▎ 摘　　要

NOVELTY - Graphene-based flame retardant is prepared by adding 1-butyl-3-methylimidazole trifluoroacetate ionic liquid solution to graphene, and uniformly stirring to obtain ionic liquid modified graphene. The ammonium magnesium phosphate is added and blended. USE - Graphene-based flame retardant for polymethacrylimide foam (claimed). ADVANTAGE - The graphene-based flame retardant has high performance, and ensure the mechanical property of the material. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing polymethacrylimide foam, which involves: (A) mixing methacrylic acid, methacrylonitrile, graphene-based flame retardant, light magnesium oxide, methacrylamide, allyl methacrylate, N-methylformamide, Isopropyl alcohol, Tert-butyl methacrylate, Benzoyl peroxide, Azobisisoheptonitrile at room temperature, pre-polymerizing obtained mixed solution under stirring conditions, and pouring the pre-polymerized mixed solution into mold; and (B) heating injected mold with the mixed solution to polymerize the mixed solution, opening mold to obtain flame-retardant polymethacrylimide PMI copolymer plate, and foaming copolymer plate to obtain polymethyl Acrylimide flame retardant foam.