Black Pigments for Molded Thermoplastic Applications - Cabot ...

Black Pigments for Molded
Thermoplastic Applications

2
Black Pigments for Molded Thermoplastic
Applications
The purpose of this brochure is to present the critical requirements for
carbon black selection in molded thermoplastic applications.
Star Diagram: Balance of Properties
A visual and accessible way to compare different carbon black
pigments on their relative suitability in molding applications is the star
diagram. This star diagram compares the performance of three black
pigments in terms of five key performance criteria. These
performance measures are discussed in more details in this guide.
Carbon Black Value Chain for Molding
Masterbatch Producers
Commodity Polymers
(eg. PE, PS, PVC, etc)
Carbon Black Suppliers
Compounders
Converters/Contractors
Equipment Manufacturers
Regular Color Molding Pigment
Medium Color Molding Pigment
High Color Molding Pigment
The value chain pictured here represents how carbon black is
supplied into the thermoplastic molding market. The carbon black is
either sold to a masterbatch producer or directly to a compounder.
This depends on whether the compounder has carbon black
dispersion capability. The compounder will dilute the masterbatch
produced internally or externally to the end use carbon black loading,
and then sell the material to a converter or contractor. The converter
will mold the final part, which will be supplied to the final equipment
manufacturer.
Engineering Polymers
(eg. ABS, PC, PA, etc)
UV
Stability
Color Strength
Masterbatch
Dilutability
Dispersability Blue Tone
Performance improves from chart center

Major Applications
The major carbon black usage in thermoplastic molding is shown in this table. The majority of carbon black
demand is found in automotive applications. Performance requirements vary depending on the final
applications, but color strength and surface appearance are common requirements expected from carbon black
compounds.
Segment
Automotive
Polymer Type Color Strength
Surface
Appearance
Exterior PP>ABS>PC/ABS>PA •• ••
Interior ABS>PP>PC/ABS>POM •••• ••••
Under the Hood PA>POM>PP •• ••
Electronics ABS blend>PC>POM •••• ••••
Household Appliances ABS blend>PC •••• ••••
• = Indicates the degree of importance of the performance requirements
Performance Measures
We have defined the performance measures for the molding of black thermoplastic compounds. We have organized
them into the following general critical requirements which may vary in importance depending on the application:
• Color Strength • UV Stability
• Carbon Black Dispersability • Blue Tone
• Masterbatch Dilutability
Mechanical Properties (Impact, Flex/Tensile Modulus, HDT) and Surface Appearance (Gloss, Pitting) are both influenced
by the carbon black loading, the carbon black dispersion quality, and the masterbatch dilution homogeneity.
Color Strength
The color strength is a measure of the total visible light absorbency of the pigmented molded polymer part. The higher the
total visible light absorbency, the darker, blacker or jetter the molded part will be. The color strength is dependent on:
• Type of Carbon Black • Carbon Black Dispersion Quality
• Carbon Black Concentration • Masterbatch Dilution Homogeneity
• Type of Polymer Matrix
Color Strength (%)
140
120
100
80
60
40
20
0
Color Strength vs. Pigment Type and
Pigment Concentration in ABS
0%
0.50% 1.50%
Pigment Concentration (%)
Regular Color Molding Pigment
Medium Color Molding Pigment
High Color Molding Pigment
Color Strength (%)
300
250
200
150
100
50
0
Color Strength vs. Pigment Type and
Pigment Concentration in Polyamide
0%
0.50% 1.00% 2.00%
Pigment Concentration (%)

