▎ 摘　　要

NOVELTY - High-efficiency flame retardant comprises graphene oxide synergistically modified by a halogen-free phosphorus-nitrogen compound of formula (I) or (II). USE - High-efficiency flame retardant for use in an epoxy resin composite materials (claimed). ADVANTAGE - The high-efficiency flame retardant has no toxicity, and good compatibility. The flame retardant is free of halogen elements, so that the flame retardant is green and environment-friendly. The phosphorus flame retardant is added, so that the flame retardant efficiency of the flame retardant is improved. The toxicity of the flame retardant is reduced, and the introduction of the phosphorus flame retardant can improve the capture of free radicals in the combustion process. The introduced nitrogen flame retardant can also play a role in diluting combustible gas and oxygen. The added graphene oxide can improve the mechanical property, the thermal property and the heat barrier property of the composite material and improve the comprehensive performance of the composite material. DETAILED DESCRIPTION - High-efficiency flame retardant comprises graphene oxide synergistically modified by a halogen-free phosphorus-nitrogen compound of formula (I) or (II). (R is phosphorus oxychloride, phenylphosphonic dichloride or hexachlorocyclotriphosphazene). INDEPENDENT CLAIMS are included for: (1) a method for preparing the flame retardant, which involves adding p-aminoacetophenone, aniline and p-toluenesulfonic acid into a three-neck flask under the protection of inert gas, heating and melting in an oil bath at 80-100 ℃, adding 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, magnetically stirring at 100-150 ℃ for 12-24 hours, performing suction filtration, washing and drying to obtain a first solid powder, dispersing graphene oxide in an organic solvent, adding triethylamine and a chlorinated compound, reacting for 8-12 hours at 0-25 ℃, decompressing, filtering, washing and drying after the reaction is finished to obtain a second solid powder, and dispersing the solid powder in an organic solvent, adding triethylamine and the first solid powder, reacting for 8-12 hours at 60-90 ℃, standing for 6-12 hours, performing reduced pressure suction filtration, alternately washing with ethanol and deionized water for multiple times, and drying in a vacuum oven to obtain a final product; and (2) use of high-efficiency flame retardant in an epoxy resin composite materials. DESCRIPTION OF DRAWING(S) - The drawing shows a vertical combustion test chart of high-efficiency flame retardant.