The development of crystallinity and transparency in irradiated polyethylene

A procedure has been developed for producing highly transparent polyethylene by use of high‐energy electron irradiation above the melting point. The polyethylene retains about 60% of its original tensile strength after receiving the optimum irradiation dose of 50 Mrad at room temperature followed by 50 Mrad at 150°C. The transparency of a 0.02 in. sample increases from about 20% to 75% under this treatment. Changes in transparency with time and temperature, during cooling of the polyethylene from 150°C. to various quench temperatures were investigated as a function of irradiation dose. The increase in transparency is a result of reduction in crystallinity, in size of crystallites and spherulites, and in rate of crystallization caused by the restraints imposed by the radiation‐induced crosslinking.