The invention discloses a DOPO-based symtriazine ring hydrogenated
benzimidazole epoxy curing agent and a preparation method thereof. The preparation method comprises the following steps: firstly, mixing a
solvent I, tricyanogen
chloride, p-hydroxy
benzaldehyde and an acid-binding agent, introducing
nitrogen gas, performing heating reaction to obtain 2,4,6-tri(4-formylphenoxy)-1,3,5-symtriazine ring; mixing a
solvent II, the 2,4,6-tri(4-formylphenoxy)-1,3,5-symtriazine ring and DOPO, introducing
nitrogen gas, and reacting to obtain DOPO-based formylphenoxy-1,3,5-symtriazine ring; dissolving the DOPO-based formylphenoxy-1,3,5-symtriazine ring in a
solvent III, dropwise adding solute into a mixture of o-phenylenediamine and the solvent III, adding a catalyst, and reacting to obtain the DOPO-based symtriazine ring hydrogenated
benzimidazole epoxy curing agent. According to the DOPO-based symtriazine ring hydrogenated
benzimidazole epoxy curing agent, vertical
combustion of cured matters passes UL94V-0 level; compared with non-
flame-retardant epoxy resin, the glass-
transition temperature is increased by 12.1% and the tensile strength is improved by 18.2%.