Effect of hygro-mechanical treatment combined with saturated steam on bamboo cell wall: Structural, chemical, and hygroscopic properties

Bamboo has shown great potential in various fields such as construction, furniture, and decoration due to its fast growth rate, short degradation cycle, strong carbon sequestration ability, and excellent mechanical properties. The effects of hygro-mechanical treatment combined with saturated steam (SC treatment) on bamboo cell walls are less studied. This study explored the effects of SC treatment at different temperatures (140°C, 160°C, 180°C) on the cell wall structure, chemical composition, and hygroscopic properties of bamboo. The study utilized Fourier transform infrared spectroscopy (FTIR) and Confocal Raman microscopy (CRM) to analyze the chemical properties of bamboo, X-ray diffraction (XRD) to analyze the crystal structure, Small Angle X-ray Scattering (SAXS) to analyze the microstructure, Brunauer-Emmett-Teller (BET) to analyze porosity, and Dynamic Vapor Sorption (DVS) to assess humidity adsorption. The lignin and hemicellulose in the bamboo were degraded under saturated steam treatment, leading to reduced stability of the bamboo fiber structure. Compression under these conditions severely damages the orderly arrangement of the fiber structure, resulting in a decrease in the microfibril orientation. The reduction in orientation significantly affected the moisture transfer rate in bamboo and the micromechanical properties of the fiber cells. Simultaneously, the reduction of lignin and hemicellulose decreases the hygroscopic properties of bamboo. The results of this study indicate that SC treatment significantly improves the crystallinity and dimensional stability of bamboo while reducing its porosity, hygroscopicity, and micromechanical properties. Among the three experimental groups, the 160°C saturation steam-compression treatment was considered the best method for significantly improving bamboo performance while maintaining structural integrity. •The mechanism of saturated steam compression of bamboo cell wall is proposed.•The relationship between saturated steam compression and fiber structure is established.•The relationship between treatment temperature and physicochemical properties is established.