Improvement in dielectric constant of carbon black/epoxy composites with separated structure by surface-modified hollow glass beads with reduced graphene oxide

The surface-modified hollow glass beads with reduced graphene oxide (rGO@HGB) were prepared by electrostatic self-assembly method and then blended with conductive carbon black (CB) and epoxy resin (EP), and were further used to prepare the CB/rGO@HGB/EP composites with segregated structure. Then microstructure, conductivity properties and dielectric properties of the composites were studied. The results show that rGO@HGB are excluded from the EP matrix, and CB particles are dispersed in the EP, forming a three-dimensional segregated percolation network in the CB/rGO@HGB/EP composites. rGO is coated on the surface of HGB to form a conductive bridge with the CB segregated conductive network, resulting in an efficient synergistic effect for improvement of conductive property and dielectric constant. Compared with CB/EP composites, the percolation threshold of CB/rGO@HGB/EP composites is significantly reduced to 0.08 vol%, and the electrical conductivity is greatly improved. The dielectric constant of 0.2 vol% CB/rGO@HGB/EP composites (600.27) at 1 kHz is 137 times higher than that of CB/EP composites (4.35), and the corresponding dielectric loss is only 0.08.