Combined Effect of High-Temperature Shear Grinding and Gamma-Radiation on the Thermal Properties of Polyethylene

During γ-irradiation of polyethylene, its gradual amorphization accompanied by a decrease in the melting point and the heat of melting occurs. Almost complete amorphization of the polymer with crosslinking occurs at a dose of 1400 Mrad according to DSC data. In this case, the polymer retains insignificant crystallinity with a melting heat of 6.2 J/g, which is almost an order of magnitude lower than the melting heat of 118 J/g of unirradiated polyethylene. Depending on the radiation dose, there are three conditional ranges of change in DSC curve parameters: at doses up to 200, from 200 to 800, and over 800 Mrad, associated with different dose dependences of the simultaneously occurring processes of crosslinking and degradation of polymer macromolecules, as well as with radiation annealing of strained areas. High-temperature shear grinding of polyethylene, destroying the crystalline structure, leads to a decrease in the absolute value of the heats of melting and crystallization of the polymer.