In situ construction of a bio-based porous coating on flexible polyurethane foam skeleton for enhanced fire safety, thermal insulation and antibacterial activity

The extreme operating conditions of aerospace interiors place stringent demands on flexible polyurethane foam (FPUF), requiring it to combine superior fire safety, thermal insulation, antibacterial activity and environmental sustainability. A series of PL-CS/FPUF composites were developed via the in situ construction of a bio-based porous coating derived from a phytic acid (PA)-lysine (Lys)-based deep eutectic solvent/chitosan (CS) system on the FPUF skeleton. The bio-based porous coating exhibited uniform distribution and strong interfacial integration while preserving the intrinsic porous structure of FPUF. The 4PL-1CS/FPUF composite exhibited excellent flame retardancy with a maximum limiting oxygen index (LOI) of 62.7%, and the peak heat release rate and the peak CO production rate were reduced by 98.2% and 77.8%, respectively, compared with pristine FPUF. Meanwhile, 4PL-1CS/FPUF also demonstrated an excellent antibacterial rate of 99.8% against Staphylococcus aureus . 2PL-1CS/FPUF exhibited a compressive strength approximately 4.5 times that of pristine FPUF after the 1st compression cycle. Although resilience was slightly affected, 4PL-1CS/FPUF still maintained a compressive strength retention rate of 85.1% after the 5th compression cycle. Furthermore, under continuous heating at 100 °C, the top surface temperature at 900 s of 4PL-1CS/FPUF was only 43.7 °C, significantly lower than that of pristine FPUF, demonstrating improved thermal insulation under direct heat exposure. These multifunctional PL-CS/FPUF composites provide an effective strategy for developing high-performance composites with integrated flame retardancy, thermal insulation and antibacterial activity, demonstrating strong potential for aerospace interior applications.