HYDROLYTIC AGING OF POLYCARBONATE .2. HYDROLYSIS KINETICS, EFFECT OF STATIC STRESSES

Plaques of bisphenol A polycarbonate (PC) were exposed to a water-saturated atmosphere at temperatures ranging from 40 to 90-degrees-C for up to 7 months. Certain samples were exposed under tensile load at 60 and 90-degrees-C, 100% RH with stresses ranging from 3.7 to 8.7 MPa. The PC molecular weight was determined by steric exclusion chromatography, and the kinetic parameters for hydrolytic chain scission were determined. It appears clearly that in the presence of tensile stresses, the hydrolysis rate is increased (at both temperatures under study) by a factor of about 10. The stress effect cannot be represented by the Eyring-Zhurkov relationship because the activation volume appears as an increasing function of the temperature and a decreasing function of time. Some possible causes of the observed stress effects are discussed (C) 1995 John Wiley & Sons, Inc.