Hydrolysis kinetics of condensation polymers under humidity aging conditions

The hydrolytic stability of polycarbonate (PC), poly(ethylene terephthalate) (PET), and resorcinol polyarylate (RPA) films was studied at 65-95 °C and 23-95% relative humidity (RH) by measuring the time to embrittlement as measured by a bending test on films. The data show that the hydrolysis of these polymers is second order in RH with overall kinetics 1/tfail = A exp(-Ea/RT) [RH]2 where tfail is the embrittlement time in days, R is the gas constant, T is the temperature in kelvins, and RH is the fractional relative humidity. The activation energy, Ea, in kJ/mol and ln(A), respectively, for the polymers were PC: 92, 24.9; PET: 129, 39.3; RPA: 102, 30.0.