Investigation of Beta - irradiation effects on the microstructure of Low Density Polyethylene (LDPE) using (PALT)

Abstract

Beta-irradiation effects on the microstructure of LDPE samples have been investigated using Positron Annihilation Lifetime Technique (PALT). These effects on the ortho-positronium (o-Ps) Lifetime 3, the free positron annihilation lifetime , the free-volume hole size (V¬h) and the free volume fraction (fh) were measured as functions of Beta irradiation - dose up to a total dose of 30.28 kGy.
The results show that the values of 3, Vh and fh increase gradually with increasing Beta dose up to a total dose of 1.289 kGy, and reach a maximum increment of 17.4%, 32.8% and 5.86%, respectively, while 2 reachs maximum increment of 211.9% at a total dose of 1.59 kGy. Above these doses, the values show nonlinear changes up to a maximum dose of 30.28 kGy.
The results are discussed in the view point that Beta - irradiation may induce degradation, cross-linking and increasing of crystallinity in the amorphous regions of LDPE