Theoretical studies on bond dissociation enthalpies for model compounds of typical plastic polymers

The polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), bisphenol A polycarbcconate (PC) comprise above 80% of plastic polymers. The bond dissociation enthalpies for model compounds of the six typical plastic polymers were calculated by using density functional theory methods, and the possible degradation mechanisms of these plastic polymers were proposed. The degradation of PE and PP is mainly main-chain random scission mechanism; the PS degradation is mainly zipper scission and main-chain random scission mechanism; the PVC degradation is mainly branched-chain scission mechanism; the PET and PC decompose mainly through C-O homolytic cleavage, C-C homolytic cleavage and concerted reaction.