Ignition of combustion modified polyurethane foam: Fid-Bau Portal

Ignition of combustion modified polyurethane foam

Putzeys, Oliver M. / Fernandez-Pello, A. Carlos / Urban, David L.

The potential danger of a fire aboard spacecraft warrants extreme care in the design and selection of spacecraft materials. Porous cushioning materials tend to be susceptible to smouldering, potentially initiated by sources much too weak to directly produce a flame, and transition to flaming, resulting in fast, highly exothermic gas phase reactions with potentially catastrophic consequences. 40 % of household fire deaths in the United States are caused by smoulder-originated fires. The present work is part of a NASA ((National Aeronautics and Space Administration) project to study the transition from smoulder to flaming of polyurethane foam under spacecraft facility conditions, i.e. microgravity, low velocity and oxidiser flows with variable oxygen concentration. Results are presented from an experimental study on the ignition of the combustion-modified (fire-retarded) polyurethane foam Pyrell (two densities, 35.3 kg/m³ and 64.0 kg/m³) in elevated oxygen concentrations, ranging from 30 % to 60 %. The samples were exposed to an external flow and variable radiant heat flux one face, and insulated on the other faces. The experiments show that Pyrell undergoes a weak smouldering reaction that requires significant assistance in the form of external heat input in order to propagate. The results also show that given sufficient oxygen and radiant heat flux, the smouldering reaction can produce enough volatile fuel and heat to trigger a gas phase ignition, i.e. a transition from smouldering to flaming, in pores in the char region. The experiments also indicate that high-density Pyrell is more ignitable than low-density Pyrell, which could be explained by the greater solid surface area for smouldering reactions to take place.