The coating based on phenolic resin gives rigid polyurethane foam excellent flame retardant properties

Abstract A flame retardant coating was designed and synthesized using phenolic resin (PF), 9,10‐dihydro‐9‐oxa‐10‐phosphazephenanthrene‐10‐oxide (DOPO), and nano‐SiO 2 as raw materials. The coating is applied to the surface of rigid polyurethane foam (RPUF) to give it a flame retardant effect. Based on the excellent adhesion of PF, the coating effectively suppresses heat transfer, and the synergistic effect of DOPO and nano‐SiO 2 improves the flame retardancy of RPUF. In addition, vertical combustion experiments have shown that when the ratio of DOPO to nano‐SiO 2 is 2:1, there is no dripping, the flame is self‐extinguishing, and the internal structure remains basically unchanged, resulting in the best flame retardant effect. The cone calorimetric test shows that the coating can effectively reduce the total heat release and heat release rate of the substrate, and the smoke release rate and total smoke release data show that its smoke suppression effect is significantly improved. Thermogravimetric analysis shows that the coating can effectively improve the residual carbon rate of RPUF, and its mechanical properties are good. This study confirms that coatings based on PF/DOPO/Nano‐SiO 2 can effectively improve the flame retardancy of RPUF, providing a potential direction for the development of green insulation materials.