Excellent Flame Retardant of Flexible Polyurethane Foams With Green Coatings by Sol–Gel Method

ABSTRACT In this study, a N/P/Si flame retardant was constructed via the sol–gel method with 3‐aminopropyltriethoxysilane (APTES) as a precursor, combined with guar gum (GG) and ammonium polyphosphate (APP), and filled into the pores of flexible polyurethane foam (PUF) via an impregnation and drying process. Encouragingly, this flame retardant exhibited excellent flame‐retardant properties. Specifically, the treated PUF was self‐extinguishing even when sprayed with a butane torch at temperatures up to 1500°C. In addition, the limiting oxygen index (LOI) increased from 18.1% to 36.6%. Most importantly, the dense char layer produced by the APTES/GG/APP flame‐retardant coating during combustion completely eliminated the melt‐drop phenomenon of the PUF. In the cone calorimeter test, the pHRR of the control sample decreased from 384.44 kW/m 2 to 193.06 kW/m 2 , the CO 2 PR was reduced by 52.19%, and the fire performance index (FPI) of the material increased from 0.016 m 2 s/kW to 0.026 m 2 s/kW. On the basis of these results, this study proposes a treatment that is simple, feasible, and capable of significantly improving the flame retardancy of ordinary open‐cell PUF.