Ultrasonic and thermal properties of γ‐irradiated low‐density polyethylene

Abstract

Abstract The ultrasonic pulse‐echo technique and differential thermal analysis were utilized to characterize and to monitor the effect of γ‐irradiation on the sonic modulus and the heat effect of low‐density polyethylene. The sonic wave velocity, sonic modulus, and specific gravity exhibit a minimum for samples irradiated at 10 Mrad. A minimum in the heat capacity was observed at 1 Mrad. The estimated relative change of the activation energy of ordering exhibits a minimum at 100 Mrad. Below 10 Mrad, the perturbation and the loss of the crystalline phase override the effect of radiation cross‐linking. From 10 to 100 Mrad, the effect of cross‐linking as well as that of crystallinity are prevailing. Oxidative degradation is dominating above 100 Mrad. © 1993 John Wiley & Sons, Inc.