Fabrication and Performance Investigation of Flame Retardant Flexible Polyurethane Composites via Polyethyleneimine/Phytic Acid LBL Self‐Assembly Coatings

ABSTRACT To bolster the fire resistance of flexible polyurethane foam (FPUF), and a series of FPUF/polyethylenimine/phytic acid (FPUF/PEI/PA) composites were prepared by layer‐by‐layer self‐assembly strategy. Furthermore, the thermal stability, flame retardancy, combustion properties, and char layer were comprehensively evaluated via thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical combustion test, microcalorimetry (MCC), scanning electron microscopy (SEM), Raman spectroscopy, and tensile testing. TG analysis revealed that the PEI/PA coatings markedly diminished the initial decomposition temperature ( T ‐5wt% ) and char residue at 800°C. FPUF‐6 extended the burning duration by 20 s, a 80% improvement compared with unmodified FPUF, with an LOI value increased to 19.2 vol%. SEM and Raman analyses of the char residues indicated that the PEI/PA coating promoted graphitization degree of the char layer. This work offered novel insights for the development of high‐performance FPUF composites.