HYDROLYTIC AGING OF POLYCARBONATE .1. PHYSICAL ASPECTS

The hydrolytic aging of an unstabilized industrial sample of polycarbo nate was studied at 40, 70, 80, and 90-degrees-C, 100% RH. The water a bsorption characteristics show that, at equilibrium, the polymer absor bs about 0.04 mol water per ester group and that the equilibrium is re ached after about 10-40 h exposure, i.e., far before irreversible chan ges of physical properties are observed. Differential scanning calorim etry reveals the combined effects of hydrolytic chain scission and phy sical aging on glass transition temperature. Investigations on tensile yield properties showed that hydrolytic chain scission leads to a sig nificant decrease of the apparent Eyring's activation volume. These ob servations strongly support the hypothesis that there are preexisting or hydrolysis-induced defects responsible for an heterogeneous distrib ution of chain scissions that would be concentrated into localized mic rodomains. (C) 1995 John Wiley & Sons, Inc.