Positron annihilation lifetime spectroscopy studies of irradiated poly(propylene-co-ethylene)/poly(ethylene-co-vinyl acetate) blends

The positron lifetimes and Doppler broadening of the annihilation line are measured in poly(propylene-co-ethylene) (PPE)/poly(ethylene-co-vinyl acetate) (EVA) blends containing 10, 30, 50 and 60 wt% PPE before and after irradiation with fast electrons. On the basis of the values of the longest-lived ortho-positronium component in lifetime spectra the radii of the free-volume holes in amorphous regions of the blends are calculated. A sharp decrease of the values of the free-volume holes radii is established for PPE content in the range 30-50 wt%. The study of the irradiated samples showed that at low electron doses (up to 100 kGy) a crosslinking process prevails while at higher doses the net effect of irradiation is scission of polymer chains. Comparison is made of the results obtained by positron annihilation spectroscopy (PAS) and wide angle X-ray diffraction (WAXD). (author)