Phosphazene-triazine cyclomatrix network polymers: some aspects of synthesis, thermal- and flame-retardant characteristics

Hydroxy phenyl-substituted cyclotriphosphazenes were synthesized by reactin g hexachlorocyclotriphosphazene with sodium phenolate and monosodium bisphe nolate. The derivatives, consisting of a mixture of multi-substituted and p artly chain-extended cyclophosphazenes, with overall functionality close to the targeted values, were transformed into the cyanatophenyl derivative. T hermal curing of the latter gave phosphazene-triazine cyclomatrix network p olymers with varying ratios of phosphazene and triazine rings in the matrix . Although they manifested diminished T-g, the cured polymers were more the rmally stable and provided higher char residue in comparison to the polycya nurate derived from bisphenol-A dicyanate. The activation energies for ther mal decomposition of the cyclomatrix networks increased with both phosphaze ne content and crosslink density, and showed a direct relationship with the ir thermal stability. The presence of phosphazene was conducive for enhanci ng the flame retardancy of the network. The flame retardancy improved with increase in crosslink density and char-yielding property of the polymer, wh ich implied that the flame-retardant action was operative in the condensed phase. (C) 2000 Society of Chemical Industry.