Hygrothermal Aging Effects in Cured Epoxies

The effect of relatively severe hygrothermal aging on the sorption and also the diffusion of water at 40°C has been studied for a number of epoxy networks comprising tetraglycidyl 4,4′-diaminodiphenyl methane, and the curing agent 4,4′-diaminodiphenyl sulphone, 4,4′-diaminodiphenyl methane and 2,2′-dichloro-4,4′-diaminodiphenyl methane. Aging at high temperatures is accompanied by a pronounced increase in sorptive capacity at 40°C consistent with a significant expansion of the network. Dry annealing of the aged network at sub- Tg temperatures collapses the expanded structure to recover the sorptive capacity of the unaged network. Preliminary studies of the sorption-desorption kinetics for aged networks indicate that the effective diffusion coefficient is not markedly affected.