A fully bio-based coating made from alginate, chitosan and hydroxyapatite for protecting flexible polyurethane foam from fire.

• Layer-by-layer assembled fully bio-based coating protected flexible polyurethane foam (FPUF) from fire. • Coated FPUF by 9 bilayers of alginate, chitosan and hydroxyapatite showed self-extinguishing behavior. • Peak heat release rate of coated FPUF by 9 bilayers of alginate, chitosan and hydroxyapatite reduced by 77.7 %. • Smoke production rate of coated FPUF by 9 bilayers of alginate, chitosan and hydroxyapatite declined by 53.8 %. The present study reports the successful synthesis of the flame-retardant and smoke-suppressant flexible polyurethane foam (FPUF) through a fully bio-based coating. Hydroxyapatite (HAP) is added to the solutions containing sodium alginate (SA) and chitosan (CH), respectively, to create negative and positive polyelectrolytes for Layer-by-Layer (LbL) assembly. The influence of the solution concentrations and bilayers numbers deposited on the flame-retardant and mechanical properties of FPUF samples is investigated systematically. Benefitting from the presence of such a fully bio-based coating, the resultant FPUF affords excellent smoke-suppressant and flame-retardant features. In particular, the FPUF coated by 9 bilayers of HAP-SA/HAP-CH exhibits significantly declined peak heat release rate, total release rate and smoke production release by 77.7 %, 56.5 % and 53.8 %, respectively. The compression test verifies the coated FPUFs exhibit lower recovery properties compared with the uncoated one. These results demonstrate that a green and cost-effective strategy is provided for producing flame-retardant, anti-dripping and smoke-suppressant FPUFs. [ABSTRACT FROM AUTHOR]