Structure property relationship in irradiated polymer blend films

Films prepared from blends of polypropylene, ethylene vinyl acetate and, propylene-ethylene copolymer have been irradiated with fast electrons in the dose range of 5-16 Mrad. The effect of irradiation has been investigated by solvent extraction, DSC, DMA and X-ray diffraction techniques. Gel fractions range from 22 percent to 80 percent. The upper limit of the molecular weight between crosslinks has been found out to be 2000g/mol. X-ray diffraction studies show no appreciable distortion of the crystal lattice up to 16 Mrad. A considerable drop in the crystallinity index is obtained only at high dose level. Nonisothermal crystallization studies show that the crystallization temperature decreases with radiation dose. The melting temperatures decrease with dose and the drop is more prominent in samples containing high percentage of polypropylene. Multiple melting peaks are observed for irradiated samples. The enthalpies of melting of EVA increase up to 5 Mrad and then decrease in samples containing high percent of polypropylene. Enthalpies of PP remain constant or slightly decrease with dose. The dynamic mechanical analysis show separate transition peaks for PP and EVA. High storage modulus at high temperature is seen only in case of samples containing high percent of EVA and irradiated with high dose level.