Synthesis Of Cyclotriphosphazene-Based Flame Retardant And Its Effect On The Flame Ratardance Of Epoxy Resin

Two single-substituent and three mixed-substituent cyclophosphazene flame retardants were designed and synthesized from hexachlorocyclo-triphosphazene, KH-550 and n-butylamine. Their chemical structures were characterized by FTIR and NMR.The flame retardancy of epoxy resin added with different flame retardants was measured by UL94 vertical burning test and LOI test. Themal stability and mechanical properties of epoxy resin with the best flame retardancy were also investigated.The flame retardant mechanism of epoxy resin added with silicon-containing cyclotriphosphazene-based flame retardant was investigated by FTIR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Scanning electron microscope (SEM).Results showed that the flame retardancy of three silicon-containing mixed-substituent cyclophosphazene was better than single-substituent cyclophosphazene. Among them,the flame retardancy of IV was the best. When the content was about 10wt%,the flame retardancy of epoxy resin could pass UL94 V-0 rating and LOI reached 31.5%;When the content was about 20%, LOI reached 33.7%. TGA results revealed addition of IV to epoxy resin decreased the initial decomposition temperature,but improved the stability under high temperature and enhanced the char yield.It has been found that the retardancy of flame retardant in epoxy resin worked in condensed phade and vapor phase.