Room Temperature Cured Silicone Rubber With Thermal Conductivity And Electrical Insulation

With the development of electronic industry, electronic components and integrated circuit tend to be integration and miniaturization, the thermal conductive and electrical insulative silicone rubber put forward higher requirements. There is an urgent need to develop an excellent silicone rubber material with thermal conductivity, electrical insulation and other comprehensive performances.In this thesis, α,ω-alkyloxypolysiloxane was used as substrate, tetramethoxysilane as crosslinking agent, dibutyltin diacetate as catalyst, Al2O3 as the main thermal conductive filler, A1N and SiC as auxiliary thermal conductive fillers, ZnO, nano TiO2, nano SiO2 and nano Al2O3 as anti settling agents, tin chelate as catalyst and methyltrimethoxysilane as crosslinking agent. The effect of the type of hydroxyl silicone oil, the type and amount of crosslinking agent and the type and amount of catalyst on the properties of silicone rubber matrix were investigated. The study found that hydroxyl silicone oil which viscosity is 1000 mPa-s was selected as the matrix silicone oil; tetramethoxysilane as crosslinking agent, the optimum dosage is 6 phr; dibutyltin diacetate or diacetyl acetone as catalyst, and the best amount of dibutyltin diacetate is 0.3 wt%. Silicone rubber prepared in this situation has good comprehensive properties. The effect of Al2O3 type, the treatment of Al2O3 and Al2O3 contents on thermal conductive and electrical insulative silicone rubber prepared by one-step method were investigated. The study showed that 10 μm Al2O3 through surface treatment by coupling agent was more suitable as conductive filler than that untreated. With the increase of alumina content, the mechanical strength, thermal conductivity, hardness and heat resistance of silicone rubber were improved, the volume resistivity and oil permeability were decreased. The experiment found that the one-step method exists defects such as the phenomenon of "viscosity swells", short storage, easy settlement and so on.Prepolymer was prepared by methoxy terminated reaction of hydroxyl silicone oil, then was mixed with conductive fillers and other additives to prepare electrical insulating and thermal conductive silicone rubber through two steps method. The two steps method improved the storage stability and solved the problem of "peak viscosity". The effect of the compound filler Al2O3/AIN, Al2O3/SiC on the properties of silicone rubber was investigated. Studies showed that compound filling furtherly improved the thermal conductivity, heat resistance and insulation performance. The effects of ZnO, nano TiO2, nano SiO2 and nano Al2O3 on the anti-sedimentation of silicone rubber were investigated. Experiment results showed that when ZnO, nano TiO2, nano SiO2 and nano Al2O3 were respectively as a single filler, and the filling amount was 8 wt%, 0.8 wt%,0.8 wt%,0.5 wt% respectively, the anti-sedimentation performance of silicone rubber was excellent. Meanwhile, the thermal conductivity of silicone rubber was improved to some extent, and the performance of insulating and mechanical was little affected.The phenyl hydroxyl silicone oil and hydroxyl silicone oil were mixed in a certain proportion as base oil to investigate the heat resistance of pure silicone rubber matrix. When the phenyl hydroxyl silicone oil content is 10 wt%, the calculative initial decomposition temperature of silicon rubber reached 467.4 ℃,67 ℃ higher than that without the addition of phenyl hydroxyl silicone oil. On the basis of the experiments, we carried out a pilot. The thermal conductivity of product reached 0.75 W/(m-K), the volume resistivity reached 8.3×1011 Ω·m and the breakdown voltage reached 15 kV/mm, which has achieved product requirements.