Structure dependence of gamma ray irradiation effects on polyurethane and epoxy resin studied by PAL technique


Positron annihilation lifetime (PAL) technique has been employed to study the microstructural changes of polyurethane (PU), EUXIT 101 and epoxy risen (EP), EUXIT 60 by Gamma-ray irradiation with the dose range (95.76 - 957.6) kGy. The size of the free volume hole and their fraction in PU and EP were determined from ortho-positronium lifetime component and its intensity in the measured lifetime spectra. The results show that the irradiation causes significant changes in the free volume hole size (Vh) and the fractional free volume (Fh), and thereby the microstructure of PU and EP. The results indicate that the γ-dose increases the crystallinity in the amorphous regions of PU and increase the cross-linking of EP.