MOLECULAR-MOTION OF SEVERAL EPOXY-RESINS AND INFLUENCE OF ELECTRON-IRRADIATION

Electron irradiation effects on the molecular motion of epoxy resins and a composite reinforced by carbon fibre were studied. The materials used were three epoxy resins that were cured by diaminodiphenylmethane: diglycidyl ether of bisphenol A (DGEBA), diglycidyl ether of bisphenol F (DGEBF) and tetraglycidyl diaminodiphenylmethane (TGDDM); and carbon-fibre-reinforced TGDDM/diaminodiphenylsulphone. A mechanical loss peak appeared for all epoxy resins in the temperature range from 50 to 100-degrees-C. The results of heat treatments indicated that this relaxation is related to the local motion of chains subjected to an internal stress produced during curing. The internal stress was more marked for the tetrafunctional epoxy (TGDDM) than for the difunctional ones (DGEBA and DGEBF). The main reaction induced by irradiation is chain scission, and the order of radiation resistance of the epoxide monomers was revealed to be TGDDM > DGEBF > DGEBA.