Spinning sustainable carbon fibres for the energy transition

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Carbon fibres are widely applied, including to reduce weight, improve fuel efficiency, and extend vehicle range. Whilst contributing to sustainability in use, they are usually made from petrochemicals. This project develops a new approach to spinning sustainably-sourced carbon fibres from lignin (derived from wood). Two patent applications from Imperial (GB applications 2208061.8 and 2208067.5) underpin the incorporation of exceptionally high proportions (>90%) of industrial lignin, and conversion to higher performance fibres with high yield. Demonstrated at single fibre scale, the project will develop the spinning process to create more uniform, more aligned fibres, with improved properties.The key will be to monitor the complex behaviour of the nanotube/lignin hybrids, in situ, during spinning, through carbonisation, and subsequent graphitisation. Intimate interactions between lignin and nanotubes enable spinning by modifying rheology, increase yield during carbonisation, template improved graphiticity at lower temperatures, and provide direct reinforcement. These effects will be evidenced and understood by detailed characterisation studies and optimised by specially grafting lignins with different chemistries. Shaffer/Launois/Paineau have recently shown that Ge-doped imogolite nanotubes provide an excellent model system for carbon nanotubes, offering similar phenomenology but much better opportunities for in situ characterisation during spinning, exploiting their monodispersity, scattering strength, and optical birefringence (doi.org/10.1021/acsami.1c00971). The project offers the opportunity to develop a new class of carbon fibres that could be developed together with commercial partners. The DoE has set targets for a low-cost, sustainable alternative to petroleum derived carbon fibre at 1.7 GPa strength, 170 GPa stiffness and <£10/kg cost.(doi.org/10.1016/j.carbpol.2020.116918) The proposed technology has the potential to reach these targets by providing a robust system using low-cost renewable lignin feedstocks (£0.3-0.5/kg), as well as low cost and inherently recyclable ionic liquid (£1/kg). There is enormous current interest in bioderived carbon fibres, including from potential commercial partners, once these key performance metrics are met.