From flattening-induced dimensional instability to steam-driven stability: An industrial-scale solution for flattened bamboo culm

Bamboo culm flattening technology, an emerging processing technique, significantly improves bamboo utilization efficiency by enlarging fundamental structural units and reducing adhesive consumption in engineered bamboo production. However, inherent structural heterogeneity and residual stresses induced during flattening often lead to warping deformation during service, substantially constraining practical applications. This study demonstrates an innovative saturated steam treatment approach that effectively enhances dimensional stability through a clean and efficient processing protocol. Our research highlighted that specimens treated at 185°C for 10 min exhibited significant improvements in dimensional stability. These enhancements are attributed to a progressive reduction in hydrophilic hydroxyl groups and changes in cellulose crystallinity. As a result, the treated specimens exhibited exceptional stability metrics, including a 65.58% reduction in oven-drying warpage and 68.43% decrease in humidity-induced deformation (1.49% warpage change from 30% to 85% RH). Significant reductions were also observed in hygroscopicity compared to untreated controls. Collectively, these findings represent an effective approach to addressing the dimensional instability issues that have long hindered flattened bamboo culms. This study offers a scalable solution to unlock flattened-bamboo’s high-value potential, fostering its integration into sustainable construction, advanced materials, and circular economy frameworks.