
and then by hydrolyzing to oxide with water.
A silane functionalized polymer is also hydrolyzed with water to
form a network crosslinked by the resultant silica particles. Elimination of

Acrylic Dental Fillers 679
CH 3 CH 3
CH CH 2
O
CH 2 CH O Al O CH CH 2
CH 3 CH 3 CH 3 CH 3
+
CH 3
O
C CH 2 C
O
O CH 2 CH CH 2
CH 3
CH 3
CH CH 2
O
CH 2 CH O Al O CH 2 CH CH 2
CH 3 CH 3
H 2 O
O
O
Al O CH 2 CH CH 2
O
Al O CH 2 CH CH 2
Figure 19.7: Functionalized Metal Oxide

680 Reactive Polymers Fundamentals and Applications
the composite shrinkage induced by removal of volatile reaction products
is attempted by utilizing ring strained alkenoxysilanes and polymerizable
solvents where all reaction by-products contribute to the SiO 2 network or
the resultant interpenetrating, matrix, organic polymer. The expected packing
disruption induced by the strained ring opening of the alkenoxysilane
is a strategy for compensating for the shrinkage induced by conversion of
double bonds to single bonds. 16
19.6.1.4 Polyamide 6 Nanofiber
Electrospun Polyamide 6 nanofibers, as non-woven fabrics, were impregnated
with the dental methacrylate of 2,2-bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane/triethylene
glycol dimethacrylate (Bis-G-
MA/TEGDMA) in order to prepare restorative composite resins. 47
The polyamide 6 nanofibers used are much softer than inorganic
fillers with a regular cylindrical shape with diameters ranging from 100
to 600 nm. Flexural strength (FS), elastic modulus (EY), and work of
fracture (WOF) of the nanofiber reinforced composite resins were significantly
increased by the admixture of relatively small amounts of Polyamide
6 nanofibers.
19.6.1.5 Silsesquioxane
A polyhedral oligomeric silsesquioxane (POSS) filler has several advantages.
POSS-filled resins typically exhibit lower mass densities and greater
stiffness, and are capable of withstanding higher temperatures, as well as
higher levels of ionizing radiation. In addition, POSS-filled resins are capable
of wetting fibers to desirably high degrees. The use of POSS with
dental resin materials, particularly the acrylate or methacrylate resins, minimizes
polymerization shrinkage and increases material toughness. The
nanoscale dimensionality of the POSS fillers also allows for better aesthetic
properties, including easier polishability and improved transparency. 9
Functionalized POSS, also known as POSS monomers are particularly
preferred. Herein one or more of the covalently bound organic groups
are reactive with at least one component of the resin composition. In some
cases, it is possible to have all of the covalently bound organic groups be
reactive. POSS monomers may be prepared, for example, by corner-capping
an incompletely condensed POSS, containing trisilanol groups with a
substituted trichlorosilane.

Acrylic Dental Fillers 681
Through variation of the substituted group on the silane, a variety
of functional groups can be placed off the corner of the POSS framework,
including halide, alcohol, amine, isocyanate, acid, acid chloride, silanols,
silane, acrylate, methacrylate, olefin, and epoxide. Preferred functional
groups are acrylate and methacrylate groups since they are involved in the
polymerization reaction.
19.6.1.6 Calcium Phosphates
Amorphous calcium phosphates (ACP) are fillers for mineral releasing
dental composites. When the ACP is stabilized by pyrophosphate (P 2 O 4−
7 )
ions, pyrophosphate retards the conversion of ACP to apatite. ACPs have
a relatively high aqueous solubility and can release Ca 2+ and PO 4− ions.
However, pyrophosphate stabilized ACP-filled composites have relatively
poor mechanical properties, because ACP does not act as reinforcing filler
such as commonly used silanized glass fillers.
ACP can be hybridized with tetraethoxysilane or zirconyl chloride
(ZrOCl 2 ) and surface-treated with 3-methacryloxypropoxytrimethoxysilane
(MPTMS) or zirconyl dimethacrylate (ZrDMA). In fact, a silica- or zirconia-hybridized
ACP moderately improves the biaxial flexural strength of
Bis-GMA/TEGDMA/HEMA/ZrDMA-based composites while maintaining
their high anti-demineralizing and remineralizing potential. Thus adequate
levels of calcium and phosphate ions are released. 50
19.6.2 Pigments
For aesthetic demands, pigments are added to provide the desired colors of
the fillings, i.e., the colors of the neighboring teeth. Pigments are inorganic
compounds of different kinds and blendings.
There have been attempts to standardize color shades to facilitate
clinical use and combining products. Many producers have adapted their
color system to the Vita R shade system (Vita Zahnfabrik Company, Germany)
and deliver a full range of shades in one-dose pre-filled tips.
19.6.3 Photostabilizers
In order to protect the materials against photo degradation, photostabilizers
are added. Photo degradation of the cured resin causes changes in color and
the mechanical properties. Most common photostabilizers are salicylates,

682 Reactive Polymers Fundamentals and Applications
in particular the phenyl esters of benzoic acid, ortho-hydroxybenzophenones,
ortho-hydroxybenzotriazoles and substituted cinnamic esters. A few
photostabilizers are shown in Figure 19.8.
19.6.4 Caries Inhibiting Agents
Caries is the damage of bone tissue (not only dental) caused by infection.
Caries dentium is the tooth decay where the dental enamel, i.e., dentin is
damaged by bacteria residing in the mouth.
Increased dental plaque supports the formation of acid metabolic
products of the bacteria that act in the decalcination of the dentin. Moreover,
sucrose acts in a similar way, as it forms dextranes that stick as
plaques and decompose into lactic acid and pyruvic acid.
Caries inhibiting agents are slow releasing fluoride agents to help
inhibit caries from forming in the adjacent tooth structure.
19.6.5 Coloring or Tint Agents
Coloring or tint agents may be included in small amounts of about 1%
or less of the total composition. Such fillers can also be selected to be
radio opaque. For example, appropriate amounts of radio opaque barium,
strontium, or zirconium glass may be used as all or as part of the filler
portion.
19.6.6 Adhesion Promoter
The compositions may include an adhesion promoter. This may be a
phosphorus-containing adhesion promoter, free from halogen atoms. Both
polymerizable and non-polymerizable phosphorus derivatives are available.
However polymerizable phosphorus materials having ethylenic unsaturation
are advantageous.
Examples of saturated and unsaturated phosphorus acid esters are
shown in Table 19.8. The phosphoric ester of Bis-GMA can be obtained
by the treatment of Bis-GMA with phosphorous oxychloride, as shown in
Figure 19.10.

Acrylic Dental Fillers 683
O
OH
O
OH
OH
OC 8 H 17
2,4-Dihydroxybenzophenone
2-Hydroxy-4-octoxybenzophenone
NC
O
O
NC
O
O
C
O
O
CN
O
O
CN
1,3-bis-[2’-cyano-3’,3-diphenylacryloyl)oxy]-2,2-bis-
{[2-cyano-3’,3’-diphenylacryloyl)oxy]methyl}propane
Figure 19.8: 2,4-Dihydroxybenzophenone (Uvinul 3000 , BASF) 2-Hydroxy-4-octoxybenzophenone
(Uvinul 3008 ) 1,3-Bis[2 ′ -cyano-3 ′ ,3-diphenylacryloyloxy]-2,2-bis-[[2-cyano-3
′ ,3 ′ -diphenylacryloyloxy]methyl]propane (Uvinul
3030)

684 Reactive Polymers Fundamentals and Applications
Compound
Table 19.8: Adhesion Promoters
Reference
Pentaerythritol triacrylate monophosphate
17
Pentaerythritol trimethacrylate monophosphate
17
Dipentaerythritol pentaacrylate monophosphate
17
Dipentaerythritol pentamethacrylate monophosphate
17
Hydroxyethyl methacrylate monophosphate
17
Methacryloyloxyethane-1,1-diphosphonic acid
51
Methacrylate-terminated phosphoric acid ester
7
4-Methacryloxyethyl trimellitate
52
2,2 ′ -Bis(α-methacryloxy-β-hydroxypropoxyphenyl)propane
diphosphonate
Bis-GMA diphosphonate
Bis-GMA diphosphate
Dibutyl phosphite
Di-2-ethylhexyl phosphite
Di-2-ethylhexyl phosphate
Glyceryl-2-phosphate
Glycerophosphate dimethacrylate
53
Glycerophosphoric acid
Methacryloxyethyl phosphate
Glyceryl dimethacrylate phosphate
CH 3
H 2 C
H 2 C C C O
O
CH 3 O CH 2
C C O CH 2 C CH 2 O
CH 3 CH 2
H 2 C C O
O
OH
P
OH
O
Figure 19.9: Pentaerythritol trimethacrylate monophosphate

Acrylic Dental Fillers 685
C
CH 2
CH 3
C
CH 2
CH 3
C
O
C
O
O
O
CH 2
CH 2
OH
CH
OH
CH
O
P
O
CH 2
CH 2
OH
O
Cl
O
Cl
P
O , H 2 O
Cl
H 3 C
C CH 3
H 3 C
C CH 3
O
O
CH 2
CH 2
OH
CH
OH
CH
O
P
O
CH 2
CH 2
OH
O
O
C
O
C
O
C
CH 3
C
CH 3
CH 2
CH 2
Figure 19.10: Phosphoric ester of Bis-GMA 51

686 Reactive Polymers Fundamentals and Applications
19.6.7 Thermochromic Dye
For aesthetic reasons, tooth-colored restoration materials are increasingly
being used in restorative dentistry. These materials have the disadvantage
that they can be visually distinguished from the natural tooth substance
only with difficulty, with the result that the removal of excess material and
also the reworking and matching of fillings is made difficult. The consequence
is that, frequently, healthy tooth substance is unnecessarily removed
or on the other hand, excess dental material is overlooked which can
then, as a retention niche, encourage the formation of plaque and lead to
periodontal problems. Also, when tooth-colored fillings are removed, because
of the poor visibility of the transition area between filling and tooth
substance, often either too much healthy tooth substance is removed or remains
of the filling are overlooked. Similar problems result when using
tooth-colored fixing materials for the cementing of tooth-colored restorations.
A dental material can be formulated, where the color can be temporarily
changed in a simple way such that the material can be visually
distinguished from the natural tooth substance, but assumes its original
color after a period sufficient for the working of the dental material. This
object is achieved by adding a thermochromic dye to the formulation.
Thermochromic dyes are preferred that are colorless at a temperature
of approx. 37°C and which change color upon heating or preferably
cooling, i.e., assume a color that can clearly be distinguished from the natural
tooth substance. At a temperature of 37°C, the color of the dental
material is thus determined by its intrinsic color.
Thermochromic dyes are based on an acid-responsive component
and an acidic component. Other thermochromic dyes are liquid crystalline
cholesterol derivatives. 54
19.7 PROPERTIES
Dental materials are standardized by several documents.
55, 56
19.7.1 Water Sorption
According to the ISO standard for dental restorative resins, a suitable resin
for its use as dental material must show a water sorption lower than

Acrylic Dental Fillers 687
50 µg/mm 3 and a solubility lower than 5 µg/mm 3 . 57 In resins and composites
based on an ethoxylated bisphenol A glycol dimethacrylate (Bis-
EMA) and a poly(carbonate)dimethacrylate (PCDMA), the water sorption
and desorption was examined in both equilibrium and dynamic conditions
in adjacent sorption-desorption cycles. The equilibrium water uptake from
all resins was very small. However, it increased as the amount of PCDMA
in the resin was increased. 58 A maximum volume increase of 2% due to
swelling was observed.
The sorption of water of polymer filling materials affects the dimensional
stability, the mechanical properties, and the bonding strength to the
tooth. The maximum water sorption and the diffusion coefficient of water
are important in determining the time-dependent mechanical properties
and time-dependent hydroscopic expansion of resins for clinical use. 59
19.7.2 Cytotoxicity
Acrylic resins have been shown to be cytotoxic as a result of the substances
that leach from the resin. The primary eluate is residual monomer. 60 However,
in organic leachables analyzed by gas chromatography-mass spectrometry,
nearly the whole volatile compounds in the formulation as well
as degradation products could be traced back. Among components detected
were monomers, comonomers, initiators, stabilizers, decomposition
products, and contaminants. In a study, 32 substances were identified and
17 were confirmed with reference substances. 61 In order to minimize the
cytotoxicity, utmost conversion must be achieved and monomers with minimal
cytotoxicity should be selected. Common compounds in dental resin
compositions have been tested with respect to estrogenic activity. Most
compounds tested in the study do not show estrogenic activity, but some
show activity. 62
19.8 APPLICATIONS
19.8.1 Filling Techniques
Compositions are applied to the tooth, preferably by syringe in incremental
layers of about 0.5 to about 2 mm and cured for about 20 to 40 seconds, depending
on the shade of the composition. Darker compositions have longer
curing times. Additional layers follow until the cavity is completely filled
to the cavosurface margin. Any excess material is removed immediately

688 Reactive Polymers Fundamentals and Applications
from the surface and the restoration is finished and polished by conventional
techniques such as diamonds, discs and polishing pastes. Such finishing
also removes any oxygen-inhibited uncured or partially cured layer
on the surface of the restoration, which if left in place, might cause staining
of the surface over time. 25
19.8.2 Primer Emulsions
A self-etching dental adhesive primer composition is used as an adhesive or
adhesion promoter to affix dental filling materials or bone cements to tooth
material. Such a composition essentially comprises an emulsion of water
immiscible polymerizable monomers, oligomers, and adhesion promoters
in water. By using an emulsion of the polymerizable substances in water,
the need for volatile organic solvents is avoided and biocompatibility is
enhanced.
Further, the composition comprises initiators, accelerators, and inhibitors
and surfactants and colloidal silica particles to aid in the formulation
of an emulsion and to help keep this stable.
For example, a polymerizable surfactant may consist of the reaction
product of isophorone diisocyanate with poly(ethylene glycol) monomethyl
ether, cured with dibutyltin dilaurate. To this product glycerol
dimethacrylate is added together with a radical polymerization inhibitor,
which grafts to the polyurethane polymer. 63 The product is a white, soft
sticky solid at room temperature, partially soluble in water to give a light
foam on shaking. The material has a melting range of about 35 to 37°C.
The polymeric and polymerizable surfactant can be emulsified in water and
phosphoric acid which provides the etching.
REFERENCES
1. M. Braden, R. L. Clarke, J. Nicholson, and S. Parker. Polymeric Dental
Materials. Macromolecular systems - materials approach. Springer, Berlin,
1997.
2. S. W. Shalaby, editor. High Performance Dental and Orthopedic Polymers
and Composites. CRC Press, Boca Raton, 2005.
3. R. Technology, editor. The Polymers in Dental Applications Collection.
Rapra Technology Ltd., Shawbury, 2004.
4. R. G. Craig and J. M. Powers, editors. Restorative Dental Materials. Mosby,
St. Louis, 11th edition, 2002.

Acrylic Dental Fillers 689
5. N. Moszner and U. Salz. New developments of polymeric dental composites.
Prog. Polym. Sci., 26(4):535–576, May 2001.
6. A. Peutzfeldt. Resin composites in dentistry: the monomer systems. Eur. J.
Oral Sci., 105(2):97–116, April 1997.
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11. D. Xie, I.-D. Chung, W. Wu, and J. Mays. Synthesis and evaluation of
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15. C. A. Khatri, J. W. Stansbury, C. R. Schultheisz, and J. M. Antonucci. Synthesis,
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Dent. Mater., 19(7):584–588, November 2003.
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repair using functionalized nanoparticles. US Patent 6 695 617, assigned
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acid-modified and non-HEMA containing glass-ionomer cement. Biomaterials,
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22. C. C. Chappelow, C. S. Pinzino, and J. D. Eick. Spiroorthocarbonates containing
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23. J. D. Oxman and D. W. Jacobs. Ternary photoinitiator system for curing
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in polymer structures. Journal of Dentistry, 32(4):321–326, May 2004.
36. L. G. Lovell, S. M. Newman, M. M. Donaldson, and C. N. Bowman. The
effect of light intensity on double bond conversion and flexural strength of a
model, unfilled dental resin. Dent. Mater., 19(6):458–465, September 2003.
37. R. L. Oréfice, J. A. C. Discacciati, A. D. Neves, H. S. Mansur, and W. C.
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(DE), May 14 2002.

20
Toners
Toners for developing electrical or magnetic latent images are used in various
processes for forming and printing images. One such image forming
process is electrophotography, which uses a photosensitive member generally
formed of a photo conductive material, and wherein an electrical latent
image is formed on the photosensitive member by various means. The
electrical latent image is developed using a toner. The toner image thus developed
is transferred to a printing material, such as paper, and then fixed
thereto by heating or pressure, or by using solvent vapor thus obtaining a
copy of the image. 1 The following types of developers are conventionally
used in dry development devices for electrophotography:
1. One-component-type magnetic developers comprising a toner containing
magnetic powder.
2. One-component-type non magnetic developers comprising a toner
containing no magnetic powder.
3. Two-component-type non magnetic developers comprising a toner
containing no magnetic powder and a magnetic carrier, which is
mixed with the toner in a fixed proportion.
4. Two-component-type magnetic developers comprising a toner containing
magnetic powder and a magnetic carrier, which is mixed
with the toner in a fixed proportion.
Various development methods using such toners have been proposed
and put into practical use. The toners used in these development methods
693

694 Reactive Polymers Fundamentals and Applications
are generally manufactured by a pulverizing method in which a coloring
agent, like a dye or pigment, is mixed with, and uniformly dispersed in,
a thermoplastic resin serving as the binder. The mixed substance thus obtained
is then finely pulverized and classified to provide a desired particle
size distribution. Toners typically contain a principal resin or toner resin,
colorant, and various functional additives such as release agents and charge
control additives.
Most toner compositions employ release agents such as waxes and/or
silicone polymers. Poly(dimethylsiloxane) resins or oils exhibit excellent
external release agent characteristics, i.e., when applied to fuser rolls, due
to their extremely low surface energy. The property is highly desirable
in contact-fusing electrophotography, because it is important to be able to
release the toner from the hot-oiled fuser roll and thus prevent hot offset.
Several different low molecular weight organic materials have been used
in the toner industry to eliminate this hot offset phenomenon. Low molecular
weight polyolefin waxes are by far the most common type of internal
release agent.
Each type of release agent has its own advantages and disadvantages.
For example, polyolefins tend to crystallize to a significant extent.
The crystallinity is between 70% and 90%. When these molecules crystallize,
they segregate from the toner resin into a separate phase and form
large wax domains which cause numerous print quality defects, as well as a
wax imbalance between the toner fines and the average size toner particles.
Poor homogeneity of these additives in the toner particles tends to cause a
number of problems. The most important issues are low toner powder flow
and variations in triboelectric charge distribution, which can lead to print
quality defects.
20.1 TONER COMPONENTS
Toners contain a primary or binder resin, known as a toner resin, such as
a thermoplastic resin, a colorant such as a dye or pigment, and a charge
control agent, releasing agents, and other additives.
Several polymers are usable as the thermoplastic binder resin, including
poly(styrene)s, styrene-acrylic resins, styrene-methacrylic resins,
polyesters, epoxy resins, acrylics, and urethanes. 2, 3
Examples of the colorant include: dyes and pigments such as
carbon black, iron black, graphite, nigrosine, metallic complex of mono-

Toners 695
azo dye, ultramarine, copper phthalocyanine, methylene blue, chrome yellow,
quinoline yellow, hanza yellow, benzene yellow, and various types of
quinacridone pigments. When the colorant is contained in a non magnetic
toner, the amount should be approximately 1% to 30%, in magnetic toners,
ca. 60%. The colorant can be coated by a UV stabilizer. 4
Toner compositions can contain charge enhancing additives, for example,
0.1% to 10% cetyl pyridinium chloride, distearyl dimethyl ammonium
methyl sulfate, metal salicylates, etc. Other charge control agents include
the sulfonated styrene-acrylate ester copolymers, calixarenes. Polymeric
charge control agents can be compatibilized with the toner resin in
the same manner as other polymeric components of the toner compositions.
Toner compositions may also include colloidal silica, metal salts and
metal salts of fatty acids such as zinc stearate as surface additives.
20.2 TONER RESINS
The heterogeneity of the toner particles in the composition is believed to
be the root cause of numerous problems throughout the serviceable life of
toner in a printing device. The print quality black-on-white defect involving
unwanted toner black spots on the printed product has been a recurring
and sometimes serious problem in certain commercial printers. The black
spots are highly visible in the background region of the print and are nonrepeating
in nature.
It is believed that the toner particle compositional uniformity is a
major factor in the existence of such defects. Heterogeneity of the toner
particles’composition is believed to be the root cause of observed selectivity
throughout the life of the cartridge.
The lack of heterogeneity in toners can be eliminated by the addition
of two functional additives reactive with each other to form a stable reaction
product. The copolymer reaction product apparently acts as a compatibilizer
to improve the dispersion of various polymeric components, such
as a release agent with the backbone structure of the toner resin.
Toners contain a primary or binder resin, known as a toner resin,
such as a thermoplastic resin, a colorant such as a dye or pigment, a charge
control agent, releasing agents, and other additives. These components will
be separately described.
Any suitable binder resin can be used as the toner resin, including
polyesters, epoxy resins, various polymers containing styrene, and acrylic

