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As a kind of thermal conductive material with good combination properties, thermally conductive rubber has been widely used in aeronautical, astronautical and electrical field where the heat needs to be dissipated. Due to its own advantages, silicone rubber is suitable to be rubber matrix, however, it has a low thermal conductivity and generally has to be filled with thermally conductive fillers.In this study, methyl vinyl silicone rubber was used as matrix and made into filled thermally conductive rubber by different methods and processes. Different thermally conductive fillers, such as silicone carbide, silicon nitride, graphite and silicon dioxide, were added into silicone rubber. The thermal performance and microstructure of samples were tested and observed by DSC, thermal conduction Analysis Instrument and SEM. There were many factors that influenced the thermal conductivity and microstructure of rubber material, The influences included filler type, filling fraction, particle size, particle shape and preparation process.The study shows that different fillers have different effects on thermal property of composite, fillers with better thermal property generally give materials higher thermal conductivity, and fillers possess sheet structure were beneficial to form thermally conductive chains, thus get a higher thermal conductivity.The thermal conductivity of thermally conductive silicone rubber increased as more fillers added into rubber, but the change of the thermal conductivity was not obvious at low filling fraction, after the fraction reached a certain amount, the accelerating rate of thermal conductivity became higher and then slowed down. This is because fillers in the composite can touch each other and form thermal conductive chains only when filling fraction reached a certain value.The sample was broke at a very low temperature, and the cross sections of samples were observed by SEM, through which we can obtain the microstructure of silicone carbide and graphite and their dispersion condition in rubber matrix. Through analyzing the relationship between microstructure and thermal conductivity of the composites, we can see that microstructure has important influences on the thermal conductivity of the material, the even distribution and fillers with sheet shape can gave a higher thermal conductivity, which is in accordance with thermally conductive chains theory.
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