Dealcoholized Room Temperature Vulcanized Thermal-Conductive Silicone Rubber With High Electrical Insulation

Dealcoholized room temperature vulcanized ?RTV? silicone rubber is a kind of environment friendly silicone rubber with performances of resistance of oxidation, high and low temperature and so on,which has been used widely in many fields. The development of high-performance silicone rubber is highly desirable in electrical and other industries with the development of science and technology. Thermal conductive filler could improve thermal conductivity of silicone rubber, but electrical insulation of the composite was usually reduced significantly. In this paper,a silicone rubber composite was prepared with both thermal conductivity and high electrical insulation.The main contents are as follows.RTV thermal-conductive silicone rubber was obtained with hydroxy-terminated polydimethylsiloxane, tetramethoxysilane, dibutyltin diacetate, and Al₂O₃ acted as substrate, crosslinking agent, catalyst and basic thermal conductive filler respectively.The effect of type, content, particle size and surface treatment of Al₂O₃ on viscosity,thermal conductivity and volume resistivity and other properties of silicone rubber were studied. 10?m spherical Al₂O₃ was selected as thermal conductive filler in the paper.Although the thermal conductivity, mechanical properties and thermal stability of the composite were improved with the increasing of Al₂O₃, however, the volume resistivity and electrical breakdown strength were decreased obviously. The settlement phenomenon was serious and it could not meet the storage requirements before silicone rubber vulcanized.With the instead of Al₂O₃ by SiO₂ partly, electrical insulation, storage stability, tensile strength and thermal stability of the compound were significantly improved. When the proportion of SiO₂:Al₂O₃ was 60:40 with the total filling amount 65 wt%,the compound has good comprehensive properties: electrical breakdown strength was 27.1 kV/mm, volume resistivity was 2.4×1015 ?·cm, tensile strength was 1.2 MPa and oil penetration rate was 2.9 %.The performances such as anti-settling performance and insulation properties of RTV thermal-conductive silicone rubber with high electrical insulation were further improved with the addition of BN,Si₃N₄, nano-TiO₂,nano-SiO₂ and nano-Al₂O₃. When the content of nano-Al₂O₃ was 1.5 % in the total weight of powder, the composite exhibited excellent comprehensive properties: electrical breakdown strength was 28.0 kV/mm,volume resistivity was 8.3×1014 ?·cm, thermal conductivity was 0.64 W/?m·K?, oil penetration rate was 0.9 % and storage stability was pretty good.The pilot test was proceeded in the 15 L double planetary mixer and the performances of the composite were basically same as the previous experimental results.