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 differentDP(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 lowerDPof PVC (DP= 1000) was different from the higherDPof PVC (DP= 3000). This was because the lowerDPof PVC was a homopolymer, while the higherDPof PVC was often produced by copolymerizing with a certain quantity of crosslinking agent (e.g., DAP and DAM). UV‐vis 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 differentDP. TGA showed that the degradation temperatures of different weight loss increased with the irradiation time. The surface morphology of the irradiated polymer films with differentDPwas observed by contact angle measurement and SEM.