Synthesis of MXene-Based functional coatings on rigid polyurethane foam surfaces: A comparative study of layer-by-layer self-assembly and hydrothermal methods

A flame retardant for rigid polyurethane (RPUF) was designed and synthesized to expand the application field of RPUF. The flame retardants, namely MXene/PEI/PA-L and MXene/PEI/PA-H, were synthesized using phytic acid (PA), polyethyleneimine (PEI), and MXene through layer-by-layer (LBL) self-assembly method and hydrothermal method, respectively. In terms of mechanical performance, MXene/PEI/PA-L imparted brittleness to RPUF while MXene/PEI/PA-H enhanced its toughness, enabling RPUF to adapt to diverse application scenarios. The flame retardant properties were evaluated via vertical combustion test, cone calorimetry test, and thermogravimetric test, and the gas phase flame retardant mechanism was analyzed by TG-FTIR. MXene/PEI/PA constituted a N-P-Ti synergistic flame retardant system. During combustion, MXene/PEI/PA formed a layered dense carbon layer to cut off the external oxygen transport channel and absorbed many oxygen-containing free radicals. MXene/PEI/PA-L demonstrated efficient smoke suppression capability, while MXene/PEI/PA-H showed superior thermal insulation performance. The ignition time (TTI) of the composite foam reached 47 s, the total smoke release (TSR) value decreased by 92 %, and the flame retardant grade reached 5VA. Coated RPUF had excellent flame retardant ability.