Research On Dielectrical Properties Of CdS@SiO₂/LDPE Composite

Polyethylene is a kind of thermoplastic resin with the excellent properties,but insulation properties of PE will be worse under high voltage for a long time.The studies show that the polyethylene added nanoparticles can improve the electrical properties of the composites effectively.In terms of electrical properties,Cadmium Sulfide（Cd S）is an ultraviolet absorber,which absorbs the photon energy generated from breakdown and inhibits the further development of collision ionization.Therefore,the breakdown property of polyethylene may be improved.Nanoscale Si O2 and LDPE constitute nanocomposites can also improve the breakdown properties of the composites.In terms of material properties,CdS@SiO₂ core shell structure is more dispersed than Si O2,and it is not easy to reunite.Based on the above reasons,the CdS@SiO₂ core shell structure was prepared by in-situ hydrolysis method and characterized by projection electron microscopy,infrared spectroscopy and XRD.It is proved that CdS@SiO₂ is coreshell structure.Then blending with LDPE prepare CdS@SiO₂/LDPE composite materials in order to test AC and DC breakdown strength under different temperature and content.The experimental results of AC and DC breakdown strength show that this kind of CdS@SiO₂/LDPE composite materials which added different contents comparing with the pure LDPE increased under normal temperature and 50 degree,but the AC and DC breakdown strength of composites decreased comparing with LDPE under 70 degrees and 90 degrees.According to the conductivity test,the current density of CdS@SiO₂/LDPE composites added different contents under normal temperature is basically the same as pure LDPE under low field strength.Under the high field strength,the current density of the composite decreased.When the content of CdS@SiO₂ is 3%,the current density is the smallest.With the decrease of concentration,the current density increases in turn.The current density of the composite increases with the increase of temperature.By measuring the dielectric properties of CdS@SiO₂/LDPE composites,it is known that the dielectric constant of composites increases slightly with increasing content,but the loss factor increases greatly.When the frequency is increased,the dielectric constant and the dielectric loss tend to decrease.