A Bio-Based Polyol with Synergetic Phosphorous and Nitrogenous Effect for Constructing Intrinsic Flame-Retardant Flexible Polyurethane Foam

Flexible polyurethane foam (FPUF) has a widespread application across aerospace, furniture and vehicles, while its flammability always arouses severe safety concerns. Herein, a novel, bio-based flame retardant, i.e. polyol (PADEA) that contains phosphorus and nitrogen elements, was successfully synthesized by using phytic acid (a bio-organic acid) and diethanolamine as crude materials. Then, PADEA partially substituted the commercial polyether polyols in the foaming process, during which PADEA reacted in situ with isocyanate to construct an inherently flame-retardant FPUF. Due to the purposive designed P-N synergistic molecular structure, PADEA can serve as a highly efficient intumescent flame-retardant (IFR) system. When 40 php (ca. 21.51wt%) PADEA was added into the system, the limiting oxygen index (LOI) of the obtained FPUF reached up to 24.1%, achieving a 22.0% increase compared to that of primitive FPUF without PADEA. Moreover, the addition of PADEA can considerably reduce the total number of melt drips in the UL-94 HB rating test. And the cone calorimeter (CC) results demonstrated a 47.08% reduction in total heat release (THR) was achieved as 40 php PADEA was added. At the end, various characterization methods were carried out, revealing the flame-retardant mechanism of PADEA both in condense and gaseous phase. This work highlights a facile and green strategy for designing functional polyol to address the flame-retardant issues of high-performance FPUF.