Epoxy resins cured with diethylenetriamine (37%–103% of stoichiometric composition) were heat treated at 120°C, and the dynamic elastic modulus and internal friction of the specimens were measured over the range of 85°–300°K. Results indicate that heat treatment causes the dynamic modulus to decrease at 85°K and at room temperature, but to increase over the region 150°–200°K. The γ- (∼150°K) and β-(∼250°K) peaks merge into a single broad peak with heat treatment, and a β′-peak is observed in the heat-treated samples. Effects of heat treatment also depend upon the amount of diethylene-triamine used.
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Hirai et al. (1973) studied this question.