696 Reactive Polymers Fundamentals and Applications
Table 20.1: Toner Composition 1
Component %
Resin binder 90.0
Carbon black 5.0
Metal salicylate 2.5
Poly(ethylene) wax 1.0
Other additives 1.0
Siloxane polymer 0.25
Styrene-maleic anhydride copolymer 0.5
Amino-siloxane polymer 0.25
acid derivatives. These may be used either singly or as mixtures.
Polyesters are not preferred, because it is difficult to place reactive
functional groups on a polyester resin backbone and because polyester resins
are more reactive than styrene polymers, increasing the tendency to
obtain random copolymers rather than block or graft copolymers.
The polymer used for toner preparations can be a random styrene/-
acrylic copolymer, crosslinked with divinylbenzene. The two functional
materials added to the toner formulation, which already contains a poly(dialkylsiloxane)
oil, are a styrene/maleic anhydride copolymer and a diamine-terminated
poly(dimethylsiloxane) polymer. The reaction takes place
between the amino end groups and the anhydride side groups. During the
extrusion and melt mixing of the toner materials, these functional groups
react to form a fairly stable amic acid bond and thus, a polysiloxane/toner
resin compatibilizer. An example for a toner composition with a styrenemaleic
anhydride copolymer and an amino-siloxane polymer as compatibilizing
agents is shown in Table 20.1.
Reactive extrusion is accomplished in a continuous twin-screw extruder
maintained within a temperature range of 135 to 210°C and at an appropriate
torque. The molten extrudate is subsequently cooled by passage
through a chilled roller assembly and the resulting ribbons are crushed. 1
20.3 MANUFACTURE OF TONER RESINS
20.3.1 Suspension Polymerization
A suspension polymerization method for the preparation of a toner has
been described. 5, 6 The organic phase, containing styrene monomer, n-

Toners 697
butyl acrylate, divinylbenzene, 2,2 ′ -azobis(isobutyronitrile), paraffin and
Phthalocyanine Blue T, is dispersed into the aqueous phase. The aqueous
phase contains polyvinyl alcohol and sodium dodecylsulfate as suspension
dispersants. Infrared studies suggest that the interactions between Phthalocyanine
Blue T and the resin are mainly caused by physical forces.
20.3.2 Terephthalic Ester Resins
The toner particles are prepared by an emulsion aggregation process. 7 The
toner resin is a sulfonated polyester made from dimethyl terephthalate, sodium
sulfoisophthalate, 1,2-propanediol, and 2.5 mol-% diethylene glycol
with dibutyltin oxide as catalyst. Subsequent to synthesis of the toner particles
and addition of pigment, poly(pyrrole) is applied to the toner particle
surfaces by an oxidative polymerization process. Using oxidants such as
ferric chloride and tris(p-toluenesulfonato)iron(III) for the oxidative polymerization
of the pyrrole monomer tends to result in formation of toner
particles that become positively charged when subjected to triboelectric or
inductive charging processes. Accordingly, toner particles can be obtained
with the desired charge polarity without the need to change the toner resin
composition, and can be achieved independently of any dopant used with
the poly(pyrrole). The poly(pyrrole) in or on the toner particles generally
imparts a high degree of color to the toner particle. These toners are usually
preferred, where black images are desired. Similarly to pyrrole monomers,
3,4-ethylenedioxythiophene can be polymerized on the toner resin. 8
20.3.3 Unsaturated Ester Resins
Examples of linear unsaturated polyesters are low molecular weight condensation
polymers formed by saturated and unsaturated diacids and diols.
The resulting unsaturated polyesters are crosslinkable in two ways:
1. Due to double bonds along the polyester chain, and
2. Due to the functional groups such as carboxyl, hydroxy, and others,
amenable to acid-base reactions.
Suitable diacids and dianhydrides include succinic acid, isophthalic
acid, terephthalic acid, phthalic anhydride, and tetrahydrophthalic anhydride.
Unsaturated diacids or anhydrides, are fumaric acid, itaconic acid,
and maleic anhydride. Suitable diols include propylene glycol, ethylene
glycol, diethylene glycol, and propoxylated bisphenol A.

698 Reactive Polymers Fundamentals and Applications
A particularly preferred polyester is poly(propoxylated bisphenol A
fumarate). A propoxylated bisphenol A fumarate unsaturated polymer undergoes
a crosslinking reaction with a chemical crosslinking initiator, such
as 1,1-di-(tert-butylperoxy)cyclohexane. The crosslinking between chains
will produce a large, high molecular weight molecule, ultimately forming
a gel.
The toners and toner resins may be prepared by a reactive melt mixing
process wherein reactive resins are partially crosslinked. For example,
low melt toner resins and toners may be fabricated by a reactive melt mixing
process comprising the following steps. 4
1. Melting reactive base resin, thereby forming a polymer melt, in a
melt mixing device.
2. Initiating crosslinking of the polymer melt with certain liquid
chemical crosslinking initiator and increased reaction temperature.
3. Retaining the polymer melt in the melt mixing device for a sufficient
residence time that partial crosslinking of the base resin may
be achieved.
4. Providing sufficiently high shear during the crosslinking reaction
to keep the gel particles formed during crosslinking small in size
and well distributed in the polymer melt.
5. Optionally devolatilizing the polymer melt to remove any effluent
volatiles.
The high temperature reactive melt mixing process allows for very
fast crosslinking which enables the production of substantially only microgel
particles, and the high shear of the process prevents undue growth of the
microgels and enables the microgel particles to be uniformly distributed in
the resin.
20.3.4 Toner Resins with Low Fix Temperature
Toners made from vinyl-type binder resins, such as styrene-acrylic resins,
may cause a problem which is addressed as vinyl offset. Vinyl offset occurs
when a sheet of paper or transparency with a fixed toner image is contacted,
for a period of time, with a polyvinyl chloride surface containing a
plasticizer used in making the vinyl material flexible such as, for example,
in vinyl binder covers, and the fixed image adheres to the PVC surface.
Crosslinked thermoplastic binder resins can be used as toners which

Toners 699
possess a low fix temperature and a high offset temperature, and which
show a substantially minimized vinyl offset. The resin composition consists
of a linear reactive base resin, an initiator, and a polyester with an
amine functionality. 2 The linear unsaturated polyester base resin is prepared
from unsaturated diacids, e.g., maleic acid or fumaric acid and diols,
like propylene glycol or propoxylated bisphenol A. Particularly suitable is
poly(propoxylated bisphenol A fumarate). An amine-containing polyester
is prepared from propoxylated 4,4 ′ -isopropylidene bisphenol A, N-phenyldiethanolamine,
and fumaric acid. A peroxide, such as tert-butyl hydroperoxide,
is used as radical initiator. In general, peroxides that thermally
decompose at higher temperatures are preferred so that the amine promoted
decomposition is favored at the polymer melt processing temperatures.
To disperse small amounts of the peroxide thoroughly in the resin,
a 0.6% master batch in poly[4,4 ′ -isopropylidenebisphenyl bispropanol bisether/fumaric
acid] is formed. The peroxide/polyester mixture can be extruded
at 120°C without decomposition of the peroxide under these conditions.
In larger scale reactions the initiator can be added to the extruder by
direct injection. To this blend in a next step, the amine containing polyester
is then blended in an extruder. The amine polyesters are added in amounts
from 1% to about 10%.
The polymers are crosslinked in the molten state under high shear
conditions, producing substantially uniformly dispersed microgels of high
crosslinking density, preferably using certain chemical initiators as crosslinking
agents in an extruder.
The amine of the polyester reacts with the initiator to form free radicals.
The tert-butoxy radical reacts with a vinyl bond in the polymer backbone
which subsequently forms a crosslink between polymer chains when
it, in turn, reacts with another vinyl bond in the polymer backbone.
The crosslinked resin produced in this way is a clean and non-toxic
polymer mixture comprising crosslinked gel particles and a noncrosslinked
portion.
20.3.4.1 Fixing Performance of the Toner
The fixing performance of a toner can be characterized as a function of the
temperature. 2 The lowest temperature at which the toner adheres to the
support medium is referred to as the cold offset temperature (COT). The
maximum temperature at which the toner does not adhere to the fuser roll

700 Reactive Polymers Fundamentals and Applications
is referred to as the hot offset temperature (HOT). When the fuser temperature
exceeds HOT, some of the molten toner adheres to the fuser roll
during fixing and is transferred to subsequent substrates containing developed
images resulting, for example, in blurred images. This undesirable
phenomenon is known as offsetting.
Between the COT and HOT of the toner is the minimum fix temperature
(MFT), which is the minimum temperature at which acceptable
adhesion of the toner to the support medium occurs, as determined by, for
example, a creasing test. The difference between MFT and HOT is referred
to as the fusing latitude.
20.3.5 Toners for Textile Printing
The imaging of textiles and other materials using thermal transfer of sublimable
dyes has been commercially practiced for more than 50 years. With
the introduction of laser printers for use with personal computers, attempts
were made with only limited success to incorporate thermal transfer sublimable
dyes into toners to be used in these printers. The printers were
intended to image in only one color, particularly black.
However, when a toner was properly formulated for this application
and a sublimable dye was incorporated into the toner, images could be
formed which could then be thermally transferred by the application of
sufficient heat to vaporize the dye.
By this method, a single color image could be formed. Since many
of these laser printers used replaceable cartridges to carry the toner to form
the image in this electrophotographic process, several of these special thermal
transfer toners could be installed in several cartridges, including toners
containing the process color dyes for cyan, magenta, and yellow color
imaging.
Using a color separation program on a personal computer connected
to such a laser printer, a skilled operator could effectively create a color
separation of a full color image and print each separation by installing in
turn the appropriate cartridge containing the indicated color: cyan, magenta,
or yellow. By this method, an image containing the appropriate cyan,
yellow and magenta thermal transfer dyes can be constructed stepwise. 9
The requirements for toner materials for good textile performance,
i.e., low initial modulus, and flexibility differ from the requirements for
production of toner powders by grinding, i.e. brittleness. 10, 11 Toner com-

Toners 701
positions for use in textile printing are available. 12
20.4 CHARACTERIZATION OF TONERS
The powder flow test is a direct determination of the amount of energy
necessary to pull apart aggregates of cohesive particles in a specified time.
The powder flow of a toner is an important aspect to consider in designing
a toner because of the required performance in the electrophotographic
process. 1
The powder flow test allows for the evaluation of the flowability of
the toner by measuring the amount of toner passing through a sieve during
a preset time relative to the initial loading of toner on the sieve. The
sieve is supported on a cantilever and is vibrated at a frequency of 60 Hz.
The intensity (amplitude) of the vibration is controlled using a voltage adjustment.
Generally, a free flowing material will tend to flow steadily and
consistently. Conversely, a non free-flowing material will tend to flow as
agglomerated particles.
The cohesiveness of the toner is also an important characteristic.
The cohesiveness affects powder flow, the lower cohesion values being
associated with higher powder flows.
To measure the cohesiveness, a measured amount of toner is placed
on a screen. Three screens of reducing size are placed in series so that the
powder goes through increasingly smaller screens.
REFERENCES
1. B. P. Livengood, B. W. Baird, and G. P. Marshall. Reactive compatibilization
of polymeric components such as siloxane polymers with toner resins. US
Patent 6 544 710, assigned to Lexmark International, Inc. (Lexington, KY),
April 8 2003.
2. P. G. Odell, S. V. Drappel, and M. S. Hawkins. Reactive melt mixing processes.
US Patent 6 114 076, assigned to Xerox Corporation (Stamford, CT),
September 5 2000.
3. K. A. Moffat, M. N. V. McDougall, R. Carlini, D. A. Hays, J. T. LeStrange,
and P. J. Gerroir. Toner compositions comprising vinyl resin and poly
(3,4-ethylenedioxythiophene). US Patent 6 689 527, assigned to Xerox Corporation
(Stamford, CT), February 10 2004.
4. S. M. Silence, E. J. Gutman, and T. R. Hoffend. Toner compositions. US
Patent 6 680 153, assigned to Xerox Corporation (Stamford, CT), January 20
2004.

702 Reactive Polymers Fundamentals and Applications
5. Y. F. Duan and Q. Zhang. Preparation of suspension polymerized color toners
and correlation between ingredients and rheological behavior. J. Imaging Sci.
Technol., 48(1):6–9, January–February 2004.
6. S. Kiatkamjornwong and P. Pomsanam. Synthesis and characterization of
styrenic-based polymerized toner and its composite for electrophotographic
printing. J. Appl. Polym. Sci., 89(1):238–248, July 2003.
7. J. R. Combes, K. A. Moffat, and M. N. V. McDougall. Toner compositions
comprising polyester resin and polypyrrole. US Patent 6 743 559, assigned
to Xerox Corporation (Stamford, CT), June 1 2004.
8. K. A. Moffat, R. Carlini, M. N. V. McDougall, D. A. Hays, and J. T.
LeStrange. Toner compositions comprising polyester resin and poly (3,4-ethylenedioxythiophene).
US Patent 6 730 450, assigned to Xerox Corporation
(Stamford, CT), May 4 2004.
9. R. J. Thompson. Color toner containing sublimation dyes for use in electrophotographic
imaging devices. US Patent 6 270 933, assigned to International
Communication Materials, Inc. (Connellsville, PA), August 7 2001.
10. W. W. Carr, D. S. Sarma, L. Cook, S. Shi, L. Wang, and P. H. Pfromm.
Xerographic printing of textiles: Polymeric toners and their performance. J.
Appl. Polym. Sci., 78(14):2425–2434, December 2000.
11. W. W. Carr, F. L. Cook, H. Yan, and P. H. Pfromm. Application of dimer
acid-based polyamide for xerographic toners for textiles printing. J. Appl.
Polym. Sci., 81(10):2399–2407, September 2001.
12. A. Verhecken and P. Sterckx. Toner composition for use in textile printing.
US Patent 6 007 955, assigned to Agfa-Gevaert, N.V. (Mortsel, BE), December
28 1999.

Index
ACRONYMS
AA
Acrylic acid, 547, 647
Ascorbic acid, 120
ABS
Acrylonitrile butadiene styrene, 213
ACH
Acetone cyanhydrin, 352
ACP
Amorphous calcium phosphates, 681
AEP
1-(2-Aminoethyl)piperazine, 563
AIBN
2,2 ′ -Azobis(isobutyronitrile), 601
AKD
Alkylketene dimer, 464
AlN
Aluminum nitride, 421
ALS
Alternating least squares, 196
AMPC
Allyl-N-(4-methyl-phenyl)carbamate, 570
APS
(3-Aminopropyl)triethoxysilane, 646
ASA
Alkenyl succinic anhydride, 464
ATBC
Acetyltributyl citrate, 366

704 Reactive Polymers Fundamentals and Applications
ATBN
Amine-terminated butadiene-acrylonitrile elastomers, 156
ATPE
Acid-group terminated poly(ethylene), 539
ATR-FTIR
Attenuated total reflectance Fourier transform infrared spectroscopy, 119,
647
ATRP
Atom transfer radical polymerization, 82, 461, 568
ATS
(3-Aminopropyl)triethoxysilane, 205
ATU
Amine-terminated chain-extended urea, 156
BAMPO
Bis(m-aminophenyl)methylphosphine oxide, 169, 171, 176
BAPP
2,2-Bis[4-(4-aminophenoxy)phenyl]propane, 342
Bis(4-aminophenoxy)phenylphosphine oxide, 169
BAPPO
Bis(4-aminophenyl)phenylphosphine oxide, 121, 172
BAPQ
2,3-Bis(4-(4-aminophenoxy)phenyl)quinoxaline-6-carboxylic acid, 412
BAQ
2,3-Bis(4-aminophenyl)quinoxaline-6-carboxylic acid, 412
BCB
Benzocyclobutene, 493
BCBE
1,2-Bis(benzocyclobutenyl)ethane, 493
BD
1,4-Butanediol, 119
BDA
1,4-Butane diamine, 121
1,2-BDE
1,4-Butanediol diglycidyl ether, 141, 205
BDK
2,2-Dimethoxy-1,2-diphenylethan-1-one, 193
BDM
4,4 ′ -Bis(maleimido)diphenylmethane, 418
BDMA
Benzyldimethylamine, 152
BDMAEE
Bis(2-dimethylaminoethyl)ether, 99, 103

Index 705
BDMB
2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 193
BenzOXA
Benzoxazole, 557
BEPTPhS
Bis(3-mercaptophenyl)sulfone, 208
BET
Brunauer Emmett Teller, 543
BHET
Bis(2-hydroxyethyl)terephthalate, 45
BHMBE
1,2-Bis-[2(2-hydroxy-5-methylphenyl)-5-benzotriazolyl]-ethane, 80
BHMF
Bis(hydroxymethyl)furan, 309
BHT
2,6-Di-tert-butyl-4-methylphenol, 677
BIAE
2-Bromoisobutyric acid ethylester, 570
Bis-A-Dima
Bisphenol A dimethacrylate, 660
Bis-GMA
2,2-Bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane, 660
Bis-M
4,4 ′ -[1,3-Phenylene(1-methyl ethylidene)]bisaniline, 498
BMDPM
4,4 ′ -Bis(maleimido)diphenylmethane, 419
BMI
4,4 ′ -Bis(maleimido)diphenylmethane, 397
4,4 ′ -Diphenylmethane bismaleimide, 547
Bismaleimide, 387
BMIE
N,N-4,4-Diphenyl ether bismaleimide, 398
Bis(4-maleimidophenyl)ether, 399
BMIM
4,4 ′ -Bis(maleimido)diphenylmethane, 398
Bis(4-maleimidophenyl)methane, 399
BMIP
2,2-Bis[4-(4-maleimido phenoxy)phenyl]propane, 398, 399
Bisphenol A bismaleimide, 398, 400
BMIPO
Bis(3-maleimidophenyl)phenylphosphine oxide, 402, 422
BMIS
Bis(4-maleimidophenyl)sulfone, 398, 399

706 Reactive Polymers Fundamentals and Applications
BMPP
2,2-Bis[4-(4-maleimido phenoxy)phenyl]propane, 434
BMPPPO
Bismaleimide(3,3 ′ -bis(maleimidophenyl))phenylphosphine oxide, 169, 171
BOX
2,2 ′ -(1,4-Phenylene)bisoxazoline, 547
BP
Benzophenone, 359, 629, 646
BPFR
Boric acid-modified phenolic resins, 257
BPO
Dibenzoyl peroxide, 568
BT
Bismaleimide triazine resins, 387
CBC
N,N ′ -Carbonylbiscaprolactam, 80
CE
Cyanate ester, 382
CHO
Cyclohexene oxide, 189
CHP
Cumene hydroperoxide, 244
CMKGM
Carboxymethyl konjac glucomannan, 121
COT
Cold offset temperature, 699
CQ
Camphorquinone, 673
CR
Controlled rheology, 588
CTBN
Carboxy-terminated butadiene/acrylonitrile copolymers, 156
CTE
Coefficient of thermal expansion, 421
CXA
Bis(1-oxyl-2,2,6,6-tetramethylpiperidine4-yl)sebacate, 602
DA
2,2 ′ -Pyromellitdiimidodisuccinic anhydride, 92
Diels-Alder reaction, 309
DAB
1,4-Diaminobutane, 630
DABCO
1,4-Diazabicyclo[2.2.2]octane, 99

