Chitosan-based transparent and flame-retardant bio-composite coatings for wooden materials with rapid fire monitoring response

Wood, as a biomaterial with abundant reserves and ease of processing, is widely used in construction, furniture, and other sectors. However, its high flammability poses significant risks, leading to substantial property damage and casualties in the event of a fire. Therefore, the development of transparent coatings that integrate passive flame retardancy with an active fire warning response is crucial yet challenging for improving the fire safety of wood materials. In this study, we present a chitosan-based transparent hybrid network by combining cost-effective biomass-derived chitosan with NaH 2 PO 4 . The optimized network exhibits impressive tensile strength (∼30 MPa) and excellent transparency .(∼83 %). When applied to wood surfaces, it significantly enhances the fire resistance of the wood subtract, achieving a limiting oxygen index (LOI) of 51.0 % and a UL-94 V0 rating. In addition, it demonstrates rapid fire alarm activation (<2 s) and reliable cyclic fire warning performance. Based on the burnt zone observation and chemical analysis, the flame-retardant mechanism was discussed. Furthermore, the flame -induced resistance transition mechanism of the chitosan composite was well investigated and presented. These remarkable properties render such chitosan-based bio-composite coatings as highly promising candidate for fire safety and protection applications of wooden construction.