Lines and Components for making Carbon Fiber
Dipl.-Ing. Erwin Glawion, Sales Manager and Dr. Dieter Zenker, Managing Director, both
Trützschler Nonwovens GmbH
In recent years carbon fiber came increasingly into the focus of the industry making parts and
machinery for extreme standards regarding sustainability and energy saving. Also the
automotive industry has already increased the share of carbon fiber composites, which could
result in huge demands in the next years, even the price per kg is much higher than other
construction materials. Trützschler has successfully started to participate in this market 3
years ago by building optimized machinery for production lines, based on experience of
almost 50 years in building man-made fiber equipment.
The Production of Carbon Fibers: A sensitive phase to phase Process
As in the past the development of carbon fiber equipment and machines often took place
independently from machine and equipment builders, it was not always easy for this industry,
to find reliable, high-sophisticated units or even complete lines. Following this idea
Trützschler and the companies Eisenmann, well known for material flow automation,
environmental technology and high temperature technology like oxidation ovens and
Ruhstrat, manufacturer of high-temperature furnaces like carbonization furnaces found each
other more than two years ago and started to work on the upper mentioned goal. All
together, complete carbonization lines, having a total length up to 250 m, can be engineered
and delivered as required by the market.
The Process Steps and the required Equipment
The prepositions for a perfect carbon fiber however are created in the polymerization and the
subsequent spinning of a suitable PAN precursor. Also these steps can be offered together
with EPC Industrial Engineering, a family-owned engineering company, specialized in
engineering of polymerization plants including utility and civil engineering. Trützschler has
developed new optimized spinning components, based on the former delivery of many PAN
textile lines and concepts, taken over from other spinning technologies.
For the so-called wet spinning process PAN powder is dissolved in solvents continuously to
get a spinning dope. The degassed dope is fed to the Trützschler Precursor Line consisting
of innovative spinning units, which assure a homogenous consistency and shape of the tows.
An even and uniform fluid flow and concentration in all coagulation and washing steps,
reliably smooth-running rollers, and the prevention of friction points are realized by
Trützschler through an intelligent combination of drive management, fluid circulations and
temperature control. In all process steps, the modular machine system allows a high
flexibility for the line configuration, exactly adaptable to the requirements.
Through the whole processing on the Precursor Line, the tows are guided by the FiberLogistic-System, a combination of surface treatment bathes, drive and process control. The
Precursor Line ends with the winding on 300 kg bobbins or plaiting of the precursor in big
cans, as the following carbonization process runs at significantly lower speed.
After unwinding or taking out from the cans again, the precursor tows are kept separately in a
wide band and are subsequently transformed into carbon fiber tows. Trützschler’s knowledge
of tow handling and the central HMI assure exactly parallel tow guiding and the overall
process control in the following steps. The first fiber-modifying process step is the oxidation
or stabilization of the PAN-precursor in the ovens of Eisenmann. The subsequent
carbonization is executed in two process steps in the furnaces of Ruhstrat. The first step of
the carbonization is done in a furnace around 700°C (LT-furnace). This furnace is directly
followed by the high temperature furnace (HT), which heats up to 1800°C. For special CFapplications graphitization is possible in an optional ultra high furnace (UHT), which works at
temperatures up to 2600°C.
After the Carbonization the tows, each consisting of several thousand fibers, each having
less than 8 microns, have to be electrolytically roughened to get a sufficient adhesion in the
final product. Subsequently a sizing has to be applied before winding on easily manageable
bobbins.
Conclusion
Trützschler and his alliance partners are the only one worldwide, which can offer complete
lines for the whole process chain, in lab-scale up to industrial production lines with an output
up to 2000 tons of carbon fiber per year. First orders are under manufacturing and the
feedback from the market is still very encouraging.