Simultaneous aging of DGEBA/MeHHPA epoxy resin under thermal heating and gamma irradiation up to 1000 kGy

Abstract

Although epoxy resins in nuclear facilities may be exposed to elevated temperatures and gamma irradiation, changes in the chemical structures and mechanical properties of a diglycidyl ether of bisphenol-A (DGEBA)/methyl hexahydrophthalic anhydride (MeHHPA) epoxy resin under these conditions have not been reported yet. In this study, we aim to understand the accelerated aging of the DGEBA/MeHHPA epoxy resin under simultaneous thermal heating and gamma irradiation. Samples were irradiated at ambient temperature and 70 °C with a dose rate of 2 kGy/h and a total dose of up to 1000 kGy. Various characterizations were performed to investigate the changes in their chemical structures and mechanical properties. The results showed that the relative oxygen content of the resin increased near the surface owing to the degradation of the main macromolecular chains, which was accompanied by a decrease in the thermal stability and glass transition temperature (Tg). Under gamma irradiation at room temperature, the tensile strength increased with the absorbed dose up to 500 kGy and then decreased with higher doses. This trend indicated that thermal heating at 70 °C significantly enhanced the degradation of the DGEBA/MeHHPA epoxy resin upon gamma irradiation.