Synthesis of bisphenol a based phosphazene-containing epoxy resin with reduced viscosity

Abstract

Phosphazene-containing epoxy oligomers (PEO) were synthesized by the interaction of hexachlorocyclotriphosphazene (HCP), phenol, andbisphenolAin amediumof excess of epichlorohydrin using potassium carbonate and hydroxide as HCl acceptors with the aim of obtaining a product with lower viscosity and higher phosphazene content. PEOs are mixtures of epoxycyclophosphazene (ECP) and a conventional organic epoxy resin based on bisphenol A in an amount controlled by the ratio of the initial mono-and diphenol. According to 31P NMR spectroscopy, pentasubstituted aryloxycyclotrophosphazene compounds predominate in the ECP composition. The relative content in the ECP radicals ofmono-and diphenolwas determined by theMALDI-TOFmass spectrometrymethod. The organic epoxy fraction, according to gas chromatograpy-mass spectrometry (GC-MS), contains 50-70 wt % diglycidyl ether of bisphenol A. PEO resins obtained in the present work have reduced viscosity when compared to other known phosphazene-containging epoxy resins while phosphazene content is still about 50wt%. Resinswith an epoxy numberwithin 12-17wt%, are cured by conventional curing agents to form compositions with flame-retardant properties, while other characteristics of these compositions are at the level of conventional epoxy materials.