Study On Dielectrical Properties Of （ZnO+Al₂O₃）/LDPE Nanocomposite

Nanocomposite is mixtures of polymer matrix and inorganic nanosized fillerparticles. The addition of inorganic fillers can improve the electric properties of thecomposites markedly. Moreover, it is also an effective way to enhance the figure ofmerit of insulation materials used in the electrical equipments and power electronicaldevice. Therefore, it can lead to the upgrading of traditional insulating materials, theenhancement of their qualities and the extention of new application fields ofdielectrics.So far, most of investigations have been focused on a single kind of nanoparticlefillers. The study of two or more kinds of nanofillers is rare. In this thesis, the lowdensity polyethylene （LDPE） is used as the base material and Al₂O₃nanoparticlesand ZnO nanoparticles modified by silane coupling agent （KH550） acted as thenanofillers. The mass ratio of two kinds of fillers is1:1. On this basis, nanocompositeis prepared via the melt blending method.And the mass fraction of filles is0.5%,3%,7%, respectively. The main efforts are devoted to the investigations on the effects ofZnO and Al₂O₃nanoparticle fillers, and their surface treatment on the dielectricalproperties of LDPE. In addition, the mechanisms corresponding to the dielectricalproperties of nanodielectrics are also discussed.In this paper, the dispersion of ZnO and Al₂O₃nanoparticles in LDPE ischaracterized by the SEM and the breakdown strength measurement. The resultsindicate that a small amount of doping nanoparticles are evenly dispersed in LDPEmatrix, while higher doping concentrations will contribute to slightly accumulation.At the same time, the nanoparticles modified by KH550will reduce the phenomenonof reunion, so nanoparticles and LDPE form the good nanocomposite system.Through the measurement of dielectric properties, such as volume resistivity,conduction current and space charge. The volume resistivity also increases, and themaximum increases to6.4times of the original values, Meanwhile, ZnO and Al₂O₃ fillers are helpful to suppress the space charge injection. And the effect is moreobvious when the concentration is3%, it is worth noting that there is scarcelyinjection when the electric field is50kV/mm. Simultaneously, the space chargesupression mechanism in LDPE matrix is discussed. It is hopeful to provide someguidance about dielectric properties improvement and mechanism discussion fornanocomposite.