Phosphorus-nitrogen containing fire retardants for poly(butylene terephthalate)

Abstract

Hexakis(phenylamino)cyclotriphosphazene, hexakis(phenoxy)cyclotriphosphazene, tris(o-phenylenediamino)cyclotriphosphazene, tris(phenylene-1,2-dioxy)cyclotriphosphazene and tris(phenylene-1-amino-2-oxy)cyclotriphosphazene have been prepared and characterized by IR and NMR spectroscopy. Phospham, a crosslinked phosphazene imide (PN2H) n, was prepared by heating hexaminotricyclophosphazene under vacuum. Phosphorus oxynitride (PON) m which is likely to be a crosslinked oxyphosphazene was prepared by intense heating of urea, melamine and phosphoric acid. These phosphorus–nitrogen containing compounds added to poly(butylene terephthalate) (PBT) at 10–20 wt% provided increase of oxygen index (OI) from 22 to 29. In spite of relatively high OI only the V-2 rating was observed in the UL94 test because of the flaming drip phenomenon. Phosphorus oxynitride was found to be an efficient char promoter for PBT. © 2000 Society of Chemical Industry