Impregnation modification of poplar wood with a 2D resin/modified silica sol composite

Poplar wood is one of the major fast-growing timber species in China, but its low density, poor dimensional stability, and insufficient mechanical performance severely limit high-value applications. Although impregnation with 2D resin (1,3-bis(hydroxymethyl)-4,5-dihydroxyimidazolidin-2-one, i.e. DMDHEU) can improve dimensional stability and strength, it often reduces toughness. In this study, an organic-inorganic composite modifier was prepared from 2D resin and silica sol, and poplar wood was modified by vacuum-pressure impregnation. The chemical structure, physical properties, mechanical performance, and thermal stability of the modified wood were systematically characterized by FTIR, XPS, SEM, TG-DTG, and mechanical testing. The results showed that 2D resin, silica sol, and wood formed a stable organic-inorganic crosslinked network through Si-O-C and Si-O-Si bonds. With 15% modified silica sol, the modified poplar exhibited excellent mechanical performance. Compared with untreated wood, the modulus of rupture and modulus of elasticity increased by 117% and 71%, respectively, and impact toughness increased by 57%, effectively overcoming the brittleness associated with pure 2D-resin modification. Meanwhile, char yield and thermal stability were markedly enhanced. This work provides a feasible strategy for high-performance modification of fast-growing poplar and a theoretical reference for the development of organic-inorganic composite wood modifiers.