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Carbon fibers (PAN-, Cellulose-, Polyolefin-based)

Carbon fibers are made of anisotropic carbon with at least 92 wt.-% and up to 100 wt.-% carbon. Carbon fibers have high tensile strength up to 7 GPa with very good creep resistance, low densities (ρ=1.75-2.00 g/cm3) and high moduli up to E ≤ 900 GPa. They lack resistance to oxidizing agents as hot air and flames, but they are resistant to all other chemical species. The good mechanical properties make carbon fiber attractive for use in composites in the form of woven textiles as well as of continuous or chopped fibers. The composite parts can be produced through filament winding, tape winding, pultrusion, compression molding, vacuum bagging, liquid molding, and injection molding. For the automotive industry, carbon fiber-reinforced polymeric composites allow for a significant reduction in weight, which is a prerequisite for battery-driven cars. More recently, carbon fibers moved into the center of interest for carbon-fiber-reinforced concrete for houses, bridges, etc. as well as for carbon-fiber reinforced compounds for, there increasingly replacing steel.

The most important precursor in the market is poly(acrylonitrile) (PAN), while pitch is used for most other carbon fiber types. However, in search of renewable and energy-efficient precursors and processes, lignin and cellulose as well as poly(olefin)-based precursors have moved into the center of interest. Current projects focus on all these precursors, aiming on better and more efficient processes for carbon fibers as well as on improved fiber properties. Research is carried out in close collaboration with the ITCF Denkendorf, where these activities are allocated in the newly established High-Performance Fiber Center (HPFC) Denkendorf.

References:
1) New Trends in High-Performance Fibers and Fiber Technology - M. R. Buchmeiser, Macromol. Mater. Eng. in press (2012)
2) Carbon Fibers: Precursors, Manufacturing and Properties - E. Frank, F. Hermanutz, M. R. Buchmeiser, Macromol. Mater. Eng. (Special Issue on Fibers), in press (2012)
3) Co(acac)2-Mediated Radical Polymerization of Acrylonitrile: Control over Molecular Weights and Copolymerization with Methyl Methacrylate - M. R. Buchmeiser, M. Marino, Macromol. Mater. Eng., in press (2012)