Enhancing Carbon Fiber Properties through Lignin-Cellulose Composites: A Comparative Study of Hardwood Vs. Softwood Lignin Sources

Abstract

Carbon fibers are integral to a wide range of applications, including automotive, construction, packaging, textiles, and emerging fields such as energy storage electrodes like flexible supercapacitors. However, concerns related to limited availability and environmental impact associated with fossil-based carbon fiber production have sparked growing interest in sustainable alternatives, particularly those derived from lignin and cellulose composites. This conference work presents a comparative analysis of the mechanical properties of lignin-cellulose composite carbon fibers derived from hardwood and softwood lignin sources, elucidating the significant influence of lignin origin on fiber performance.Our study focuses on the advantages and disadvantages of utilizing a composite of hardwood lignin vs. softwood lignin with cellulose in carbon fiber production, comparing these materials to commercially available carbon fibers. We emphasize the mechanical performance of these composite fibers, specifically highlighting the tensile strength and tensile modulus as a key metric. Notably, our results demonstrate that carbon fibers derived from hardwood lignin/cellulose composites exhibit superior mechanical strength compared to those from softwood lignin/cellulose composites. To gain fundamental insights into the reasons behind this mechanical disparity, we employed Raman spectroscopy to analyze the carbon structures within the fibers. Our findings revealed that carbon fibers produced from hardwood lignin exhibited a higher degree of graphitization, helping in achieving of typically desirable pre-graphite turbostractic carbon structures. These structural enhancements significantly contributed to the improved mechanical characteristics observed. In summary, our research underscores the critical importance of lignin source selection in the production of lignin-cellulose composite carbon fibers. The mechanical performance of these fibers is closely linked to the carbon morphology influenced by the lignin source. Therefore, understanding and controlling the lignin source from hardwood or softwood is pivotal for tailoring carbon fiber properties to meet specific application requirements. This study not only advances the knowledge in sustainable carbon fiber production but also offers valuable insights into achieving desirable properties for a wide range of applications, including advanced energy storage systems and structural materials.