Features of Charge State of Nanocomposites of Ultrahigh Molecular Weight Polyethylene + α-SiO2

This paper presents the results of the study of electret properties of composite materials based on ultrahigh molecular weight polyethylene (UHMWPE) and nano-dispersed amorphous silica filler α-SiO₂ (aerosil) depending on the volume content of silicon dioxide and the absorbed dose D γ-irradiation at room temperature, using the method of thermally stimulated depolarization (TSD). It was found that an introduction of up to 5% of spherical nanoparticles of amorphous α-SiO₂ silicon dioxide with a diameter of 20 nm in UHMWPE first increases and then reduces the electret characteristics of the composites. UHMWPE + 1% α-SiO₂ has the maximum value of the electret potential difference and the stability of the electret state.          It was shown that preliminary g-irradiation affects the electret properties of the studied composite material, which is associated with its increased electrical conductivity and a high charge relaxation rate. The observed increase in the initial surface charge density s_el. of UHMWPE compositions is associated with the presence of energy traps of injected charge carriers. Based on the analysis of the spectra of TSD, it was shown that the thermal stability of electrets from the UHMWPE composite + 1% α-SiO₂ is improved. The nature of the TSD current of pre-γ-irradiated films once again proves that after γ-irradiation, the injected charges from the corona zone mainly accumulate in the near-surface layers of the irradiated samples. The results of TSD suggest that the relaxation of the electret state in the materials under study occurs due to the bulk conductivity.