Laponite-based inorganic-organic hybrid coating to reduce fire risk of flexible polyurethane foams

Abstract Flexible polyurethane (FPU) foam as a primary softening material is utilized in soft furnishings of upholstered mattresses and furniture. High flammability of this soft furnishing material usually leads to residential fires, causing severe fatalities. In the present study, we proposed a bio-based and environmentally-friendly flame retardant multilayered coating consisted of laponite (LAP), branched polyethyleneimine (BPEI), sodium alginate (SA) and chitosan (CH) that was deposited onto FPU foams to enhance their fire safety property. Based on the thermogravimetric analysis results, it was indicated that after the deposition of LAP, the thermal stability of the coated FPU foams increased sharply. Foam treated with 9 quad layers (QL) of BPEI/SA/CH/LAP multilayered coating showed self-extinguishing behavior in an open flame burning test. Furthermore, the values of peak heat release rate (PHRR), total heat release (THR) and smoke release rate (SPR) of the coated FPU foams reduced considerably in comparison to those of the pure FPU foam. Specifically, 9 QLs of BPEI/SA/CH/LAP declined the PHRR and the THR by 74% and 42.6%, respectively. The coated FPU foam also showed self-extinguishing and anti-dripping features in an open flame testing. Therefore, it can be stated that LAP-based coating has incredible benefits in decreasing fire risk of FPU foams. Moreover, the flame retardant mechanism of this LAP-based multilayered coating was proposed. The LAP-based coating functioned as a physical insulating barrier that successfully retarded the permeation of the flammable volatiles, heat and oxygen. Hence, the significant decrease in PHRR with the self-extinguishing behavior was achieved, implying promising potential of this LAP-based multilayered coating to enhance the fire safety of FPU foams.