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

The intensity I3 of ortho-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 I3. Positron trapping on polar EVA is suggested to be responsible for the sensitive effects of EVA.