Investigation Of Dielectric Properties Of Micro-nano ZnO/LDPE Composites With Different Shapes

Modification of insulating materials for cables by doping and blending technology to improve composite materials,breakdown electric field,insulation resistance coefficient and reduction of thermal resistance coefficient are the key to solve insulation aging of power cable.Nano-fillers have obvious effects on inhibiting the accumulation of space charge in polyethylene and improving its breakdown electric field strength.Micron fillers have outstanding electrical corrosion resistance and thermal properties due to their large particle size.Whether the doping of micro and nano fillers will affect the space charge and DC breakdown of the matrix materials due to their synergistic effect has not been further studied.In this paper,low density polyethylene(LDPE)was used as matrix material.The nanospheres,microspheres,microneedles,microspheres-nanospheres and microneedles with an average particle size of 30 nm and a diameter of 1.5-3 um and a length of 20-30 um were prepared by melt blending method and two-step method,respectively,with 0.5%,1% and 3% of nanospheres,microspheres,microspheres and microneedles.-Nanospherical ZnO/LDPE composites.The morphology of needle-shaped ZnO particles was observed by scanning electron microscopy(SEM)and polarized light microscopy(PLM).The Zn-O bonds of the composites were characterized by Fourier transform infrared spectroscopy(FTIR).The crystallinity and melting peak temperature of the composites were measured by differential scanning calorimeter(DSC).The micrometers,nanometers and micrometers of pure low density polyethylene and composite fillers were compared and studied.-Dielectric spectrum,breakdown and conductivity of nanocomposites.The doping of spherical ZnO particles changed the crystallinity of the composites to a certain extent.The crystallinity of nanospherical composites was the most obvious.With the increase of the content of needle-shaped ZnO particles,the crystallinity of micron needle-shaped composites decreased.The material has obvious needle structure and characteristic absorption peak of zinc oxide.The AC and DC breakdown field strengths of the composites with needle-like ZnO particles are lower than those of pure LDPE,and decrease with the increase of filler content.The breakdown field strength is the lowest when the filler content is 3%.The AC and DC breakdown field strengths of the composites with spherical ZnO particles are increased.The breakdown field strengths of micro-and nano-composite materials are between micron needles and nanospherical composites.With the increase of electric field strength and temperature,the conductivity of LDPE and various composites increases.The addition of micron needle zinc oxide can significantly improve the conductivity of ZnO/LDPE composites and increase with the increase of its content.The relative dielectric constant and tangent value of loss angle of all composites are greater or approximately equal to pure LDPE.However,in the whole frequency range,the dielectric constant of micron needle-nano spherical ZnO/LDPE composites is lower than that of LDPE,which provides a theoretical basis for new insulation with low dielectric loss.