Index 707
DAPB
2,6-Di(4-aminophenoxy)benzonitrile, 417
DAPNPT
2,4-Di(2-allylphenoxy)-6-(2-naphthyloxy)-1,3,5-triazine, 417, 419
DBA
2,2 ′ -Diallyl bisphenol A, 164, 381, 382, 397, 398, 417, 418
DBBA
3,5-Di-tert-butyl-4-hydroxybenzyl acrylate, 632
DBMX
α,α ′ -Dibromo-m-xylene, 428
DBTDL
Dibutyltin dilaurate, 80, 107, 114, 567
DBTO
Dibutyltin oxide, 567
DCDPT
1,4-[Di(4-cyanato diphenyl-2,2 ′ -propane)]terephthalate, 387
DCHE
7,26-Dioxatrispirobicyclo[4.1.0]heptane-4,5 ′ -1,3-dioxane-2 ′ ,2 ′′ -
1,3-dioxane-5 ′′ ,4 ′′ -bicyclo[4.1.0]heptane, 665, 667
DCM
4,4 ′ -Diamino-3,3 ′ -dimethyldicyclohexylmethane, 175
DCP
Dicumyl peroxide, 541, 609, 623, 629
DD
1,10-Decanediol, 117
DDM
4,4 ′ -Diaminodiphenylmethane, 402, 414, 423
4,4 ′ -Methylenedianiline, 402
DDS
4,4 ′ -Diaminodiphenylsulfone, 153, 158, 175
DEAEMA
Diethylaminoethyl acrylate, 626
Diethylaminoethyl methacrylate, 675
DEGDA
Diethylene glycol diacrylate, 638
DEM
Diethyl maleate, 542, 623
DEPN
N-tert-Butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, 603
DEPT NMR
Distortionless enhancement by polarization transfer nuclear magnetic
resonance spectroscopy, 293

708 Reactive Polymers Fundamentals and Applications
DGDPI
1,3-[Di(4-glycidyloxy diphenyl-2,2 ′ -propane)]isophthalate, 387
DGEBA
Bisphenol A diglycidyl ether, 139
Diglycidyl ether of bisphenol A , 150
DGEBTF
Adduct of 2-chlorobenzotrifluoride and glycerol diglycidyl ether, 150
DHBP
2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, 516, 546, 591
DHPDOPO
10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide,
169
DICY
Dicyandiamide, 402
DMAA
N,N-Dimethylacrylamide, 647
DMAB
2,4-Diamino-4 ′ -methylazobenzene, 176
4-Dimethylaminobenzoin, 193
3-DMABA
3-Dimethylaminobenzoic acid, 193
4-DMABA
4-Dimethylaminobenzoic acid, 193
DMABAL
4-Dimethylaminobenzaldehyde, 193
DMAEMA
2-(Dimethylamino)ethyl methacrylate, 82
DMAMP
2-(Dimethylamino)-2-(hydroxymethyl)-1,3-propanediol, 265
DMBA
4-Dimethylamino-1-butanol, 119
Dimethylol butanoic acid, 93, 121
DMCDA
5-(2,5-Dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic
anhydride, 180
DMEA
N,N-Dimethylethylethanolamine, 119
DMPA
2,2-Dimethoxy-2-phenylacetophenone, 359
Dimethylol propionic acid, 120
DMPT
N,N-Dimethyl-p-toluidine, 669

Index 709
DMT
Dimethyl terephthalate, 35
DMTA
2-Dimethylamino-2-methyl-1-propanol, 264
DNS-EDA
5-Dimethylaminonaphthalene-1-(2-aminoethyl)sulfonamide, 197
DOPO
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 112, 168, 169,
405, 422
DPD
p-Phenyl diamine, 400
DPHS
Bis(3-diethylphosphono-4-hydroxyphenyl)sulfide, 169
DSC
Differential scanning calorimetry, 43, 114, 623
DSC-SSA
Differential scanning calorimetry-successive self-nucleation and annealing,
631
DSDA
3,3 ′ ,4,4 ′ -Diphenylsulfone tetracarboxylic dianhydride, 342
DTBP
Di-tert-butyl peroxide, 591
DVB-BCB
Bis(benzocyclobutenyl)-m-divinylbenzene, 502
DVS-BCB
Bis(benzocyclobutenyl)divinyltetramethylsiloxane, 502
DYBP
2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, 516
E-BCB
1,2-Bis(4-benzocyclobutenyl)ethylene, 502
e-EPDM
Epoxidized ethylene propylene diene, 212
E/EA
Ethene/ethyl acrylate copolymer, 214
EAA
Ethylene-co-acrylic acid, 555
Ethylene/acrylic acid copolymers, 213, 549
EBPDMA
Ethoxylated bisphenol A dimethacrylate, 660
EBS
N,N ′ -Ethylene-bisstearamide, 513
EDA
Ethylene diamine, 93, 121

710 Reactive Polymers Fundamentals and Applications
EDMAB
Ethyl-4-dimethylamino benzoate, 193, 669, 673, 675
EG
Ethylene glycol, 117
Expandable graphite, 112
EGMA
Ethylene/glycidylmethacrylate copolymer, 213, 540
Poly(ethylene-co-glycidyl methacrylate), 552
EHMOXA
Ethyl hydroxymethyl oxazoline, 557
EO
Ethylene oxide, 571
EPDM
Ethylene propylene diene monomer, 606, 632
EPIDA
((3-(4-(1-(4-(3-(Bis-carboxymethylamino) 2-hydroxy-propoxy)
phenyl)-1-methyl-ethyl) phenoxy) 2-hydroxypropyl) carboxy
methylamino) acetic acid, 123
EPN
Epoxy-novolak, 416
EPPHAA
1,2-Epoxy-3-phenoxypropane, 159
EPR
Ethylene/propylene rubber, 557, 606, 632
EPR-g-GMA
Ethylene/propylene rubber grafted with GMA, 540
EPR-g-MA
Ethylene/propylene rubber grafted with maleic anhydride, 564
EVA
Ethylene/vinyl acetate, 153, 456
EVALSH
Mercapto-modified EVA, 560
EY
Elastic modulus, 680
12F-PEK
Fluorinated poly(aryl ether ketone), 160
FA
Furfuryl alcohol, 307, 312
6FDA
Hexafluoropropylidenebisphthalic dianhydride, 342
FP
Ratio of formaldehyde to phenol, 270

FPC
Flexible printed circuits, 412
FS
Flexural strength, 680
FTIR
Fourier-transform infrared (spectroscopy), 114
GLYMO
3-Glycidoxypropyltrimethoxysilane, 205, 326
GMA
Glycidyl methacrylate, 141, 213, 635, 648, 660, 661
GPC
Gel permeation chromatography, 525
GPE
Glycidyl phenyl ether, 186
GPN
General-purpose novolak resins, 242
GTL
Glycol trilinoleate, 638
H3M
Hexa(methoxymethyl)melamine, 263
HAB
3,3 ′ -Dihydroxy-4,4 ′ -diaminobiphenyl, 342
HAP
Hexa(allylamino)cyclotriphosphonitrile, 548
HBA
Hydroxybenzoic acid, 498
HBP
Hyperbranched polymers, 144
HCPA
4-Hydroxybutyl-2-chloro-2-phenylacetate, 570
HD
1,6-Hexanediol, 184
Hydrazine monohydrate, 121
HDDMA
1,6-Hexanediol dimethacrylate, 660
HDI
1,6-Hexane diisocyanate, 75
HDPE
High density poly(ethylene), 542
HEMA
2-Hydroxyethyl methacrylate, 123, 351, 518
HEMAN
Hydroxyethyl methacrylate maleic anhydride adduct, 660
Index 711

712 Reactive Polymers Fundamentals and Applications
HHPA
Hexahydrophthalic anhydride, 163
HIPS
High impact poly(styrene), 536
HMDI
4,4-Methylene biscyclohexyl diisocyanate, 73
HME
Hexafunctional methacrylate ester, 660
HMF
5-Hydroxymethylfurfural, 308, 309
HMTA
Hexamethylenetetramine, 263, 264
HNA
Hydroxynaphthoic acid, 498
HON
High ortho novolak resins, 242
HOT
Hot offset temperature, 700
HPA
2-Hydroxypropyl acrylate, 20
HPM
N-(4-Hydroxyphenyl)maleimide, 402, 416
HPN
High para novolak resins, 242
HQ
Hydroquinone, 498
HR
Resiliency foams, 107
HTEP
(6-Hydroxy)hexyl-2-(trimethylaminonio)ethyl phosphate, 119
HTPDMS
Hydroxy-terminated poly(dimethylsiloxane), 414
IA
Itaconic acid, 620, 629
IC
Integrated circuites, 421
IEM
2-Isocyanatoethyl methacrylate, 351, 660
IFSS
Interfacial shear strength, 434
IPDI
Isophorone diisocyanate, 75

Index 713
IPN
Interpenetrating polymer network, 382
IPO
2-Isopropenyl-2-oxazoline, 573, 630
IPP
Isotactic poly(propylene), 547
IPPA
Poly(2,2-di(4-phenylene)propane phthalate-co-2,2-di(4-phenylene)propane
isophthalate), 390
IR
Isoprene rubber, 632
KCD
3-Ketocoumarin, 209
Kevlar
Poly(p-phenylene terephthalamide), 563
LC
Liquid cristalline, 146
Liquid crystal, 208
LCDs
Liquid crystal displays, 208
LCGIC
Light curable glass-ionomer cements, 663
LCP
Liquid crystalline polymers, 549
LDI
Lysine-diisocyanate, 120
LDPE
Low density poly(ethylene), 213, 542, 612, 620
LEC
Light-emitting electrochemical cell, 123
LLDPE
Linear low density poly(ethylene), 542, 635
LOI
Limiting oxygen index, 405, 501
LPA
Low-profile additives, 26
MA
Maleic anhydride, 521, 541, 612, 637
Myristic acid, 366
MA-g-PP
Maleic anhydride-grafted-poly(propylene), 563
MAC-10
11-Methacryloyloxy-1,1-undecanedicarboxylic acid, 671

714 Reactive Polymers Fundamentals and Applications
MBA
Methacryloyl-β-alanine, 660, 663
MBL
α-Methylene-γ-butyrolactone, 665
MCDEA
4,4 ′ -Methylene bis(3-chloro-2,6-diethylaniline), 158
MDA
4,4 ′ -Methylenedianiline, 158, 175
MDEA
Methyldiethanolamine, 359
MDI
p,p ′ -Methylene diphenyl diisocyanate, 113
Diphenylmethane diisocyanate, 74
MDP-BMI
1,1 ′ -(Methylene di-4,1-phenylene)bismaleimide, 423
MDPE
Medium density poly(ethylene), 539
MEHQ
Hydroquinone monomethyl ether, 677
MeTHPA
3-Methyl-1,2,3,6-tetrahydrophthalic anhydride, 180
MF
Melamine/formaldehyde, 303
MFI
Melt flow index, 587
MFN
Melt flow number, 587
MFR
Melt flow rate, 587
MFT
Minimum fix temperature, 700
MKEA
4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)ammonium
hexafluoro antimonate)benzophenone, 189–191
MMA
Methyl methacrylate, 634
MMT
Montmorillonite, 20
MOPIP
1-(2-Methoxyphenyl)piperazine, 116
MPD
2-Methyl-1,3-propanediol, 14

Index 715
MPDA
m-Phenylene diamine, 272
MPGE
4-(N-Maleimidophenyl)glycidyl ether, 398, 402, 404
MPS
Maleic anhydride grafted poly(styrene), 637
Mercaptopropyltrimethoxysilane, 343
MPTMS
3-Methacryloxypropoxytrimethoxysilane, 681
MPTS
3-Methacryloxypropyl-trimethoxysilane, 351, 365
MWD
Molecular weight distribution, 608
NBR
Acrylonitrile-butadiene, 53
Nitrile rubber, 540
NHCPA
N-(2-Hydroxyethyl)-2-chloro-2-phenylacetamide, 570
NLO
Nonlinear optical, 209
1 H-NMR
Proton nuclear magnetic resonance spectroscopy, 140
NPG
N-Phenylglycine, 193
NT-D
1-(α-Naphthyl)-3,3-di(2-hydroxyethyl)-triazene-1, 93
OCDI
4,4 ′ -Diphenylmethane carbodiimide, 547
ODOPB
2-(6-Oxid-6H-dibenz[c,e][1,2]oxa-phosphorin-6-yl)-1,4-benzenediol, 168
ODOPM
2-(6-Oxid-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methanol, 168
ODPA
4,4 ′ -Oxydiphthalic anhydride, 498
OMT
Organophilic montmorillonite, 111
OPIA
(4-Octyloxyphenyl)phenyliodonium hexafluoroantimonate, 192
OPP
Oriented poly(propylene), 460
OXA
Ricinoloxazoline maleate, 634

716 Reactive Polymers Fundamentals and Applications
PA
Polyamide, 463
PA6
Poly(ε-caprolactam), 550
Polyamide 6, 213, 629
PAI
Polyamide-imide, 419
PAVE
Perfluoro (alkyl vinyl ether), 467
PBA
Pentabromobenzyl acrylate, 501
PBO
2,2 ′ -(1,3-Phenylene)bis(2-oxazoline), 564
PBT
Poly(benzo[1,2-d4,5-d ′ ]bisthiazole-2,6-diyl)-1,4-phenylene, 495
Poly(butylene terephthalate), 214, 525, 541
PBZT
Poly(p-phenylene benzobisthiazole), 498
PCB
Printed circuit board, 378
PCDMA
Poly(carbonate)dimethacrylate, 660
PCL
Poly(ε-caprolactone), 517
PDClPO
Poly(2,6-dichloro-1,4-phenylene oxide), 555
PDS
Polydioxanone, 488
PE-g-MA
Poly(ethylene) grafted with maleic anhydride, 549
PECH
Poly(epichlorohydrin), 111, 112
PEEK
Poly(ether ether ketone), 154
PEEK
Poly(ether ether ketone), 418
PEEK-C
Phenolphthalein poly(ether ether ketone), 155
PEEK-T
Poly(ether ether ketone) based on tertiary butyl hydroquinone, 155
PEG
Poly(ethylene glycol), 400

Index 717
PEG-MA
Poly(ethylene glycol)methacrylate, 518
PEG-PDMS
Block copolymer of poly(ethylene glycol) and poly(dimethylsiloxane), 643
PEGDMA
Poly(ethylene glycol)dimethacrylate, 662
PEI
Polyetherimide, 417
PEN
Poly(ethylene 2,6-naphthalate), 555
PEO
Poly(ethylene oxide), 153, 206, 533
Poly(ethylene-octene) copolymer, 551
PET
Poly(ethylene terephthalate), 342, 540
PETA
Pentaerythritol triacrylate, 516
PF
Phenol/formaldehyde (resin), 242
PFS
Phenol/formaldehyde sulfonate, 274
PG
Propylene glycol, 366
PGA
Polyglycolic acid, 488
PGE
Phenyl glycidyl ether, 142
PHB
Poly(p-hydroxybenzoate), 555
PHBV
Poly(β-hydroxybutyrate-co-β-hydroxyvalerate), 517
PL
β-Propiolactone, 119
PLA
Poly(lactide), 521
Polylactic acid, 488, 519
PLE
Photopolymerizable liquid encapsulants, 211
PMDA
Pyromellitic dianhydride, 180, 524
PMMA
Poly(methyl methacrylate), 153, 533

718 Reactive Polymers Fundamentals and Applications
PO
Propylene oxide, 571
POSS
Polyhedral oligomeric silsesquioxane, 680
PP
Poly(propylene), 607, 617
PP-g-MA
Maleated poly(propylene), 541
PPA
Poly(2,2-di(4-phenylene)propane phthalate), 390
PPDE
Poly(phthaloyl diphenyl ether), 418
PPE
Poly(2,6-dimethyl-1,4-phenylene ether), 565
Poly(phenylene ether), 214, 463
Poly(phenylene ether)s, 564
PPG
Polyoxypropylene glycol, 390
PPIDE
Poly(phthaloyl diphenyl ether-co-isophthaloyl diphenyl ether), 418
PPO
Poly(2,6-dimethyl-1,4-phenylene oxide), 549, 555
PPOH
3-Phenyl-1-propanol, 567
PPS
Poly(phenylene sulfide), 559
PPTDE
Phthaloyl diphenyl ether-co-terephthaloyl diphenyl ether, 418
PPV
Poly(p-phenylene vinylene), 124
PPy
Poly(pyrrole), 161
PROXYL
2,2,5,5-Tetramethyl-1-pyrrolidinyloxy, 602
PS
1,3-Propanesulfone, 119
Poly(styrene), 152, 557
PSA
Pressure-sensitive adhesives, 82, 460
PSC
1-Pyrenesulfonyl chloride, 196
PT
Phenolic cyanate/phenolic triazine copolymer, 386

Poly(thiophene), 645
PT-D
1-Phenyl-3,3-di(2-hydroxyethyl)-triazene-1, 93
PTFE
Poly(tetrafluoroethylene), 647
PTMEG
Poly(tetramethylene ether), 513
PTMG
Polytetramethylene glycol, 119
PTT
Poly(trimethylene terephthalate), 536
PU
Polyurethane, 69
PU/PAN
Polyurethane/polyacrylonitrile, 117
PUA
Polyurethane-acrylate, 116
PUDMA
Polyurethane dimethacrylate, 659, 660
PUE
Polyurethane elastomer, 111
PVC
Poly(vinyl chloride), 98
PVDF
Poly(vinylidene fluoride), 561
PVDH
Poly(vinylidene difluoride-co-hexafluoropropylene), 435
QA
N,N ′ -(4-Aminophenyl)-p-benzoquinone diimine, 400
QDM
o-Quinodimethane, 495
re-HDPE
Recycled high density poly(ethylene), 542
REC
Rectorite, 109
RIE
Reactive ion etching, 504
RMGICs
Resin-modified glass ionomer cements, 663
RTD
Residence time distribution, 514
RTM
Resin transfer molding, 400
Index 719

720 Reactive Polymers Fundamentals and Applications
S-g-PMA
Starch graft poly(methyl acrylate), 639
s-PS
Syndiotactic poly(styrene), 212
SAN
Poly(styrene-co-acrylonitrile), 153
Styrene/acrylonitrile copolymers, 214
SAXS
Small-angle X-ray scattering, 314
SBR
Styrene butadiene rubber, 465, 632
SDS
Sodium dodecyl sulfate, 644
SEB
Poly(styrene-b-(ethylene-co-butylene)), 542
SEBS
Styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer, 542
SEBS-g-MA
Styrene-ethylene/butylene-styrene triblock copolymer, 541
SEM
Scanning electron microscopy, 551
SG
Styrene/glycidyl methacrylate, 212
SiOC
Silicon oxycarbide, 338
SIPO
2-Isopropenyl-2-oxazoline, 573
SIS
Poly(styrene-b-isoprene-b-styrene), 461
SMA
Styrene/maleic anhydride copolymer, 549, 630, 635
SOC
Spiroorthocarbonates, 665
SOE
Spiroorthoesters, 665
SPE
Solid polymer electrolytes, 122
SSO
Silsesquioxane, 199
SUS
10-Undecenyl sulfate, 644
TA
Tartaric acid, 120

TAA
Tris(2-aminoethyl)amine, 484
TAIC
Triallyl isocyanurate, 211
TAP
Tris(2-allylphenoxy)triphenoxy cyclotriphosphazene, 435
TAT
Tris(2-allylphenoxy)-s-triazine, 435
TBAEMA
Diethylaminoethyl acrylate, 627
TBBPA
2,6,2 ′ ,6 ′ -Tetrabromobisphenol A, 32
Tetrabromobisphenol A, 3
TBPA
Tetrabutylphosphonium acetate, 515
TCDM
Tetrahydrofurfuryl cyclohexene dimethacrylate, 660
TDI
Toluene diisocyanate, 73, 407
TDS
Transdermal delivery system, 366
TEA
Triethylamine, 121, 264
TEC
Triethyl citrate, 366
TEGDI
1,2-Bis(isocyanate)ethoxyethane, 73
TEGDMA
Triethylene glycol dimethacrylate, 659, 660, 675
TEMPO
2,2,6,6-Tetramethyl-1-piperidinyloxy, 603, 643
Tetramethyl-1-piperidinyloxy, 568
TEMPO
2,2,6,6-Tetramethyl-1-piperidinyloxy, 602
TEOS
Tetraethoxysilane, 167, 325
TFE
Tetrafluoroethylene, 467
TGDDM
Tetraglycidyl diaminodiphenylmethane, 524
Tetraglycidyl-4,4 ′ -diaminodiphenylmethane, 144, 153
THF
Tetrahydrofuran, 309
Index 721

