Effect of novel methoxyl functionalized polysiloxanes on thermal conductivity and fluidity of alumina-filled silicone pastes

Three kinds of trimethoxysilyl-functionalized siloxane oligomers with different structures were prepared through condensation and hydrosilylation reactions to increase the volume fraction of Al₂O₃ fillers in the polysiloxane matrix and improve their dispersibility. The surface modification effect of the oligomers with different structures on the Al₂O₃ particles and their influence on the thermal conductivity, thermal resistance, and cone penetration of the thermal interface materials filled with the modified Al₂O₃ particles were studied in detail. The thermal conductivity and cone penetration of the composite material prepared from the Al₂O₃ particles treated with the α-trimethylsilyloxyl-ω-trimethoxysilylethyl-terminated PDMS oligomers showed a decreasing trend with the increase of the degree of polymerization of the siloxane segment. The thermal conductivity and cone penetration of the thermal interface material filled with Al₂O₃ particles treated with the α, ω-bistrimethylsilyloxyl-terminated PDMS oligomers bridged by (MeO)₃Si(CH₂)₂MeSiO segment and the methoxyl-functionalized tris(trimethylsilyloxyl-terminated polydimethylsiloxyl)silane oligomers showed a trend of first increasing and then decreasing with the increase of the length of the siloxane chain segment. The α, ω-bistrimethylsilyloxyl-terminated PDMS oligomers bridged by (MeO)₃Si(CH₂)₂MeSiO segment showed the best modification effect on Al₂O₃ fillers when the degree of polymerization n = 9. It could be used to prepare a thermally conductive silicone paste with an Al₂O₃ particle filling volume fraction of 88.0 vol%, a thermal conductivity reached up to 9.119 W / (m· K), and a 1/4 cone penetration of about 55.0.