Melting of polyolefins in different organic matrices after plastic deformation at high pressure

Abstract

Mixtures of ultra-high-molecular-weight high-density polyethylene (UHMWPE), low-density polyethylene (LDPE), and polypropylene (PP) with various low-molecular-weight compounds were subjected to plastic deformation under a pressure of 1 GPa on an anvil-type high-pressure apparatus. The analysis of the mixtures was carried out by the DSC method and it was found that the thermograms of the deformed mixtures in the temperature range of 30-100°C contain endothermic peaks of melting of small polymer crystals and exothermic peaks of cold crystallization. The enthalpies of melting of polymers in mixtures could be either higher or lower than the enthalpies of melting of the initial polymers. Exothermic peaks were present on the thermograms of mixtures with fluorescein at temperatures above the Tm of polymers. Exo- and endothermic peaks below the Tm of polymers, as well as exothermic peaks above the Tm of polymers, were associated with the epitaxial growth of polymer crystals. The characteristics of thermal processes in deformed mixtures correlated with the amount of CH3 groups in macromolecules.