722 Reactive Polymers Fundamentals and Applications
THFMA
Tetrahydrofurfuryl methacrylate, 660
TLCP
Thermotropic liquid crystalline polymer, 553
TMB
1,2,4-Trimethoxybenzene, 193
TMDSC
Modulated differential scanning calorimetry, 194
TME
1,1,2,2-Tetramethoxyethane, 286
TMI
1-(Isopropenylphenyl)-1,1-dimethylmethyl isocyanate, 82
3-Isopropenyl-α,α-dimethylbenzene isocyanate, 546
TMPAE
Trimethylolpropane mono allyl ether, 3
TMPTA
Trimethylolpropane triacrylate, 351, 513, 638
TMPTMA
1,1,1-Trimethylolpropane trimethacrylate, 660
TMTEA
Trimercaptotriethylamine, 208
TOF-SIMS
Time of flight single ion monitoring mass spectroscopy, 647
TPA
Terephthalic acid, 35
TPGDA
Tripropylene glycol diacrylate, 638
TPMK
2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 193
TPP
Triphenyl phosphite, 565
TPPA
Poly(2,2-di(4-phenylene)propane phthalate-co-2,2-di(4-phenylene)propane
terephthalate), 390
TPS
Thermoplastic starch, 559
TPT
2,4,6-Triphenylpyrylium tetrafluoroborate, 485
TPU
Thermoplastic polyether polyurethanes, 122
TRIS
1,1,1-Trimethylolpropane triacrylate, 632

Index 723
TSFA
Triarylsulfonium hexafluoroantimonate, 208
TTT
Time-temperature-transition, 195
UBMI
Urethane-modified bismaleimide, 166
UDMA
1,6-Bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane, 659
Di-2-methacryloxyethyl-2,2,4-trimethylhexamethylenedicarbamate, 660
Urethane dimethacrylate, 675
UF
Urea/formaldehyde, 11, 253, 286
UHMF
Ultra high melt flow, 605
UHMWPE
Ultra-high molecular weight poly(ethylene), 646
UP
Unsaturated polyester, 117
VAc
Vinyl acetate, 634
VDAC
Vinylbenzyldodecyldimethyl ammonium chloride, 20
VEUH
Vinylester-urethane hybrid resins, 212
VOAC
Vinylbenzyloctadecyldimethyl ammonium chloride, 20
VOCs
Volatile organic compounds, 11, 267, 311
VTEOS
Vinyltriethoxysilane, 631
VTMS
Vinyltrimethoxysilane, 631
WOF
Work of fracture, 680
WPU
Waterborne polyurethane, 121
XPS
X-ray photoelectron spectroscopy, 119, 645
ZrDMA
Zirconyl dimethacrylate, 681

724 Reactive Polymers Fundamentals and Applications
CHEMICALS
Abietic acid, 410, 411, 449
Acetaldehyde, 243
Acetic anhydride, 309, 407, 639
Acetoacetoxy methyl methacrylate, 616
Acetone cyanhydrin, 352
Acetonitrile, 148
2-Acetoxyethyl-dibutyltin, 108
2-Acetoxyethyl-dibutyltin chloride, 108
p-Acetoxystyrene, 182
Acetylacetone peroxide, 36
Acetyl chloride, 79
Acetyl peroxide, 592
Acetyltributyl citrate, 366
Acrolein, 349, 352
Acrylamide, 290, 369, 523, 648
Acrylic acid, 11, 91, 119, 151, 290, 350, 351, 547, 551, 560, 645–647
Acrylonitrile, 87, 104, 645
Acryloyl-β-alanine, 660
Acryloyl glutamic acid, 660
Adipic Acid, 35
Adipic acid, 3, 44, 89, 90
Allo-ocimene, 449
Allyl acetoacetate, 678
Allyl alcohol, 12
Allyl alcohol propoxylate, 35
Allyl-4-[(4-N-allyl-N-ethyl)aminophenylazo]-α-cyanocinnamate, 436
Allylamine, 434
Allyl bromide, 34
Allyl chloride, 139, 150
1-Allyl-2-cyanatobenzene, 373
Allyl cyanoacrylate, 473
Allyl-4-[(4-N,N-diallyl)aminophenylazo]-α-cyanocinnamate, 436
Allyl glycidyl ether, 142, 199, 200, 205, 571
7-Allyloxy-2-naphthol, 411
2-Allylphenol, 391, 418, 419
4-Allylphenol, 391
Allylsuccinic anhydride, 671
Aluminium(III)acetylacetonate, 381
Aluminum bromide, 311
Aluminum isopropoxide, 521
Aluminum isopropyloxide, 182

Aluminum nitride, 421
Aluminum tri-sec-butylate, 678
Aluminum trichloride, 311
4-Amino-benzocyclobutene, 498
o-Aminobenzoic acid, 13
N-2-Aminoethyl-3-aminopropyl-tris(2-ethylhexoxy)silane, 483
N-Aminoethyl piperazine, 175, 177
1-(2-Aminoethyl)piperazine, 563
1,3-Aminoethylpropanediol, 557
m-Aminophenol, 243
o-Aminophenol, 557
p-Aminophenol, 142
N,N ′ -(4-Aminophenyl)-p-benzoquinone diimine, 400
1-(3 ′ -Aminopropyl)imidazole, 99
(3-Aminopropyl)triethoxysilane, 23, 110, 205, 316, 414, 646
Ammonium polyphosphate, 32, 111, 112
Ammonium sulfate, 311
O,O-tert-Amyl-O-(2-ethylhexyl)monoperoxy carbonate, 596
tert-Amyl hydroperoxide, 591
Amylopectin, 639
Amylose starch, 639
tert-Amylperoxybenzoate, 36
tert-Amylperoxy-2-ethylhexanoate, 596
4-(tert-Amylperoxy)-4-methyl-2-pentanol, 591, 592
tert-Amylperoxyneodecanoate, 596
tert-Amylperoxypivalate, 596
Anatase, 365
Aniline, 74, 75
9-Anthroic acid, 197
Antimony trioxide, 25, 32, 34, 357, 378
Ascorbic acid, 120, 334, 668, 669
Atropine, 344
2-Azabicyclo[2.2.1]heptane, 99, 100
2,2 ′ -Azobis(2-acetoxy)propane, 557, 601
2,2 ′ -Azobis(2-amidinopropane)hydrochloride, 369
2,2 ′ -Azobis(cyclohexanenitrile), 601
2,2 ′ -Azobis(2,4-dimethyl-4-methoxyvaleronitrile), 601
2,2 ′ -Azobis(2,4-dimethylvaleronitrile), 359, 601, 641
2,2 ′ -Azobis(2-ethylpropionitrile), 642
2,2 ′ -Azobis(isobutyronitrile), 35, 359, 601, 641, 697
2,2 ′ -Azobis(2-methylbutyronitrile), 35, 601
Barbituric acid, 668–670
Index 725

726 Reactive Polymers Fundamentals and Applications
Barium metaborate, 357
Barium sulfate, 19
Barium titanate, 23
Benzenesulfonic acid, 324
Benzil, 673
Benzocyclobutene, 493
1-Benzocyclobutenyl-1-bromoethyl ether, 495
1-Benzocyclobutenyl-1-hydroxyethyl ether, 495
1-Benzocyclobutenyl vinyl ether, 493, 495
Benzoguanamine, 301
Benzoic acid, 51
Benzoic acid 2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl ester, 615
Benzoin isobutyl ether, 673
Benzoin methyl ether, 37, 673
Benzoin phenyl ether, 673
Benzophenone, 359, 629, 646, 673
p-Benzoquinone, 17, 168, 367, 481, 623, 670
Benzoxazole, 557
Benzoyl chloride, 79
Benzyldimethylamine, 152
2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 193
Benzyl methacrylate, 153
1-Benzyl-5-phenylbarbituric acid, 669
N-Benzylpyrazinium hexafluoroantimonate, 184
N-Benzylquinoxalinium hexafluoroantimonate, 184
Benzyl tetrahydrothiophenium hexafluoroantimonate, 184
Benzyltrimethylammonium chloride, 205, 402
Betulin, 449
Bicumene, 627
Bicyclo[4.2.0]octa-1,3,5-triene, 493
Bis-p-aminocyclohexylmethane, 175
2,5-Bis(aminomethyl)bicyclo[2.2.1]heptane di(methylisopropylketimine), 176
1,2-Bis(aminomethyl)cyclobutane, 179
Bisaminomethylcyclohexane, 175
3,5-Bis(4-aminophenoxy)benzoic acid, 82
Bis(4-aminophenoxy)phenylphosphine oxide, 169
2,2-Bis[4-(4-aminophenoxy)phenyl]propane, 342
2,3-Bis(4-(4-aminophenoxy)phenyl)quinoxaline-6-carboxylic acid, 412
Bis(m-aminophenyl)methylphosphine oxide, 169, 171, 176
Bis(3-aminophenyl)phenylphosphine oxide, 402
Bis(4-aminophenyl)phenylphosphine oxide, 121, 172
2,3-Bis(4-aminophenyl)quinoxaline-6-carboxylic acid, 412
1,3-Bis(3-aminopropyl)tetramethyldisiloxane, 142

Index 727
2,6-Bis-4-benzocyclobutene benzo[1,2-d:5,4-d ′ ]bisoxazole, 493, 496
Bis(benzocyclobutenyl)-m-divinylbenzene, 502
Bis(benzocyclobutenyl)divinyltetramethylsiloxane, 502
1,2-Bis(benzocyclobutenyl)ethane, 493
1,2-Bis(4-benzocyclobutenyl)ethylene, 502
2,6-Bis(4-benzocyclobutenyloxy)benzonitrile, 493
4,4 ′ -Bis(sec-Butylamine)dicyclohexylmethane, 93
4,4 ′ -Bis(sec-Butylamine)diphenylmethane, 93
Bis(4-tert-Butylcyclohexyl)peroxydicarbonate, 36, 359
Bis(4-tert-butyl-1-isopropyl-2-imidazolyl)disulfide, 479
α,α ′ -Bis(tert-butylperoxy)diisopropyl benzene, 597
1,1-Bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 51, 362
((3-(4-(1-(4-(3-(Bis-carboxymethylamino) 2-hydroxy-propoxy)
phenyl)-1-methyl-ethyl) phenoxy) 2-hydroxypropyl) carboxy
methylamino) acetic acid, 123
1,7-Bis(chlorotetramethyldisiloxy)-m-carborane, 336, 337
Bis(4-cyanatocumyl)benzene cyanate, 374
1,1-Bis(4-cyanatophenyl)ethane, 196, 377
Bis(4-cyanatophenyl)ether, 377
2,2-Bis(4-Cyanatophenyl)1,1,1,3,3,3-hexafluoropropane, 377
Bis(4-cyanatophenyl)methane, 377
1,3-Bis(4-cyanatophenyl-1-(1-methylethylidene))benzene, 377
1,3-Bis(4-cyanatophenyl-1-(methylethylidene))benzene, 377
2,2 ′ -Bis(4-cyanatophenyl)propane, 382
2,2-Bis(4-cyanatophenyl)propane, 377, 388
Bis(4-cyanatophenyl)thioether, 377
1,3-Bis[2 ′ -cyano-3 ′ ,3-diphenylacryloyloxy]-
2,2-bis-[[2-cyano-3 ′ ,3 ′ -diphenylacryloyloxy]methyl]propane, 683
2,2-Bis(4,4-di-tert-butylperoxycyclohexyl)propane, 592
Bis(2,6-dichlorobenzoyl)-(4-propylphenyl)phosphine oxide, 37, 39
4,4 ′ -Bis(diethylamino)benzophenone, 193
Bis(3-diethylphosphono-4-hydroxyphenyl)sulfide, 169
Bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, 37
4,4 ′ -Bis(dimethylamino)benzophenone, 189
Bis(2-dimethylaminoethyl)ether, 99, 103
N,N-Bis(3-dimethylamino-n-propyl)amine, 102
Bis(3-(N,N-dimethylamino)propyl)amine, 99
N,N-Bis(3-dimethylaminopropyl)formamide, 105
N,N-Bis[3-(dimethylamino)propyl]formamide, 103
N,N ′ -Bis(3-dimethylaminopropyl)urea, 105
Bis(3,5-dimethyl-4-cyanatophenyl)methane, 377
4,4-Bis(N,N-dimethyl-N-(2-ethoxycarbonyl-1-propenyl)ammonium hexafluoro
antimonate)benzophenone, 187, 189–191

728 Reactive Polymers Fundamentals and Applications
Bis(dimethylsilyl)benzene, 335
1,2-Bis(2,3-epoxycyclohexyloxy)propane, 202
Bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 141
Bis[3-(2,3-epoxypropyl thio)phenyl]sulfone, 141
Bis(3-glycidyloxy)phenylphosphine oxide, 169
Bishydantoin, 142
2,2-Bis(4-hydroxy-3,5-dibromophenyl)propane, 357
Bis(2-hydroxy-3,5-dimethylbenzyl)ether, 260
Bis(2-hydroxy-3,5-dimethyl-benzyl)methylene, 260
Bis(2-hydroxyethyl)terephthalate, 45
Bis(hydroxyethyl)-p-toluidine, 669
2,2-Bis[p-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane, 661
4,4 ′ -Bis(2-hydroxy-3-methacryloylpropoxy)biphenyl, 664
Bis(hydroxymethyl)furan, 309
1,2-Bis-[2(2-hydroxy-5-methylphenyl)-5-benzotriazolyl]-ethane, 80
2,2-Bis(4-hydroxyphenyl)butane, 243
Bis(4-hydroxyphenyl)methane, 243
2,2-Bis(4-hydroxyphenyl)propane, 243
N,N ′ -Bis(2-hydroxypropylaniline), 93
Bis[N-(3-imidazolidinylpropyl)]oxamide, 103
1,2-Bis(isocyanate)ethoxyethane, 73
Bismaleimide(3,3 ′ -bis(maleimidophenyl))phenylphosphine oxide, 169, 171
1,3-Bis(maleimido)benzene, 414
4,4 ′ -Bis(maleimido)diphenylmethane, 397, 398, 405, 407, 418, 419, 425
1,3-Bis(maleimidomethyl)cyclohexane, 398, 414
1,3-Bis(4-maleimido phenoxy)benzene, 400
1,4-Bis(4-maleimido phenoxy)benzene, 400
2,2-Bis[4-(4-maleimido phenoxy)phenyl]propane, 388, 398, 399, 434
Bis(4-maleimidophenyl)ether, 399
Bis(4-maleimidophenyl)methane, 399
3,3 ′ -Bis(maleimidophenyl)phenylphosphine oxide, 402, 422
Bis(3-maleimidophenyl)phenylphosphine oxide, 402, 422
4,4 ′ -Bismaleimidophenylphosphonate, 398
Bis(4-maleimidophenyl)sulfone, 398, 399
Bis(3-mercaptophenyl)sulfone, 208
1,6-Bis(methacryloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane, 659
2,2-Bis[4-(3-methacryloxy-2-hydroxypropoxy)phenyl]propane, 660
2,2 ′ -Bis(α-methacryloxy-β-hydroxypropoxyphenyl)propane diphosphonate, 684
Bis(2-methacryloyloxyethyl)hydrogen phosphate, 671
Bis[2-(methacryloyloxy)ethyl]phosphate, 665
1,1-Bis(3-methyl-4-cyanatophenyl)cyclohexane, 377
Bis(1-methyl-imidazole)zinc(II)diacetyl-acetonate, 381
Bis(1-methyl-imidazole)zinc(II)dicyanate, 381

Index 729
Bis(1-methyl-imidazole)zinc(II)dioctoate, 381
Bis-1,3-methyl-1,2,3,4,5-pentamethylcyclopenta-2,4-diene benzene, 429
Bis(methyl salicyl)carbonate, 515
Bis[N-(3-morpholinopropyl)]oxamide, 103
Bismuth neodecanoate, 108
Bis(4-nitrophenyl)phenylphosphine oxide, 121
2,2-Bis(4-(oligo(ethoxy))phenyl)propane diacetate, 672
2,2-Bis(4-(oligo(ethoxy))phenyl)propanedimethacrylate, 672
Bis(1-oxyl-2,2,6,6-tetramethylpiperidine4-yl)sebacate, 602, 603
Bisphenol A, 35, 142, 148, 150, 180, 243, 246, 514
Bisphenol A bismaleimide, 398, 400
Bisphenol A dicyanate, 381, 389, 390
Bisphenol A diglycidyl ether, 139
Bisphenol A diglycidyl ether dimethacrylate, 658
Bisphenol A dimethacrylate, 660
Bisphenol B, 243
Bisphenol F, 142, 243
4,4 ′ -Bis(o-propenylphenoxy)benzophenone, 417
Bis(4-(1,2,4-triazoline-3,5-dione-4-yl)phenyl)methane, 410
Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 52
Bis(3,5,5-trimethylhexanoyl)peroxide, 359
Boric acid, 101, 257, 321, 419
Boric anhydride, 311
Boron fluoride, 311
Boron trifluoride, 183, 315, 453, 481
1-Bromobenzocyclobutene, 495
Butadiene diepoxide, 141
1,4-Butane diamine, 121
1,4-Butanediisocyanate, 120
1,2-Butanediol, 44
1,4-Butanediol, 35, 44, 52, 110, 113, 119, 142, 245, 291
2,3-Butanediol, 44
1,4-Butanediol diglycidyl ether, 141, 205
1,3-Butanediol dimethacrylate, 662
cis-2-Butene-1,4-diol, 5
tert-Butyl acrylamide, 642
n-Butyl acrylate, 26, 91, 345, 349, 351, 365, 538, 642, 697
tert-Butyl acrylate, 569
tert-Butyl alcohol, 186
tert-Butyl catechol, 42, 481
tert-Butylcumyl peroxide, 36
n-Butyl cyanoacrylate, 473, 475
N-tert-Butyl-1-dibenzylphosphono-2,2-dimethylpropyl nitroxide, 602

730 Reactive Polymers Fundamentals and Applications
n-Butyl-4,4-di(tert-butylperoxy)valerate, 596
N-tert-Butyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, 602, 603
N-tert-Butyl[(1-diethylphosphono)-2-methyl-propyl]nitroxide, 602
o-tert-Butyl-di-1-piperidinylphosphonamidate, 184, 186
N-tert-Butyl-1-di(2,2,2-trifluoroethyl)phosphono-2,2-dimethylpropyl nitroxide,
602
Butylene oxide, 85
O,O-tert-Butyl-O-(2-ethylhexyl)monoperoxy carbonate, 596
tert-Butyl hydroperoxide, 36, 362, 591, 597, 699
tert-Butyl hydroquinone, 481
O,O-tert-Butyl-O-isopropyl monoperoxy carbonate, 596
n-Butyl methacrylate, 351, 365, 637, 638
tert-Butyl methacrylate, 569
2-(3-tert-Butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzothiazole, 356
N-tert-Butyl-1-(2-naphthyl)-2-methylpropyl nitroxide, 602
tert-Butylperoxyacetate, 596
tert-Butylperoxybenzoate, 28, 36, 40, 360, 362, 596, 597
tert-Butylperoxy-2-ethylhexanoate, 36, 596
tert-Butylperoxyisobutyrate, 596
tert-Butylperoxyisononanoate, 596
tert-Butylperoxymaleate, 596
tert-Butylperoxyneodecanoate, 596
tert-Butylperoxypivalate, 596, 641
tert-Butylperoxy-3,5,5-trimethylhexanoate, 596
N-tert-Butyl-1-phenyl-2-methylpropyl nitroxide, 602
p-tert-Butylphenyl salicylate, 356
Butyl stearate, 476
n-Butyl vinyl ether, 190
2-Butyne-1,4-diol, 5
Butyraldehyde, 243
γ-Butyrolactone, 264
Calcium hydroxy apatite, 678
Calcium stearate, 28, 589
Calixarene, 187
Camphene, 449
Camphorquinone, 662, 673
ε-Caprolactam, 80, 536, 546
N,N ′ -Carbonylbiscaprolactam, 80
Carboxymethyl chitin, 121
Carboxymethyl konjac glucomannan, 121
N-(p-Carboxyphenyl)maleimide, 200
o-Carboxy phthalanilic acid, 3, 13
3-Carboxy-2,2,5,5-tetramethyl-pyrrolidinyloxy, 602

