Quantification of Environmental Stress Cracking in Polymer Blends through Eyring Modeling

Abstract

The effect of blending polycarbonate (PC) with an amorphous copolyester (PCTG) and a crystallizable polyester (PBT) on the environmental stress cracking (ESC) resistance was studied. The determination of the ESC resistance for the blend was accomplished through tensile testing in a fluid environment utilizing an Eyring-type activated process to describe ESC. It was found that the miscible blend, PC/PCTG, displayed a rule of mixtures for ESC resistance to all fluids tested except ether resistance. The immiscible blend, PC/PBT, displayed a significant negative deviation from the rule of mixtures for ESC resistance, except for ether resistance, which has been attributed to the development of stress sites for craze initiation at the interface between the blend components on the surface of the test sample. The differences in ether resistance compared to the trends found for the fluid ESC resistance in this study were attributed to possible changes in crystallization for the samples tested in ether. The data suggests that strongly swelling fluids, e.g. diethyl ether in the presence of PC, may cause densification from polymer crystallization resulting in voids that facilitate in the initiation and growth of crazes.