Mechanisms of formation of volatile aromatic pyrolyzates from poly(vinyl chloride)



The formation of volatile aromatic pyrolyzates in poly(vinyl chloride) has been studied by pyrolysis–gas chromatography–mass spectroscopy. Results from isotopic labeling experiments with perdeutero-PVC suggest that the aromatic pyrolyzates can be divided into three general classes with respect to their formation mechanisms: (1) intramolecular—benzene and naphthalene are formed almost exclusively via intramolecular cyclization reactions; (2) mixed intra/intermolecular—styrene and indene can be formed either intramolecularly or via transfer of one hydrogen atom between PVC chains; (3) intermolecular—toluene and methylnaphthalene can be formed via transfer of one or two hydrogen atoms between chains. The isotopic distributions observed in the labeling experiments can be reasonably well explained without involving crosslinking (intermolecular C[BOND]C bond formation) reactions.