Cardanol, 243
Cardene, 493
Cardol, 243
Carene, 449, 452
Carophyllene, 449
β-Carotine, 449
Casein, 121, 122
Cassava starch, 545
Catechol, 17, 481
Celluloid, 658
Cellulose, 545
Cetyl pyridinium chloride, 695
Chitosan, 118, 545
Chloranil, 17
Chloro acetic acid, 474
Chlorobenzene, 324
p-Chlorobenzoyl peroxide, 592
4-Chloro-3,5-diamino-benzoic acid isobutylester, 93
Chlorodibutyltin hydride, 108
1-Chloro-2,3-epoxypropane, 139
Chloroethyl diazoacetate, 631
m-Chloroperbenzoic acid, 205
Chloroplatinic acid, 333
3-Chloro-1,2-propanediol, 111
Chlorosulfonic acid, 434
Choline octoate, 334
Chrysanthemol, 449
Cinnamic acid, 208
Citric acid, 52, 311
Cobalt acetylacetonate, 38
Cobalt 2-ethylhexanoate, 360
Cobalt(II)acetylacetonate, 381
Cobalt octoate, 28, 38
Copper phthalocyanine, 695
Cornstarch, 248, 343, 639
Creatinine, 636
Creosote, 344
m-Cresol, 243, 268
o-Cresol, 168, 244, 275, 387
p-Cresol, 243, 268
Cumene hydroperoxide, 36, 244, 591, 671
α-Cumylperoxyneodecanoate, 596
Cupric oxide, 387
Index 731

732 Reactive Polymers Fundamentals and Applications
Cuprous oxide, 387
3-(2-Cyanatophenyl)propyltrimethoxysilane, 391
3-(4-Cyanatophenyl)propyltrimethoxysilane, 391
2-Cyanoacrylate, 480, 483
2-Cyanoacrylic acid, 477
4 ′ -Cyano-4-biphenyloxyvaleric acid, 663, 664
Cyanoethylmethylaniline, 673
Cyanogen bromide, 374
Cyanuric chloride, 419
Cyclobutabenzene, 493
Cyclobutarene, 493
1,4-Cyclohexane diamine, 93
1,4-Cyclohexanedimethanol, 49, 154
Cyclohexanone peroxide, 362
Cyclohexene, 147
Cyclohexene oxide, 189
Cyclohexenoic acid, 201
Cyclohexyl methacrylate, 350, 351
2-Cyclohexyl-5-methylphenol, 243, 268
Cyclopentylamine, 289
Decabromodiphenyloxide, 31, 32
Decalin, 632
Decanedioic acid bis(2,2,6,6-tetramethyl-piperidin-1-oxyl-4-yl), 615
1,10-Decanediol, 117
Decanoyl peroxide, 592
1-Decene, 147
Diabietylketone, 410
3,5-Diacetyl-1,4-dihydrolutidine, 284
2,2 ′ -Diallyl bisphenol A, 164, 381, 382, 397, 398, 400, 417, 418, 424, 425, 427,
428
(4-(N,N-Diallyl)-4 ′ -nitrophenyl)azoaniline, 436, 437
2,4-Di(2-allylphenoxy)-6-N,N-dimethylamino-1,3,5-triazine, 417, 419
2,4-Di(2-allylphenoxy)-6-(2-naphthyloxy)-1,3,5-triazine, 417, 419, 420
1,4-Diallyl phenyl ether, 400
Diallyl phthalate, 8
3,5-Diaminobenzoic acid, 109
1,4-Diaminobutane, 630
1,2-Diaminocyclohexane, 175
4,4 ′ -Diaminodibenzyl, 80
2,4-Diamino-3,5-diethyl toluene, 175
2,6-Diamino-3,5-diethyl toluene, 175
Diaminodiethyl toluene, 175
4,4 ′ -Diamino-3,3 ′ -dimethyldicyclohexylmethane, 175

Index 733
4,4 ′ -Diaminodiphenylmethane, 142, 163, 167, 175, 178, 196, 198, 402, 407, 414,
423
4,4 ′ -Diaminodiphenylsulfone, 153, 158, 163, 175, 176, 178, 198
2,4-Diamino-4 ′ -methylazobenzene, 176
2,6-Di(4-aminophenoxy)benzonitrile, 417
3,5-Diaminophenyl-4-benzocyclobutenylketone, 498
(N-4,6-Diamino-1,3,5-triazin-2-yl)-1,3,5-triazine-2,4,6-triamine, 299
Diaminotricyclododecane, 179
2-(3,5-Di-tert-amyl-2-hydroxyphenyl)benzotriazole, 356
Di-tert-amyl peroxide, 592
1,1-Di(tert-amylperoxy)cyclohexane, 592
2,2-Di(tert-amyl)peroxypropane, 592
1,5-Diazabicyclo[4.3.0]non-5-ene, 483
1,4-Diazabicyclo[2.2.2]octane, 99–101
1,8-Diazabicyclo[5.4.0]undec-7-ene, 483, 484
1,5-Diazobicyclo[4.3.0]non-5-ene, 102
1,5-Diazobicyclo[4.3.0]non-5-ene, 101
1,8-Diazobicyclo[5.4.0]undec-7-ene, 101, 102
o-Diazonaphthoquinone, 268
1,2,5,6-Dibenzocyclooctadiene, 495
Dibenzodiazyl disulfide, 479
Dibenzoyl peroxide, 36, 40, 359, 486, 568, 592, 597, 668
N,N-4,4-Dibenzylbismaleimide, 398, 412
1,1-Dibromo-2,2-bis(4-cyanatophenyl)ethylene, 377
Dibromoneopentylglycol, 34
Dibromostyrene, 34
α,α ′ -Dibromo-m-xylene, 428
Dibutoxybis(acetylacetonato)titanium(IV), 421
Di-tert-butyl fumarate, 571
3,5-Di-tert-butyl-4-hydroxybenzyl acrylate, 632
2-(3,5-Di-tert-butyl-2-hydroxyphenyl)benzotriazole, 356
2-(3,5-Di-tert-Butyl-2-hydroxyphenyl)-5-chlorobenzothiazole, 356
3,5-Di-tert-butyl-4-hydroxyphenyl-propanoic acid, 622
2,6-Di-tert-butyl-4-methylphenol, 677
Di-tert-butyl peroxide, 40, 591, 592
2,2-Di(tert-butylperoxy)butane, 592
1,1-Di(tert-butylperoxy)cyclohexane, 592
1,1-Di-(tert-butylperoxy)cyclohexane, 698
α,α ′ -Di(tert-butylperoxy)diisopropylbenzene, 557
1,3-Di(2-tert-butylperoxyisopropyl)benzene, 597
1,4-Di(tert-butylperoxyisopropyl)benzene, 592, 599
Di(2-tert-butylperoxyisopropyl)benzene, 597
1,1-Di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 51, 592, 638

734 Reactive Polymers Fundamentals and Applications
o,o-Di-tert-Butyl phenylphosphonate, 184
Dibutyl phosphite, 684
Dibutyl phthalate, 475, 476
o,o-Di-tert-butyl-1-piperidinylphosphonamidate, 184, 186
1,3-Di-n-butyltetramethyldisilazane, 338
1,3-Di-tert-butyltetramethyldisilazane, 338
Dibutyltin bis(2,3-dihydroxypropylmercaptide), 107, 108
Dibutyltin bis(4-hydroxyphenylacetate), 107, 108
Dibutyltin diacetate, 107, 331
Dibutyltin dilaurate, 80, 107, 108, 114, 381, 414, 567, 688
Dibutyltin dilauryl mercaptide, 107
Dibutyltin dimercaptide, 107
Dibutyltin oxide, 184, 567, 697
2,5-Dicarboxyaldehyde-furan, 309
Dichloroacetic acid, 40
Dichlorobenzaldehyde, 206
1,1-Dichloro-2,2-bis(4-cyanatophenyl)ethylene, 377
Dichlorobis(triphenylphosphine)platinum(II), 333
Dichlorodimethylsilane, 343, 414
Dichloroethane, 147
Dichloromethane, 381, 434
1,3-Dichlorotetramethyldisiloxane, 336, 337
Dicumyl, 627
Dicumyl hydroperoxide, 597
Dicumyl peroxide, 36, 362, 541, 597, 609, 623, 629
4,4-Dicyanatobiphenyl, 377
1,4-[Di(4-cyanato diphenyl-2,2 ′ -propane)]terephthalate, 387
Dicyandiamide, 176, 299, 300, 402
Dicyclohexylmethane-4,4 ′ -diisocyanate, 73, 75
Dicyclohexylperoxydicarbonate, 596
o,o-Dicyclohexyl phenylphosphonate, 184
Dicyclopentadiene, 6, 7, 35, 454
Didodecyl fumarate, 52
1,3-Didodecyloxy-2-glycidyl-glycerol, 141
1,3-Diethenyl-1,1,3,3-tetramethyldisiloxane, 333
2-(2-N,N-Diethylaminoethoxy)ethanol, 99, 105
Diethylaminoethyl acrylate, 626, 627
Diethylaminoethyl methacrylate, 675
Diethylaminopropylamine, 175, 177
Diethyl-2,2-dicyanoglutarate, 471
Diethylene glycol, 3, 11, 15, 44, 89, 93, 103, 200, 697
Diethylene glycol diacrylate, 638
Diethylenetriamine, 87, 175, 177

Index 735
Di(2-ethylhexyl)peroxydicarbonate, 596
Di-2-ethylhexyl phosphate, 684
Di-2-ethylhexyl phosphite, 684
Diethylketone, 593
Diethyl maleate, 542, 623
Diethyl malonate, 80
Diethyl sebacate, 476
Diethylsuccinate, 536, 550
2,4-Diethylthioxanthone, 188
Diethyltoluene diamine, 93
N,N-Diethyltoluidine, 479
1,3-[Di(4-glycidyloxy diphenyl-2,2 ′ -propane)]isophthalate, 387
Diglycidyl tetrahydrophthalate, 525
1,3-Dihexyltetramethyldisilazane, 338
1,2-Dihydrocyclobutabenzene-3,6-dicarboxylic acid, 493, 495, 496, 498
9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 112, 168, 169, 405, 422
Dihydrophthalimide, 410
1,4-Dihydroxybenzene, 622
2,4-Dihydroxybenzophenone, 356, 683
4,4 ′ -Dihydroxybiphenyl, 663
4,4 ′ -Dihydroxychalcone, 208, 209
3,3 ′ -Dihydroxy-4,4 ′ -diaminobiphenyl, 342
2,2 ′ -Dihydroxy-4,4 ′ -dimethoxybenzophenone, 356
1,4-Di(2-hydroxyethyl)hydroquinone, 93
Dihydroxyethyl-p-toluidine, 666
α,α ′ -Dihydroxyl-poly(butyl acrylate), 82
2,2 ′ -Dihydroxy-4-methoxybenzophenone, 356
2,7-Dihydroxynaphthalene dicyanate, 377
10-(2,5-Dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide,
169
Diisobutyl aluminum hydride, 521
1-Diisobutylene, 453
2-Diisobutylene, 453
4,4 ′ -Diisocyanato dicyclo hexylmethane, 73
Diisopropylbenzene mono hydroperoxide, 591
1,4-Dilithio-1,3-butadiyne, 336
Di-2-methacryloxyethyl-2,2,4-trimethylhexamethylenedicarbamate, 660
o,o ′ -Dimethallyl bisphenol A, 418
3,9-Di(p-methoxybenzyl)-1,5,7,11-tetra-oxaspiro[5.5]undecane, 184, 185
Dimethoxydiethoxysilane, 325
2,2-Dimethoxy-1,2-diphenylethan-1-one, 193
2,2-Dimethoxy-2-phenylacetophenone, 37, 359
N,N-Dimethylacetamide, 412, 623

736 Reactive Polymers Fundamentals and Applications
N,N-Dimethylacrylamide, 647
Dimethylamine, 156, 419
4-Dimethylaminobenzaldehyde, 193, 666
3-Dimethylaminobenzoic acid, 193
4-Dimethylaminobenzoic acid, 193
4-Dimethylaminobenzoin, 193
4-Dimethylamino-1-butanol, 119
2(Di-methylamino)ethanol, 104
2-(Dimethylamino)ethyl methacrylate, 82, 83
2-Dimethylaminoethyl urea, 105
2-(Dimethylamino)-2-(hydroxymethyl)-1,3-propanediol, 253, 265
5-Dimethylamino-3-methyl-1-pentanol, 99
2-Dimethylamino-2-methyl-1-propanol, 253, 264, 265
5-Dimethylaminonaphthalene-1-(2-aminoethyl)sulfonamide, 197
4-Dimethylaminophenethanol, 666
2-[4-(Dimethylamino)phenyl] ethanol, 669
3-Dimethylamino-1,2-propanediol, 110
1-(3-Dimethylaminopropoxy)-2-butanol, 104, 105
N-(3-Dimethylaminopropyl)-2-ethylhexanoic acid amide, 99
4-Dimethylaminopyridine, 199
Dimethyl ammonium methyl sulfate, 695
N,N-Dimethylaniline, 39, 192
N,N-Dimethylbenzylamine, 99, 180
2,5-Dimethyl-2,5-bis(benzoylperoxy)hexane, 182
N,N-Dimethylcyclohexylamine, 99
2,6-Dimethyl-3,5-diacetyl-1,4-dihydropyridine, 284
2,5-Dimethyl-2,5-di(benzoylperoxy)hexane, 592
2,5-Dimethyl-2,5-di(tert-butylperoxy)hexane, 516, 546, 591, 592, 594, 607, 621
2,5-Dimethyl-2,5-di-tert-butylperoxyhexane, 595
2,4-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, 573
2,5-Dimethyl-2,5-di(tert-butylperoxy)-3-hexyne, 516, 557, 592, 595, 597
Dimethyldichlorosilane, 327
Dimethyldiethoxysilane, 325
2,5-Dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane, 592
2,5-Dimethyl-2,5-di(hydroperoxy)hexane, 591
N,N-Dimethyl-N ′ ,N ′ -di(2-hydroxypropyl)-1,3-propane diamine, 483
Dimethyldimethoxysilane, 325, 331
2,3-Dimethyl-2,3-diphenylbutane, 627
N,N-Dimethylethanolamine, 99, 100
N,N-Dimethylethylamine, 99
N,N-Dimethylethylethanolamine, 119
N,N-Dimethylformamide, 544, 623
2,5-Dimethylhexene-2,5-diperoxyisononanoate, 596

Index 737
1,1-Dimethyl-3-hydroxybutyl-3-(carboxy)-5-norbornene-2-ylperoxycarboxylate,
624
1,1-Dimethyl-3-hydroxybutyl-2-(carboxy)perbenzoate, 624, 626
1,1-Dimethyl-3-hydroxybutyl-2-(carboxy)peroxycyclohexanecarboxylate, 624
1,1-Dimethyl-3-hydroxybutyl hydroperoxide, 626
1,1-Dimethyl-3-hydroxybutyl-6-(hydroxy)peroxyhexanoate, 624
1,1-Dimethyl-3-hydroxypropyl-3-(carboxy)peroxypropanoate, 624
1,2-Dimethylimidazole, 101
Dimethyl itaconate, 630
Dimethylmelamine, 300
Dimethylol butanoic acid, 93, 121
α,α ′ -Dimethylol propionic acid, 124
Dimethylol propionic acid, 120
4,5-Dimethyl-2-oxo-1,3,2-dioxathiolane, 482
N,N-Dimethyl-p-phenylene diamine, 6
N ′ ,N ′ -Dimethylpiperazine, 99
3,5-Dimethylpyrazole, 80
Dimethyl sebacate, 476
Dimethyl terephthalate, 35, 697
3,5-Dimethylthio-toluene diamine, 93
N,N-Dimethyl-p-toluidine, 479, 669, 672
2,4-Dinitrotoluene, 74
Dinonylphenol cyanate, 374
Dioctyl adipate, 476
Dioctyl glutarate, 476
Dioctyl phthalate, 476
7,26-Dioxatrispirobicyclo[4.1.0]heptane-4,5 ′ -1,3-dioxane-2 ′ ,2 ′′ -
1,3-dioxane-5 ′′ ,4 ′′ -bicyclo[4.1.0]heptane, 665, 667
3,23-Dioxatrispirotricyclo[3.2.1.0[2.4]]octane-6,5 ′ -1,3-dioxane- 2 ′ 2 ′′ -
1,3-dioxane-5 ′′ ,7 ′′′ -tricyclo[3.2.1.0[2.4]octane], 185
5-(2,5-Dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic
anhydride, 180
Dipentaerythritol pentaacrylate monophosphate, 684
Dipentaerythritol pentamethacrylate monophosphate, 684
Diphenylchlorosilane, 325
Diphenyldimethoxysilane, 325
N,N ′ -Diphenylethane-1,2-diamine, 6
N,N-4,4-Diphenyl ether bismaleimide, 398
o,o-Di-1-phenylethyl phenylphosphonate, 186
N,N ′ -Diphenylhexane-1,6-diamine, 6
Diphenyliodoniumhexafluorantimonate, 666
Diphenyl iodonium hexafluoroantimonate, 192
Diphenylmelamine, 300

738 Reactive Polymers Fundamentals and Applications
N,N-4,4-Diphenylmethanebismaleimide, 398, 412
4,4 ′ -Diphenylmethane bismaleimide, 547
4,4 ′ -Diphenylmethane carbodiimide, 547
4 ′ ,4 ′ -Diphenylmethane diamine, 87
Diphenylmethane-4,4 ′ -diisocyanate, 69
4,4 ′ -Diphenylmethanedimaleimide, 410
Diphenylphosphine, 334
3,3 ′ ,4,4 ′ -Diphenylsulfone tetracarboxylic dianhydride, 342
1,3-Diphenyltetramethyldisilazane, 338
Dipropylene glycol, 44
2,2 ′ -Dipyridyl disulfide, 479
2,3,8,9-Di(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane, 141
2,3,8,9-Di(tetramethylene)-1,5,7,11-tetraoxaspiro[5.5]undecane
spiroorthocarbonate, 185
2,14-Dithiacalix[4]arene, 248
4,4 ′ -Dithiodianiline, 176
6,6 ′ -Dithiodinicotinic acid, 479
1,3-Divinyl-1,1,3,3-tetramethyldisiloxane, 333
Dodecanoyl peroxide, 592, 597
1-Dodecene, 147, 638
2-Dodecen-1-yl succinic anhydride, 544
Dodecenyl succinic anhydride, 180
Dodecyl acrylate, 615
Dodecyl aldehyde, 484
Dodecyl diacid, 516
Dodecyl mercaptane, 641
Dodecylphenol, 381
Eosine, 673
Epichlorohydrin, 139–141, 148, 150, 173
Epoxy allyl soyate, 141
Epoxychlorotriazine, 565
2-(3,4-Epoxycyclohexyl)ethyl(methyl)dimethoxysilane, 326
2-(3,4-Epoxycyclohexyl)ethyl(phenyl)diethoxysilane, 326
2-(3,4-Epoxycyclohexyl)ethyltriethoxysilane, 326
2-(3,4-Epoxycyclohexyl)ethyltrimethoxysilane, 326
3,4-Epoxycyclohexyl-methyl-3,4-epoxycyclohexane carboxylate, 141
3,4-Epoxycyclohexylmethyl-3 ′ ,4 ′ -epoxycyclohexane carboxylate, 187
Epoxy methyl soyate, 141
E-12,13-Epoxyoctadeca-E-9-enoic acid ester, 141
1,2-Epoxy-3-phenoxypropane, 159, 167
2,3-Epoxypropoxy methacrylate, 663
2,3-Epoxypropyl(methyl)dimethoxysilane, 326
2,3-Epoxypropyl(phenyl)dimethoxysilane, 326

2,3-Epoxypropyltriethoxysilane, 326
2,3-Epoxypropyltrimethoxysilane, 326
2,3-Epoxypropyltrimethylammonium chloride, 523
exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalic anhydride, 142
exo-3,6-Epoxy-1,2,3,6-tetrahydrophthalimidocaproic acid, 142
17-β-Estradiol, 366
Ethanolamine, 289, 561
2-Ethenylisopropanol, 333
Ethenylphenyloxirane, 141
2-Ethoxyethyl cyanoacrylate, 473
Ethyl acrylate, 91, 213, 214, 290, 351
Ethylal, 286
Ethylaluminum dichloride, 451
Ethylamine, 289, 315
Ethyl-(4,4 ′ -bismaleimidophenyl)phosphonate, 402, 422
Ethyl α-(bromomethyl)acrylate, 189
Ethyl cyanoacetate, 471
Ethyl 2-cyanoacrylate, 472
Ethyl cyanoacrylate, 473, 489
Ethyl-3,3-di(tert-amylperoxy)butyrate, 596
Ethyl diazoacetate, 631
Ethyl-3,3-di(tert-butylperoxy)butyrate, 596
N-Ethyldiisopropanolamine, 675
Ethyl-4-dimethylamino benzoate, 193, 662, 666, 669, 673, 675
N,N ′ -Ethylene-bisstearamide, 513
Ethylene carbonate, 84
Ethylene diamine, 86, 88, 93, 121, 454
3,4-Ethylenedioxythiophene, 697
Ethylene glycol, 3, 11, 89, 93, 117, 363, 369, 407, 495, 517, 697
Ethylene glycol antimonite, 34
Ethylene glycol dimethacrylate, 351, 662
Ethylene oxide, 6, 85, 88, 173, 353, 566, 571
Ethylene propylene diene monomer, 606
Ethylene/propylene rubber, 557, 606
Ethyl formate, 264
2-Ethylhexyl acrylate, 151, 349, 351, 642
2-Ethylhexyl alcohol, 352
2-Ethylhexyl N-methacryloylcarbamate, 351, 352
Ethyl hydroxymethyl oxazoline, 557
Ethylmelamine, 300
Ethyl methacrylate, 351, 365, 366
Ethyl N-methacryloylcarbamate, 352
2-Ethyl-4-methylimidazole, 176
Index 739

