Organic–inorganic hybrid of silica sol to promote flame retardant and mechanical properties of wood

As a potential building material, fast-growing wood (such as poplar) is prone to easy combustion and having poor mechanical properties, which limit its application range. In order to improve the reinforcing effect of SiO₂ on poplar wood, we propose a method of immersing silica sol into wood smoothly. In this method, the sol and a non-ionic surfactant are first treated via organic–inorganic hybridization. This surfactant has a strong penetration effect, and the sol is introduced into the wood through hybridization. By impregnating the wood, the flexural strength and flexural modulus of elasticity increased by 79.7% and 89.5%, and the compressive strength along the grain increased by 105.1%. The treated wood also showed flame retardation, reducing the heat release rate (HRR), carbon dioxide yield (CO₂Y), total heat release (THR), specific extinction area (SEA) and total smoke release (TSR), with delaying ignition and burn-through time. This method incorporates silica sol in wood via physical filling and chemical bonding, thereby improving the mechanical and flame retardation properties of wood as an outdoor building material.