Method for grafting maleic anhydride with bisphenol A epoxy resin free radicals

The invention relates to a modification method of epoxy resins, in particular to a method for grafting maleic anhydride with bisphenol A epoxy resin free radicals, which is characterized in that the method comprises the following steps of 1) selecting raw materials according to the mass ratio of bisphenol A epoxy resin to dioxane solvent to maleic anhydride to free radical initiator of 100 to 75 to 30 to (3 to 6); 2) preheating the bisphenol A epoxy resin in the dioxane solvent to be fully dissolved; rising the temperature to 80 to 90 DEG C; adding the maleic anhydride and the free radical initiator for three times, wherein the interval time of each material addition is 3h; finishing the material addition; continuing a constant temperature reaction for 3h; and taking out the materials to prepare grafting products. The grafting products prepared by the method maintain basically unchangeable epoxide groups in original epoxy resin molecules and simultaneously have anhydride functional groups so that the reaction