Effects of morphology on transvinylene formation in irradiated polyethylene

PE samples of various densities were subjected to various doses of ionizing radiation. Also varied were the draw ratio and the thermal treatment (before and after irradiation). Each sample was subjected to FTIR, DSC and bulk density measurements. The results show that irrespective of the irradiation conditions, draw ratio, or thermal treatment, the absorbance per unit thickness at 1305, 1897 and 2018 cm-1 is a linear function of crystallinity. Also the absorbance per unit thickness at each of these lines is constant up to 1 MGy. The absorbance measurements at 965 cm-1 combined with the optical pathlength, dose, crystallinity and extinction coefficients (in amorphous and crystalline PE) for transvinylene (TV) lead to these results: (1) TV is produced with a yield of 0.09 μmol/J in the amorphous region and 0.21 in the crystalline region, irrespective of morphology; (2) after melting and recrystallization, the TV is preferentially redistributed in the amorphous region