Investigation On Dielectric Properties In Polyvinyl Micro/Nano-Composites

The addition of inorganic nanoparticles into the pol ymer can improve the crystallization behavior and a series of dielectric properties.However,due to the small particle size and big surface energy of nano particles,it is easy to reunite in the blending process.Inorganic micron particles have excellent thermal conductivity and electrical corrosion resistance.They can also be used as filler to modify polymer.If the micron particles and nano particles are blended into the polymer together,by adjusting the ratio of micron particles and nano particles,because of the synergy,the dielectric properties of composites might be more superior than the only nanocomposites or only micro composites.In this paper,the matrix is low density polyethylene,MMT particles treated by ultrasonic exfoliation become to the nano filler,and the micro filler is Si O2 particles.Pure polyethylene samples,nanocomposites,micro composites and micro/nano-composites are prepared by melt blending method.Firstly,the microstructure of the material is characterized by DSC test and PLM test,then the material is chemically characterized by FTIR.Then the dielectric strength,polarization behavior,dielectric loss and conductance of the four materials are compared.Finally,electrical treeing experiments are carried out on four specimens at different voltage levels and different temperature levels to study the electrical treeing aging characteristics.The experimental results show that,the addition of inorganic particles into the polyethylene can improve the crystallization of polyethylene,increase the crystallinity and decrease the cell size.The addition of inorganic particles does not change the structure of the polyethylene molecule itself.A new chemical force is formed between two inorganic particles and inorganic particles and interfaces.The addition of micron particles can obviously improve the breakdown strength of the material;nanoparticles can reduce the dispersion of the breakdown field strength,the breakdown performance of the micro/nanocomposite material is the best.The polarization behavior inside the medium will become complicated due to the addition of inorganic particles,so there will be more interface loss.Because of the synergistic effect between particles,the loss of micro/nano-composites will be maintained at a relatively low level.The conductivity of composites is lower than that of pure polyethylene samples and the effect of temperature on the conductivity of samples is reduced.It is concluded that the addition of inorganic particles will improve the diele ctric properties of polyethylene matrix.Under the same conditions,the length of electrical branch growth in micro/nano-composite is the shortest and the morphology of branches is denser.It shows that the property of resisting electrical tree in micro/nano-composite is excellent.At high temperature,the critical temperature point of electric tree branches from brush to branch is obviously high in micro/nano-composites.When the cable operating temperature is high,micro/nano-composites is not easy to cause breakdown due to the development of electrical tree.