Researchers at Washington University in St. Louis (WashU) have developed a process for producing renewable carbon fiber from lignin. Lignin is a carbon-rich waste material generated by the paper pulping and biorefining industries. The process also uses functionalized single-walled carbon nanotubes to improve the fiber's internal structure and mechanical performance.
“For the first time, this allows us to create renewable carbon fiber that reaches the high standard of quality used in automobile manufacturing,” said Joshua Yuan, the Lucy & Stanley Lopata Professor and chair of energy, environmental and chemical engineering at WashU McKelvey Engineering. Yuan also directs the NSF Carbon Utilization Redesign for Biomanufacturing (CURB) Engineering Research Center at WashU.
The research addresses the use of polyacrylonitrile (PAN) in conventional carbon fiber production. PAN is petroleum-derived and can account for up to 50% of carbon fiber manufacturing costs, according to the research team. By incorporating lignin into the precursor, the researchers reduced PAN use by half. The approach also delivered a reported 25% reduction in production costs.
The team then focused on the internal structure of the resulting fiber. Functionalized single-walled carbon nanotubes were introduced into the precursor to influence crystallization during processing. “Crystallization alignment is critical for carbon fiber quality,” Yuan said.
The manufacturing process starts with a lignin-PAN precursor solution containing the carbon nanotubes. The solution is converted into fiber through wet spinning. The fiber then undergoes tension-assisted heat treatment and an optimized carbonization step. The researchers said these stages increase the content and alignment of crystallites within the carbon fiber.
“All these together allow us to create lignin-based renewable carbon fiber that has highly aligned crystalline structure,” Yuan said. The resulting material is designed to reach mechanical performance levels suitable for automotive applications, while reducing reliance on petroleum-derived feedstocks.
The automotive sector is an initial target, but the potential applications extend across other composite markets. Carbon fiber is used in sports equipment, wind turbines, aerospace structures, and other reinforced plastic applications. “Carbon fiber reinforces plastics and has very broad application,” Yuan said. The research was published in Matter under the title “Transforming renewable carbon fiber performance, economics, and sustainability via oriented crystallization design.”
Source: WashU | Newsroom
