Low-density polyethylene/ethylene-vinyl acetate copolymer (LDPE/EVA) blend was irradiated by y-ray a n d then expanded by heat as a foamed material. T h e EVA content in the LDPE/EVA blend was benefited to form a gel. T h e gel fraction of the irradiated LDPE/ EVA blend increased with the increasing of its EVA content in a given dose. T h e gel fraction values of LDPE/EVA blend with 30% EVA content were higher than those of other blends in a same given dose; its gel fraction value was 1.7 times as those values of the L D P E without EVA. T h e gel fractions of the LDPE/EVA blend were increased with radiation dose in oxygen, in air, a n d in nitrogen, a n d the formation of gel was limited by oxygen. T h e oxidation products of the foam of the LDPE/EVA blend were observed in nitrogen, in air, a n d in oxygen by Fourier transform IR spectra. T h e LDPE/EVA blend system has no protection effect from oxidation in comparison with the LDPE system without EVA, which has less oxidation product than those without EVA in a same given gel fraction.
T h e gel fraction of the LDPE/EVA blend around 25--35%, radiation dose 25 f 5 kGy, irradiated by y-ray in air or in nitrogen, with higher expansion ratio (19), smaller cell diameter (0.175 mm), lower apparent density (0.042 g/cm3), higher tensile strength (0.40 MPa), and longer elongation at break (290-360%) foam of the LDPE/EVA blend were selected. These were optimum conditions for application in this system. T h e relations among gel fraction of the LDPE/EVA blend, expansion ratio, apparent density, average cell diameter, and mechanical properties of the foam were discussed. (0 1996 .John Wiley & Sons, Inc.