A review of some 170 publications summarises currently knowledge on the thermal decomposition, smoke emission and smoke toxicity of polyurethanes, and on the effects of different flame retardants and additives on suppressing smoke emissions and toxicity.
The paper notes that smoke emissions from polyurethanes (PU) depend on the polymer structure (PUs with carbodimide groups or aliphatic polyester polyols will generate more char, and so less smoke), and also depend on the fire conditions (oxygen concentration, irradiance temperature which causes polymer decomposition). The authors note that condensed phase flame retardants (PIN char generation) can reduce smoke release from PU, as can some nitrogen PIN FRs and carbon-based FR additives, and that metal hydroxides (e.g. the PIN FRs: ATH, MDH) have high specific surface areas and can absorb smoke and toxic gases. FRs which act mainly in the gas phase or release acidic gases (such as chlorine containing TCPP, or liquid phosphate DMMP or DOPO-phosphonamidates) can increase smoke and carbon monoxide. The paper summarises a range of metal-based PIN FR synergists (ferrites, copper oxides, copper cobalate, zinc stannates/hydrostannates, zinc-aluminium, zinc-iron, zinc-boron and zinc-tin compounds, boric silicon, molybdenum compounds, organic metal compounds such as ferrocenes, sulphur compounds, organic acids) and also metal chlorides.
“Recent studies on the decomposition and strategies of smoke and toxicity suppression for polyurethane based materials”, X. Liu, J. Hao & S. Gaan, RSC Advances 2016: 6 74742-74756 http://dx.doi.org/10.1039/c6ra14345h