Radiation Resistance of Ethylene-Propylene Terpolymer Vulcanized by Sulfur I. Basic Ingredient Compounding Material

The radiation resistance of ethylene-propyleneethylidene norbornene terpolymer (EPDM) vulcanized with sulfur was studied. Several mechanical properties of original EPDM demonstrate maxima with irradiation. The property values at the maxima are observed to be a function of the gel fraction which was varied over a wide range by choice of the amounts of sulfur curing agent and accelerator. The deterioration of the materials by irradiation was evaluated by observing the change from these maximum values. EPDM with higher gel fractions showed less deterioration than that with lower gel fractions. The dose rate affects the mechanical properties. This is interpreted as evidence of a diffusion limited oxidation reaction during irradiation. At dose rates less than 1 x 105 rad/h, the effect is insignificant and the data are realistically considered to reflect changes which may occur in the containment area of a nuclear reactor with a nominal dose rate of 100 rads/h. Hardness can be taken as a parameter to evaluate the deterioration.