Improving the Fundamental Properties of Lignin-based Carbon Fiber for Transportation Applications

The Department of Energy Freedom Car Program has shown that domestic vehicle fuel consumption can be dramatically decreased by reducing the overall weight of production vehicles. Carbon fiber composites provide an attractive route to this goal. Significant automotive use of carbon fiber technology will require substantial increases in fiber production coupled with decreases in fiber price to ~$7/kg. Based on low-cost, high-volume, carbon yield, and melt-spinnability, Kraft lignin blends were selected as an alternative carbon fiber feedstock. Current studies have established the ability to melt-spin small tows of 10-20 micron diameter fibers. These tows were subsequently stabilized, carbonized, and graphitized with properties approaching those needed for transportation applications and reasonable yields. With feasibility established, project focus has shifted to development of cost-effective, scaleable technology to process byproduct Kraft lignin to remove unwanted contaminants (ash, cellulosic fibers, particulates, organic volatiles, and water), improve as-spun structure of raw and carbonized fibers, and increase resin-fiber adhesion. This paper reports results of studies to improve the fundamental properties of lignin-based carbon fibers. Later studies focusing on methods for improvement of fiber handlability, plasticity, surface coatings to improve spoolability and decrease water sorption, and spinning process optimization are planned.