Effects of water on epoxy cure kinetics and glass transition temperature utilizing molecular dynamics simulations

Effects of water on epoxy cure kinetics are investigated. Experimental tests show that absorbed water in an uncured bisphenol-F/diethyl-toluene-diamine epoxy system causes an increase in cure rate at low degrees of cure and a decrease in cure rate at high degrees of cure. Molecular simulations of the same epoxy system indicate that the initial increase in cure rate is due to an increase in molecular self-diffusion of the epoxy molecules in the presence of water. Effects of water on the glass transition temperature (T-g) of the crosslinked thermoset are also studied. Both experiments and simulations show that water decreases T-g. Both types of results indicate that T-g effects are small below 1% water by weight, but that T-g depression occurs much quickly with increasing water content above 1%. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1150-1159