Polyurethane/poly[bis(carboxylatophenoxy)phosphazene] blends and their potential as flame-retardant materials

A functionalized polyphosphazene, poly[bis(carboxylatophenoxy) -phosphazene ], was blended with a structural polyurethane via reactive mixing of the po lymer with diisocyanate and diol prepolymers. The thermal stabilites of the resultant foams were analyzed by thermogravimetric analysis (TGA). The cha r yields at both 400 degrees C and 600 degrees C increased relative to the pure polyurethane upon increasing the amount of polyphosphazene from 5 wt% to 20 wt%. At higher incorporations, the char at 400 degrees C, remained th e same, but the char at 600 degrees C continued to increase. The combustion behavior of these foams was analyzed both qualitatively, by a horizontal f lame test, and quantitatively, by oxygen index (OI) measurements. Both of t hese tests indicated an increase in flame resistance at loadings of 20 wt% and above.