竹纤维的多壁层结构与关键化学组分对湿热处理的响应机制

Hygrothermal treatment is one of the efficient and green methods in improving the dimensional stability, durability and resistance to biological deterioration of bamboo materials and products. In this project, indepth research is conducted on the key scientific problem of “the properties of bamboo fiber cell wall depend on its changes from physical and chemical structure”. Because of the multi-lamellate construction of bamboo fibers with alternate thick and thin layers, high resolution microscopic imaging and structure characterizing technology was used to observe the influences of hygrothermal treatment on the nano-laminated structure, orientation of microfibril, crystallinity and porosity of bamboo fiber cell walls. Also, by the means of spectroscopic analysis technology, we focus on investigating the change of chemical composition of cellulose, hemicellulose, and lignin in bamboo fiber cell walls during hygrothermal treatment, especially the change of chemical structure, characteristic functional groups and hydroxyl in cellulose and hemicellulose that differs greatly in principal component and content from that in wood. On this basis, the cell wall mechanical characterization techniques were adopted to further verify the response mechanism of static and dynamic mechanical properties of bamboo fibers on the changes of Micro-nano structure and macromolecular chemistry compositions. Try to reveal the effect mechanism of hygrothermal treatment on the multi-lamellate construction and key chemical compositions of bamboo fibers at cellular, sub cellular and molecular level. This study will promote the reasonable application of bamboo resources and provide scientific basis for environmental modification and producing optimization of bamboo materials and products.

湿热处理是提高竹材及制品尺寸稳定性、耐久性和抗生物劣化性的高效环保的改性方法。本项目紧紧围绕“竹纤维细胞壁的物化结构变化决定其性质”这一关键科学问题进行深入研究，针对竹纤维薄厚交替的多壁层结构特点，采用高分辨的显微成像和结构表征技术，系统观察湿热处理对竹纤维细胞壁的壁层结构、微纤丝走向和结晶度、孔隙度的影响；利用光谱分析技术，重点解析湿热处理过程中细胞壁关键组分纤维素、半纤维素和木质素的化学构成变化，尤其是与木材中主成分和含量差异较大的半纤维素多糖、木质素大分子的化学结构、特征官能团及羟基变化；在此基础上，结合细胞壁力学表征技术，进一步验证竹纤维的静态和动态力学特性对细胞壁微纳结构和大分子化学构成变化的响应机制。力图在细胞、亚细胞和分子水平上，揭示竹纤维的多壁层结构与关键化学组分对湿热处理的作用机理。研究成果将促进竹材资源的合理应用，并为竹材及制品的环保改性和工艺优化提供科学依据。

湿热处理是提高竹材及制品尺寸稳定性的高效环保的改性方法。本项目采用高分辨的显微成像、光谱分析及细胞壁纳米力学表征技术，证实了湿热处理后，竹纤维的细胞壁出现了明显的分层，纳米级的孔隙大量出现（AFM粗糙度增加近2倍），比表面积增加了47.13%。同时，羟基含量随湿热处理温度的升高而降低，关键化学组分半纤维素部分降解，220ºC处理后，乙酰基中的C=O减少，木糖全部分解，部分木质素也发生降解，表现为β-O-4键含量降低了54.32%，β-5键消失，PCE（对香豆酸酯）含量减少了23.91%，竹材的尺寸稳定性显著增加。与纤维细胞不同，薄壁细胞中的木质素与碳水化合物的降解几乎同时发生。湿热处理温度越高，纳米力学响应越明显，但是高于180ºC后，化学成分降解加剧，纳米力学性质降低，故180ºC为最佳的湿热处理温度。 本研究在细胞、亚细胞和分子水平上揭示了竹纤维的多壁层结构与关键化学组分对湿热处理的响应机理。研究成果将促进竹材资源的合理应用，并为竹材及制品的环保改性和工艺优化提供科学依据。相关研究结果发表于《Industrial Crops and Products》、《Cellulose》、《Planta》等重要学术刊物，并多次在本行业学术会议上进行交流；项目目前共计发表学术论文7篇，其中SCI收录4篇；培养博士和硕士研究生5名。