Objective Bamboo suffers from poor natural permeability. Traditional resin impregnation enhances its strength, while it concurrently increases brittleness and reduces toughness, failing to meet the demands for high-strength and high-toughness applications. To address this, this paper proposes a modification method combining deep eutectic solvent (DES) pretreatment with polyvinyl alcohol (PVA) impregnation, aiming to simultaneously enhance the strength and toughness of bamboo and elucidate the underlying reinforcement and toughening mechanisms.

Method Using Phyllostachys edulis as raw material, bamboo was pretreated with a lactic acid/choline chloride DES system to improve its toughness by enhancing internal porosity and permeability. Subsequently, the DES-pretreated bamboo was impregnated with PVA as a modifier. The synergistic mechanism of DES and PVA was thoroughly investigated by characterizing the treated bamboo’s micromorphology, pore structure, dimensional stability, and mechanical properties.

Result DES pretreatment increased the porosity of bamboo. The specific surface area of pretreated bamboo was maximally enhanced by 49.96% compared with the untreated group, with a higher proportion of macropores and mesopores among the newly formed pores, providing more space for subsequent PVA impregnation. Compared with untreated bamboo, the impact toughness of pretreated bamboo was maximally increased by 10.97%, while its flexural strength exhibited a slight decrease. After PVA impregnation, both the strength and toughness of modified bamboo were enhanced. Notably, bamboo specimens pretreated with DES (110 ℃, 2 h) followed by PVA impregnation showed increases of 14.50% in impact toughness, 6.65% in flexural strength, and 34.33% in elastic modulus compared with the untreated bamboo. Micromorphological characterization revealed that PVA filled the pores within cell lumina and intercellular spaces, strengthening intercellular connections and effectively dispersing external loads, thereby achieving simultaneous improvements in both strength and toughness.

Conclusion The combined DES pretreatment and PVA impregnation effectively breaks through the bottleneck in bamboo modification where achieving both high strength and high toughness is difficult, significantly enhancing bamboo’s application potential in fields such as furniture and construction engineering. Furthermore, the low weight gain rate of modified bamboo and the recyclability of DES further reduce raw material costs, facilitating industrial-scale implementation.