Research On Electrothermal Properties Of Silicone Rubber By Zinc Oxide Whisker And Silicon Carbide Whisker

In recent years,with the progress of science and technology,the increasing power of high-voltage and high-power equipment will produce more heat;Low-power electronic equipment is gradually developing in the direction of small size and high efficiency,and the internal components are closely arranged,which is easy to generate heat accumulation.In order to improve the heat dissipation efficiency,it is necessary to continuously optimize the thermal interface materials.Filled thermal conductive composites are widely used because of their simple preparation process.For the traditional spherical packing,the percolation threshold of thermal conductivity is high.So high thermal conductivity is usually achieved by higher filling amount.However,too much filling will greatly lose the insulation performance of the matrix.How to reduce the filling amount is very important.In this paper,thermal conductive silicone rubber was prepared with silicone rubber as matrix,zinc oxide whisker（T-ZnO_w）and silicon carbide whisker（Si C_w）as fillers,and its electrothermal performance was tested.We will explore the influence of whisker modification,orientation and mixing on its thermal conductivity and electrical properties.We modified the whiskers.T-ZnO_w was modified by calcination and coupling agent（KH550）respectively.Calcination modification is to remove surface hydroxyl groups.The calcined T-ZnO_w hardly disperses in water,and the phenomenon of sinking to the bottom is serious.It shows that the calcination modification of T-ZnO_wis successful.KH550 is used to modify the surface hydroxyl groups,and reduce that hydrophilicity of T-ZnO_w surface.The infrared spectrum of KH550 modified T-ZnO_wshowed amino characteristic peak.It shows that KH550 modification of T-ZnO_w is successful.Si C_w was coated with magnetic material（Fe₃O₄）.In this way,the magnetic field can be used to orient and distribute it in the matrix.The coated modified Si C_wwas characterized by scanning electron microscope（SEM）and X-ray diffraction（XRD）.The result shows that Fe₃O₄ successfully coated Si C_w.T-ZnO_w and modified T-ZnO_w were filled into two-component additive liquid silicone rubber,and silicone rubber samples with different mass fractions were prepared.Compared with Maxwell-Eucken thermal conduction model,it is found that T-ZnO_w can form thermal conduction path faster than spherical particles.SEM characterization of its cross section shows that the modified T-ZnO_w is more closely connected with silicone rubber,and can improve the thermal conductivity effectively,breakdown field strength and dielectric properties.In order to study the effect of whisker mixing and orientation on the thermal conductivity of silicone rubber,samples of Si C_w silicone rubber with different mass fractions were prepared.The coated modified Si C_w was filled into silicone rubber and cured under magnetic field.The 10wt%oriented Si C_w silicone rubber sample was prepared.Silicone rubber was filled with coated modified Si C_w and T-ZnO_w according to the ratio of 1:1,and cured under magnetic field.The oriented hybrid silicone rubber silicone rubber sample with a total amount of 10wt%was prepared.It was found that the Si C_w in the oriented SiC_w silicone rubber sample was oriented by SEM.At 10wt%,the thermal conductivity is 72%higher than that of pure silicone rubber and 40%higher than that of Si C_w silicone rubber.However,the breakdown field strength and volume resistivity decreased.The hybrid orientation of whiskers can improve the thermal conductivity faster.Compared with the oriented Si C_w sample,its thermal conductivity,breakdown field strength and volume resistivity are all better.We simulated and analyzed the oriented SiC_w silicone rubber samples and Si C_wsilicone rubber samples with 10wt%content by COMSOL simulation software.The thermal conductivity of them is obtained by steady-state method.According to the simulation data analysis,the thermal conductivity of oriented Si C_w sample is 170%higher than that of pure silicone rubber and 68%higher than that of Si C_w sample.The increase rate of thermal conductivity is higher than that calculated by experimental data（72%,40%）.But the trend is the same.It can be proved by experiments and simulations that oriented whiskers can greatly improve the thermal conductivity and reduce the filling amount.