740 Reactive Polymers Fundamentals and Applications
Ethylmethylphosphinic anhydride, 379
N-Ethylmorpholine, 99–101
Ethyltriethoxysilane, 325
Ethyltrimethoxysilane, 325
Ethynyl cyclohexanol, 334
Ferric acetylacetonate, 107, 182
9-Fluorenyl tetramethylene sulfonium hexafluoroantimonate, 187
Fluorohectorite, 163
Formaldehyde, 243, 245, 248, 310, 400, 416, 471
Formic acid, 95, 304
Fumaric acid, 3, 699
Furan, 308, 407
2,5-Furandicarboxylic acid, 308
2-Furan formaldehyde, 308
Furfural, 243, 308
Furfuraldehyde, 308
Furfuryl alcohol, 308–310, 407
2-Furfurylmethacrylate, 308
Glutamic acid, 147
Glutaric acid, 44, 90
Glutaric anhydride, 180, 205, 626
Glycerol, 3, 86, 89, 93, 363, 412, 522, 523, 559, 638
Glycerol diglycidyl ether, 141
Glycerol dimethacrylate, 688
Glycerophosphate dimethacrylate, 684
Glycerophosphoric acid, 684
Glyceryl dimethacrylate phosphate, 684
Glyceryl-2-phosphate, 684
Glyceryl triacetate, 476
Glyceryl tributyrate, 476
3-Glycidoxypropyl(methyl)dibutoxysilane, 326
3-Glycidoxypropyl(methyl)diethoxysilane, 326
3-Glycidoxypropyl(methyl)dimethoxysilane, 326
3-Glycidoxypropyltributoxysilane, 326
3-Glycidoxypropyltriethoxysilane, 326
(3-Glycidoxypropyl)trimethoxysilane, 210
3-Glycidoxypropyltrimethoxysilane, 205, 326, 391
Glycidyl acrylate, 12, 369
Glycidyl methacrylate, 12, 141, 213, 536, 537, 554, 616, 635, 648, 660, 661
Glycidyl phenyl ether, 186
Glycol trilinoleate, 638
Glyoxal, 243, 286
Guttapercha, 449

Hectorite, 18
3,3,4,4,5,5,5-Heptafluoro-1-pentene, 345
Heptamethyltrisiloxane, 328
Heptanoic anhydride, 639
2-Heptanone, 268
HET acid, 3, 5, 32–34
HET anhydride, 180
Hexa(allylamino)cyclotriphosphonitrile, 548
Hexabromocyclododecane, 627
2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-Hexadecafluoro-decane-1,10-diol, 150
2,4-Hexadienedioic acid, 573
1,5-Hexadiyne, 493
Hexafluoroisobutene, 148
Hexafluoropropene, 366
4,4 ′ -Hexafluoropropylidenebisphthalic dianhydride, 342
Hexafunctional methacrylate ester, 660
Hexahydro-4-methylphthalic anhydride, 180
Hexahydrophthalic acid, 142
Hexahydrophthalic anhydride, 163, 180
Hexakis(methoxymethyl)melamine, 164
Hexakis(methylol)melamine, 263
Hexa(methoxymethyl)melamine, 263
1,1,4,4,7,7-Hexamethylcyclo-4,7-diperoxynonane, 592
Hexamethyldisilazane, 338
Hexamethyldisiloxane, 331
1,6-Hexamethylene-bis(2-furanylmethylcarbamate), 412
N,N ′ -Hexamethylenebismaleimide, 410
Hexamethylene diamine, 175, 177, 289
1,6-Hexamethylenediisocyanate, 659
Hexamethylene diisocyanate, 73, 119, 407
Hexamethylenetetramine, 262–264
Hexamethylol melamine, 300, 302
Hexamethylphosphoramide, 623
3,3,6,6,9,9-Hexamethylcyclo-1,2,4,5-tetraoxanonane, 592
1,6-Hexane bismaleimide, 398
1,6-Hexane diamine, 84
Hexane-1,6-diamine, 69
Hexane-1,6-diisocyanate, 69
Hexanediol diglycidyl ether, 150
1,6-Hexanediol dimethacrylate, 660, 662
n-Hexanol, 12
1-Hexene, 643
tert-Hexyl hydroperoxide, 671
Index 741

742 Reactive Polymers Fundamentals and Applications
n-Hexyl isocyanate, 82
tert-Hexylperoxybenzoate, 36
High density poly(ethylene), 542
Hydrazine, 88, 93
Hydrazine monohydrate, 121
Hydroquinone, 16, 17, 22, 481, 498, 555
Hydroquinone monomethyl ether, 672, 677
4-Hydroxyacetanilide, 159
α-Hydroxy-acetophenone, 37
3-Hydroxy-1-azabicyclo[2.2.2]octane, 99, 105
Hydroxybenzoic acid, 498
2-Hydroxybenzoquinone, 481
2-[2-Hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 356
4-Hydroxybutyl acrylate, 91
4-Hydroxybutylvinyl ether, 428
3-Hydroxy-1,1-dimethylbutylperoxyneodecanoate, 596
2-Hydroxy-4(2,3-epoxypropoxy)benzophenone, 142
2-Hydroxyethyl acrylate, 27, 91
2-Hydroxyethyl methacrylate, 123, 206, 351, 518, 558
Hydroxyethyl methacrylate, 660
Hydroxyethyl methacrylate monophosphate, 684
(6-Hydroxy)hexyl-2-(trimethylaminonio)ethyl phosphate, 119
2-Hydroxy-4-methoxybenzophenone, 356
2-Hydroxy-4-methoxy-4 ′ -chlorobenzophenone, 356
2-Hydroxymethyl-4,6-dimethylphenol, 260
5-Hydroxymethylfurfural, 308, 309
2-Hydroxy-2-methyl-1-phenyl-1-propane, 485
2-Hydroxy-2-methylphenylpropane-1-one, 11, 37
2-Hydroxy-2-methyl-1-phenyl-propan-1-one, 37, 38
Hydroxy-2-methyl-1-phenyl-propanone, 193
3-Hydroxymethyl quinuclidine, 105
Hydroxynaphthoic acid, 498
2-Hydroxy-4-octoxybenzophenone, 356, 683
2-(2 ′ -Hydroxy-5 ′ -tert-octylphenyl)benzotriazole, 356
N-(4-Hydroxyphenyl)maleimide, 402, 414, 416
N-(p-Hydroxy)phenylmaleimide, 389
2-Hydroxypropyl acrylate, 20, 210, 642
1-(2-Hydroxypropyl)imidazole, 99
p-Hydroxystyrene, 151
6-Hydroxy-5-[(4-sulfophenyl)azo]-2-naphthalenesulfonic acid, 481
(4-(2-Hydroxytetradecyloxyphenyl))phenyliodoniumhexafluoroantimonate, 192
4-Hydroxy-2,2,6,6-tetramethyl-piperidin-1-oxyl, 615
4-Hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 602

1-(3 ′ -(Imidazolinyl)propyl)urea, 99
4-(3-Iodopropyl)benzocyclobutene, 643
Isobutenylsuccinic anhydride, 672
Isobutyl cyanoacrylate, 473
Isobutyl vinyl ether, 190
2-Isocyanatoethyl methacrylate, 351, 363, 660, 661
Isophorone diamine, 93, 175
Isophorone diisocyanate, 73, 76, 110, 118, 120, 121, 124
Isophthalic acid, 3, 5, 35, 45, 89, 154, 697
Isophthaloyl bis-4-benzocyclobutene, 493, 496
Isophthaloyl dichloride, 516
3-Isopropenyl-α,α-dimethylbenzene isocyanate, 546
2-Isopropenyl-2-oxazoline, 573, 630
1-(Isopropenylphenyl)-1,1-dimethylmethyl isocyanate, 82, 83
Isopropoxybenzoin, 673
Isopropyl alcohol, 167, 369
Isopropyl chloride, 324
Isopropyl myristate, 476
Isosebacic acid, 44
Itaconic acid, 3, 27, 620, 629
Itaconic anhydride, 672
3-Ketocoumarin, 209
Lauric acid, 476
Laurolactam, 572
Lauroyl peroxide, 359, 362, 592
Lauryllactam, 513
Lead naphthenate, 107
Lead octoate, 107
Limonene, 142, 448, 449
Linear low density poly(ethylene), 542, 635
Linoleic acid, 638
Lithium stearate, 515
Longifolene, 449
Low density poly(ethylene), 542, 620
Lupeol, 449
Lysine-diisocyanate, 73, 120
Magnesium hydroxide, 539
Magnesium oxide, 564
Maleated poly(propylene), 541
Maleic anhydride, 3, 15, 35, 113, 494, 541, 612, 616, 637
p-Maleimidobenzoic anhydride, 424
4-(N-Maleimidophenyl)glycidyl ether, 398, 402, 404
4-Maleimidophenyl isocyanate, 407
Index 743

744 Reactive Polymers Fundamentals and Applications
Manganese(III)acetylacetonate, 483
Manganese octoate, 38
Melam, 299
Melamine cyanurate, 32, 111–113
Melamine phosphate, 169, 526
Melem, 299
Melon, 299
Menthane diamine, 175, 177
2-Mercaptoethanol, 82, 641
3-Mercapto-1,2-propanediol, 108
Mercaptopropyltrimethoxysilane, 343
Methacrylamide, 369
2-Methacrylamide-2-methylpropenesulfonic acid, 571
Methacrylate-terminated phosphoric acid ester, 684
Methacrylic acid, 11
Methacrylic anhydride, 84
Methacryloxyethyl phosphate, 684
4-Methacryloxyethyl trimellitate, 684
3-Methacryloxypropoxytrimethoxysilane, 681
(3-Methacryloxypropyl)trimethoxysilane, 23, 24
3-Methacryloxypropyl-trimethoxysilane, 351, 365
Methacryloyl-β-alanine, 660, 663
Methacryloyl chloride, 82, 87
Methacryloyl glutamic acid, 660
Methacryloyl isocyanate, 351, 352
Methacryloyloxyethane-1,1-diphosphonic acid, 684
2-Methacryloyloxyethyldihydrogen phosphate, 671
2-Methacryloyloxyethyl isocyanate, 351
2-(Methacryloyloxy)ethyl phosphate, 665
11-Methacryloyloxy-1,1-undecanedicarboxylic acid, 671
2-Methoxybenzyl-1,3-propanediol, 184
2-Methoxyethyl cyanoacrylate, 473
Methoxyethylmorpholine, 103
2-Methoxy-1-methylethyl cyanoacrylate, 473
m-Methoxyphenol, 243
p-Methoxyphenol, 481
1-(2-Methoxyphenyl)piperazine, 116
1-Methoxypoly(oxyethylene)benzocyclobutene, 493, 495
Methoxypropyl cyanoacrylate, 488, 489
4-Methoxy-2,2,6,6-tetramethyl-1-piperidinyloxy, 602
Methyl acrylate, 8, 349, 351, 365, 637, 639
Methylal, 286
Methylamine, 289

Index 745
9-Methylanthracene, 385
2-Methyl-2,4-bis(2,3-epoxycyclohexyloxy)pentane, 202
Methylbutynol, 334
p-Methylcalix[6]arene, 189
Methyl cyanoacrylate, 473
4-Methylcyclohexylmethyl methacrylate, 350, 351
Methyldichlorosilane, 327
N-Methyldiethanolamine, 675
Methyldiethanolamine, 359
2-Methyl-2,5-dioxo-1-oxa-2-phospholane, 32, 33
3-Methyl-1-dodecyn-3-ol, 334
4,4 ′ -Methylene bis(2-chloroaniline), 93
4,4 ′ -Methylene bis(3-chloro-2,6-diethylaniline), 93, 158
4,4 ′ -Methylene bis[3-chloro-2,6-diethylaniline], 176
4,4-Methylene biscyclohexyl diisocyanate, 73
4,4 ′ -Methylene bis(cyclohexyl isocyanate), 111
Methylene bis(4-phenyl isocyanate), 245
α-Methylene-γ-butyrolactone, 660, 665
4,4 ′ -Methylenedianiline, 158, 175, 402
p,p ′ -Methylene diphenyl diisocyanate, 113
4,4 ′ -Methylene diphenyl diisocyanate, 73
1,1 ′ -(Methylene di-4,1-phenylene)bismaleimide, 416, 423
N-(1-Methylethyl)-1-cyclohexyl-1-(diethylphosphono)nitroxide, 602
2,2 ′ -[(1-Methylethylidene) bis[(2,6-dibromo-4,1-phenylene)oxy]]
bis[4,6-bis[(2,4,6-tribromophenyl)oxy]]-1,3,5-triazine, 169
1,1 ′ -(1-Methylethylidene)bis(4-(1-(2-furanylmethoxy)-
2-propanolyloxy))benzene, 410
2,2 ′ -[(1-Methylethylidene)bis(4,1-phenyleneoxymethylene)]bis(oxirane), 150
Methylethylketone, 593
Methylethylketone peroxide, 28, 36, 597
Methylethylketoxime, 80
(4-(1-Methylethyl)phenyl)(4-methylphenyl)iodonium tetrakis
pentafluorophenylborate, 192
2-Methylfuran, 313, 433
5-Methylfurfural, 308
5-[2-(5-Methyl furylene vinylene)]furancarboxyaldehyde, 317, 318
3-Methyl-3-hydroxymethyl quinuclidine, 105
2-(5-Methyl-2-hydroxyphenyl)benzotriazole, 356
1-Methylimidazole, 101, 102, 176
Methylisobutylketone, 593
Methylisobutylketone peroxide, 593, 597
Methylisopropylketone, 593
Methyl-p-maleimidobenzoate, 424

746 Reactive Polymers Fundamentals and Applications
Methylmelamine, 300
Methyl methacrylate, 8, 27, 351, 352, 354, 362, 365, 507, 634, 670
Methyl N-methacryloylcarbamate, 351–353
2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 193
N-Methylmorpholine, 99, 101, 479
Methyl nadic anhydride, 180
7-Methyl-1,6-octadiene, 643
2-Methylolphenol, 267
4-Methylolphenol, 267
2-Methylphenol, 259
4-Methylphenol, 259
Methylphenylchlorosilane, 325
Methylphenyldichlorosilane, 328
Methylphenyldiethoxysilane, 325
Methylphenyldimethoxysilane, 325
1-Methylpiperazine, 104
2-Methyl-2-(4-piperidyl)-1,3-propanediol, 105
2-Methyl-1,3-propanediol, 6, 14
1-Methyl-3-propyl-5-butylmelamine, 300
2-Methyl-1,3-propylene diol, 93
Methylpropylketone peroxide, 40
2-Methyl-2-(4-pyridyl)-1,3-propanediol, 105
N-Methyl-2-pyrrolidone, 412, 421
Methyl salicylate, 515
α-Methylstyrene, 8, 328, 358
3-Methyl-1,2,3,6-tetrahydrophthalic anhydride, 180
Methyltetrahydrophthalic anhydride, 163, 180
Methyltricaprylylammonium chloride, 148
Methyltrichlorosilane, 327
Methyltriethoxysilane, 325
Methyltrimethoxysilane, 325, 331
Methyltris(methylethylketoxime)silane, 331
Methylvinyldimethoxysilane, 325
Mica, 19, 109
Monomethyl itaconate, 630
Montmorillonite, 20
cis,cis-Muconic acid, 573
cis,trans-Muconic acid, 573
Myrcene, 449, 465
Myristic acid, 366
Nadic anhydride, 400, 401, 637
1,5-Naphthalene diamine, 175, 178
1,5-Naphthalene diisocyanate, 73

Index 747
Naphthalene-1,5-diisocyanate, 69
β-Naphthol, 243
2-Naphthol, 419
1,2-Naphthoquinonediazide, 268
Naphthoquinonediazidesulfonic acid, 268
1-(α-Naphthyl)-3,3-di(2-hydroxyethyl)-triazene-1, 93
Natural rubber, 456, 461, 568
Neopentyl(diallyl)oxy tri(dioctyl)pyrophosphatotitanate, 25
Neopentyl glycol, 3, 5, 44, 90, 245, 362
Nitrokonjac glucomannan, 117
3-Nitroperoxybenzoic acid, 148
4-Nitroperoxybenzoic acid, 148
4,4 ′ -Nitrophenylazoaniline, 210
o-Nitrotoluene, 74
p-Nitrotoluene, 73
Nonafluorohexene, 345
Nonylphenol, 381
Norbornane diketimine, 176
5-Norbornene-2,3-dicarboxylic anhydride, 400
1-Octadecanethiol, 514
2,2,3,3,4,4,5,5-Octafluoro-hexane-1,6-diol, 150
Octamethylcyclotetraoxysilane, 540
1-Octene, 147
2-Octen-1-ylsuccinic anhydride, 671
n-Octylamine, 483
2-Octyl cyanoacrylate, 473
Octyl mercaptane, 641
(4-Octyloxyphenyl)phenyliodonium hexafluoroantimonate, 192
p-Octylphenyl salicylate, 356
Oxalic acid, 242
2-(6-Oxid-6H-dibenz[c,e][1,2]oxa-phoshorin-6-yl)-1,4-benzenediol, 141
2-(6-Oxid-6H-dibenz[c,e][1,2]oxa-phosphorin-6-yl)-1,4-benzenediol, 168
2-(6-Oxid-6H-dibenz[c,e][1,2]oxaphosphorin-6-yl)methanol, 168
4-Oxo-2,2,6,6-tetramethyl-1-piperidinyloxy, 602
2,2 ′ -Oxybis(N,N-dimethylethanamine), 103
4,4 ′ -Oxydianiline, 407
3,3 ′ -(Oxydi-p-phenylene)bis(2,4,5-triphenylcyclopentadienone), 410
4,4 ′ -Oxydiphthalic anhydride, 498
Palmitic anhydride, 639
Paraformaldehyde, 243, 245, 257, 262, 472
Pentabromobenzyl acrylate, 501
Pentaerythritol, 86, 90, 245, 291, 526, 622
Pentaerythritol triacrylate, 516

748 Reactive Polymers Fundamentals and Applications
Pentaerythritol triacrylate monophosphate, 684
Pentaerythritol trimethacrylate monophosphate, 665, 684
1,2,3,4,5-Pentamethylcyclopenta-1,3-dienide, 428
N,N,N ′ ,N ′ ,N ′′ -Pentamethyldiethylene triamine, 99
3,6,6,9,9-Pentamethyl-3-(ethyl acetate)1,2,4,5-tetraoxacyclononane, 592
3,6,6,9,9-Pentamethyl-3-n-propyl-1,2,4,5-tetraoxacyclononane, 592
2,4-Pentandione, 27
Perfluoro (alkyl vinyl ether), 467
Peroxyacetic acid, 147
Perylene(peri-dinaphthalene), 384
Phellandrene, 449
Phenol, 243, 259, 295, 307, 344, 452, 640
Phenolphthalein, 412
Phenolphthalein poly(ether ether ketone), 155
N-(1-Phenylbenzyl)-((1-diethylphosphono)-1-methyl ethyl)nitroxide, 602
Phenyl-(4,4 ′ -bismaleimidophenyl)phosphonate, 402, 422
3-Phenyl-3-tert-butylperoxyphthalide, 592
p-Phenyl diamine, 400
N-Phenyldiethanolamine, 699
N-Phenyl-1-diethylphosphono-2,2-dimethylpropyl nitroxide, 602
N-Phenyl-1-diethylphosphono-1-methyl ethyl nitroxide, 602
1-Phenyl-3,3-di(2-hydroxyethyl)-triazene-1, 93
1,3-Phenylene-bis(2-oxazoline), 514
2,2 ′ -(1,3-Phenylene)bis(2-oxazoline), 564
2,2 ′ -(1,4-Phenylene)bisoxazoline, 547
3,3 ′ -(p-Phenylene)bis(2,4,5-triphenylcyclopentadienone), 410
m-Phenylene diamine, 175, 178, 198, 272, 414
N,N ′ -m-Phenylenedimaleimide, 410, 547
N,N ′ -o-Phenylenedimaleimide, 410
N,N ′ -p-Phenylenedimaleimide, 410
4,4 ′ -[1,3-Phenylene(1-methyl ethylidene)]bisaniline, 498
Phenyl glycidyl ether, 142, 194
N-Phenylglycine, 193
2-Phenyl-2-imidazoline, 483
N-Phenylmaleimide, 182, 416, 428
Phenylmelamine, 300
Phenyl N-methacryloylcarbamate, 351–353
N-(1-Phenyl-2-methylpropyl)-1-diethylphosphono-1-methyl ethyl nitroxide, 602
o-Phenylphenol, 168
Phenylphosphonic acid, 186
3-Phenyl-1-propanol, 567
Phenyltrimethoxysilane, 30, 325
Phlogopite, 291

