High Thermal Stability, Efficient Flame Retardancy, and Smoke Suppression for Rigid Polyurethane Foams Based on Biobased and Phosphorus–Nitrogen‐Based Flame Retardants

ABSTRACT As the most widely used material, the flammability of polyurethane foam has limited its further development. To improve the flame retardancy of PUF, glycerol (GMF)‐, sodium alginate (SGMF)‐, and lignosulfonate‐modified melamine formaldehyde (LGMF) were prepared in this study. Meanwhile, to further improve the flame‐retardant properties, phosphorus–nitrogen flame‐retardant BH was prepared by utilizing diethanolamine and diethyl phosphite, and compounded with the above‐modified resins to prepare rigid polyurethane foams (GBPU, SGBPU, and LGBPU). A series of test results show that the modified GBPU, SGBPU, and LGBPU have thicker pore walls and smaller pore diameters than the flame‐retardant foam merely using BH (BPU). The carbon layer of those three foams after combustion is not only thick, but also very uniform and dense, and the limiting oxygen index increases to 28.2%–29.6%. During the combustion process, the peak heat release rate and total heat release decreased by 15.0%–30.7% and 59.1%–71.3%, respectively. It is particularly noteworthy that the toxic gas release of the modified foam is significantly reduced after combustion, in which the CO generation is reduced to 0.0005 kg/kg −1 , and the CO 2 generation is reduced to 0.28 kg/kg −1 , showing excellent environmentally friendly characteristics.