Nitrogen-containing products from the thermal decomposition of flexible polyurethane foams

The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec-trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen-containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.