DETERIORATION OF ORGANIC POLYMERS 



1093 



is proof that secondary peroxides or peroxidic radicals can decompose by 

 the chain spHtting process. That they do not decompose exclusively by that 

 mechanism is shown by the high yield of tetralone obtained from the de- 

 composition of tetralin hydroperoxide. 



The mechanisms outhned, while certainly not complete, are adequate to 

 account for the chain scission type of oxidative deterioration of many plastics 

 and rubbers. The degradation of chlorine bearing plastics such as polyvinyl 

 chloride and polyvinylidene chloride, while also being caused by oxygen and 

 being energized by light and heat, is not believed to follow the patterns out- 



Table II 



Field Results on Samples of Naturally Aged Neoprene Jacketing 



(From Drop Wire)* 



* From a paper by G. N. Vacca, R. H. Erickson and C. V. Lundberg^**) 



lined above. The first step here is reported^^ •'*^ "^ to be the elimination of 

 hydrogen chloride with introduction of a double bond, which makes the 

 loss of more HCl easier and also increases the oxidizability. 



Cross-Linking Resulting from Oxidation 



The second important effect of oxidation of polymers is cross-Unking. 

 This is of great consequence only with unsaturated compounds and these 

 are principally the rubbers. If cross-linking is the dominant reaction (as it 

 usually is on neoprene, GR-S, and the nitrile rubbers) the result is a decrease 

 in elongation and an increase in hardness without a loss in tensile strength. 



