Environmental Effects

Abstract

Although polymers have a very desirable resistance to chemical attack they may be susceptible to slow degradation even when exposed to what appear to be rather benign conditions. Degradation leads to deterioration in mechanical properties and is caused by a breakdown in the polymer structure due to one or more factors. The most common factors causing degradation are thermal effects, oxidation, photo-degradation, chemical attack, hydrolysis and radiation. Defects caused by one form of degradation will frequently act as sites for further attack e.g. traces of oxygen introduced during processing may lead to the formation of carbonyl groups in polyolefins which act as sites for UV absorption and lead to photo-degradation. Degradation can be due to oxidation by agents as apparently benign as atmospheric oxygen and hence antioxidants are frequently incorporated into polymer products both to protect the polymer during molding where the high temperatures employed makes it very susceptible to oxidation and to provide long term protection against oxygen attack.