Dielectric And Thermal Properties Of MMT/SiC/EP Micro/Nano Composite

In high-voltage power system,the uneven distribution of electric field exists in cable accessories and large motor stator ends,which leads to the increase of the cost of design,manufacture and maintenance of high-voltage equipment.In order to solve this problem,composite materials with nonlinear conductivity are often used to realize the adaptive matching between the conductivity of the material and the applied electric field strength,so as to improve the uneven distribution of electric field on the insulating medium.In this paper,epoxy resin(EP)as matrix,silicon carbide(Si C)and montmorillonite(MMT)as inorganic fillers were used to prepare micro,nano and micro nano composite materials.X-ray diffraction(XRD)and scanning electron microscopy(SEM)were used to characterize the lamellar structure of montmorillonite and the micro morphology of the composite;The conductivity and breakdown field of the composites were measured at different electric field strength and temperature,and the carrier migration behavior was analyzed.The dielectric properties and glass transition temperature at different frequencies and temperatures were measured,and the interfacial polarization and molecular segment motion were analyzed.The effects of micro and nano fillers on the electrical and thermal properties of the composites were investigated.The results show that: montmorillonite and silicon carbide are evenly dispersed in epoxy resin,montmorillonite lamellar structure has a good degree of peeling,and there is no obvious agglomeration phenomenon.For the composite with single micron filler,the conductivity of the composite is significantly improved by doping micron Si C,and the nonlinear conductivity appears β-Si C ratio α-Si C.The conductivity and nonlinear coefficient of Si C composites are large.The conductivity and nonlinear coefficient of the composites increase with the increase of the particle size and content of Si C.For the micro nano composite,the conductivity of the composite changes with the addition of montmorillonite.With the increase of montmorillonite content,the conductivity of the composite decreases,the nonlinear coefficient increases,and the threshold field strength increases.The nonlinear coefficient of EP/5M/α3-S100(EP:MMT:Si C=1:0.05:1)is 2.65,which is 2.9 times of EP/α3-S100(EP:Si C=1:1).The results show that there is no obvious change of ionic conductivity barrier at low temperature,but the barrier becomes larger at high temperature.However,the ionic conductivity barrier of the micro nano composite increases in the low temperature region and the high temperature region.The results show that the introduction of micro Si C can reduce the breakdown field strength of the composites,while the introduction of montmorillonite can increase the breakdown field strength,but it is still less than that of pure epoxy resin.The breakdown field strength of EP/5M/α3-S100 is better than EP/α3-S100,increased by28%.With the increase of montmorillonite content,the breakdown field strength first increases and then decreases.With the increase of Si C content,the increasing trend of dielectric constant and dielectric loss is more obvious,and the temperature turning point decreases.The results show that the introduction of montmorillonite can reduce the dielectric constant and dielectric loss of the composites,and the dielectric properties at low temperature are more stable and the turning point is higher.If the content of nano filler is too high,the dielectric constant and dielectric loss will increase.The glass transition temperature of epoxy resin decreases and the thermal conductivity increases with the introduction of micro Si C.The glass transition temperature increases and the thermal conductivity increases with the introduction of montmorillonite EP/5M/α3-S100 is better than EP/α3-S100.The glass transition temperature and thermal conductivity increased by 15% and 112%.