Photodegradation and Photooxidation Processes in Polymers

The photooxidation and photodegradation of polymers continues to attract some interest but is not as widespread as in previous years. Review articles have appeared dealing with poly(2,6-dimethyl-l,4-phenylene oxides) , photocatalyst fibres, polymers with azo links and accelerated weathering specifications. Other articles of interest include the design of an integrating sphere for repeatability in polymer ageing and the use of FTIR for monitoring the photostability of clearcoats . 

At 77 K irradiation of polyethylene produces allyl radicals while the application 

2 PoIy(vinyl halides) - Biodegradable PVC has been made by grafting sucrose acrylate to the surface of the polymer,while the effects of weathering have been examined on UPVC windows. Here comparable studies were undertaken in order to compare natural with artificial ageing conditions. 

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This prompted us to review the work on the decomposition of hydroperoxides and in particular to determine what portion of the hydroperoxides that decomposes leads ultimately to bond scission. It is important to point out in this context that it is possible in principle for a polymer to oxidize extensively without losing its physical properties. The most important process in the breakdown of physical properties is bond scission in the backbone of the polymer chain. This can be best determined by measurements of the molecular weight of a photooxidizing or photodegrading polymer. In our laboratories we have studied this process by automatic viscometry which permits a very precise measurement of bond scission in polymers the apparatus has been described previously (12). For these studies we prepared a singlet-oxygen adduct of cis-polyisoprene by the following scheme ... 

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