Abstract
This paper describes the effects of α-Al2O3 nanosheets on the direct current voltage breakdown strength and space charge accumulation in crosslinked polyethylene/α-Al2O3 nanocomposites. The α-Al2O3 nanosheets with a uniform size and high aspect ratio were synthesized, surface-modified, and characterized. The α-Al2O3 nanosheets were uniformly distributed into a crosslinked polyethylene matrix by mechanical blending and hot-press crosslinking. Direct current breakdown testing, electrical conductivity tests, and measurements of space charge indicated that the addition of α-Al2O3 nanosheets introduced a large number of deep traps, blocked the charge injection, and decreased the charge carrier mobility, thereby significantly reducing the conductivity (from 3.25 × 10−13 S/m to 1.04 × 10−13 S/m), improving the direct current breakdown strength (from 220 to 320 kV/mm) and suppressing the space charge accumulation in the crosslinked polyethylene matrix. Besides, the results of direct current breakdown testing and electrical conductivity tests also showed that the surface modification of α-Al2O3 nanosheets effectively improved the direct current breakdown strength and reduced the conductivity of crosslinked polyethylene/α-Al2O3 nanocomposites.
Highlights
Polymer nanocomposites have attracted increasing attention in recent years owing to their improved direct current (DC) dielectric properties and applications as high-voltage DC (HVDC) cable insulation materials
The resulting nanocomposites were press molded at 356 K under a pressure of 16 MPa, yielding two different films with thicknesses of about 150 μm and 300 μm, respectively, which were used for the subsequent DC voltage breakdown testing and measurements of space charge
The square specimens with a thickness of 0.15 mm and a side length of 11.5 cm were prepared for the high-voltage breakdown testings, and the round specimens with a thickness of 0.3 mm and a diameter of 8 cm were prepared for the DC electric conductivity tests and measurements of space charge
Summary
Polymer nanocomposites have attracted increasing attention in recent years owing to their improved direct current (DC) dielectric properties and applications as high-voltage DC (HVDC) cable insulation materials. The addition of these inorganic nanoparticles suppresses the accumulation of space charge, reduces the electrical conductivity, and increases the breakdown strength of insulating materials to various degrees [5,6,7,8,9,10,11,12,13,14,15] This has been attributed to the introduction of deep trapping states resulted from the generated interface regions by nanoparticles, which can largely reduce charge carrier mobility. They may Materials 2020, 13, 1333; doi:10.3390/ma13061333 www.mdpi.com/journal/materials inorganic nanoparticles suppresses the accumulation of space charge, reduces the electrical conductivity, and increases the breakdown strength of insulating materials to various degrees [5–. The resulting nanocomposites were press molded at 356 K under a pressure of 16 MPa, yielding two different films with thicknesses of about 150 μm and 300 μm, respectively, which were used for the subsequent DC voltage breakdown testing and measurements of space charge
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