Ammonium polyphosphate-melamine synergies in thermal degradation and smoke toxicity of flexible polyurethane foams

Polyurethane (PUR) foams can lead to fatal fires in the presence of an ignition and oxygen source. Obviously, the problem is not the mere loss of PUR foams properties but essentially, the smoke and toxic gases which are the main factors responsible for fire hazards. This paper reports on the main approaches taken to improve the smoke evolution and toxicity of isophorone diisocyanate (IPDI) based PUR foams which are the incorporation of ammonium polyphosphate (APP), melamine (M) and its combinations as additive flame retardants (FRs). In order to better understand the fire behavior, the influence of incorporated FR on the thermal degradation mechanism was also analyzed by means of thermogravimetry coupled to infrared spectroscopy (TGA-FTIR). In addition, foams were characterized in terms of smoke evolution and toxicity of released gases both asphyxiant and irritant using a smoke density chamber coupled to infrared spectroscopy (NBS-FTIR). Data showed that the mixture of APP and M in different amounts reduced the smoke generation and the concentration of harmful gases, underlying a synergetic effect for the combination of both flame-retardants.