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.