Basic materials and processes for cost-efficient carbon fibers of the future
Currently, more than 95 % of carbon fibers are produced from special “precursor fibers”. These precursor fibers usually contain a polyacrylonitrile (PAN) polymer. Due to the high price of the mineral-oil based polymer and the expensive production processes, the cost of the precursors account for 50 % of the carbon fiber costs. Given the high cost of the fiber production itself along with expensive composite production processes, usage of this exceptional material is limited to high-end applications.
Essentially, the production of carbon fibers consists of a three-stage process: The chemical stabilization of the PAN fiber takes place at temperatures up to 300°C. The next stage, “carbonization”, takes place at over 1000°C. The last step is the surface treatment, which is essential for further processing. One goal of the MAI Green project is to specifically examine and modify these stages. Reaction pathways are to be identified, explained and understood by conducting fundamental analyses of the chemical reactions along the process chain. The intended result is to determine a use-optimized parameter set for the cost-efficient production of carbon fibers made from PAN-precursors.
Another way to reduce the costs of producing carbon fibers is to use an alternative material for the precursors, such as biopolymer lignin, for example. Lignin is derived from pulp production as a waste product. Use of lignin as a precursor material for carbon fiber production is thus the subject of current research. Principally, it has been shown that carbon fiber can be made from lignin in a melting spinning process, however its use is extremely limited because it is difficult to reach acceptable purity levels and production processes are not currently optimal. Therefore, high-performance fibers that can be used in industrial applications cannot be realized. This is where MAI Green comes into play
Figure: "Green" carbon fiber on "green" precursor
An additional focus of the project is to examine and produce customized lignin as an alternative raw material for the production of carbon fiber as well as establish a process chain suitable for this raw material.