Organic-Inorganic hybrid polymeric flame retardant coating for fire safety rigid polyurethane foam

Rigid polyurethane foams (RPUFs) are widely used for their excellent performance but are limited by their flammability. Flame-retardant coatings are an effective solution to address this issue without compromising their mechanical properties. Herein, flame-retardant copolymer poly(HBA-co-VBS) is synthesized via radical copolymerization of hydroxybutyl acrylate (HBA) and sodium 4-vinylbenzenesulfinate (VBS). A series of transition metal oxide-loaded halloysite nanotubes (Mo-HNTs, Co-HNTs) and hexagonal boron nitride (Mo-BN, Co-BN) are synthesized via impregnation method to prepare organic–inorganic hybrid flame-retardant coatings. The coated RPUFs reach V-0 rating in the UL-94 test with higher LOI over 31 %. Co-HNTs sample exhibits the best flame-retardant performance with the lowest PHRR (142.5 kW m −2 ) and lowest THR (49.9 MJ m −2 ). Inorganic nanoparticles reduce toxic gas emissions, especially CO emission, due to the catalysis effect of Mo and Co. This research provides a novel approach to design high-performance flame-retardant coatings.