Chemical and Oxidative Degradation

The effect of chemical constituents in the environment or the presence of solvents can cause polymers to undergo chemical reactions and/or change in their chemical make-up. Usually, this is accompanied by some amoxmt of heat since the bond-making and bondbreaking process involves evolution and absorption of heat. Thermochemical degradation in commonly observed in polymers such as polyethylene (PE) and polypropylene 

Ozone addition to EPDM-like polymers can cause rapid cross-linking and chain scission [27]. Depending on conditions and the nature of the epoxy material, one of the two mechanisms can become dominant. If ozone reacts with a different kind of polymer such as polyvinyl alcohol (PVA), chain scissions remain dominant, but lead to different products due to disproportionation and other side reactions [28]. There is also evidence that the concentration of ozone present in the environment does not have a significant impact on the degradation of the polymer, and is always a slow process [29]. 

From the examples given earlier, a few important points can be noted regarding thermochemical degradation of polymers the overall degradation is affected greatly by the chemical structure of the polymer (bond type, bond strength, branching) and the chemical environs where it is used. 

Nitrosoamide nitrites, other low molecular weight products 

Temperature/°C Apparent initial rate based on weight of sample (% min) Activation energy (Kcal mole ) 

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