Synthesis of oligomeric epoxycyclotriphosphazenes and their properties as reactive flame-retardants for epoxy resins

GRAPHICAL ABSTRACT ABSTRACT Hydroxyaryloxycyclophosphazenes containing 2–4 OH groups have been synthesized by the substitution of chlorine atoms of hexachlorocyclotriphosphazene via the reaction with sodium phenolates of halogenophenols followed by the interaction with sodium monophenolate of diphenylolpropane. Oligoepoxyphosphazenes (OEPs) with molecular masses up to 2000 and the contents of epoxy groups, phosphorus, and halogens atoms about 5–8, 5–8, and 5–11%, respectively, have been obtained via the interaction of the aforementioned phosphazenes with epichlorohydrin. The curing of the OEPs with amines or acid anhydrides gives rise to the formation of self-extinguishing composites. The incorporation of the OEPs (5–75 wt %) into commercial epoxy resins followed by their curing, results in the formation of composites with excellent nonflammability or capability of self-quenching, and good dielectric, heat resistant and mechanical properties. It has been established that mixtures of common epoxides with different amounts of the OEPs can be synthesized by a “single-reactor” method.