An amine-terminated curing agent for epoxy resin based on hexachlorocyclotriphosphazene was synthesized. Its chemical structure was characterized by H-1-NMR, FT-IR, and elemental analysis. The curing temperature was determined by differential scanning calorimeter. The thermal stability, hydrophobicity, flame retardancy, and insulation property of the epoxy resin cured by the as-prepared curing agent were superior to those of the epoxy resin cured by 4,4-diaminodiphenylsulfone. The epoxy resin cured by the new curing agent obtained the best heat-moisture resistance when the ratio of amino protons and epoxy group was 1.2 : 1. The temperature reached 318 and 376 degrees C when the weight loss was 5 and 10% meanwhile the residue at 800 degrees C was above 64%. The material achieved UL94 V-0 rating and the water absorption was only 0.57%. The electric insulation property was also improved especially when it was compared in wet conditions at water absorption saturation. (c) 2013 Wiley Periodicals, Inc.