2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P09 VOLATILE DEGRADATION PRODuCTS OF
POLyuREThANE FOAMS
DAnIELA MáCOVá, TEREZA TOBIáŠOVá and JOSEF
ČáSLAVSKý
Institute of Chemistry and Technology of Environmental Protection,
Faculty of Chemistry, Brno University of Technology,
Purkyňova 118, 612 00 Brno, Czech Republic,
xcmacova@fch.vutbr.cz
Introduction
Polyurethanes are the world’s sixth most abundant synthetic
polymer. The most of their production represent flexible
polyurethane foams. At the end of their life-cycle they are
often deposited on waste dumps, where they degrade under
the influence of various environmental factors; photodegradation
and hydrolysis are the main routes. After that, their
degradation products can be distributed in the environment.
In common, synthetic polymers are not prone to environmental
degradation. Therefore, they could stay there for a long
time. Their degradability can be improved by addition of the
biodegradable filler.
The generation of volatile products has been reported
from the photo- and thermal degradation of many polymers.
1–4 Complex mixtures of degradation products of this
type were for example identified in starch-based polymers 5 .
Till now, there is no information about volatile compounds
generated during photodegradation of synthetic polyurethane
with biodegradable filler. Several studies have been developed
on the UV degradation of aromatic polyurethane. Such
photo-degradation has already exhibited formation of free
radicals, recombination, scission of bonds, crosslinking and
oxidation reactions 6,7 .
This paper is focused on the identification of volatile
photodegradation product of polyurethanes modified
by biodegradable filler using Solid Phase Microextraction
(SPME) and Gas Chromatography linked to Mass Spectrometry.
The SPME method was selected in the experiment for
its fastness, simplicity and environmental friendness.
Experimental
M a t e r i a l a n d S a m p l i n g
Polyurethane foam modified with biodegradable filler
like carboxymethyl cellulose, acetylated potato starch, cellulose
acetate, 2-hydroxyethyl cellulose and wheat protein
were prepared at the Institute of Material Chemistry at Faculty
of Chemistry, Brno University of Technology.
For sampling of volatile compounds the system consisting
of quartz tube with Teflon cover and two SPME holders,
the first with polyacrylic fibre (PA) 85 µm and the second with
polydimethylsiloxane fibre (PDMS) 100 µm (both Supelco,
USA) and UV lamp (high-pressure mercury discharge tube,
λ = 254 nm), was set-up. The system is shown on Fig. 1.
s351
Fig. 1. System for sampling of VOCs formed by photodegradation
of polymer
G C - M S a n a l y s i s
Separation and identification of volatile compouds from
UV-induced polyurethane foam photodegradation was realized
using Agilent 6890n gas chromatograph coupled with
Agilent 5973 mass selective detector (Agilent Technologies,
Germany). HP-5MS column 30.0 m × 0.25 mm × 0.25 μm
was used for the separations. The injector and transfer line
temperature was 270 °C. The GC oven temperature program
for PDMS fibre was: 4 min at 40 °C, then increased
at 15 °C min –1 to 100 °C, then 8 °C min –1 to 270 °C, then
15 °C min –1 to 280 °C. For the compounds desorbed from
PA fibre the column temperature program was slightly modified:
4 min at 40 °C, increased at 10 °C min –1 to 230 °C, then
15 °C min –1 to 280 °C. Injection/desorption of analytes from
SPME fibres was realized in splitless mode. Helium was used
as the carrier gas at a constant flow of 1 ml min –1 . Ion source
temperature was 230 °C, electron ionization at 70 eV was
used. Quadrupole analyzer of the MSD was operated in scan
mode within a range 30–550 amu, solvent delay was 4 min.
Identification of separated compounds was based on nIST 05
spectral library search.
Results
Seven types of polyurethane foams with different fillers
and reference foam without filler were irradiated by UV lamp
during this study. Volatile compounds were sorbed on PA and
PDMS fibers and desorbed, separated and detected by GC-
MS technique.
All identified compound are listed under chromatograms
(Figs. 2. and 3.). Many various compounds have been
identified.
Group of branched and non-branched aliphatic hydrocarbons
containded: pentadecane, hexadecane, heptadecane,
2,6,10,14-tetramethylpentadecane, 2,6,10,15,19,23-hexamethyl-2,6,10,14,18,22-tetracosahexaene
(Squalene). These
compounds are probably formed by homolysis of bonds in
soft part of polyurethane.
Group of ketone and fatty acid esters contained: 6,10dimethyl-5,9-undecadiene-2-one,
methylester of dodecanoic
acid and isopropylester of tetradecanoic acid.
By photo-oxidation of alkenes hydroperoxides were
formed – 1,3-dioxane and 2-methyl 1,3-dioxane.