A Waterborne Biobased Flame-Retardant Coating with Transparency, Solvent Resistance, and Self-Healing Ability

Water-based flame-retardant coatings have attracted more and more attention as versatile strategies for improving the fire safety of flammable polymeric materials. However, the perfect combination of environmental protection, water resistance, durability, optical transparency, and strong interface adhesion is still extremely challenging. Herein, we report a biobased, transparent, and multifunctional flame-retardant coating (GBPK-LDH) constructed from gum arabic, phytic acid, borax, and KH560, reinforced by layered double hydroxide (LDH) nanosheets. The coating has high optical transparency, excellent water resistance, and various organic solvent resistance. Due to the synergistic effect of abundant hydrogen bonds, dynamic borate interaction, and silane-induced interface coupling, GBPK-LDH coating has strong adhesion to different substrates, with a maximum shear strength of 1.73 MPa, and has a self-healing behavior triggered by humidity and temperature. When coated on flexible polyurethane foam (FPUF), the coated foam shows excellent flame retardancy and achieves a rapid self-extinguishing effect. It is worth noting that compared with the control FPUF, the peaks of heat release rate and total smoke production were reduced by 42.5 and 50.0%, respectively. Moreover, the GBPK-LDH coating also helps to improve the mechanical properties of FPUF, including a significant increase in tensile strength, while maintaining excellent resilience and constant thermal insulation. Furthermore, the coating can also provide effective fire protection for other flammable substrates, such as rigid polyurethane foam and wood, highlighting its wide applicability. This study proposes a sustainable and scalable strategy for the development of high-performance biobased multifunctional water-based coatings.