Influence of UV absorber on photodegradation processes of poly(vinyl chloride) with different average degrees of polymerization

摘要

The influence of UV absorber (Chimassorb81) 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, FTIR, contact angle measurement, and scanning electron microscopy (SEM). The PVC films with different (DP) over bar (1000 and 3000), which contained 0.3 or 0.5 phr Chimassorb81, were prepared by solution casting. It was carried out by exposing specimens to xenon-arc light source with a spectral irradiance of 0.68 W/(m(2) nm) at 63 degrees C. It is found that the Chimassorb81 is efficient photostabilizer for PVC with different D-A. Although the Chimassorb81 delays the photodegradation of PVC, it does not influence the Rhotodegradation mechanisms of PVC with different (DP) over bar. The main photodegradation reaction for the lower (DP) over bar of PVC is dehydrochlorination in the initial stage of UV-irradiation, and then the crosslinking and chain scission reactions occurred after long irradiation. However, the main reaction of the higher (DP) over bar of PVC is not dehydrochlonnation but crosslinking and chain scission in the initial stage of UV-irradiation. The results of carbonyl index, C-CI index, contact angle measurement, and SEM also show that the photostability of Chimassorb81 is more effective for the higher (DP) over bar of PVC, especially in the presence of higher concentration of Chimassorb81.