Development of high stiffness carbon fibres from lignin

Carbon fibres (CFs) are high-value components of composite materials and are used as reinforcing agents for structural applications. Lignin has been researched as a potential replacement for petroleum-based CFs due to its high carbon content, low environmental impact, and cost-effectiveness. Despite the environmental and economic advantages lignin offers, CFs produced from lignin are considerably weaker when compared to existing PAN based CF. Here, Precursor fibres (PFs) are subjected to UV irradiation and subsequent thermostabilisation in tension to increase polymer chain alignment and minimise fibre diameter down to 7 μm. Toluene diisocyanate (TDI) is used as a reactive coating for the PFs to aid thermostabilisation, increase carbon yield (CY) and modify final mechanical properties. Each composition was fully characterized using thermal, mechanical, and structural analysis. Beyond state-of-the-art sustainable CFs with a tensile modulus of up to 279.04 ± 97.71 GPa have been achieved, placing lignin-based CF as a potential replacement of PAN T300 grade fibres. However, tensile strengths still require improvement via continuous carbonisation processes, along with optimisation of carbonisation temperatures and carbon microstructures. This significant result places lignin-based CF as a potential replacement of PAN T300 grade fibres.