木材细胞壁热响应特性及其对细胞腔形变自调节机制作用研究

The shrinkage and swelling characteristics of wood have always been a problem that affects the processing and utilization of wood and its products. Heat treatment can improve the dimensional stability of wood, but there is still a lack of in-depth research on its modification mechanism. Therefore, the research subject will be Larix kaempferi (Lamb.) Carr.. Using advanced instruments combined with wet chemical composition analysis and immunohistochemistry, the study on thermal response characteristics of wood cell wall and the self-regulation mechanisms of cell lumen deformation in the process of untreated and heat-treated wood moisture absorption and desorption will be systematically carried out. The change of ultrastructure and chemical composition distribution of wood cell wall will be studied during the vacuum heat treatment process. And the molecular structure of chemical composition and lignin-carbohydrate complex of heat-treated wood will be comprehensively analyzed. Besides, the gas components released by the wood during heat treatment process and the interactions between them and wood chemical composition will be studied. Furthermore, the deformation law of wood cell wall and lumens in the process of untreated and heat-treated wood absorption and desorption will be elucidated. And the relationship between wood cell lumen deformation and ultrastructural as well as chemical changes of cell wall will be established. The self-regulation mechanism of wood cell lumen deformation and the effect of thermal on it will be explored. Research results will provide the scientific basis for optimizing the technology of wood heat-treatment, new ideas for improving the dimensional stability of wood, and important guiding significance for the modification and utilization of wood.

木材干缩湿胀特性一直是影响木材及其制品加工利用的难题，热处理可以有效提高木材尺寸稳定性，但是其改性机理尚缺乏深入研究。为此，本项目拟以人工林日本落叶松木材为研究对象，采用现代分析仪器结合湿化学法和免疫组织化学法，研究真空热处理过程木材细胞壁热响应机理以及木材热处理前后水分吸着解吸过程细胞腔形变的自调节机制。探讨热处理过程木材超微结构及其化学成分微区分布变化趋势；揭示热作用对木材主要化学组分和木质素-碳水化合物复合体分子结构的影响；解析热处理过程中木材释放的小分子物质及其与木材化学组分间可能发生的聚合反应；阐明木材热处理前后细胞壁/腔吸湿形变规律，建立木材水分吸着解吸过程细胞腔形变与细胞壁超微构造及化学特性变化的相互关系，探索木材细胞腔形变自调节机制及热作用对其的影响。研究成果可为木材热处理技术优化、升级提供理论基础，也为改善木材尺寸稳定性研究提供新思路，对木材改性加工利用具有科学指导意义。

真空热处理是在真空条件下以热辐射方式为主对木材进行加热的一种环境友好热改性方法。本研究以我国东北主要用材树种落叶松木材为研究对象，采用真空热处理技术，优选不同处理条件（温度180、200和220°C，处理时间6h），利用扫描电镜、激光扫描共聚焦显微镜、傅里叶变换红外成像显微镜、氮气吸附等手段结合湿化学法，研究木材细胞壁热响应机理及细胞腔形变自调节机制。结果表明，落叶松木材以管胞为主，细胞中存在具缘纹孔和单纹孔，与晚材相比，早材纹孔多且大；落叶松早材孔隙率大于晚材，热处理前后早材和晚材中都存在微孔和中孔，并且二者微孔和中孔孔容均随热处理温度升高而减小，而大孔呈现先增加后降低趋势；真空热处理改善了落叶松早晚材吸湿性，细胞壁化学组分中羟基等吸湿性基团数量减少，其中晚材吸湿性降低更显著；红外成像显微镜显示热处理后早晚材细胞壁半纤维素降解和木质素重新分布；热处理早晚材细胞壁弹性模量随处理温度增加先升高后降低，晚材比早材弹性模量增加较多，热处理后细胞壁硬度也显著增加；对比未处理木材提取的纤维素呈棒状且表面有序平行结构，热处理后木材纤维素变弯曲且表面呈扭曲结构，同时热处理木材提取的纤维素碳链缩短，纤维素结晶度增加，其中Ⅱ型占比提高、Ⅰ型降低；热作用过程中落叶松木材产生醛酮、有机酸、有机醇、芳香族化合物、烷烃以及萜烯类化合物等挥发性成分，不同热处理温度条件下释放的挥发性有机物成分差异较大；热处理木材吸湿过程其细胞腔形变也呈现规律性变化。本研究为木材真空热处理技术优化、升级提供了理论支撑，为该技术转化应用提供了科学指导。