Transparent, hard-wearing and bio-based organic/silica hybrid coating for bamboo with enhanced flame retardant and antifungal properties

As an abundant natural resource, bamboo with enhanced flame retardancy and mildew resistance after surface treatment has a wider range of applications. Although several organic or metal oxide coatings have been used on bamboo, their basic properties such as transparency and durability are neglected, which limits their practical application. Herein, we prepared a new organic–inorganic coating by thermal curing between vanillin-derived epoxy (VEP) and hyperbranched siloxane (HPSi). The curing process of VEP/HPSi coating was analyzed with FTIR. When the mass ratio of VEP and HPSi was 20:28, the obtained Schiff base hybrid coating exhibited visible light transmittance over 90% and the highest pencil hardness of 9H. The mechanical properties of the coating were investigated by nanoindentation (hardness: 0.208 GPa, elastic modulus: 2.677 Gpa) and impact test. Impressively, the fabricated coating showed remarkable solvent wipe resistance (Xylene and ethanol: 1000 cycles) and continuous abrasion (cheesecloth test: 5000 cycles). In addition, the hydrophobic and dense coating endowed the coated bamboo excellent mildew resistance even in high humidity (97%). Due to the high thermal stability, the coated bamboo presented a significant enhanced flame resistance with a limiting oxygen index value of 29.1%. From a broader perspective, the Schiff base hybrid coating with excellent comprehensive performance and facile preparation process display great potential for practical application for bamboo or other substrates.