The influence of ultraviolet (UV)-irradiation on the photodegradation mechanism of different average degrees of polymerization ((DP) over bar) of poly(vinyl) chloride (PVC) with UV-irradiation time was investigated by viscosity-average molecular weight determination, UV-vis spectroscopy, Fourier transform infrared (FTlR), thermogravimetric analysis (TGA), contact angle measurement, and scanning electron microscopy (SEM). PVC films with different (DP) over bar (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/m(2) nm) at 63 degrees C. It was found that the photodegradation mechanism of the lower UP of PVC ((DP) over bar = 1000) was different from the higher (DP) over bar of PVC ((DP) over bar = 3000). This was because the lower (DP) over bar of PVC was a homopolymer, while the higher (DP) over bar of 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 different (DP) over bar. TGA showed that the degradation temperatures of different weight loss increased with the irradiation time. The surface marphology of the irradiated polymer films with different (DP) over bar was observed by contact angle measurement and SEM. (C) 2007 Wiley Periodicals, Inc.