Our modern societies are built on the mobility of the individual. Travelling to and from work, trips for leisure and shopping, or journeys to holiday destinations are integral part of our lives. The most popular means of transportation today is the private car, with an EU-average driving distance of 12 000 km/a. Households in the EU have on average 1.4 cars, which equals to almost 0.7 cars per adult. In 2016, the global car production has surpassed the 70 million mark for the first time. This numbers make it clear that irrespective of whether and when the mobility of our society will shift to electric vehicles, solutions are needed to increase the fuel and energy efficiency of transportation to mitigate effects of climate change and account for the continuous depletion of fossil fuels. One key strategy is to reduce the weight of the vehicle by replacing metal components through lightweight composite materials. In particular carbon fiber reinforced composite (CFRC) elements offer significant weight reduction while maintaining the strength and safety properties. Carbon fibers are still predominantly produced from polyacrylonitrile (PAN) precursor filaments and remain an expensive commodity. For this reason, CFRCs are mostly found in high-end applications such as space- and aircrafts or low-volume products like sports and leisure equipment. However, they remained unattractive for products, which require bulk amounts at considerably reduced costs like the automotive sector.
Despite numerous initiatives worldwide to develop low-cost CFs from alternative precursor materials, no viable solutions have yet emerged. Biopolymers such as cellulose or lignin as renewable precursor for carbon fibers are experiencing a renaissance because respective precursor filaments can be produced substantially cheaper than state-of-the art PAN filaments. However, those bio-based CFs still suffer from two distinct limitations: (i) the strength properties are still not on the level of steel; (ii) refining wood to isolate cellulose pulp and lignin requires processes that add to the costs of the precursor filament and render the price of the resulting CFs still too high.
WoCaFi’s aim was to overcome those hurdles by turning wood in its entirety into high-quality continuous filaments to be converted into low-cost bio-based carbon fibers. Instead of separating the constituents of wood and processing them in isolated form (pure cellulose or lignin fibers) or combining wood pulp with technical lignin, wood is only mildly pretreated and dissolved directly into a special solvent to be spun into filaments. In addition, less energy input is expected for the carbonization phase, reducing the overall costs even further. Thus, a new low-price category of CFs is envisioned, which is suitable for all applications with property requirements in the mid-range.
The overall objectives of WoCaFi are:
• Produce multi-component filaments that contain two or more biopolymers homogeneously distributed across the fiber matrix.
• Elucidate the interaction of different biopolymers (cellulose-lignin, cellulose-hemicellulose, cellulose-chitosan) during pyrolysis and identify synergistic effects that increase the carbon yield and promote the formation of the carbon network.
• Build on the above knowledge-base to convert the entire wood matrix into high-quality precursor filaments and turn them into fully-biobased CFs.
