Polyolefins Under the Action of Light

It is characteristic that polyolefins can be arrai ed in the following series with respect to stability to ultraviolet irradiation, just as in thermal oxidation polypropylene-low-pressure polyethylene-copolymer-high-pressure polyethylene. Branching of the polymer chains also reduces the stability in photodestruction. 

At the present time there is a comparatively large number of works in the literature studying the mechanism of the photooxidative destruction of polyolefins. Unfortunately, most of them are devoted to high-pressure polyethylene, in view of which it does not seem possible to make any comparison between individual types of this class of polymers. However, the general picture of the photooxidation possesses much in common with the thermal process of oxidation and differs from the latter mainly in the stage of initiation. 

Ultraviolet irradiation intensifies the oxidation of the polymer, the rate of oxygen absorption increasing with the light intensity [82] and with increasing temperature [83]. 

Such a composition of the products confirms the decomposition of the carbonyl groups of the compounds. 

In view of this it is assumed that the decomposition proceeds according to the schemes  

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