Heat Release of Polyurethanes Containing Potential Flame Retardants based on Boron and Phosphorus Chemistries

Abstract Using a polyurethane of methylene diphenyl isocyanate and 1,3-propane diol, several new non-halogenated aromatic boron and phosphorus flame retardants were evaluated for heat release reduction potential using the pyrolysis combustion flow calorimeter (PCFC). The polyurethanes were prepared in the presence of the potential flame retardants via solvent mixing and copolymerization methods, and were then analyzed via spectroscopic methods to determine if the flame retardant was still present in the final product. PCFC testing on the resulting products showed that the flame retardant molecule can have different effects on heat release depending upon how it is mixed into the polyurethane. Some materials showed strong effects on heat release reduction when reacted into the polyurethane during copolymerization, while others were more effective at heat release reduction when simply solvent blending into the polyurethane. The results from this screening study show that flame retardant chemical structure and its environment in the polymer (covalently bonded vs. noncovalent interactions) greatly affects flammability behavior. From the combined data, aromatic boronates were found to be very effective at reducing heat release and inhibiting melt flow during thermal decomposition, as were some aromatic phosphonic acid terephthalic acid and terephthalate derivatives.