Maleimide-epoxy resins: preparation, thermal properties, and flame retardance

Maleimide modified epoxy compounds were prepared through reacting N-(4-hydroxylphenyl)maleimide (HPM) with diglycidylether of bisphenol-A. Triphenylphosphine and methylethylketone were utilized in the reactions as a catalyst and a solvent, respectively. The resulting compounds possessed both oxirane ring and maleimide group. The kinetics of the curing reactions of the maleimide-epoxy compounds and amine curing agents, 4,4-diaminodipheylmethane (DDM) and dicyandiamide (DICY), were studied. Incorporation of maleimide groups into epoxy resins provided cyclic imide structure and high cross-linking density to the cured resins, to bring high glass transition temperatures (179 °C) and good thermal stability (above 380 °C) to the cured resins. High char yields in the thermogravimetric analysis and high limited oxygen index values (25.5–29.5) were also observed for the cured resins to impy their good flame retardance.