Influence of foam density on burning behavior of polymer bead foams

Foamed plastics are increasingly employed due to the high demand in functional materials with reduced weight. Bead foams in general offer low weight and excellent thermal insulation properties combined with extremely high freedom in design. Though foams show increased risk of ignition and heightened heat release, literature on burning behavior is rather limited. Therefore, this study investigates density-dependent burning behavior of commercial bead foams like expanded polypropylene (EPP) and expanded modified polyphenyleneether (E-mPPE) by cone calorimetry. The results are compared to existing studies on the density-dependent burning behavior of different foams, mainly expanded polystyrene and foamed polyurethane. The importance of density as a characteristic is highlighted by the linear dependence of total heat emission on density for all investigated polymers, making a prediction of thermal loads possible. The peak heat release rate of flame-retarded EPP and E-mPPE was found not to be dependent on density, indicating an increased homogeneity by addition of flame retardant.