Microwave-accelerated synthesis of silica nanoparticle-coated graphite nanoplatelets and properties of their epoxy composites

Silica nanoparticle-coated graphite nanoplatelets (GNPs) as a thermally conductive and electrically insulating filler for epoxy composites were prepared by a base-catalyzed sol-gel reaction with polyvinylpyrrolidone-modified GNPs under microwave irradiation for 5 min. The surface resistivity of the silica nanoparticle-coated GNPs increased to 1.62 × 104 Ω/sq from 1.16 × 101 Ω/sq for the raw GNPs because the silica nanoparticles provide an electrically insulating property. Moreover, the silica nanoparticle-coated GNPs/epoxy composite at a 2 wt% filler loading ratio retained an electrical insulating value of 9.68 × 1012 Ω/sq. The silica nanoparticle-coated GNPs/epoxy composites significantly enhanced the thermal conductivity and the critical stress intensity factor of the composite at 2 wt% filler loading by 77.6% and 34.1%, respectively. On the other hand, the mechanical properties of raw GNPs/epoxy composite were decreased by the addition of GNPs. The increased properties of silica-coated GNPs/epoxy composites were explained in terms of the formation of strong interactions with filler and epoxy matrix.