A UV-curable coating constructed from bio-based phytic acid, D-sorbitol and glycine for flame retardant modification of rigid polyurethane foam

When confronted with a fire, the flammability of rigid polyurethane foam (RPUF) makes it extremely easy to start a fire. In this work, a green biomass derived flame retardant coating was synthesized with phytic acid as acid source, D-sorbitol as carbon source and glycine as gas source. A simple UV curing technique was used to improve the flame retardancy of RPUF. Coated RPUF exhibited high limiting oxygen index values of up to 39.7% and successfully met UL-94 testing criteria with V-0 rating. In comparison to control RPUF, coated RPUF showed an extended ignition time of 3s, a remarkable reduction of 60% in the peak heat release rate, and possessed commendable smoke suppression property. The flame retardant mechanism was analyzed, unveiling the emergence of compact char residue on the surface of coated RPUF after burning, accompanied by the liberation of non-combustible gases. Therefore, these results demonstrated that cost-effective UV-curable flame retardant coating forms protective char layer on the surface of RPUF, providing efficient flame retardancy while preserving its excellent properties.