Influence of cure treatment on extent of reaction and glassy modulus for BADGE‐DDM epoxy resin

The extent of conversion of epoxy groups cured with diaminodiphenyl methane, a diamine, at 100°C was approximately 100%, and the glass‐transition temperature (T ) was found to be an increasing function of cure time with very large increases with extended postcure treatments at 180°C. However, this considerable increase in the Tg with postcure at 180°C was not due to the reactions of epoxy and amine groups. The specific volume reduced with the Tg to a minimum at 103° for the cured samples but showed a very slight increase with the Tg for the postcured samples. It was also found that the glassy modulus (Eg) was a linear decreasing function of the Tg. There were two separate relationships between the Eg and the rubbery modulus that depended on the cure conditions and suggested that the “structure” formed due to cure at a temperature of 100°C was different than that at postcure, which was 180°C. The most sensitive structural parameter for these cured epoxy resins was their T .