Additives-induced alteration of PVC pyrolysis pathways and emission profiles

Thermal treatment of polyvinyl chloride (PVC) raises environmental concerns due to toxic byproduct emissions, yet how commercial additives regulate pyrolysis pathways remains poorly understood. Here, we pyrolyzed PVC cables and pellets at 300-700 °C under air or nitrogen and comprehensively characterized products via target and non-target analysis. A total of 746 compounds were identified. Additives like phthalate esters (PAEs) and chlorinated paraffins (CPs), together with reaction conditions appeared to strongly influence secondary product formation. Additives were predominantly released at 300 °C. At higher temperatures, they degraded, forming benzoic acid and shorter-chain CPs (C8-C9). PVC skeleton pyrolysis generated substantial secondary byproducts, with polycyclic aromatic hydrocarbons (PAHs) reaching the highest emission factor (45.3 mg/g PVC), exceeding values from motor vehicles and coal combustion. Temperature-dependent pathways showed enhanced cyclization at high temperature, producing aromatics and PAHs. Oxygen promoted oxidative reactions, increasing oxygenated species like benzoquinone and furan. Notably, CPs underwent decomposition into secondary products in addition to their release from the PVC matrix, whereas PAEs facilitated interactions with PVC‑derived intermediates. Risk assessment indicated potential concern from anthracene, naphthalene and phenanthrene. Overall, this study demonstrates that plastic additives fundamentally modulate PVC pyrolysis through direct release and secondary transformation, providing mechanistic insight into pollutant emissions during PVC thermal treatment and informing improved plastic waste management strategies.