The formation of volatile pyrolyzates form poly(vinyl chloride)

The formation of volatile pyrolyzates in poly(vinyl chloride) has been studied by pyrolysis–gas chromatography–mass spectroscopy. Isotopic distributions of pyrolyzates from experiments with perdeutero‐PVC show that pure conjugated aromatic pyrolyzates (e.g., benzene, styrene, naphalene, biphenyl, anthracene) are formed mostly via intramolecular cyclization. Mixed aromatic‐alphatic pyrolyzates (e.g., toluene, indene, methylnaphthalene) are formed at least partially via intermolecular (crosslinking and/or hydrogen transfer) mechanisms. Direct scission of the PVC chain to form chlorine‐containing pyrolyzates is a very minor degradation pathway. Most chlorine‐containing “pyrolyzates” from PVC are due to secondary reactions of HCl with the environment or with non‐PVC compounding ingredients. No evidence was found for oxygen‐containing pyrolyzates derived from the PVC backbone under conditions of nonflaming pyrolysis in air.