Boron phenolic resin/silica sol coating gives rigid polyurethane foam excellent and long‐lasting flame‐retardant properties

Abstract In this paper, a boron phenolic (BPR)/silica sol (Si‐sol) coated flame retardant was prepared, and the flame retardant was coated on the surface of rigid polyurethane foam (RPUF) to make it have excellent flame‐retardant effects. The molecular structure of BPR and Si‐sol was analyzed by FTIR, and the influence of the coating on the cells was observed with an optical microscope. It was evident from the test results of the cone calorimeter that the peak heat release rate (PHRR) and total heat release (THR) of RPUF were reduced by 45% and 37.7%, respectively. The limit oxygen index and vertical combustion test results indicated that the LOI reached 35%, and UL‐94 reached the V‐0 level. The aging experiment was conducted on the coated RPUF material, and the results showed that the material has long‐lasting flame‐retardant properties. The possible flame‐retardant mechanism was analyzed.