Effects of curing on the glass transition temperature and moisture absorption of a neat epoxy resin

Apparent glass transition temperature (T_g) measurements were made on smaples of a neat epoxy resin that had been cured at four different temperature and for four different times at each temperature. The apparent T_g data increase with cure time toward an asymptote that was dependent on cure temperature. The asymptotic dependence of T_g on cure temperature may be explained by the effect of cure temperature on the reaction rates and available reaction sites. The asymptotic increase with cure time may be understood in terms of the resin's extent of cure. Moisture-conditioning studies were also made and the amount of moisture absorbed was correlated with the extent of cure. The absorbed moisture's interaction with the resin's molecular structure was deduced to by primarily at hydroxyl sites.