Role of two stage pyrolysis in fire growth on flexible polyurethane foam slabs

A series of experiments designed to characterize fire behavior on flat 1.2 m × 1.2 m samples of commercial non‐fire‐retarded flexible polyurethane foam were performed. Time‐resolved heat release and mass loss rates were measured. Experimental parameters varied, including foam thickness (5.1 and 10.2 cm) and burning angle (+25°, +12.5°, 0°, ?12.5°, and ?25°). Polyurethane foam is typically produced by reacting a multifunctional isocyanate with a polyol. The foam used here was formed by reacting toluene diisocyanate and a polyol based on a condensed polyether of polypropylene oxide. Earlier cone calorimeter studies of this foam had revealed a clear two stage pyrolysis behavior in which the heated foam first released a gaseous fuel derived from the isocyanate component, while leaving behind a liquid produced primarily from the polyol, which only gasified and burned following additional heating. The subsequent burning behavior of the polyol‐derived liquid is shown in this work to play a crucial role in the maximum heat release rate and total heat released by the fires spreading across the foam slabs. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.