Electrical Properties Of BN/LDPE Nanocomposite Film With High Thermal Conductivity

The cable generates heat during continuous operation.The thermal conductivity of the polyethylene material is low and the heat is difficult to dissipate,which causes heat aging to become a key issue affecting the service life and safety performance of the insulation material.Secondly,in the process of HVDC transmission,the accumulation of space charge will cause severe distortion of the local electric field,which will seriously affect the aging and breakdown performance of the insulating material.Therefore,the preparation of polyethylene-based composite materials with high thermal conductivity and excellent electrical properties and research on its influence mechanism will provide reference for the use of polyethylene as a material for high-voltage direct current transmission cables.In this regard,this paper focuses on the thermal and electrical properties of BN/LDPE nanocomposites,and takes the space charge characteristics as the entry point.The influence mechanism of different doping concentrations on the electrical properties of BN/LDPE composites is discussed in depth.BN/LDPE nanocomposite films with different doping concentrations were prepared by melt blending and hot pressing.Scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR)were used to characterize the nanoparticle dispersion,cross-section morphology and structural composition of the film,and the doping effect of the nanocomposite was confirmed.The results show that by controlling the temperature of hot pressing and the time of pressurization during the experiment,a uniform dispersion of nano-BN/LDPE composite film can be prepared.The electroacoustic pulse method was used to characterize the space charge distribution of BN/LDPE composite films doped under different field strengths at 40 k V/mm and during short circuit.The experimental results show that the boronic charge doping effectively suppresses the accumulation of space charge.This may be due to the introduction of a large number of traps in the matrix after doping the nanoparticles,and trap trapping the injected carriers to form a reverse electric field,effectively suppressing further injection of carriers,thereby effectively suppressing the accumulation of space charges.The dielectric constant,dielectric loss and breakdown strength of the BN/LDPE composite films with doping ratios of 1%,3%,5%,and 10% were measured by a broadband dielectric spectrometer.The experimental results show that a small amount of boron nitride is incorporated to increase the dielectric constant of the polymer and increase the breakdown field strength,which has an outstanding influence on the insulation performance of the lifted film.The thermal conductivity test of the BN/LDPE composite film with pure boron nitride film and boron nitride doping concentration of 1%,3%,5% and 10% was carried out by laser thermal conductivity tester.Analysis of the experimental data shows that since boron nitride has good thermal conductivity,the thermal conductivity of the composite film can be improved after doping,and the thermal conductivity is significantly improved.