Effect of graphene nanosheets on morphology, thermal stability and flame retardancy of epoxy resin

Effect of graphene nanosheets (GNS) on morphology, thermal stability and flame retardancy of epoxy resin (ER) was investigated. GNS was partially exfoliated, large and flat graphene flakes exists in ER/GNS nanocomposites. GNS changed the decomposition pathway of ER at high temperature, enhanced the thermal stability and promoted the formation of char residue. The compactness of both the surface and the bottom char residues were significantly improved with the addition of GNS. Furthermore, GNS can effectively decrease melt flow and inhibit the flammable drips of ER during combustion. Incorporation of 3 wt% of GNS increased the LOI value of ER from 15.7 to 21.0 and reduced the total heat release from 33.37 to 28.20 kJ/m2. The peak heat release rate presented earlier increase and later decrease trend with the increase of GNS content due to the competition between the effect of thermal conductivity and barrier property of GNS.