Improvement in flame retardancy of polyurethane dispersions by newer reactive flame retardant

A novel phosphorus containing reactive flame retardant was synthesized and incorporated successfully in polyurethane backbone to obtain flame retardant aqueous polyurethane dispersions (FRPUDs). The reactive flame retardant compound was synthesized by using phosphorus oxychloride (1 mole) and N-methylaminoethanol (3 mole). The structure of synthesized phosphorus containing triol was confirmed by FTIR, 1H NMR and 31P NMR spectrometry. Further, polyurethane prepolymer was modified with phosphorus containing triol compound in various amounts (30, 40 and 50% on equivalent basis) and FRPUDs were prepared. PUD films were applied on wood and mild steel panels and air dried. It was then characterized for mechanical, chemical, thermal and flame retardant properties. It was observed that all FRPUDs exhibited good mechanical properties and improved flame retardancy as compared to the conventional one. The maximum limiting oxygen index (LOI) value of 37 was obtained for FRPUD containing 0.8 mass% of phosphorus and 1 mass% of nitrogen. The flame retardancy was greatly depending on the phosphorus content and increased with increase in phosphorus content.