Radiation degradation pathways

Thus, there are three possible pathways for the radiation degradation of polymer molecules neutral radical, cation-radical and/or anion-radical intermediates. Interest in the formation of these three types of reaction intermediates has fluctuated over the years with the utilization of different techniques and with the particular interests of different investigators. It is likely that all three species will be produced, but their relative importance in the degradation mechanism will depend on the chemical structure of the polymer. Evidence for their involvement will depend on the experimental methods used and the temperature and time scale of observation. In this paper we illustrate our investigations of many of the fundamental aspects of the radiation degradation of polymers through studies of series of polymers and copolymers. 

Information about the degradation pathways occurring in polyolefins exposed to vacuum-ultraviolet radiation (VUV) were obtained by MALDI-TOF analysis of oligomers formed by VUV photolysis of linear C36-alkane. ° Both molar masses and end-groups of degradation product were studied. 

UV stabilisers protect polymers by restricting UV penetration to the surface and therefore confine the damage to surface layers. Protection is important because the energy possessed by UV radiation is sufficient to break chemical bonds. The initial breakage can either be by a radical (Norrish type I) or non-radical (Norrish type II) pathway. The effects are similar to degradation of the polymer by oxidation routes the radical intermediates can be neutralised by anti-oxidants. 

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