AC dielectric properties of functionalized SiO2/UV-XLPE nanocomposites

Aiming at the problem that nano-SiO2 materials are easy to agglomerate in XLPE matrix, nano-SiO2 was introduced into the network structure of UV-XLPE by using sulfhydryl double bond click chemistry and surface modification technology of nano materials, which improves the dispersion of nano-SiO2 in XLPE matrix and introduces more deep traps; The polar groups on the surface of functionalized nano-SiO2 also change the interface characteristics between it and XLPE matrix, so as to improve the dielectric properties of functionalized SiO2/UV-XLPE nanocomposites. The structure of the material was characterized by 1H NMR, FTIR and SEM. The dielectric constant of the material at power frequency was measured under the condition of εr and tanδ. The effect of high dielectric shell on the temperature dependent dielectric properties of functional nano-SiO2 was discussed. The distribution of trap energy levels in the material was explored by TSC test, and the AC breakdown characteristics of the material were tested under a certain temperature gradient. With the increase of temperature, the thermal motion of impurity molecules in the composites intensifies, making the relative dielectric constant ε r decreases with the increase of temperature, and the contribution of dipole steering to dielectric loss increases gradually, so the tangent of loss angle tan δ showing a growing trend. In addition, the functionalized nano-SiO2 introduces many deep traps that capture electrons in the interface. These deep traps limit the migration of carriers and significantly improve the high-temperature AC breakdown strength. Among them, the AC breakdown field strength of 1.5wt%TMPTA-s-SiO2 is the highest, and the characteristic breakdown field strength is 5.8% higher than that of pure XLPE at 80 ℃, with the best breakdown resistance stability at high temperature. © 2022 Editorial Department of Electric Machines and Control. All rights reserved.