Apparatus for investigating the burning and dripping of vertically oriented polyurethane foams

The burning and dripping behaviour of polyurethane (PU) foam is crucial for upholstered furniture fires due to the melting and dripping behaviour of the foam that results in a pool fire under the furniture, which enhances the combustion. The sample feeding vertical cone is developed to investigate the two-dimensional small-scale burning and dripping behaviour of vertically oriented PU foams where a constant irradiance is maintained at the exposed surface by means of automatic sample compensation. Seven different PU foams were investigated and classified as conventional foam or char-forming foam according to the observed surface phenomena during exposure to heat fluxes. The burning and dripping behaviour is found to depend on the foam density as well as the solid-phase char formation by the presence of fire retardant additives. The total mass loss rate and the dripping rate increase with higher foam density and with the presence of char formation. In contrary, the vaporisation rate is favoured at lower foam density and with the absence of char formation. Flexible foams of low density without the ability to form char tend to achieve low dripping rate where majority of the mass loss is via vaporisation, contributing directly to the gas-phase combustion.