高性能改性木质素/聚合物凝胶纺纤维的构筑及其机械增强机理研究

Compared with conventional carbon fiber precursor materials and high-performance fiber fillers, lignin is very promising in high-performance fiber application since it is an earth-abundant biopolymer and has very low cost. However, the poor fiber spinnability and lignin fiber's low draw ratio due to its three-dimensional amorphous structure limited its wide application in high-performance fibers. Although chemical modification or lignin/polymer blending methods have been proposed, the enhancement of the mechanical performance of fibers is not significant. Therefore, poor fiber spinnability and low mechanical performance of lignin-based fibers are the remaining problems faced by researchers. In this proposal, esterification will be used to modify lignin structure with bio-based molecules containing multiple hydroxyl groups to enhance lignin’s affinity with polyvinyl alcohol (PVA) for the fabrication of high-performance fibers. The influence of modified lignin on the spinnability of polymer solutions, the structure of gel fibers and the draw ratio of the solid fibers will be elucidated. Moreover, the relationship between lignin/polymer affinity and mechanical properties of fibers will be revealed together with the mechanical reinforcement mechanism of modified lignin. Finally, bio-based high-performance gel-spun fibers will be achieved at the optimized conditions. This project will provide groundbreaking knowledge on understanding the structure-property-processing relationship of high-performance modified lignin/polymer fibers, it will lead to a breakthrough in the field of fabricating low-cost, high-performance bio-based polymeric fibers.

与传统碳纤维原料及高性能纤维增强材料相比，生物基分子木质素在高性能纤维的开发上有取材丰富、价格低廉的优势。但其复杂分子结构导致熔融纺成型困难、纤维牵伸倍率低；分子改性及将其与聚合物共混对纤维机械性能提升效果甚微，因此木质素在高性能纤维领域的开发应用受到了限制。本项目以提高凝胶纺木质素/聚乙烯醇纤维的机械性能为目的，拟利用酯化反应将含有多羟基的生物基小分子与木质素的酚羟基或脂肪族羟基结合，提高木质素的极性及其与极性聚合物基体的亲和性，构筑凝胶纺生物基高性能纤维。通过研究改性木质素对纤维成型过程中溶液可纺性、凝胶形态结构及固体纤维的牵伸倍率的影响规律，揭示木质素与聚合物亲和性对纤维机械性能的作用机制，阐明改性木质素机械增强纤维的机理，实现纤维机械性能的最优化条件，为设计开发低成本的高性能生物基聚合物纤维提供新思路、新方法和一定的理论支撑。

作为取材丰富、价格低廉的生物基分子，木质素在高性能纤维的开发上巨大潜力。然而木质素的分子结构复杂，直接纺丝成型困难；分子改性及将其与聚合物共混对纤维机械性能提升效果甚微，因此木质素在高性能纤维领域的开发应用受到了限制。本项目以提高凝胶纺木质素/聚乙烯醇纤维的机械性能为目的，利用不同的化学反应将含有多羟基的小分子与木质素结合，提高了木质素的极性及其与极性聚合物基体聚乙烯醇的亲和性，有效构筑了凝胶纺生物基高性能纤维（低木质素含量时断裂强度高达1.3GPa，高木质素含量时断裂强度高达1.1GPa）。本项目通过研究不同含量改性木质素对纤维成型、结构与性能的影响，明确了改性后的极性木质素对凝胶纺聚乙烯醇纤维的增强机理，对生物基高性能纤维的发展提供新的理论依据。