Oak Ridge National Labs (ORNL)
in Tennessee is finishing construction of a pilot plant that will be able to
produce up to 25 tons per year of carbon fiber from low-cost lignin and other feedstocks.
Successful startup of the technology could pave the way for
much wider use of carbon-fiber composites in cars, wind turbines and other
industrial applications.
"Through its investment in the Carbon Fiber Technology
Facility (CFTF), the federal government is facilitating the commercialization
of a full-scale manufacturing process for carbon fiber that is cheap enough to
be purchased by auto and wind turbine companies," says Fred Baker, a scientist
in the Materials Science and Technology Div.'s (MSTD) Carbon Materials
Technology group.
The U.S. Dept. of Energy last year provided ORNL with $34.7
million in American Recovery and Reinvestment Act funding to build the Carbon
Fiber Technology Facility.
The funding will allow ORNL to consolidate its carbon-fiber
composite research from three scattered buildings.
The ORNL estimates that every 10 percent reduction in
vehicle weight increases by 5 to 8 percent the miles a vehicle can travel for
the same input of energy. The weight of an engine could be reduced up to 60
percent if carbon composites were used extensively in the vehicle.
Widespread use of carbon composites is a game changer for
large aircraft such as the Boeing Dreamliner
787 and the Airbus
XWB 350. The enormous benefit of carbon composites in aircraft justifies
the price of $10 to $20 per pound. Experts feel that widespread use in cars
will require prices of carbon fiber to drop to around $5 to $7 per pound.
Use of carbon fibers is limited to high-end cars with
premium prices. One example is the Corvette ZR1, which features carbon-fiber
dual-port front fenders, a carbon-fiber raised hood with window and a full-width,
body-color carbon-fiber rear spoiler.
PAN and Lignin
The new facility at Oak Ridge will house a conventional
conversion line for producing carbon fiber from low-cost precursors, including
polyacrylonitrile (PAN), a polymer derived from petroleum, and lignin, which is
derived from wood and switchgrass.
The facility will also have a melt spin line that will
produce precursor fibers from raw materials such as lignin from paper mills and
from biorefineries that separate lignin from cellulose. A biorefinery at
Vonore, TN will use technologies developed by the Bioenergy Sciences Center at
ORNL and the University of Tennessee to economically break down cellulose into
sugars and ferment them to make cellulosic ethanol fuel.
Feedstocks include switchgrass and wood from hybrid poplar
trees.
Melt spinning is a commonly used process to make nylon,
polyester and other fibers used in various textile products.
"Melt spinning is cheaper than wet spinning because 100
percent of the feedstock materials is converted to fiber as they pass through
the spinneret," says Cliff Eberle, an engineer in the Polymer Matrix Composites
Group of ORNL's Materials Science and Technology Div. "In solution spinning
used for the PAN process, only about 20 percent of the material passing through
the spinneret is PAN, with the rest being solvent. Furthermore, recovering the
solvent and complying with environmental regulations make the PAN process
costly."
Baker says that melt spinning can produce a low-cost carbon
fiber from lignin. The precursor generally accounts for half the production cost.
A highlight of Baker's work was the demonstration that high-purity lignin can
be isolated from the "black liquor" of the paper-making process without an
expensive purification step. The cellulosic ethanol fuel process is a route to
even higher purity lignin.
ORNL is managed by UT-Battelle for the Dept. of Energy.
Photo: The Corvette
ZR1 makes extensive use of carbon composites to reduce weight and boost
performance.Source: General Motors
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