Index 749
Phosgene, 70
Phosphorus oxychloride, 186
Phthalic anhydride, 3, 5, 14, 35, 44, 89, 103, 113, 154, 180, 556, 626, 697
Phthaloyl chloride, 390
Picric acid, 17
Pimaric acid, 449
Pimelic acid, 44
Pinane hydroperoxide, 591
α-Pinene, 449
β-Pinene, 449
Piperidine, 186
Polyamide 6, 629
Poly(benzo[1,2-d4,5-d ′ ]bisthiazole-2,6-diyl)-1,4-phenylene, 495
Poly(butylene terephthalate), 214, 525, 541
Poly(ε-caprolactam), 550
Poly(ε-caprolactone), 480, 517, 518, 522, 523, 525
Poly(carbonate)dimethacrylate, 660
Poly(2,6-dichloro-1,4-phenylene oxide), 555
Poly(2,6-dimethyl-1,4-phenylene ether), 565
Poly(2,6-dimethyl-1,4-phenylene oxide), 549, 555
Polydioxanone, 488
Poly(2,2-di(4-phenylene)propane phthalate), 390
Poly(2,2-di(4-phenylene)propane phthalate-co-2,2-di(4-phenylene)propane
isophthalate), 390
Poly(2,2-di(4-phenylene)propane phthalate-co-2,2-di(4-phenylene)propane
terephthalate), 390
Poly(epichlorohydrin), 111, 112
Poly(ether ether ketone), 154
Polyetherimide, 417
Poly(ethylene-co-glycidyl methacrylate), 552
Poly(ethylene glycol)dimethacrylate, 351, 363, 662
Poly(ethylene glycol)methacrylate, 518
Poly(ethylene 2,6-naphthalate), 555
Poly(ethylene-octene) copolymer, 551
Poly(ethylene oxide), 153, 206, 533
Poly(ethylene terephthalate), 342
Poly(glycolic acid), 480
Polyglycolic acid, 488
Poly(p-hydroxybenzoate), 555
Poly(β-hydroxybutyrate-co-β-hydroxyvalerate), 517
Poly(3-hydroxybutyric acid), 480
Polyhydroxy fullerene, 144
3,4-Poly(isoprene), 459

750 Reactive Polymers Fundamentals and Applications
Poly(lactic acid), 480
Polylactic acid, 488, 519
Poly(lactide), 521
Poly(methyl methacrylate), 153, 533
Poly(oxypropylene)diamine, 205
Polyoxypropylene glycol, 389, 390
Poly(p-phenylene benzobisthiazole), 498
Poly(phenylene ether), 214
Poly(phenylene sulfide), 559
Poly(phthaloyl diphenyl ether), 418
Poly(phthaloyl diphenyl ether-co-isophthaloyl diphenyl ether), 418
Poly(propylene), 607
Poly(propylene oxide)diamine, 176
Poly(styrene), 152, 557
Poly(styrene-co-acrylonitrile), 153
Poly(styrene-b-(ethylene-co-butylene)), 542
Polysulfone, 390
Poly(tetramethylene ether), 513
Polytetramethylene glycol, 119
Poly(thiophene), 645
Polyurethane dimethacrylate, 659, 660
Poly(vinyl acetate), 26
Poly(vinyl chloride), 98
Poly(vinyl chloride-co-vinyl acetate), 26
Poly(vinyl chloride-co-vinyl acetate-co-maleic anhydride), 26
Poly(vinylidene difluoride-co-hexafluoropropylene), 435
Poly(vinylidene fluoride), 561
Potassium hydroxide, 16
Pristine, 20
1,2-Propanediol, 44
Propanephosphonic anhydride, 379
1,3-Propanesulfone, 119
2-Propenylphenol, 418
β-Propiolactone, 119
Propionaldehyde, 243
Propionamide, 263
4-Propoxy-2,2,6,6-tetramethyl-piperidin-1-oxyl, 615
Propylamine, 289
N-Propyldiethanolamine, 675
1,2-Propylene glycol, 3, 11, 14
Propylene glycol, 89, 93, 363, 366, 697
Propylene oxide, 6, 85, 86, 88, 545, 571
1-Pyrenesulfonyl chloride, 196

Pyrogallol, 481
2,2 ′ -Pyromellitdiimidodisuccinic anhydride, 92
Pyromellitic dianhydride, 36, 166, 180, 524
Pyrophosphoric acid, 489
Quinacridone, 695
o-Quinodimethane, 495
3-Quinuclidinol, 105
Rectorite, 109
Resin-modified glass ionomer cements, 663
Resorcinol, 243
Resorcinol dicyanate, 377
Retinol, 449
Rice starch, 629
Ricinoloxazoline maleate, 634
Rosin, 450
Rutile, 365
Sago starch, 544
Salicylaldehyde, 147
Salicylic acid, 103
Sebacic acid, 3, 45
Silicon oxycarbide, 338
Sisal, 25, 553
Sodium ascorbate, 334
Sodium dodecyl sulfate, 644
Sodium dodecylsulfate, 697
Sodium hypochlorite, 148
Sodium stearate, 565
Sodium sulfoisophthalate, 697
Sorbitol, 522
Sorbitol monoethoxylate, 522
Soy flour, 121
Squalene, 449
Stannous octoate, 107, 525
Starch, 121
Strychnine, 344
Styrene, 616
Styrene butadiene rubber, 465
Styrene-ethylene/butylene-styrene triblock copolymer, 541
Styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer, 542
Styrene oxide, 141, 142
p-Styrenesulfonic acid, 571, 647
Succinic acid, 90
Sucrose, 86, 205
Index 751

752 Reactive Polymers Fundamentals and Applications
Sulfanilamide, 146, 176
3-Sulfolene, 481
5-Sulfonatoisophthalic acid, 11
Sulfonic acid, 119, 324, 481, 644
2-Sulfonyl(meth)acrylate, 571
Sulfur dioxide, 472, 481, 482
Tapioca starch, 545
Tartaric acid, 120, 311
Terephthalic acid, 3, 5, 11, 35, 45, 89, 498, 555, 697
Terephthaloylbis(4-oxybenzoic) acid, 141
Terephthaloyl dichloride, 498, 516
Terpinene, 449
α-Terpineol, 201
Terpinolene, 449, 454
2,6,2 ′ ,6 ′ -Tetrabromobisphenol A, 32
Tetrabromobisphenol A, 3, 142, 168, 169, 357
Tetrabromophthalic anhydride, 3, 32, 33
α,α,α ′ ,α ′ -Tetrabromo-o-xylene, 493
Tetra-n-butylammonium chloroacetate, 103
Tetra-n-butylammonium cyanoborohydride, 484
Tetra-n-butyl ammonium fluoride, 483
Tetrabutylphosphonium acetate, 515
Tetrabutyltitanate, 421
Tetrachloromethane, 623
Tetrachlorophthalic anhydride, 27
1-Tetradecene, 147
Tetraethoxysilane, 110, 167, 325, 345, 681
3,3 ′ ,5,5 ′ -Tetraethyl-4,4 ′ -diaminodiphenylmethane, 175
Tetraethylene glycol dimethacrylate, 662
N,N,N ′ ,N ′ -Tetraethylethylene diamine, 483
Tetrafluoroethylene, 467
Tetraglycidyl diaminodiphenylmethane, 524
Tetraglycidyl-4,4 ′ -diaminodiphenylmethane, 144, 153
Tetrahydrofuran, 85, 309, 366, 414, 666
Tetrahydrofurfuryl cyclohexene dimethacrylate, 660
Tetrahydrofurfuryl methacrylate, 660, 661
Tetrahydrophthalic anhydride, 11, 180, 697
Tetrahydrophthalimide, 309
Tetrakis(4-hydroxyphenyl)ethane, 142
1,1,2,2-Tetramethoxyethane, 286
Tetramethoxysilane, 30, 325
Tetramethylammonium pivalate, 106
N,N,N ′ ,N ′ -Tetramethyl-1,3-butane diamine, 483

Index 753
Tetramethyldivinyldisiloxane, 331
N,N,N ′ ,N ′ -Tetramethylethylene diamine, 483
2,2,6,6-Tetramethyl-4-hydroxypiperidine-1-oxyl monophosphonate, 602
2,2,6,6-Tetramethyl-1-piperidinyloxy, 602, 603, 643
Tetramethyl-1-piperidinyloxy, 568
2,2,5,5-Tetramethyl-1-pyrrolidinyloxy, 602, 603
m-Tetramethylxylene diisocyanate, 75, 76
Tetrapropoxysilane, 325
Thermoplastic starch, 559
2,2 ′ -Thiobis[4-tert-butylphenol], 248
Thiourea, 299
Thiuram disulfide, 608
Tin-di-n-butyl-di-3,5-amino benzoate, 109
Tin oxide, 357
Titanium n-butoxide, 200
Titanocene, 673
Toluene diamine, 86
2,4-Toluene diisocyanate, 73, 123
2,6-Toluene diisocyanate, 73
Toluene diisocyanate, 407
p-Toluenesulfonic acid, 15, 79, 242, 311, 312, 324, 400
Tosyl isocyanate, 108
Triallyl cyanurate, 8, 10
Triallyl isocyanurate, 211, 548
2,5,8-Triamino-1,3,4,6,7,9,9b-heptaazaphenalene, 299
Triarylsulfonium hexafluoroantimonate, 208
1,5,7-Triazabicyclo[4.4.0]dec-5-ene, 483
1,3,5-Triazine-2,4,6-triamine, 299
Tributylamine, 675
Tri-n-butylborane, 668
Tributylborane, 672
Tributylphosphine, 483
1,2,4-Trichlorobenzene, 567
Tri(p-chloro phenyl)phosphine, 253
Tri(p-cresyl)phosphate, 476
Tricresyl phosphate, 357
Triethanolamine, 86, 104, 208, 284, 293, 669, 675
Triethylamine, 99, 101, 121, 253, 264, 265, 514, 544
Triethylborane, 670
Triethyl citrate, 366
Triethylene diamine, 101
Triethylene glycol diacrylate, 369
Triethylene glycol dimethacrylate, 659–661, 675

754 Reactive Polymers Fundamentals and Applications
Triethylene glycol divinyl ether, 10
Triethylene glycol methylvinyl ether, 187
Triethylenetetramine, 175
Tri(2-ethylhexyl)phosphate, 476
Triethyl phosphate, 111, 112, 476
Triethyl phosphite, 623
3,6,9-Triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, 594, 607
Triflic acid, 185, 322
Trifluoromethanesulfonic acid, 185
3,3,3-Trifluoropropyltrimethoxysilane, 325
Triglycidyl isocyanurate, 141
Triglycidyloxy phenyl silane, 141, 168, 169
Triisopropanolamine, 675
Trimellitic anhydride, 11
Trimercaptothioethylamine, 176
Trimercaptotriethylamine, 208
1,2,4-Trimethoxybenzene, 193
Trimethoxysilane, 391
3-(Trimethoxysilyl)propyl methacrylate, 631
Trimethylamine, 268
2,4,6-Trimethylbenzoyldiphenylphosphine oxide, 37, 39, 662
Trimethylborate, 311
Trimethylchlorosilane, 327
3,7,11-Trimethyl-1-dodecyn-3-ol, 334
Trimethylene glycol-di-p-aminobenzoate, 93
3,5,5-Trimethylhexanoyl peroxide, 592
Trimethylmelamine, 300
Trimethylolethane, 245
1,1,1-Trimethylolpropane, 76, 89, 93
Trimethylolpropane, 3, 86, 89, 245
Trimethylolpropane diallyl ether, 11
1,1,1-Trimethylolpropane dipropenyl ether, 10
Trimethylolpropane mono allyl ether, 3
1,1,1-Trimethylolpropane triacrylate, 473, 632
Trimethylolpropane triacrylate, 351, 513, 638
1,1,1-Trimethylolpropane trimethacrylate, 660
Trimethylolpropane trimethacrylate, 27
Trimethylolpropyl trimethacrylate, 662
2,4,6-Trimethylphenol, 259
4-Trimethylsiloxybenzocyclobutene, 493
Trioctyl trimellitate, 476
Trioxane, 243
Triphenylphosphine, 253

Triphenylphosphine oxide, 428
Triphenyl phosphite, 565
2,4,6-Triphenylpyrylium tetrafluoroborate, 485
Tripropylamine, 675
Tripropylene glycol diacrylate, 638
Tris(2-allylphenoxy)-s-triazine, 435
Tris(2-allylphenoxy)triphenoxy cyclotriphosphazene, 435
Tris(2-aminoethyl)amine, 484
Tris(2-chloroethyl)phosphate, 357
2,3-Tris(dibromopropylene)phosphate, 627
2,4,6-Tris(dimethylaminomethyl)phenol, 106, 179
1,3,5-Tris(3-dimethylaminopropyl)-s-hexahydrotriazine, 101
N,N ′ ,N ′′ -Tris(5-hydroxy-3-oxapentyl)melamine, 300
1,1,1-Tris(4-hydroxyphenyl)ethane, 210
Tris(2-hydroxyphenyl)phosphine oxide, 169
Trismercaptopropionate, 427
Tris(p-toluenesulfonato)iron(III), 697
2,4,6-Tris(2,4,6-tribromophenoxy)-1,3,5-triazine, 169
Trypsin, 647
Turpentine, 450
10-Undecene-1-ol, 644
10-Undecenyl sulfate, 644
Urethane dimethacrylate, 675
Vanadium acetylacetonate, 38
Vermiculite, 273, 291
Vernonia oil, 141
Vinyl acetate, 290, 634
Vinylbenzyldodecyldimethyl ammonium chloride, 20
Vinylbenzyloctadecyldimethyl ammonium chloride, 20
Vinyl-4-tert-butylbenzoate, 638
N-Vinyl carbazole, 190
4-Vinyl-1-cyclohexene, 328, 329
Vinylcyclohexene epoxide, 141
N-Vinylformamide, 285
Vinylidene fluoride, 366
Vinyloxazoline, 573
Vinylpyridine, 8
1-Vinyl-2-pyrrolidinone, 290
N-Vinyl pyrrolidone, 641
Vinylpyrrolidone, 52
p-Vinyltoluene, 8
Vinyltriethoxysilane, 631
Vinyltriethylsilane, 631
Index 755

756 Reactive Polymers Fundamentals and Applications
Vinyltrimethoxysilane, 325, 631
Vinyltrimethylsilane, 631
Wollastonite, 23, 24
Zeolite, 109
Zinc chloride, 311
Zinc 2-ethylhexanoate, 360
Zinc hexacyanocobaltate, 87
Zinc hydroxystannate, 32
Zinc naphthenate, 381
Zinc octoate, 334, 381
Zinc stearate, 25, 695
Zirconium hydroxide, 357
Zirconium oxide, 677, 678
Zirconium tetrachloride, 179
Zirconyl chloride, 681
Zirconyl dimethacrylate, 681

