Thermally stable and flame-retardant aromatic phosphate and cyclotriphosphazene-containing polyurethanes: synthesis and properties

A novel flame retardant (4‐diphenylphosphoryloxyphenoxy)(4‐hydroxyphenoxy)cyclotriphosphazene (PPPZ) was prepared and characterized by FT‐IR, 31P‐NMR and 1H‐NMR spectroscopy. Polyurethanes that contained aromatic phosphate groups attached to cyclotriphosphazene, with various phosphorus contents, were prepared from PPPZ, poly(propylene glycol), 1,4‐butanediol, and 2,4‐toluene diisocyanate by one‐step polymerization. The polymers prepared were characterized by FT‐IR, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and oxygen index (LOI) measurements. The effect of the concentration of PPPZ on the thermal behavior of the polyurethane was studied. The results indicated that the glass transition temperature (Tg) of the polyurethane increased with the concentration of PPPZ. The PPPZ‐containing polyurethanes exhibited slightly higher temperatures of degradation and higher char yields than PPPZ‐free polyurethanes. Moreover, the LOI of the polyurethanes increased with increasing PPPZ content. Also studied was the possible mechanism of the flame retardancy. Copyright © 2005 John Wiley & Sons, Ltd.