Different photodegradation processes of PVC with different average degrees of polymerization

The influence of ultraviolet (UV)-irradiation on the photodegradation mechanism of different average degrees of polymerization (DP) of poly(vinyl) chloride (PVC) with UV-irradiation time was investigated by viscosity-average molecular weight determination, UV-vis spectroscopy, Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), contact angle measurement, and scanning_electron microscopy (SEM). PVC films with different DP (800, 1000, 1300, 3000) were prepared by solution casting. It was carried out exposing specimens to a xenon-arc light source with a spectral irradiance of 0.68 W/(m² nm) at 63°C. It was found that the photodegradation mechanism of the lower DP of PVC (DP = 1000) was different from the higher DP of PVC (DP = 3000). This was because the lower DP of PVC was a homopolymer, while the higher DP of PVC was often produced by copolymerizing with a certain quantity of crosslinking agent (e.g., DAP and DAM). UVvis and FTIR spectroscopy studies provided some results concerning the structure of the irradiated PVC, and the carbonyl index and C-Cl index were induced to study the process of PVC photodegradation with different DP. TGA showed that the degradation temperatures of different weight loss increased with the irradiation time. The surface morphology of the irradiated polymer films with different DP was observed by contact angle measurement and SEM.