Thermally Reduced Graphite Oxide and Mechanochemically Functionalized Graphene as Functional Fillers for Epoxy Nanocomposites

In this study we examine graphene with different shape, size, functionality and electrical conductivity as carbon nanofiller for epoxy (EP) composites. Thermally reduced graphite oxide (TRGO) and a nitrogen doped derivative (N‐TRGO) are compared with multilayer graphene (MLG) derived from milling of graphite. Whereas wet grinding of graphite forms stable non‐functionalized MLG dispersions, solvent free dry grinding of graphite under N 2 and CO 2 pressure allows for mechanochemical functionalization of graphite. TRGO and N‐TRGO show best exfoliation, highest electrical conductivity and efficient matrix reinforcement at low percolation threshold. As compared to TRGO, wet and dry grinding represent cost‐effective routes to MLG and afford EP composites with improved stiffness at higher filler content. These fillers offer great promise for application in carbon/polymer composites going well beyond the scope of epoxy resins.