Preparation And Properties Of Thermally Conductive And Electrically Insulating Silicone Rubber Composites

Recent development in electronics technology has resulted in the miniaturization and integration of electronic devices, and thus heat dissipation is becoming a key factor that restricts working performance and life of those devices. Thermally conductive silicone rubber composites have been recently paid to increasing attention due to its excellent properties such as wonderful electrical insulation, good thermal and chemical stability, high temperature-resistivity and oil-resistivity, etc.In this paper, thermally conductive and electrically insulating silicone rubber composites were prepared, with methyl vinyl silicone rubber (MVQ) and addition-cured liquid silicone rubber as the matrix and aluminum nitride (AlN) and silicon carbide (SiC) as the conductive fillers, respectively. The thermal conductivity, mechanical performance, electrical insulating property, as well as thermal stability of the prepared composites were tested and analyzed thereafter.The investigation results showed that thermal conductivity of the silicone rubber composites was increased with growth of filler content. With the same filling content, filler of larger size exhibited greater effect than that of smaller size on improving thermal conductive property of the composites. In another aspect, the thermogravimetric results indicated that the addition of each kind of the two fillers significantly improved thermal stability of the composites.As for the high-temperature vulcanized silicone rubber composites, with the increase of filler content, the tensile strength was enhanced initially but then it got decreased with further addition of the filler, while the elongation at break showed continual decrease. Besides, although both the volume resistivity and surface resistivity suffered increasing drop with greater filler content, the composites possessed good electrical insulating property.As for the addition-cured liquid silicone rubber composites, different methods of treatment with the same content of n-decyltrimethoxysilane produced different effects on the thermal conductivity of the samples. When the fillers were pre-treated with the n-decyltrimethoxysilane, the compatibility and interfacial adherence between filler and matrix were improved and thus the thermal conductivity of the composites was increased. However, when the coupling agent was directly added to the mixture, the thermal conductivity was slightly decreased. Compared with the up-to-the-date thermal conductive silicone rubber commodity on the market, the samples prepared in this paper are of medium thermal conductivity, lower density and greater hardness. How to further increase thermal conductivity and reduce hardness of the composites is a subject that needs continual investigation.