Photodegradation of plasticized poly(vinyl chloride) (PVC) stabilized by different thermal stabilizers including organic calcium complex and mercaptide organotin was investigated. Plasticized PVC sheets prepared by an open twin-roller mill and plate vulcanizing machine were exposed to xenon-arc light with the irradiance of 0.51 W/ (m 2 Ánm) at 658C. A much better color stability displayed by mercaptide organotin than organic calcium complex has been confirmed by digital photos and color difference. This can be explained that the more effective mercaptide organotin minimizes the amount of thermal damage from processing thus favours subsequent UV weathering. Carbonyl index and decomposition activation energy (E a1 ) obtained from attenuated total refection-Fourier transform infrared spectra (ATR-FTIR) and thermogravimetric (TG) analysis, respectively, further indicate that plasticized PVC sheets containing mercaptide organotin have more excellent UV resistance. Mechanical tests reveal that photodegradation of PVC is accompanied by the predominant process of chain scission on the surface of samples. POLYM. ENG. SCI., 51:624-631, 2011. ª

The effect of the combination of a UV absorber (Chimassorb 81) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, thermogravimetric (TG) analysis, and viscosity-average molecular weight determination. Films of PVC containing 0.5 phr of Chimassorb 81, with and without 2 phr of a thermal stabilizer, were prepared by solution casting. Then the accelerated UV weathering of the films was carried out under xenon light with an irradiance of 0.51 W/(m 2 Á nm) at 658C. The results showed that both Chimassorb 81 and the mixture of Chimassorb 81 with the organic calcium complex showed good behavior in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of Chimassorb 81 and methyltin mercaptide significantly accelerated initial color development during the final 200 h of exposure because of the UV sensitivity of the organotin. Moreover, when Chimassorb 81 and the methyltin mercaptide were used together to stabilize PVC films, the expected antioxidant effect of the mixture was not observed, in contrast to the behavior found with other stabilized systems, perhaps because the Chimassorb 81 had been depleted by the methyltin mercaptide during the UV irradiation. The TG analysis revealed that ultraviolet irradiation had caused severe destruction of the PVC chains. However, addition of Chimassorb 81 or the combination of Chimassorb 81 with the organic calcium complex effectively prevented the destruction, as was demonstrated by changes in the activation energies for thermal degradation.

The influence of relatively nontoxic thermal stabilizers including different types of organic calcium complex (Ca/Zn system of liquid stabilizers) and organotin on photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurement, viscosity‐average molecular weight determination, UV–vis spectroscopy, Fourier transform infrared (FTIR), and thermogravimetric (TG) analysis. PVC films containing relatively nontoxic thermal stabilizers were prepared by solution casting and then exposed to xenon‐arc light source with the irradiance of 0.51 W/(m2·nm) at 65°C. Two major chain processes, photodehydrochlorination and photo‐oxidation, occur simultaneously during photodegradation of PVC. It has been confirmed by both color difference and UV–vis spectra that during the former 300 h of irradiation, organic calcium complex stabilizers retard photodehydrochlorination as well as initial color development of PVC films while organotin stabilizers remarkably accelerate photodehydrochlorination after 100 h. Relative carbonyl index (RCI) is first introduced to the analysis of FTIR results, which implies that organotin has a better ability to inhibit photo‐oxidation than organic calcium complex and ensures longer stabilization time. The antioxidation of mercaptan organotin has been observed because it is an effective decomposer of peroxides and hydroperoxides. TG analysis reveals that some unstable structures generated due to the irradiation of ultraviolet can easily split away off from PVC macromolecular backbones under relatively low temperature. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

The effect of the combination of a benzotriazole type of UV absorber (UV326) with different types of thermal stabilizers, including an organic calcium complex and an organotin mercaptide, on the photodegradation of poly(vinyl chloride) (PVC) was investigated by color difference measurements, UV-vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and viscosityaverage molecular weight (M Z ) determinations. Films of PVC containing 0.5 phr of UV326, with or without 2 phr of thermal stabilizer, were prepared by solution casting and subjected to accelerated UV weathering under xenon light with an irradiance of 0.51 W/(m 2 nm) at 658C. The results revealed that both UV326 and the mixture of UV326 with the organic calcium complex displayed good performance in inhibiting the photodehydrochlorination and photooxidation of PVC. In contrast, the combination of UV326 and the methyltin mercaptide remarkably accelerated the discoloration of PVC when the irradiation time increased from 300 to 400 h because of the UV sensitivity of the organotin. However, carbonyl index data indicated that a hydrogen abstraction reaction did not take place between UV326 and the methyltin mercaptide, so that the photooxidation of the PVC film was prevented effectively during the whole period of exposure, a result which may be attributed to the strong steric hindrance effect of the tert-butyl group at the 3-position of the phenyl ring in UV326. The changes of M Z were in good accordance with the results obtained from other characterizations.