(590b) Enabling Commercially Viable Green Carbon Fiber By Tuning Lignin Chemistry

Carbon fiber is popular in applications where the ratio of tensile strength to weight is important, such as the aerospace, automobile, wind turbine, construction, infrastructure, and sporting goods industries. For example, lightweight vehicles partly constructed with carbon fiber improve fuel efficiency, reducing greenhouse gas emissions from the transportation sector. Despite increasing demand, carbon fiber is mostly applied to higher-end products due to its high costs attributed to its precursor costs. In this context, low-cost carbon fibers produced using polyacrylonitrile-alternative precursors are attractive in various industrial applications. According to DOE, low-cost carbon fibers with a tensile strength of 1.72 GPa and a modulus of 172 GPa could be widely used in automobile industries for bodies and parts without compromising performance. Lignin is a promising precursor for low-cost green carbon fiber due to its abundant availability at low costs and high fixed carbon content. Unfortunately, its poor mechanical properties hinder the market entry of lignin-based carbon fiber.

This talk will introduce our approaches for producing high-quality lignin-based carbon fibers. The poor mechanical properties of lignin-based carbon fibers are mainly attributed to the irregular and highly branched molecular structure of lignin lacking in orientation. To address this intrinsic defect of lignin, we previously synthesized melt-spinnable arylate thermoplastics with linearity from lignin bio-oil by applying a controlled radical polymerization method. Using the new thermoplastic polymer as a precursor, we achieved carbon fibers with an average tensile strength of 1.7 GPa and tensile modulus of 182 GPa. In a recent study, we innovated carbon fiber production by developing a thermo-mechanically controlled and lignin-tailored method. By coupling the thermochemistry and mechanochemistry of lignin, we manipulated chemical reactions and altered the microstructure evolution. As a result, lignin-based carbon fibers with unprecedented tensile properties were obtained at surprisingly low temperatures. Three carbon fibers produced using raw lignins without premodifications or additives had tensile strength and modulus of 2.45 GPa and 236 GPa, 2.11 GPa and 215 GPa, 2.2GPa and 225GPa, respectively. Our findings suggest promising opportunities to produce commercially viable low-cost green carbon fibers from broad lignins, advancing lignin valorization.