GAMMA-RADIATION INDUCED CROSS-LINKING OF POLYETHYLENE ETHYLENE VINYLACETATE BLENDS

Low density poly(ethylene/ethylene-vinylacetate) blends were exposed to gamma radiation at doses between 100 and 160 kGy, at room temperature, to study the effects of a trifunctional acrylic monomer, TMPTMA, and two antioxidants on their properties. The effects of irradiation on mechanical behavior, crosslinking/dose ratio, thermal aging and crystallinity were studied. Gel fractions up to 0.7 and 30% increments in crosslinking/dose ratio were obtained. Noticeable changes in mechanical properties; tensile strength, elongation at break, Young modulus and hardness were also observed. The effects on crystallinity of both irradiation and a post-irradiation thermal treatment were analyzed by X-ray diffraction. Crystallinity was not significantly affected by irradiation but it decreased after the aging treatment. The latter effect is associated with crosslinking and probably with active species (e.g. free radicals) remaining in the crystalline phase for a long time after irradiation. Possible chemical reactions and alternative irradiation methods are also discussed.