Modification of the optical band gap of polyethylene by irradiation with electrons and gamma rays

Irradiation of polymers has become an important technique in producing special materials for electronic applications. In this study, the effects of electron and gamma irradiation on ultra-high-molecular-weight polyethylene (UHMWPE) samples have been studied using UV-Vis absorption spectroscopy. The UHMWPE samples were irradiated with electron and gamma rays with doses ranging from 25 kGy up to 500 kGy. An increase in the optical absorption and a shifting from the UV-Vis towards longer wavelengths were observed. Concomitantly, a pronounced decrease in the optical band gap was recorded as a function of dose level. The optical band gap Eg varied from 2.86 eV for a pristine sample down to 1.98 eV and 2 eV for samples irradiated with gamma rays and electrons at the highest doses, respectively. A correlation between Eg and the number of carbon atoms N in a formed cluster is discussed in terms of a modified Tauc equation.