凝胶纺丝法制备木质素基碳纤维原丝及其结构调控

The production cost of carbon fibers is the main restrictive factor for its application and popularization. Lignin as raw material has abundant, renewable, and low cost advantages. The routing using lignin as raw material thus becomes one of the most costeffective technology for carbon fibers production. The mechanical properties of lignin carbon fiber need be improved. The performance of carbon fiber depends on the precursor structure. The key to improve the lignin carbon fiber mechanical properties is to obtain high-quality the precursor. In order to obtain the lignin-based precursor, we use 1,4 - butanediol to extract wood flour and the coupling agent to modify Lignin. With these lignin as raw material, lignin-based carbon fiber precursor could be prepared by gel spinning. The main contents include: to study the variation of the molecular structure of lignin during extraction process and the coupling reaction by IR, UV, NMR and other analytical instruments, and the aggregation structure during the fiber forming process was investigated using XRD, scanning electron microscopy, pressure mercury analyzer. Aiming to regulate the structure of lignin carbon fiber precursor for promoted the performance of carbon fiber, this study will provide new technical route for the preparation of low cost carbon fiber as well as technical support for the sustainable development of carbon fibers industry.

利用木质素制备碳纤维已成为降低碳纤维生产成本的新的有效途径。但目前木质素碳纤维的力学性能还有待提高。优质木质素原丝是提高碳纤维性能的关键点。本项目使用1、4-丁二醇蒸煮木粉提取木质素，然后加入偶联剂调控木质素分子结构，最后采用凝胶纺丝制备木质素原丝；通过调控木质素分子结构和纤维成形工艺过程，获得结构均一性好、取向度高的优质原丝。主要研究内容包括：利用红外、紫外、核磁等分析仪器，研究提取过程和偶联反应中木质素分子结构变化规律；使用XRD、扫描电镜，压汞仪等分析手段，研究凝胶纺丝过程中纤维结构形成历程和变化规律；建立木质素分子结构及其原丝结构的调控方法；揭示木质素纺丝液成形过程中的聚集态结构变化规律，建立木质素纺丝液成形过程的动力学模型。本研究将有利于提高木质素原丝的质量，阐明木质素原丝制备过程中纤维结构形成机理和变化规律，为提高木质素碳纤维性能及木质素碳纤维尽快实现工业化生产奠定理论和技术基础。

本项目首先优化了高沸醇法提取木质素的工艺，获得适合用于制备碳纤维的木质素原料；研究了化学或共混改性木质素后产物性能，获得木质素溶液凝胶规律和凝胶点；最后通过纺丝制备出木质素基碳纤维原丝。本项目的研究结果有利于增加对木质素基原丝制备过程的认识，为木质素基碳纤维的制备提供技术支持。项目发表学术论文3篇，培养博士研究生2名。主要研究内容和成果如下：.1、高沸醇提取木质素的最佳工艺条件是：温度为220℃、丁二醇浓度为80%、反应时间为1 h、固液比是8ml/g。所获得的高沸醇木质素含碳量为64.31%，分子量Mw为3778，分子量分布为1.52；羟基含量为5.332mmol/g；灰分为0.25%。.2、通过化学改性或共混改性均能使木质素形成凝胶态。向木质素中加入少量1、4-丁二醇可以调节木质素形成凝胶点温度，凝胶点温度是从-20.15到17.55℃；凝胶点温度与体系中丁二醇的含量有负相关性。而木质素与5%糠醛混合后体系的凝胶点温度为24.21℃。.3、二苯甲烷二异氰酸酯改性木质素所制备膜的最大拉伸强度和断裂伸长率可达到41.6 MPa和2.2%；但残碳率较低，仅为30%左右，说明其不适合用于提高木质素基碳纤维力学性能。.4、利用聚丙烯腈共混改性木质素可以制备木质素基原丝；通过控制改性木质素纺丝液的凝固工艺，可以获得中空木质素基原丝。调控纺丝液组分和凝固浴组分是获得中空木质素基原丝的关键。.5、采用凝胶纺丝制备出高沸醇木质素基原丝。形成凝胶态的木质素可纺性好，凝胶纺丝制备木质素基原丝时工艺稳定性好，但去凝胶化后木质素基原丝失去柔韧性，导致后处理工艺困难。