Production of lignin filaments: Several lignins have been produced and evaluated for filament spinning using a small-scale monofilament apparatus. More than 100 kg of the selected parent lignin was produced. Thermal treatments were performed and multifilament spinning was investigated at up to the about 1000-filament scale.
Turning the lignin filaments into carbon fibres: Different methods for stabilisation such as UV irradiation, crosslinker addition and isothermal heating of the fibres were used to assist and facilitate stabilization. Pre-stabilization of fibers, at lower temperatures, showed the most promising results and reduced the main stabilization time significantly.
Surface chemistry and physical properties of the lignin-based carbon fibres were evaluated. Plasma treatment is a safe and effective method for improving fibre/matrix adhesion by adding surface functional groups on the fibre surface.
Process upscaling: Different pre-treated lignins were analysed regarding their potential large-scale spinning behaviour. With these results the plant setup, spinneret design, process parameters and winding conditions were adapted to the unique spinning behaviour of lignin.
Spinning trials were performed with all lignin samples in near-industrial scale. Continuous processing was possible on a standardised single screw extruding system without any gas inclusions which allows an easy scale-up to existing production plants. A new spinning concept was developed which allows continuous spinning and winding with automatic spool change. It is based on a spin-carrier where the outer envelope component can be removed in a continuous after-treatment process to gain a 100 % lignin precursor yarn. A 1000 filaments precursor yarn was produced. The stabilization of the precursor fibre could not be realized with existing commercially available stabilization ovens and alternative stabilization technologies needs to be further investigated.
Product application development: Fabrics, matrices and manufacturing methods for reference composites were selected. A suitable experimental methodology has been identified and tuned on the early stage fibres. The fibres were characterised with a single fibre tensile test. A car bracket-component and a back plate were selected as a benchmark reference for thermoplastic and thermoset demonstrator. The bracket was redesigned for composite manufacturing. The thermoset demonstrator has been designed from SMC production technique and with commercial material data. Both thermoset and thermoplastic composites have been manufactured. All the manufactured composites have been characterised via tensile, compression and short beam testing to determine the tensile and compression modulus and strength as well as the short beam strength. The results show that the lignin carbon fibre produced are performing in line with or better than previously presented in the literature. Computer simulations of the demonstrator with material data from all benchmark materials and the lignin carbon fibre have been carried out and show great weight saving potential by using lignin carbon fibre.
Techno-economic evaluation: A simulation model, integrating lignin extraction from a pulp mill, melt spinning and carbon fibre conversion, was developed for techno-economic evaluations of an up-scaled industrial process. The estimated production cost of the GreenLight carbon fibre (CF) was 12.6 EUR/kg (to be compared with cost estimates of PAN-based CF of ~16 EUR/kg). A sensitivity analysis showed a reduction in production cost, down to 6.5-7.1 EUR/kg, through cooperation with existing melt spinning and carbon fibre plants. The number of holes per spinneret in the melt spinning process has a significant impact on the total production cost.
The GreenLight process has a global warming potential (GWP) of 1.50 kg CO2eq/kg CF with production and use of chemicals as the main contributors. This number is 35 % lower than the GWP for glass fibre production and an order of magnitude lower than PAN-based CF. The socio-economic impact of the GreenLight process is mainly increased employment, increased export and stakeholder participation.
Dissemination: A dedicated project website has been developed and updated alongside with an internal communication tool. A visual identity, including logos, templates and style guide has been created for the project. In addition, there are postcards, posters, flyers and a generic project presentation, which can be used for external events. Dissemination activities have been chosen to effectively market the outcomes of the project to a targeted audience. The results of the project have been presented at scientific and industrially relevant conferences.
