The kinetics of polyarylate hydrolytic embrittlement

The hydrolysis of polyarylate in water between 55 and 98°C was found to be a zero-order process with an activation energy of 19.2 kcal/mol, determined by changes in molecular weight. The equation for the effect of temperature on the rate of hydrolysis is ln k = 34.1 ? 10⁴/T, where k is in day^?1. The decrease in molecular weight is accompanied by a loss in ductility. The transition from a ductile to brittle failure in tension occurs at M?_w of about 35,000 and M?_n of 12,700. At 27°C (80°F) and high humidity environment this would occur after 21 years. But during injection molding, the material, if not properly dried, would embrittle in a matter of seconds.