Effects of electrical discharges and deformation on the electrophysical and mechanical properties of high-pressure polyethylene

Abstract

Studies of the mechanical electrophysical properties of polymers and their modifications under the simultaneous influence of electrical discharges and mechanical force are presented. It is shown that a decrease in the electrophysical characteristics of the studied polymer materials in the presence of a tensile mechanical force leads to the accumulation of bulk charges in them and the formation of submicrocracks. This is indicated by the established relationship between the processes of formation and development of submicrocracks with the accumulation of bulk charge in polymers. These processes in their physical essence are elementary acts of destruction of polymer dielectrics, the development of which is determined by experimental conditions. It was found that when methylphenyltolylamine is introduced into the composition of high-pressure polyethylene, the structure of the resulting polymer modifications changes markedly. Therefore, a change in their dielectric losses and specific volume electrical resistivity should be expected. Indeed, as follows from the experimental data, the introduction of the proposed additive into high-pressure polyethylene in an optimal amount contributes to an increase in their volume resistivity by an order of magnitude and a decrease in dielectric losses. The authors have made an assumption that the detected decrease in the electrical strength of the films of the original and modified high-pressure polyethylene under the simultaneous influence of mechanical load on them is explained by the accelerated accumulation of bulk charges and the growth of microcracks, as a result of which ionization processes are intensively taking place in the developing inhomogeneities of the polymer dielectric. As follows from the results obtained, as the degree of mechanically stressed state of the samples increases, their durability decreases. This indicates that, along with a high electric field, one of the reasons for the appearance of bulk charges and inhomogeneities in the form of microcracks in polymer dielectrics is their mechanically stressed state.