Thermally modified timber (TMT) reduces hygroscopicity, increases dimensional stability, and decay resistance. Although there is a substantial amount of research on heat-treated wood, investigations on the sensitivity of cell wall swelling behavior to water variation are limited. Therefore, this study focused on the swelling behavior of TMT from cellular and chemical perspectives. The effects of heat treatment on the hygroscopicity and swelling behavior of the wood cell walls were studied using dynamic vapor sorption and confocal laser scanning microscopy. Changes in the chemical composition and cellulose crystallinity were studied using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray diffraction. The results revealed that the hygroscopic swelling of latewood significantly decreased with increasing treatment temperature, reducing the anisotropy of the wood cell swelling. The hygroscopicity of wood was reduced by heat treatment, and a clear decrease in hysteresis was observed at elevated treatment temperatures. The FTIR spectra indicated that both hemicellulose and lignin were degraded. The crystallinity and lateral size of the cellulose increased after heat treatment. Similar changes in the chemical composition and crystallinity of cellulose were observed in the latewood and earlywood.

中文翻译：

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从细胞和化学角度观察热改性木材的膨胀行为

热改性木材 (TMT) 降低吸湿性，提高尺寸稳定性和耐腐性。尽管对热处理木材进行了大量研究，但对细胞壁膨胀行为对水变化的敏感性的研究仍然有限。因此，本研究重点从细胞和化学角度研究TMT的溶胀行为。使用动态蒸汽吸附和共焦激光扫描显微镜研究了热处理对木材细胞壁吸湿性和膨胀行为的影响。使用衰减全反射傅里叶变换红外光谱 (ATR-FTIR) 和 X 射线衍射研究了化学成分和纤维素结晶度的变化。结果表明，随着处理温度的升高，晚材的吸湿膨胀显着降低，降低了木材细胞膨胀的各向异性。热处理降低了木材的吸湿性，并且在升高的处理温度下观察到滞后现象明显降低。FTIR 光谱表明半纤维素和木质素均被降解。热处理后纤维素的结晶度和横向尺寸增加。在晚材和早材中观察到纤维素化学成分和结晶度的类似变化。FTIR 光谱表明半纤维素和木质素均被降解。热处理后纤维素的结晶度和横向尺寸增加。在晚材和早材中观察到纤维素化学成分和结晶度的类似变化。FTIR 光谱表明半纤维素和木质素均被降解。热处理后纤维素的结晶度和横向尺寸增加。在晚材和早材中观察到纤维素化学成分和结晶度的类似变化。