757
GENERAL INDEX
Index Terms
Links
Ablative properties
allyl boron compounds 419
AC-calorimeters 194
Acceleration
gelation 168
polymerization 42 477
Accelerators 38
crosslinking 331
crown ethers 478
cyanoacrylates 477
dental polymers 669
ester-type 264
Acetals
cosolvents for UF 286
cyclic 91 658
dichlorobenzaldehyde 206
melamine/urea/formaldehyde resins 286
Acetylation
sisal 553
starch 639
Acid-base reactions 697
Acidolysis reaction
poly(carbonate) 561
polyester 555
Acoustic ceiling tiles 303
Acrylic resins
films 365
Adhesion
amino-functionalized polysiloxane 345
coupling agent 391
coupling sites 269
cyanate ester resin 391
dental polymer 682
graphite/bismaleimide composite 435
hybrid resins 160
interfacial 523
interlaminar 19
plasma activation 648
self-assembling polymers 343
sisal fibers 553
tackifiers 456
terpene phenol resin 463
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758
Index Terms
Links
to glass fibers 8 23
to Kevlar fiber 434
to nonpolar substrates 483
to oily surfaces 156
Aerobic degradation 519
Aerodams 517
Aerospace applications 24 197 322
Aerospaceapplications 373
Agave sisalana 552
Agricultural applications 245 295 308
Alder-ene reaction 400 642 643
Alkenoylcarbamates 352
Allophanate 92
Amalgam replacement 657
Amphiphilic polymers 141
Anti-punk properties 255
Antibodies 433
Anticarcinogenic activity 142
Antifoaming agents 340
Antifouling compositions 344
Antioxidants 338
chewing gum 466
grafted 632
Antiplasticizers 159
hyperbranched polymers 144
Antistatic formulations 167 360
Aryl cyanates
hydrolysis 375
Autocatalysis
isocyanate 114
phenol 179
Autocatalytic curing 379 382 427
Autocatalytic polyol 88
Automotive applications 98 160 203 241 322 517
Backbiting 423 520
Backcoats 343
Bagasse 24 307
Base-catalyzed
equilibration polymerization 325
inorganic bases 253
Batch cell method 353
Batteries 167 363
lithium 122
Benzene yellow 695
Beverage containers 525
Binders
abrasive 266
friction 266
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759
Index Terms
Links
glass fibers 251 266 294 316
petroleum recovery 266
sand 266 316
Bioabsorbable polymers 488
Biocomposites 363
Biodegradability
poly(lactide) 521
starch 522
Biodegradable
composites 161
compositions 517
epoxy-polyester resins 205
grafted polymer 518
Lysine-diisocyanate 73
poly(lactide) 521
polyesters 52
terpene resins 459
Biofibers 161
Biuret 92 96
Blow molding 524
Blowing
chemical 94
epoxy resins 203
formic acid 95
physical 95
Blowmolding 517
Bonding
adhesive 648
adhesives 475
chemical 24 154 254
covalent 648
hydrogen 122 488 639
interfacial 22 161 212
interphase 152 535
polyolefin substrates 485
primers 482
Bone cement 49 52 688
Bookbindery 462
Boron trifluoride complexes 175 179
Bottles 46 519
Bragg reflector mirrors 504
Brake composites 273
Bridges
dental 672
ether 286
methylene 248 251 286 312
methylene-ether 310
phenoxy 261
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760
Index Terms
Links
silicon groups 402
Brittleness 1 155 255 397 466 501
519 700
Brunauer Emmett Teller equation 543
Bubbles 38 273 356 462
Building materials 47 204 340 360 365 368
Bumpers 517
Cables 341 631
Calcification 120
Capacitors 164 363
Capillary flow microreactor 304
Carbon
glass-like 271 313
Carbon black 694
Carbonylation
propyne 353
urethane 70
Carboxybetaine
grafting 119
Carboxylation 272
Caries 682
Cashew nut shell liquid 25
Cassava 544
Cast elastomers 69
Casting 47 116 182 204
polymerization 358
sand binders 313
steel 294
syrups 349
Catalysis
acidolysis 561
copolyesterification 14
enzymatic degradation 488
isomerization 6
latent 107
titanium dioxide 428
urethane 103
zwitterions 103
Catalysts
addition-fragmentation 190
delayed-action 103 179
latent 107 176 184 311 386
organometallic 106
Cavitation
shear banding 152
ultrasonic curing 312
Ceiling temperature 482 510 511 617 620
Cement
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761
Index Terms
Links
bone 52
dental 669
furan resins 313
Ceramics
aluminum nitride 421
microcellular 338
synthesis by pyrolysis 336
Chain
branching 608
entanglements 26 166
reversible termination 567
Chain extenders 110 121 156 400 514 524
diols 31
for polyesters 52
glycols 92
photosensitive 92
waterborne 93
Chain extension
BCB 498
Diels-Alder reaction 407
diglycidyl compound 525
Michael addition 407
polyaddition 524
Chain scission 534 590
shear induced 614
UV 365
Chain stoppers 330 498
undecanol 3
Chain transfer 184 343 514 587 631
mercaptan 82 641
Charge carrier 51
Charge control
toner 51
Charring
agents 112
aromatic polyesters 89
Chelates 38 122 123 182
Chemoreceptors 189
Chewing gums 465
Chitin
N-deacetylation 118
Chlorodioxins 292
Chlorofluorocarbons
blowing 95
Chlorosulfonation 434
Chromatography
packing materials 314
stationary phases 189
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762
Index Terms
Links
Chrome yellow 695
Chromophore
conjugated furans 317
Disperse Orange 3 209
maleimide 427
phenylazo-benzothiazoles 210
Clay, see also Oganoclays 162
Hectorite 18
macroporous 271
nanocomposites 540
organo 162
organophilic 20
Rectorite 109
Cloud point 152 157 195 454 458
Co-condensation
melamine and urea 302
urea resins 286
Co-continuous phase 27 167 389 390 417 543
Coagulation 304
Coal-tar pitches 315
Coalescence
dispersed droplets 211
dispersed phase 538 540
prevention 546
viscosity dependence 211
Coatings 1 3 48 86 120 180
203 322 365 422 463
waterborne 203
Coconut shells 270
Coefficient
diffusion 687
extinction 192
friction 50 199 465
heat transfer 509
thermal conductivity 509
thermal expansion 146 375 400
Cohesion 352 461 701
Cohesion energy density 621
Colloidal silica 688 695
Colorant 51 466
Colorants 694
Coloration 15
Coloring agents
toners 694
Comb-like polymers 82 87 484
Combustion 30 116 292 336 666
Comonomer assisted grafting 633
Compatibilizers
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763
Index Terms
Links
block copolymers 157
epoxy resins 212
grafted polymers 615
UP resin 49 53
Composites 397
hydrophobic 665
rigid rod-like 498
wood flour 541
Condensation
base-catalyzed 471
Calixarenes 189
crosslinking 334
hydrolytic 322
intermolecular 330
Knoevenagel 472
resols 247
Conducting glues 167
Conducting paints 167
Conductivity
electric 207
ionic 123
thermal 19 207 377 386 421 509
Consolidation
restoration materials 205
sand 317
Controlled-release
drugs 304
fertilizers 206
Coordination catalysts 182
Copolymerization
cationic 187
Corona discharge 482 646
Corrosion
problems 96 103 379
resistance 12 51 203 313 378
Cotackifiers 456
Coupling agent 328
for compatibilization 548
for sisal fibers 25
silane 24 161 343 658
Crack front 158
Crack front bowing 158
Crack propagation 158
Crack trapping mechanism 23
Crazing 358
Critical solution temperature 461
Crosslinkers 472 501
Crosslinking inhibitor
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764
Index Terms
Links
N,N-dimethylformamide 623
Crown ethers
accelerators 478
polymerization retarder 187
Crystallinity reduction 89 122 213 543 564
Curing
fluorescence response 196 381
microwave 198 427 498 676
ultrasonic 312
Cycloaddition 317 410 495
anisotropic 208
Cyclocondensation
phenols 248
Cyclotrimerisation 379 382
Cyclotrimerization 379 388
Cytocompatibility
polyurethane 120
Cytotoxicity 687
HEMA monomer 663
spiroorthocarbonates 185
Deep-drawing 559
Degradation
acid 115
competitive crosslinking 53
controlled rheology 618
enzymatic 366
glycolytic 200
hydrolytic 118 431
mechanism 601
microbial 459
photo 365
thermal 21 116 387
Dehydrobromination 645
Dehydrochloration 148
Dehydrochlorination 101 204 637 645
Dehydrodecarboxylation 410
Dendrimers 80 144 484
Depolycondensation
polyurethane 116
Depolymerizable systems 488
Depolymerization 45 459 526
Devices
electronic 164 167 211
electrophotography 693
medical 341
optical 209
photocopying 341
Diacyl peroxides 36 593
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765
Index Terms
Links
Diatomaceous earth 539
DiBenedetto equation 424
Dicarboxylic acid
a,b-unsaturated 19
Dielectric analysis
a-relaxation 195
Dielectric loss factor 195
Diels-Alder polymerization 410 428
Diels-Alder reaction 15 309 400 411 434 643
o-xylylene 495
retro 260 313 410 433
Diisocyanates
blocked 79
Dimer
a-methyl styrene 641
Dimerization
isocyanates 106
Dinnerware 303
Dip-coating 270
Discoloration 87 98 669
Dispersive mixing 518
Disproportionation termination 605
Diterpenes 448
Donor-acceptor complex 144
Drug release 366
Dual initiator system 28
Dynamic fracture toughness 22
Elasticity
improvement 269 300
melt 517 538
Electrochromic devices 122
Electrochromic windows 207
Electrodeposition 203
Electroless plating 215
Electrolytes
gel-type 207
photosensitive 317
solid 122 207 363
Electronparamagnetic resonance 646
Electrophotography 693 694
Emission suppressants 11 18 255
End groups
amino 565
carboxyl 214
functionalization 569
Enzymatic synthesis 84
Epoxidation reaction 146 147
Estrogenic activity
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766
Index Terms
Links
dental resins 687
Exchanger
cation 481
Exfoliation
nanoclays 111
nanocomposites 163
Expandable graphite 33 111
Explosive polymerization 190
Fermentation 517 521
Ferroelectric film 362
Fibers 161 332
Aramid 310
binder 257 294 321
biodegradable 521
carbon 24
coupling agent 161
cure inhibiting 24
fused-silica 96
glass 23 678
graphite 385
insulation 267
jute 25
Kevlar 434
mineral wool 317
natural 24
poly(ethylene) dyeing 646
polyester 89
sisal 552
strength improvement 315
Fillers 19 259 331 677
dental 84
flame retardant 378
natural fibers 24
plant-based 21
Film blowing 524
Flame retardants 31 111 168 291 356
Flammability 33 303 378 501
Flash point 336 600
Flexibility enhancers 154
Flip-chip manufacturing 206
Flocculation
sewage treatment 265
Flory-Huggins interaction parameter 533
Flow improvers 52
Fluorescence response 196
Fluorocarbons
blowing 95
Flyash 21
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767
Index Terms
Links
Foams 109 266 273
ceramic 122
flexible 86
floral applications 266
microcellular 338
PET 524
rigid 76 86
Footwear 560
Formaldehyde
dispersions 257
exothermic hazards 254
free 275
hydroxylamine titration 275
low emission types 255
ratio to phenol 250
reduction 256
resol resins 257
scavengers 256
Foundries
furan binders 316
Foundry sands 294
Fragrant oil
encapsulation 304
Friedel-Crafts
alkylation 569
catalysts 311 452
reaction 405
Fries rearrangement 514
Furan
photosensitive polymer
electrolyte 317
Functionalization
block copolymers 542
macromonomer 82
montmorillonite 20
of nitrile rubber 560
poly(lactide) 520
poly(propylene) 546 617
star branched polymers 163
terminating reagents 567
Furniture coatings 37 47
Gardner scale 458
Gel coat 5 10 12 18
Gel point 41 194 388 424
thermal mechanical analysis 42
Gelling 96
catalysts 94
hybride resins 30
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768
Index Terms
Links
inhibition 338
preliminary 16 322
reduced contraction 676
viz. blowing 101
Gels
drug delivery system 206
thermoreversible 435
Glass transition temperature
IPN 29
modelling 153
structure properties relationships 44
Gloss polyesters 19
Glue resins 283
Graphite 694
Gratings 504 644
Grignard
reagents 321
synthesis 328
Halomethylation 272
Hantz reaction 284
Hanza yellow 695
Hardeners 176 263
Hemp 23
Hildebrand solubility parameter 452 455
Himalaya pine 449
Hindered amine light stabilizers 36
Hock process 140
Holography 209 644
Hot-melt adhesive 459 462
reactive 114
Hot-melt extrusion
adhesives 460
Household applications 203 341 360 361 368
Hydrocarbonylation
ethene 353
Hydrogels 205
Hydroperoxides 590
Hydrosilylation 328 616 643
aromatic compounds 328
crosslinking 335
inhibitors 333
platinum complexes 333
silicones 199
Hydrosylilation 391
Ignition point
peroxides 591
Image
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769
Index Terms
Links
latent 693
Indene resins 462
Inhibitor
coloring 17
silicones 327
trimerization 106
Inhibitors
anionic polymerization 480
crosslinking 623
grafting 623
hydrosilylation 333
radical polymerization 16 17 328 352 677
Iniferter Method 567
Initiation
ultrasonic 628
Initiator systems
dual 676
Initiators
anionic 428 485
atom transfer radical
polymerization 461
cationic 183
controlled rheology 589
dental polymers 669
dual 28
encapsulated 384
functionalized 624
iniferter method 567
latent 186
peroxide 35
radical 358 387
redox 658
UV-sensitive 48
Insertion
carbene 631
epoxide 182
epoxy 386
intercalation 162
vinyl monomer 568
Intercalation 162 540
melt processing 109
Interfacial slip 534
Interlayers
charged 162
Intramolecular cyclization 423
Intumescence 113 526
Ionomers
acrylic modified polyolefins 554 555
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770
Index Terms
Links
polyurethane 110
Iron black 694
Isocyanates
comb-like 82
phosgene-free synthesis 70
Isomerization
allyl ether 10
oxazoline 386
propylene oxide 87
unsaturated polyester 6
Jute 23 25 259
Karstedt catalysts 328 333 391
Keratinization 487
Ketone Peroxides 36
Kinetics
autocatalytic curing 153 257
crosslinking 117
curing 40 114 166 669
cyclotrimerization 389
grafting 623
infrared spectroscopy 423
intragallery curing 163
isomerization 6
monitoring 193
peroxide decomposition 599
photopolymerization 675
polyesterification 14
polymerization 249
self-catalyzed reaction 16
water content 262
Knoevenagel reaction 472
Laminates
continuous fibers 161
hyperbranched polymers 145
printed circuit boards 385
Lenses 208
Lignin 523
Low-profile additives 21 26
Lubricants 160
Macroradicals 516 612 618 621 624 633
poly(propylene) 547
Mandioca 544
Manicure compositions 486
Manihot 544
Manioc 544
Mannich
bases 179
reaction 264
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771
Index Terms
Links
Marble
artificial 361
conservation 365
Masterbatches
peroxides 595
Mechanochemistry 612
Melt condensation 14 16
Melt phase boundaries 531
Membranes
carbon 270
dialysis 636
drug release 366
molecular sieves 270
polyurethane 109
reactive 206
thermally stable 435
Mercury porosimetry 543
Mesomorphic phases 553
Metallocene catalyst 642
terminal unsaturation 569
Metallocene salts 485
Methylene blue 695
Methylolation 286
Michler’s ketone 189
Microcapsules 296
controlled-release of drugs 304
Microcracking 44 159
Microfibrils 555
Microfiltration membranes 270
Microgels 151 698 699
Microvoids 26 44
Microwave curing 197
Mixer
batch 53 566
Brabender 550
cavity transfer 612
extruder 513 531
Plasti-Corder 555
static 612
Modifiers
alkenyl 374
conductivity 161
epoxy adhesives 203
epoxy resins 112
impact strength 606
interphase 537
liquid rubber 156
melt strength 524
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772
Index Terms
Links
polyterpene resins 462
tiazone 289
toughness 212 290 389 417
unaturated polyester 6
urea resins 300
Modulus
compression 21
elastic 121 199 377
flexural 20 21 378 389 590
shear 434
storage 388 405 643
tensile 20 45 544 553
Moisture barriers 460
Molecular sieve 270 522
Monomer reactivity ratios 28 40 635
Monoterpenes 448
Multi-initiator systems 676
Multiring monomers 405
Multivariate analysis 196 432
Müller-Rochow process 327
Nail chapping 486
Nanocomposites 22 532 540
clay 540
intercalation 20
layered silicate 111 162
montmorillonite 111
rectorite 109
silica 110
silicate 377
Nanofibers 678 680
Nanofillers
silsesquioxane 421
Nanoparticles
layered silicate 164
metal oxide 678
titanium dioxide 22
Nanotubes 161
Natural rubber 366 449
epoxidized 22
Nematic
acrylics 663
film 208
network 146
Neoprene rubber 461
Network
breaking 201 313
hybrid 31 167
interlock 29
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773
Index Terms
Links
interpenetrating 28 29 117 164 210 388
429
liquid crystalline 146
nonazeotropic composition 40
porous 435
reduction of crosslink density 374
reinforcement 247
reversible 201
silicone 331
unsaturated polyester 1
Nigrosine 694
Nitroxides
cyclic 568
Nitroxyl radicals 602
Nonlinear optics 209 435
Novolak 142
bismaleimide-modified 421
cyanate ester 377
diallyl bisphenol A 400
epoxy resin 168 387
resin 241 247
thermoplastic 640
toughener for 466
Nucleation 304 390 551
Number
acid 16
Avogadro 621
hydroxyl 89
Sherwood 510
Optical applications 141 176
benzocyclobutene 504
Optical resins 207
Organisms
aquatic 344
Organoclays 18 20 162
Oxamides 103
Ozone
depletion potential 95
resistance 340 461 560
treatment 503
Paintability 571
Paper release agents 341
Paraffin wax 19 455
Particle collisions 538
Peresters 36 595
Peroxides
flash points 600
half-lifes 600
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774
Index Terms
Links
Phase transfer catalyst 148 514
Phosgenation 73 74
Phosgene
reaction of bisphenol 514
Phosphorylation 272
Photo curing 197 485
Photoalignment method 208
Photochemical
bromination 645
chlorination 645
generation of dienes 411
reaction 209 317
Photodimerization
chalcone 208
Photoinitiators 36 52 186 384 673
cationic 188
radical 193
visible light 190
Photopolymerization 30 675
cationic 186 189
postpolymerization 187
radical 206
Photoresist
gratings 504
negative 92 384
positive 268
Photostability 209
Photostabilizers 681
Phytotoxicity 317
Pine resin 450
Plasma treatment 644
Plasticizers
cyanoacrylate esters 475
Plasticizersepoxy resins 167
Polyamide 6
g-crystals 551
Polyesterimides 418
Polymerization
anionic 485
coordinative 182
emulsion 154 555
Enthalpy 511
Entropy 511
furfuryl alcohol 316
living 82
metathesis 512
multibranching 144
suspension 340 696
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775
Index Terms
Links
Polymers
heat-resistant 110 325 342 414 428
hyperbranched 144 212 412 484
self-healing 296
telechelic 568
Polyphosphazenes 208
Polyurea resins 92
Polyurethane
waterborne 122
Postcure treatment 197 414 425 675
Postpolymerization
photo curing 187
Pot life 17 40 42 179 182 384
Pour point depressants 49 52
Powder coatings 48
Prepregs 386 397
Pressure-sensitive adhesive
hot-melt 642
Primers 482 483 688
Printed circuit boards 162 204 332 342 385
Printing inks 186 454
Printing medium
ink-jet 368
toner 693
Promoters
adhesion 615 663 682
amine 29
dental polymers 668
redox 37
silicone synthesis 327
visbreaking 274
Pulse-cure method 676
Pyrones
cycloadduct 410
Quinoline yellow 695
Radical
b-scission 593 608
branching 516
chlorination 645
copolymerization 40
coupling 534
diffusion control 29
grafting 521 541 611 614
grafting kinetics 623
induced decomposition 627
inhibitor 670
initiator 34
photoinitiator 186
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776
Index Terms
Links
polymerization kinetics 42
scavenger 643
stable 601 614
telomerization 82
Radical polymerization
atom transfer 567 568 569
bismaleimides 412
chain transfer 343
cyanoacrylate 485
living 567
ring opening 665
Reactive solvents 210 246
Reactors
bent loop 509
Recombination termination 618
Reductive amination 92 104
Reinforcing materials
epoxides 161
unsaturated polyesters 23
Relaxation
dipol 195
viscoelastic 389
Renewable resources
vegetable cellulose 307
Residence time 507 508 513 571 590 608
613 698
Resistance
hydrolytic 3 90
impact 22 31 554 571
thermal 20 50
Reworkable resins 201
Rigidity control 8 44 89
Ring and ball method 458
Rubber tackifier 6
Rutherford back-scattering technique 646
Salicylates
ultraviolet absorbers 356
Sanitary products 47 341 361 462 558
Sawdust 21 24
Scaffold 119
Scavengers
acid 90
formaldehyde 251 256
Schiff bases 147
Schotten-Baumann reaction 663
Schulz-Flory distribution 88
Scission
homolytic 601
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777
Index Terms
Links
Sealants 341 460
Self-extinguishing
unsaturated polyesters 32
Sequence length
reactivity 14
Sesquiterpenes 448
Sewage treatment
phenol/formaldehyde resins 265
Shrinkage 35 42 107 198 662
cationic polymerization 666
control 27
cyclic monomers 665
low profile additive 28
measurements 28
strain 676
Silacrown compounds
preparation 478
promoter 478
Silaferrocenophanes 325
Silly putty 321
Silsequioxane resins 322
Sisal 23
Sizing agents 463
Softening point 458 462
Soil amendment 295
Solubility parameters
peroxides 621
solvents and polymers 457
Solvents
aprotic 412
Solvolysis 37 114 200
Spin-coating 210
Spoilers 517
Stabilizers
acid 472
efficiency 622
foam 340
polyvinyl chloride 204
storage time 79 480
UV 573
Starch
acetylated 639
amylose 639
blend 522 523
cassava 545
corn 248 639
esterification 639
grafted 517 637 639
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778
Index Terms
Links
modified 523
rice 629
sago 544
tapioca 545
thermoplastic 559
Steam
activation 272
distillation 450
hydrolysis 526
treatment 259
Stereolithography 367
Steric hindrance 14 101 166 424 425 427
639
Storage time
inhibitors 17
phenolic resin 268
unsaturated polyester resin 18
Strength
bond 475
cohesive 472
compressive 13 19 267 498 663
flexural 20 21 24 25 322 332
384 388 389
peel 156 199 385 456
tensile 22 29 111 117 121 159
291 389 431 435 484 544
563 630
Sulfonation 272
Supercritical carbon dioxide 618
Superglues 471
Surface metallization 215
Swelling
chromatography support 315
drug delivery system 206
jute 259
Syrups
casting 349
Tackifier 366 456
Tackifying resin
waterborne 460
Tapes
adhesive 203 342 462
Tapioca 544
Tempera paintings 366
Tetraterpenes 448
Thermal cracking 274
Thermal transfer ribbons 342
Thermochromic dyes 686
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779
Index Terms
Links
Thermolabile linkages 201
Thermolysis 184
peroxyketals 626
recycling 200
Thermotropic polymers 498 553
Thickeners 480
Thixotropic
additives 18
resins 13
Tint agents
dental polymers 659 682
Tissue adhesives 487 488
Toners
bisphenol A fumarate 51
low fix temperature 698
styrene-acrylic resin 698
textile printing 700
Top coat 5
Tougheners 212 417
dendrimers 144
rubbers 156
Toxicity
isocyanates 79
maleic anhydride 622
silacrown ethers 478
tissue adhesives 487
Transesterification 5 89 200 264 472 478
515 525 554
zinc acetate 45
Trimerization 381
Triterpenes 448
Trommsdorff effect 29 42
Ultrasonic
assisted extrusion 532
curing 312
initiation 628
reactor 115
Ultraviolet absorbers 36 356
Ultraviolet stabilizers 36
Unsaturated polyesters
Π-interactions 30
waterborne 10
Urdiol 84
Urethane dimethacrylates 84
Uretonimine 77
Vector fluids 549
Vinyl offset 698
Vinyl staining 98 105
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780
Index Terms
Links
Visbreaking 274
Viscosity
branched polymers 525
chain stopper 668
controlled rheology 590
grafting 618
hot-melt adhesives 462
interfacial slip 534
intrinsic 524 573
liquid crystalline polymer 554 663
reactive diluents 400
thickeners 480
vis-breaking processes 606
Visible light sensitizer 190
Vitrification 166 195 367
Wagner-Jauregg reaction 425
Wastewater treatment plants 519
Water sorption 431 678 686
Wetting agent 317
Whiskers 161
Xanthens 259
Yucca 544
Zwitterionic salts 103
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