Synthesis and Property of Flame Retardant Epoxy Resins Modified with 2-(Diphenylphosphinyl)-1,4-benzenediol

2-(Diphenylphosphinyl)-1,4-benzenediol(DPO-HQ) was synthesized by the reaction of diphenylphosphine oxide(DPO) with 1,4-benzoquinone(BQ), and characterized by Fourier transform infrared(FTIR), and nuclear magnetic resonance(H-1 NMR, C-13 NMR, P-31 NMR) spectrometries. The thermal stability of DPO-HQ was investigated by thermogravimetric analysis(TGA). Flame retardant epoxy resin was synthesized based on DPO-HQ. The thermal properties and burning performance of cured epoxy resins were measured by differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), limited oxygen index(LOI) and vertical burning test(UL-94V). The morphologies of cured epoxy resins after combustion were investigated by scanning electron microscopy(SEM) and electron probe microanalysis(EPMA). Moreover, the thermal stability(both in air and in N-2) of DPO-HQ and its cured epoxy resin was compared with that of 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO-HQ) and its cured epoxy resin. The thermal stability of DPO-HQ is comparable with that of DOPO-HQ, while the thermal stability of cured epoxy resin based on DPO-HQ is better than that based on DOPO-HQ.