Cu(0) and Cu(II) decorated graphene hybrid on improving fireproof efficiency of intumescent flame-retardant epoxy resins

To explore the synergism and mechnism of diverse forms of copper-decorated graphene on improving the fireproof efficiency of ammonium polyphosphate (APP) based polyamide-cured epoxy resin (EP), Cu(0) and Cu(II) decorated graphene hybrids (Cu2+-GO, Cu-rGO and CuO-GNS) were prepared through facile methods and used as synergists in EP/APP system. Cu2+-GO exhibits better synergistic effect with APP than Cu-rGO and CuO-GNS on reducing heat release of EP. Because Cu2+ is easier than Cu and CuO to go through various oxidation states and intermediates, which catalyze EP/APP system rapid formation of protective char layer containing crosslinked junctions of P (V) organic phosphates and Cu (II) salts. CuO-GNS exhibits better smoke suppression and harmful gases reduction in EP/APP matrix, such as aliphatic hydrocarbons, aromatic compounds and CO, due to its better conversion of CO to CO2 through a redox cycle. This work provides a promising strategy for preparation of EP with excellent flame retardancy and smoke suppression at low addition.