Unlocking degradation mechanisms in prodegradant-modified PVC under UV irradiation: Insights into abiotic degradation

The development of oxo-biodegradable polyvinyl chloride (PVC OBD) is an emerging field aimed at addressing the environmental impact of PVC by enhancing its degradability. Rigid and shrink films of PVC were fabricated via calendering and blown film extrusion. Subsequently, as much as 3% of prodegradant additive (PDA, commercial name = Oxium®) was added to produce PVC OBD. All samples were then subjected to 250 h of UV-A irradiation (ASTM D6954 Tier 1) followed by accelerated abiotic weathering for 15 months. The findings clarify a competitive degradation mechanism in which radical recombination and crosslinking are induced by early-stage UV exposure, and then the presence of PDA significantly enhances degradation. Analysis via GPC, FTIR, and SEM revealed that PDA catalyzed a shift from early-stage photodegradation (crosslinking) to extensive chemical degradation (oxidative chain scission). This resulted in significant variation of molecular weight, carbonyl formation, and severe morphological embrittlement, whereas control samples remained chemically stable. These findings establish the mechanistic degradation of PVC OBD pathways, validating its potential for applications with high risks of environmental leakage.