Study on the physico-mechanical properties and mechanisms of poplar wood co-modified by anoxic high-temperature heat treatment and impregnation with silica sol/phenolic resin

Abstract

Addressing the challenges of fast-growing poplar wood in construction, decoration, and furniture, including low density, insufficient strength, poor toughness, and suboptimal dimensional stability, this study introduces an innovative organic/inorganic impregnation-heat treatment technique. This method significantly enhances the physico-mechanical properties of poplar wood and overcomes issues associated with thermosetting resin modification, such as reduced impact toughness, uneven resin penetration, and wood swelling. Utilizing in situ polymerization with silica sol and phenolic resin, specifically with particle sizes between 8 and 15 nm, the process markedly improves wood permeability and overall properties through vacuum pressure impregnation and heat treatment. The findings indicate a 54.42 % increase in the wood's density. Optimized heat treatment at 180 °C for 1 h significantly enhances dimensional stability and reduces water absorption, with the ASE value reaching up to 69.3 %. Furthermore, the impregnation-heat treated wood exhibits a 50.19 % increase in bending strength to 81.6 MPa, a 103.93 % increase in modulus of elasticity to 16.5 GPa, and a 29.42 % increase in impact toughness to 92.5 kJ/m2, demonstrating substantial improvements over the raw material. FT-IR analysis reveals the presence of Si-O-Si vibration peaks, indicating the effective penetration of silica sol. TGA analysis displays the treated material's superior thermal stability compared to the raw material. XRD analysis confirms that the impregnation and heat treatment processes have not adversely affected the wood's crystalline regions but have instead reduced hygroscopicity and enhanced stability. SEM analysis showed that the composite impregnation liquid effectively penetrated and distributed within the wood cells. These results open new theoretical and technical pathways for enhancing the physico-mechanical properties of fast-growing poplar wood.