Investigations of water and high energy radiation interactions in an epoxy

Differential scanning calorimetry (DSC) and infrared spectroscopy (IR) have been used to study the crosslinked epoxy system tetraglycidyl-4,4′-diaminodiphenyl methane cured with diaminodiphenyl sulfone. Samples cured at various temperatures were soaked in distilled water for extended periods or irradiated with 0.5 Me V electrons and ⁶⁰Co gamma. DSC results show that the standard-cured (137°C for 2 h and 160°C for 5 h) dry samples have a T_g around 190°C and a large exothermic reaction at about 260°C. The latter is attributed to further reaction of curing agent with the epoxide rings. The exothermic energy is about 124 cal/g for an uncured specimen, 42 cal/g for standard cured specimen, and 20 cal/g for soaked samples containing 4% H₂O. The exothermic energy is shown to decrease monotonically with the ionizing radiation dosage. IR results show a reduction in the intensity of the epoxide band as the exothermic energy is decreased.