Wet-spinning and carbonisation of water coagulated lignin/bio-based thermoplastic polyurethane precursor fibres

Carbon fibres (CF) find applications as a reinforcement high-performance composite materials due to their high strength-to-weight ratio. Lignin has widely been explored as a replacement to the current commercial petroleum-based CF. While melt-spinning is promising for lignin processing, it challenges large-scale production since 95 % of commercial CF use wet-spinning technique. Here, a cost-effective and scalable spinning method has been developed using a water only coagulation bath to produce fibres from commercially and abundantly available Kraft lignin (KL) and bio-based thermoplastic polyurethane (TPU). Characterisation of precursor material revealed the strongest lignin-TPU interaction and the highest carbon yield at a 60:40 wt ratio. This optimised composition has been spun through refined process parameters to achieve desired fibre morphology. A tensile strength of 618.2 ± 64.71 MPa, and a tensile modulus of 34.77 ± 5.10 GPa have been achieved at a fibre diameter of 23.8 µm, placing wet-spun lignin-TPU CF as a sustainable and cost-effective alternative for non-structural components.