Photochemical reactions of the aldehyde group

The UV radiation affects aldehyde groups in polymers in the same way as ketone groups that is, Norrish reactions of type I and II are involved in the photochemical process [116]. These reactions are not very important in the photo-oxidative degradation of polymers, because the aldehyde groups are exclusively found at chain ends namely, 

The content of aldehyde groups in the final product of polypropylene photodegradation is 7%. In the case of polyethylene degradation these groups are completely absent [6]. The relatively lower amount of aldehyde groups in the products of polyolefine photo-oxidation is due to the fact that they absorb radiation and subsequently react as above [278]. 

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