Amorphous silica-coated graphite particles for thermally conductive and electrically insulating resins

A thermally conductive and electrically insulating composite filler was produced by surfactant assisted sol-gel coating of amorphous silica on flake graphite. Amorphous silica-coated graphite (a-Si coated grp) obtained using a cationic surfactant showed the best enhancement of the insulating coating. The resulting a-Si coated grp/boehmite/polybutylene terephthalate polyester resin composite exhibited a high volume resistivity, exceeding 1.0 × 1014 Ω cm at an applied voltage of 500 V, and a thermal conductivity of 3.3 W/m K at 22.9 vol.% a-Si coated grp loading. The heat releasing performance of the developed resin composite in actual light-emitting diodes bulb housings was compared with conventionally used thermally and electrically conductive resin. This comparison revealed that the new composite released heat more effectively. This innovative technology, which may solve the trade-off between material properties and cost, will be available for a broad range of thermally conductive resin applications that simultaneously require thermal conduction and electrical insulation.