Organic–inorganic hybrid material containing silica–alumina sol and ether polymer for flame retardant wood with decay resistance and excellent mechanical properties

Poplar wood, which is primarily used to manufacture wood-based panels, furniture, and paper, is a fast-growing plantation wood that is produced with high yields; however, its poor mechanical properties and perishability limit its application. Herein, we propose a method that enables silica–alumina sol to penetrate wood smoothly. In this method, silica–alumina sol is added into an ether polymer by blending, and the mixture is completely stirred until hybridization. The ether polymer introduces the silica–alumina sol into wood via pressure impregnation. Poplar wood treated with this hybrid material has excellent mechanical properties; the maximum bending strength and modulus of elasticity are 112.9 MPa and 16.89 GPa, respectively, and the compressive strength along the grain is 111.5 MPa. Moreover, the treated poplar wood exhibits decay resistance and flame retardancy properties. After 12 weeks of decay resistance testing, the average mass loss is 8.35%–18.52% (that of untreated wood is 32.33%–62.06%). The treated wood exhibits 40.5% and 52.4% smaller total heat release and total smoke production, respectively, than the untreated wood. This method incorporates silica–alumina sol in wood via physical filling and chemical bonding, thereby improving the mechanical and flame retardancy properties of wood as an outdoor building material.