Study On Synthesis Of New Halogen-free Phosphazene Flame Retardants And Their Flame-retardant Epoxy Resin Application

Epoxy resin is one of the most widely used polymers resin due to its good chemical stability, superior electrical property and excellent mechanical property. However, its flame retardant property is poor, which greatly limits its more widely used.Phosphazene compounds contain phosphorus and nitrogen in their chemical structures the chlorine atom can easily be replaced,and thus the cyclic phosphazene compound can be made to improve the flame retardancy of epoxy resin.In this study, two phosphazene compounds were prepared and added into the epoxy resin, the flame retardancy and the possible mechanism of flame are explored. The main contents of this paper are as follows:1. A novel phosphazene compound (HECP) was synthesized from hexachlorocyclotriphosphazene, ethylene glycol and sodium hydride. The effects of reaction conditions on the yield of HECP were investigated. the structure of HECP was characterized by FT-IR, NMR.2. The ideal conditions were obtained:the molar ratio of ethylene glycol, sodium salt and HCCP was 10:1, the temperature of the reaction was 35℃, reaction time was 12 h and the yield of HECP was 88%.3. The phosphazene compound(HPCP) successfully prepared via nucleophilic substitution from hexachlorocyclotriphosphazene, phenol, sodium hydride. The structure of HPCP was characterized by FTIR and NMR.4. The flame retardant epoxy resin added with two different phosphazene compounds were prepared, The mechanical properties, hydrophobic properties, electrical properties, thermal stabilities and the flame retardant properties were studied. And what’s more, the possible retardant mechanism was investigated, the results showed that:To keep the mechanical properties of epoxy resin, the content of the phosphazene compounds didn’t exceed 10wt%. The surface of the epoxy resin added with two different phosphazene still was hydrophobic.The electric resistance of epoxy resin was still good. Two phosphazene flame retardants improved thermal stability under high temperature and the final char yield of epoxy resin sample, the flame retardancy correspondingly improved. The Epoxy resin with 10%HECP, 10% HPCP achieved LOIs above 28% and flammability rating of UL94 V-1.5. The possible retardant mechanism of HECP and HPCP was investigated by SEM and fourier transform infrared spectroscopy(FTIR), the results showed that:HPCP dominated by gas-phase flame retardant mechanism and HECP had a solid-phase flame retardant mechanism.