Abstract
The synergistic effects of zinc oxide (ZnO) Micro/Nano particles simultaneously filled in low-density polyethylene (LDPE) on the space charge characteristics and electrical properties has been investigated by melt blending micro-scale and nanoscale ZnO additive particles into LDPE matrix to prepare Micro-ZnO, Nano-ZnO, and Micro-Nano ZnO/LDPE composites. The morphological structures of composite samples are characterized by Polarizing Light Microscopy (PLM), and the space charge accumulations and insulation performances are correlated in the analyses with Pulse Electronic Acoustic (PEA), DC breakdown field strength, and conductance tests. It is indicated that both the micro and nano ZnO fillers can introduce plenty of heterogeneous nuclei into the LDPE matrix so as to impede the LDPE spherocrystal growth and regularize the crystalline grains in neatly-arranged morphology. By filling microparticles together with nanoparticles of ZnO additives, the space charge accumulations are significantly inhibited under an applied DC voltage and the minimum initial residual charges with the slowest charge decaying rate have been achieved after an electrode short connection. While the micro-nano ZnO/LDPE composites acquire the lowest conductivity, the breakdown strengths of the ZnO/LDPE nanocomposite and micro-nano composite are, respectively, 13.7% and 3.4% higher than that of the neat LDPE material.
Highlights
Low density polyethylene (LDPE), as a nonpolar polymeric polymer material, has been widely used in insulated cable of the power system [1,2,3] because of its high insulation resistance, low dielectric constant, and dielectric loss with minimal influence from temperature and frequency
When the applied direct current (DC) electric field increases to 20 kV/mm, substantial positive space charges accumulate near applied DC electric field increases to 20 kV/mm, substantial positive space charges accumulate near the anode in neat LDPE and a spot of homo-charges with the maximum charge density of 1.4 C·m−3 the anode in neat LDPE and a spot of homo-charges with the maximum charge density of 1.4 C·m-3 arises at the location of 100 μm near the cathode in the nano-zinc oxide (ZnO)/LDPE composite
When the applied DC electric field increases to 20 kV/mm, substantial positive space charges accumulate near the anode in neat LDPE and a spot of homo-charges with the maximum charge density of 1.4 C·m-3 arises at the location of 100 μm near the cathode in the nano-ZnO/LDPE composite
Summary
Low density polyethylene (LDPE), as a nonpolar polymeric polymer material, has been widely used in insulated cable of the power system [1,2,3] because of its high insulation resistance, low dielectric constant, and dielectric loss with minimal influence from temperature and frequency. Cheng Xia blended nano-ZnO particles with polyethylene matrix and studied the effects of different corona aging time on space charge distribution and pressure characteristics of materials [22]. Until now, the further study of whether the co-doping of nano-fillers and micro-fillers in polymer matrix materials will improve space charge distribution and DC breakdown strength due to a synergistic effect has not been reported in literature. Micro/nano-scale zinc oxides (ZnO) are characteristic multifunctional materials with high chemical stability and good biological compatibility, which has unique catalytic, electrical, optical, mechanical, and antibacterial properties that could have been employed in various applications. The space charge distribution, DC breakdown field strength, and conductivity are tested to explore the modification mechanism of space charge and electrical properties attributed to filling nano and micro ZnO particles into polyethylene material
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