Thermal decomposition of polyamides in the presence of poly(vinyl chloride)

Thermal decomposition of aliphatic and aromatic polyamides (polyamide-12, p olyamide-6,6 and poly(1,4-phenylene terephthalamide) (Kevlar)) with poly(vi nyl chloride) (PVC) was examined by pyrolysis-gas chromatography/mass spect rometry. Polyamide-PVC mixtures (typical mass ratio 1:1) were pyrolysed at 700 and 900 degreesC. It was found that the presence of PVC promoted the hy drolytic decomposition routes of amide groups and volatile nitrile formatio n from all examined polyamides due to the hydrogen chloride eliminated from PVC under pyrolysis. In the presence of PVC an elevated yield of alkenenit riles was observed from polyamide-12. Benzeneamine is produced from Kevlar instead of benzenediamine in the presence of PVC, and the evolution of benz oic acid, benzenenitrile and benzeneisocyanate is promoted. At 900 degreesC pyrolysis temperature enhanced hydrogen cyanide evolution was observed fro m polyamide-12 and polyamide-6,6 in the presence of PVC. Mechanisms are pro posed for the hydrogen chloride assisted formation of nitriles. (C) 2001 El sevier Science B.V. All rights reserved.