Halogen‐Free Coatings Combined with the Synergistic Effect of Phytic Acid and Montmorillonite for Fire Safety Flexible Polyurethane Foam

Abstract To overcome defects of some synthetic flame retardants, water‐based coatings using ammonium phytate (AP) and montmorillonite (MMT) as low‐cost renewable materials are fabricated to improve the flame retardancy of flexible polyurethane foam (FPUF). The flame‐retardant FPUF with uniform coatings can avoid melt‐dripping during the vertical flame test (UL‐94), and AP5MMT5/FPUF (flame‐retardant FPUF with the 5:5 weight ratio of AP:MMT in the solutions) reaches a UL‐94 V‐0 rating. A remarkable conclusion can be found that AP and MMT present a synergistic effect under the appropriate proportions. The thermal stabilities of flame retardant FPUF at higher temperature zones are enhanced. Furthermore, flame‐retardant samples prevent the flame from spreading on the surface of FPUF. Cone calorimetry results reveal 67% (AP5MMT5/FPUF) reduction of peak heat release rate relative to pure FPUF, and the release of toxic smoke significantly decreases. AP can catalyze the carbonation of FPUF, and MMT is heated and dehydrated to form a silicon‐containing barrier layer. AP/MMT coatings can form stable and solid physical char layers, which act as a barrier to heat and oxygen exchange, and the release of volatiles is delayed and inhibited. This work introduces a green plan for improving the fire safety of FPUF.