Preparation And Properties Of Thermal Conductive Silicone Rubber

With the increasing integration and miniaturization of electronic equipment,and the increasing capacity and power density of power batteries,more and more heat is generated during work,and heat dissipation has become a key technology restricting the development and safe operation of equipment.Low density heat conducting resin,heat conducting film and potting adhesive with high thermal conductivity and good insulation properties are the key materials to support the development of related technologies.Silicone rubber has the advantages of chemical corrosion resistance,high and low temperature resistance,good insulation,but at the same time,its poor thermal conductivity,mechanical properties and other shortcomings limit its application in many fields.In this paper,the silicone rubber is filled with different thermally conductive fillers to improve its thermal conductivity and mechanical properties,and the influence of the distribution of fillers in the rubber matrix on the thermal conductivity of the composite material is explored.The thermal conductivity of silicone rubber composite was improved by the filling of fillers.Thermal conductive silicone rubber was prepared by filling MWCNT,G and BN into silicone rubber.The results shows that the thermal conductivity of the composite increases with the increase of the filling amount.The thermal conductivity of blank silicone rubber is 0.22 W/m-1·K-1,the MWCNT/silicone rubber composite with 12%filling mass ratio reaches 0.73 W/m-1·K-1,increasing 227.3%;GNs/silicone rubber composite with 12%filling mass ratio reaches 1.10W/m-1·K-1,increasing 395.7%.When the filling amount is low,because the filler particles in the system are isolated from each other,it is difficult to form a thermal conductivity chain,and the thermal conductivity increases slowly;however,with the increase of filler particles,it is easier to contact each other and form a thermal conductivity path,so that the thermal conductivity increases rapidly.MWCNT/GNs composite filler filled with silicone rubber shows better reinforcement effect and higher thermal conductivity.It is the result of the synergism between the two fillers of different shapes and the ?-?interaction between fillers and between fillers and benzene rings in the matrix.The size of filler has an important influence on the thermal conductivity and mechanical properties of composite.In this paper,conductive silicone rubber was prepared by filling BN with the diameter of 2 ?m,10 ?m and 24 ?m,respectively.Under the same filling amount,the filler with large diameter improves the thermal conductivity of the composite material better.This is because the fillers with larger sheet diameter are more likely to contact each other to form a heat conduction chain,so that the heat conductivity can be increased faster.The tensile strength curves show different trends.The tensile strength curve of the composites filled with 2 ?m BN increases first and then decreases.This is because the rubber matrix plays a leading role when the filler content is low,and the filler itself has a certain reinforcement effect,so that the tensile strength of the material is improved;while with the increase of filler particles in the system,the filleris easy to agglomerate,and the interface bonding force between the filler and the matrix is weak,which is easy to produce stress concentration,so that the tensile strength is reduced.The filler with a large sheet diameter has a cutting effect on the rubber matrix,so the damage to mechanical properties is more obvious,and the tensile strength curve shows a downward trend.Dopamine hydrochloride was used to modify the surface of BN,and the surface of BN was coated with a layer of polydopamine.The study found that the modified BN silicone rubber showed better mechanical properties and higher thermal conductivity,indicating that the polydopamine layer on the surface of BN improved the interface adhesion between the filler and the polymer matrix.By repeatedly extruding the compounded rubber,the linear MWCNTs are better dispersed in the rubber and oriented in the extrusion direction,making the silicone rubber with a higher thermal conductivity.Using freeze-drying technology,the GO/deionized water dispersion is made into a three-dimensional packing network(3D-GO),and using silicone rubber to make a composite.It was found that the higher thermal conductivity(0.318W/m-1·K-1,0.372W/m-1·K-1)can be achieved at lower filler loading(1.5%,2%).It is found that the orderly distribution of fillers is beneficial to the improvement of thermal conductivity by simulating the two dispersion states of fillers in the matrix.