An architecturally inspired protective char barrier strategy for flame-retardant polyurethane nanocomposite coatings with efficient photothermal self-healing and anticorrosion

Fire and corrosion pose significant challenges to personnel safety and offshore equipment. Inspired by the architectural structure, we propose a new coating, PPU-PDA@hBN, with integrated photothermal self-healing, anticorrosion, and flame-retardant capabilities. This coating was prepared by dispersing 5 wt% PDA@hBN nanosheets within a phosphorus (P)-containing polyurethane (PPU) matrix. Upon combustion, the P promotes the dehydration of the polymer, forming a char layer, in synergy with PDA@hBN, creating an architecturally inspired protective char barrier. By suppressing heat transfer, the PPU-PDA@hBN exhibits a 27.2% higher limiting oxygen index (LOI) and a 64.73% reduction in peak heat release rate (p-HRR) compared to pure polyurethane. The architecturally inspired protective char barrier strategy can effectively improve flame retardancy. Moreover, photothermal self-healing can be achieved. PDA@hBN serves as a photothermal agent, triggering self-healing within 10 min of NIR irradiation and restoring 99% of the original tensile strength. Additionally, the well-dispersed nanosheets create a maze-like barrier, ensuring effective anticorrosion. The |Z|_0.01Hz of PPU-PDA@hBN recovered to 10⁶ Ω·cm², similar to the PU. According to the ASTM B117 salt spray test standard, PPU-PDA@hBN can withstand 16 days of salt spray corrosion. This strategy offers a new design paradigm for a self-healing integrated anticorrosion and flame-retardant coating (SIAFC).