Determination of the long‐term hydrolytic stability of polycarbonate engineering resins

The hydrolytic degradation of polycarbonate resins is a first‐order process in terms of the decrease in average molecular weights under a relative humidity (RH) and temperature. Two analysis procedures have been developed for making life‐cycle predictions of polycarbonate at any combination of humidity and temperature. The first prediction procedure uses an Arrhenius equation derived for determination of the activation energy of polycarbonate hydrolysis tested at various temperatures under a constant RH. The rate constants at any combination of temperature and RH can be determined for a new resin tested at three or more RHs under a temperature, since the logarithm of the Arrhenius intercept has a linear empirical relationship with RH. The second prediction procedure uses a linear relationship between the logarithm of the rate constant and RH derived from the humid‐aging of polycarbonate tested at various RHs under a constant temperature. The rate constants at any combination of temperature and RH can be determined for a new resin tested at three or more temperatures under a RH, since the intercept of the above linear relationship has another linear empirical relationship with temperature.