The influence of UV-irradiation on poly(vinyl chloride) modified by iron and cobalt chlorides

摘要

The influence of ultraviolet radiation (λ= 254nm) on thin PVC films modified by addition of l-5%(wt.) iron (Ⅲ) chloride or cobalt(Ⅱ) chloride is reported. The photoinduced degradation, oxidation and dehydrochlorination were studied using Gel Permeation Chromatography, viscometry, UV-Visible and FTIR absorption spectroscopy. The photocrosslinking yield was estimated by separation of insoluble gel. Sample morphology was observed by optical microscopy. It was found that both salts change the course of photochemical reactions in PVC. These changes depend on salt type and content as well as on time of UV-irradiation. FeCl_3 and CoCl_2 hinder main chain scission in PVC in the initial stage of irradiation (after 1 h) but accelerate this reaction during prolonged exposure (10―30 h). Photodehydrochlorination is retarded in doped PVC (with the exception of PVC + l%CoCl_2). PVC photocrosslinking is less efficient in the presence of additives after longer period of degradation. The influence of salts on photo-oxidation is different―Fe chloride slightly decelerates whilst Co chloride accelerates the formation of carbonyl groups in PVC. The differences of both salts on photooxidative degradation in PVC are caused by their varying chemical nature and by differences in sample morphology.