Polystyrene oxidative degradation

Oxidative degradation can also occur in other polymers including natural rubber, polystyrene, polypropylene, nylons, polyurethanes, and most natural and naturally derived polymers. With the exception of fluo-ropolymers, most polymers are susceptible to oxidation, particularly at elevated temperature or during exposure to ultraviolet hght. Oxidation usually leads to increasing brittleness and deterioration in strength. 

The role of singlet oxygen in the oxidative degradation of polymers has been pointed out by several authors,e.g.for polyethylene (36.56),polypropylene (59)>polystyrene (57>60), poly(vinyl chloride)(58,61) cmd rubber (62-66) and reviewed by Rabek cmd R nby (54> 55) ... 

Nemphos, S. P., Oxidative Degradation of Deuterated Polystyrenes, Ph.D. thesis,... 

Oxidative studies on resins with different polymer backbones and functionalities have been performed as accelerated tests.The data is shown in Table 17 for polystyrene and polydiallylamine resins. Although the polydiallylamine resins have a higher initial capacity, they are much more susceptible to oxidative degradation. When the polystyrene resin has a mixture of primary and secondary amino groups or when a hydroxy-containing group is attached to the amine of the functional group, the susceptibility to oxidation is enhanced. Thus one can understand the lower thermal limit for Type II anion resins compared to Type I resins. 

Various chromophore groups, colouring the polymer yellow to brown, are formed during the oxidative degradation of polymers. The production of such groups was identified in the case of polystyrene [2, 255], but their structure is not yet entirely elucidated. Achhammer et al. [2] suggested that the colour of oxidized polystyrene is due to quinomethane formed by the reaction of polystyryl radicals ... 

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