Bio-Based Self-Assembly and Hydrophobic Modification for Simultaneously Enhancing Flame Retardancy and Water Resistance of Wood

As an important renewable building material, wood’s flammability significantly limits its application range. This study addresses the environmental pollution issues associated with traditional flame retardants by developing an eco-friendly flame retardant system based on natural biomaterials. Utilizing layer-by-layer self-assembly techniques, sodium phytate, chitosan, sodium alginate, and sodium methyl silicate were sequentially deposited onto the wood surface to construct a multifunctional composite coating. A multifunctional composite coating was constructed on wood surfaces through layer-by-layer self-assembly technology, involving successive deposition of phytic acid sodium, chitosan, sodium alginate, and methyl silicate sodium. Characterization results indicated that the optimized sample WPCSMH achieved a limiting oxygen index of 34.0%, representing a 12% increase compared to untreated wood. Cone calorimetry tests revealed that its peak heat release rate and total heat release were reduced by 57.1% and 25.3%, respectively. Additionally, contact angle measurements confirmed its excellent hydrophobic properties, with an initial contact angle of 111°. Mechanistic analysis reveals that this system significantly enhances flame retardant performance through a synergistic interaction of three mechanisms: gas phase flame retardancy, condensed phase flame retardancy, and free radical scavenging. This research provides a sustainable and innovative pathway for developing environmentally friendly, multifunctional wood-based composites.