Fire behaviors of two-layer coated latex foam with an extremely thin surface layer under bottom ventilation conditions

Latex foam based upholstered furniture has been widely used in our daily lives. Its high fire risk can be reflected by its extremely thin surface layer together with a cellular structure sponge. Therefore, through this study, an experimental study was carried out to address the fire behaviors of typical latex foams, including cotton, hemp, silk, and blending coated latex foam. The thermal properties and structure of these fabric materials and latex foam were analyzed experimentally, together with the analysis of the heat transfer mechanism and the calculation of flame spread rate. Experimental results showed that the thin surface fabric covered on the surface of the latex foam could prolong the combustion process for more than 150 s. The peak bottom flame area of the silk coated sample was only 40 % of the uncoated one. The combustion residues of the surface fabric after the extinguishment were found composing of carbonized fabric and white ash. It was then known that the cotton fabric shows significant effects on the combustion processes due to dense residues. The average flame spread rate of the coated samples was about 22 % of those uncoated ones. The porosity of the fabric residues on the surface played a key role in the flame spread on the latex foam surface. A flame spread rate model was developed and validated for the first time that considered the fabric porosity, which could provide a useful tool for the relevant fire risk evaluation for those practical fire scenarios with multi-layer combustible.