Carbon Black Dispersability
Carbon black dispersability is the ease with which the pigment can be wetted with the masterbatch carrier resin and
subsequently be de-agglomerated. This performance measure is primarily dependent on the morphology of the carbon
black pigment. It can be approximated by calculating the strength of an agglomerate, in other words, the attractive force
one needs to overcome to separate the agglomerates into discrete carbon black aggregates. This measure is
independent of the system one uses to disperse the black pigment.
Masterbatch Dilutability
Masterbatch dilutability describes the ease with which the pigment is released by the masterbatch carrier resin and is
evenly distributed in the dilution resin. When masterbatch dilution is unsatisfactory, non-homogeneous pigmentation or
poor mechanical properties may occur in the molded part. This performance measure is dependent on:
• Melting point of masterbatch carrier resin (lower melting point ☞ better dilutability)
• Viscosity of masterbatch (lower viscosity ☞ better dilutability)
• Compatibility of masterbatch resin with dilution resin (better compatibility ☞ better dilutability)
• Type of Carbon Black
• Loading of the Carbon Black in the Masterbatch (lower loading ☞ better dilutability)
Masterbatch dilutability can be approximated
and compared by measuring the melt
viscosity of a given masterbatch formulation.
The selection of the correct carbon black can
save substantial formulation cost when
masterbatch dilutability is critical.
Regular Color
Molding Pigment
Medium Color
Molding Pigment
High Color
Molding Pigment
Regular Color
Molding Pigment
Medium Color
Molding Pigment
High Color
Molding Pigment
1750 1800 1850 1900 1950 2000 2050 2100 2150 2200
0
Viscosity Comparison of Carbon Black Pigments in
ABS at a Shear Rate of 100 sec -1
Viscosity (Pa-sec) @ 230°C
Viscosity Comparison of Carbon Black Pigments in
Polyamide at a Shear Rate of 100 sec -1
200 400 600 800 1000 1200 1400
Viscosity (Pa-sec) @ 240°C
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Ultra-Violet Light Stability
When exposed to sunlight, plastics degrade as manifested by color changes, surface cracking, and loss of
mechanical properties. A chemical reaction initiated by absorption of UV light breaks chemical bonds present in
polymers near the surface of the exposed substrates. The breaking of chemical bonds produces free radicals that
attack other bonds and further propagate this autocatalytic chain reaction. It is understood that by adding carbon
black, UV stability of polymers can be enhanced. Carbon black is an ultra-violet light absorbing additive that dissipates
this energy through heat generation. This performance measurement is dependent on:
• Type of carbon black
• Carbon black concentration
• Dispersion of the carbon black
Regular Color
Molding Pigment
Medium Color
Molding Pigment
High Color
Molding Pigment
Blue Tone
A lot of misunderstanding exists around this performance measure.
Very often it is a visual appreciation. Hence one confuses blue
undertone with color strength. We define blue tone as the undertone
of the molded part measured within the CIELAB coordinates, e.g. the
b* value. The blue tone is dependent on:
• Type of carbon black
• Carbon black concentration
• Type of polymer matrix
UV Light Stability Performance Predictor
0 20 40 60 80 100 120
Relative UV Protection Prediction Value
A lower value represents better UV performance
Cabot has designed black pigments for the molding applications to
offer polymer masterbatch and compound producers the best
balance of color strength, UV Stability, blue tone, dispersability and
dilutability. This technical brochure is designed to allow you to select
the black pigment that will deliver the best value to your application.
Cabot representatives can provide you with a star diagram comparing
those pigment grades of your interest. Please call them for further
details on Cabot’s product line.
Blue Tone (Hunter b*)
0
-0.2
-0.4
-0.6
-0.8
-1
-1.2
-1.4
Blue Tone vs. Pigment Type and
Pigment Concentration in Polyamide
0% 0.50% 1.00% 2.00%
Pigment Concentration (%)
Regular Color Molding Pigment
Medium Color Molding Pigment
High Color Molding Pigment
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North America:
Cabot Corporation
Business and Technical Center
157 Concord Road
Billerica, MA 01821-7001
USA
Tel: (978) 663-3455
Tel: (800) 462-2313 (Technical Service)
Fax: (978) 670-7035 (Technical Service)
Tel: (800) 526-7591 (North America Customer
Service)
South America:
Cabot Brasil Industria e Comercio Ltda
Av. Joao Castaldi 88
04517-900 Sao Paulo, SP
BRAZIL
Tel: +55 11 5536 0388
Fax: +55 11 5542 6037
Middle East/Africa:
Cabot Specialty Chem. Inc.
Jebel Ali Free Zone
LOB 15, Office 424
Dubai
UNITED ARAB EMIRATES
Tel: +971 4 8871 1800
Fax: +971 4 8871 1801
The data and conclusions contained herein are based on work believed to be reliable; however, Cabot
cannot and does not guarantee that similar results and/or conclusions will be obtained by others.
This information is provided as a convenience and for informational purposes only. No guarantee
warranty as to this information, or any product to which it relates, is given or implied. CABOT
DISCLAIMS ALL WARRANTIES EXPRESS OR IMPLIED, INCLUDING MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE AS TO (i) SUCH INFORMATION, (ii) ANY PRODUCT OR (iii)
INTELLECTUAL PROPERTY INFRINGEMENT. In no event is Cabot responsible for, and Cabot does not
accept and hereby disclaims liability for, any damages whatsoever in connection with the use of or
reliance on this information or any product to which it relates.
www.cabot-corp.com/plastics
Europe:
Cabot
Interleuvenlaan, 5
B - 3001 Leuven
BELGIUM
Tel: +32 16 39 24 00
Fax: +32 16 39 24 21
Pacific/Asia:
Cabot Australasia Pty. Ltd
PO Box 19
300 Millers Road
Altona, Victoria 3018
AUSTRALIA
Tel: +61 3 9391-1622
Tel: +61 3 9392-0149 (Customer Service)
Fax: +61 3 9391-9370 (Sales)
Fax: +61 3 9399-2131 (Purchasing)
Cabot Specialty Chemicals, Inc.
Level 14, MNI Tower 2
11, Jalang Pinang
50450 Kuala Lumpur
MALAYSIA
Tel: +60 3 2164-8352
Fax: +60 3 2162-0253
CB/MOLD.THERMO/07.01/E