Low permittivity epoxy nanoporous composites filled with hollow nanosilica

An epoxy nanoporous composite (NPC) filled with hollow nanosilica exhibits lower permittivity than unfilled epoxy resin. The hollow nanosilica is a silica nanoparticle containing a nanometric closed pore. To investigate the effect of the closed pore of hollow nanosilica, the particle porosity and permittivity of NPC filled with hollow nanosilica and NPC filled with mesoporous silica, the pores of which were open at the particle surface, were compared. The nanometric pores of hollow nanosilica and mesoporous silica were unfilled and partially filled with epoxy resin, respectively. The relative permittivity of NPC filled with hollow nanosilica was lower than that of NPC filled with mesoporous silica mainly owing to the closed pore of the hollow nanosilica. Moreover, the existence of the nanometric pore in hollow nanosilica negligibly affected the breakdown strength. These results indicate that the hollow nanosilica is applicable to insulating composites as a filler that can lower the permittivity of the epoxy composites even to a value lower than that of unfilled epoxy resin.