Comprehensive study of positronium formation in polymer blends between polyethylene and ethylene-vinylacetate copolymer

The intensity I-3 Of or tho-positronium (o-Ps) in a polymer blend system consisting of polyethylene (PE) and ethylene-vinylacetate (EVA, random copolymer with a vinylacetate content of about 14%) was measured as functions of EVA weight content (Phi = 0-100%), electric field (E = 0-60 kV/cm), positron irradiation time (t = 0-200 h) and temperature (T = 100-300 K). It was found that the addition of small amounts of EVA to PE significantly alters the electric field, positron irradiation time and temperature dependence of I-3. Positron trapping on polar EVA is suggested to be responsible for the sensitive effects of EVA. (C) 2000 Elsevier Science Ltd. All rights reserved.