Research from Washington University in St. Louis could soon lead to lighter, stronger carbon fiber materials and stronger plastics with a milder environmental impact. The main ingredient needed for these improvements is lignin, an essential compound for most plants but considered waste by industry.
The key to unlocking lignin’s potential was to chemically alter some of its properties. High Molecular Weight Esterified Linker Lignin (HiMWELL) was designed by the group of Joshua Yuan, professor and chair of Washington University’s Department of Energy, Environmental, and Chemical Engineering at the McKelvey School of Engineering in St. Louis .
The research was published August 11 in the journal Question.
The researchers knew that, combined with polyacrylonitrile (PAN), the newly designed HiMWELL lignin could become a precursor to better carbon fiber and could also enable the development of recyclable plastics with better properties.
Already, carbon fiber is known to be a strong and stiff, yet lightweight and premium material. It’s used as structural reinforcement in everything from tennis rackets to airplanes, and carbon fiber frames reduce weight and improve safety in high-end vehicles. It has been integrated wherever possible into some of the fastest super and hypercars.
Yuan’s earlier work identified three main obstacles to bringing lignin into the equation: Neither lignin’s chemical structure nor its molecular weight are uniform, making it difficult to combine with other polymers. And it has a high number of OH groups, a reactive couple of oxygen and hydrogen that attract water – not ideal for building a stiff material like carbon fiber. These discoveries inspired Yuan and Jinghao Li, principal investigator at the University of Washington, to rethink the structures of lignin.
In developing a technique to chemically modify these properties, Yuan said, “We have really created a type of lignin that is quite unique.
When combined with PAN, HiMWELL-based carbon fiber has record tensile strength and has shown better mechanical properties than standard carbon fiber. When added to recyclable polymer blends, HiMWELL improved mechanical properties and also improved UV protection.
“Finally, we have a technology path for lignin to be used for carbon fibers,” Yuan said. And maybe one day, “You’ll turn this trash into a car shell.”
The US Department of Energy’s Office of Energy Efficiency and Renewable Energy and Bioenergy Technologies supported the work.
The research is supported by the U.S. Department of Energy, Grant # EE0008250
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Material provided by Washington University in St. Louis. Original written by Brandie Jefferson. Note: Content may be edited for style and length.