Radiation Resistance of Ethylene-Propylene Rubbers Cured by Peroxide

The radiation resistance of ethylene-propylene-ethylidene norbornene terpolymer (EPDM) cured by peroxide was studied. Some properties of EPDM showed maxima with irradiation. The gel fraction dropped rapidly following the maximum, at a rate which increased with decreasing dose rate. The dose rate affects the rate of deterioration of mechanical properties; the lower the dose rate, the more the deterioration per unit of absorbed dose. No effect of original gel fraction on the deterioration rate was observed in this study. This is in contrast with the results of a previous study in which EPDM vulcanized by sulfur showed less deterioration in the samples with higher gel fractions than those with lower gel fractions [1]. It is suggested that the high radiation resistance of EPDM vulcanized by sulfur is attributed to the presence of sulfur atoms in the specimen, but not to the existence of crosslinks themselves, since radiation resistance increases in proportion to the concentration of sulfur in the rubber.