Green flame-retardant flexible polyurethane foam based on polyphenol-iron-phytic acid network to improve the fire safety

Flexible polyurethane foam (FPUF) is one of the most promising cushioning materials, but its high flammability limits its further application. Here, a flame retardant coating was constructed on the foam surface by dipping based on tea polyphenols (TP), phytic acid (PA) and Fe2(SO4)3·xH2O. The results reveal that the flame retardant coating can dramatically improve the fire safety of FPUF. FPUF/TP-Fe-3PA can pass the UL-94 V-0 rating and the limiting oxygen index reaches 26.2%. Meanwhile, the peak heat release rate and total smoke production of FPUF/TP-Fe-3PA are reduced by 67.7% and 66.7%, compared with those of pure FPUF. Moreover, the flame retardant coating can keep more isocyanates in the condensed phase during the thermal degradation process. The flame-retardant and smoke suppression mechanisms are proposed. What is more, the existence of the flame retardant coating has little effect on the resilience of FPUF. This work provides a simple, green and renewable flame retardant FPUF.