Preparation and properties of epoxy resin composites containing hexaphenoxycyclotriphosphazene

Hexaphenoxycyclotriphosphazene (HPCTP) was synthesized by a nucleophilic substitution reaction between hexachlorocyclotriphosphazene and phenol. The chemical structure of HPCTP was then characterized by Fourier transform infrared spectroscopy as well as H-1 and P-31 nuclear magnetic resonance spectroscopy. The synthesized HPCTP was incorporated into the diglycidyl ether of bisphenol A to prepare epoxy resin (EP) composites using 4,4-diamino diphenylmethane as curing agent. The thermal and flame-retardant properties of cured samples were investigated by differential scanning calorimetry, thermogravimetric analysis, UL-94 vertical burning test, and cone calorimetry. Evaluation of thermal properties demonstrated that the resulting composites achieved high thermal stability with high char yields. The UL-94 V-0 rating was easily achieved with the addition of HPCTP, and the heat release intensity simultaneously decreased. Results of scanning electron microscopy and energy-dispersive x-ray spectroscopy confirmed that HPCTP can enhance the thermal stability and flame retardancy of epoxy resin.