Some aspects of the photolysis and photooxidation of polyethylene containing ketone groups

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Abstract
Studies of the photodegradation of polyethylene containing 2 wt % methyl vinyl ketone (MVK) and methyl isopropenyl ketone (MIPK) show that the relative quantum yields of Norrish type I and II photolysis are strongly dependent on the structure of the ketone carbonyl. The type 1 process, leading to free radical formation, is particularly efficient in the MIPK copolymer, somewhat less so in the MVK copolymer, and very low in ethylene‐carbon monoxide copolymers where the carbonyl group is in the chain backbone. In the presence of oxygen, this difference shows up strongly in the rate of photooxidation. Backbone carbonyl groups have very low efficiency in initiating photooxidation of solid polymer films, while the side chain ketone groups initiate rapid photooxidation.