Researchers have developed a novel method for turning plant-derived lignin into carbon fiber. Image: WashU/Jason Yuan.
Researchers have developed a novel method for turning plant-derived lignin into carbon fiber. Image: WashU/Jason Yuan.

A study by researchers at Washington University in St. Louis could soon lead to lighter, stronger carbon-fiber materials and stronger plastics with a gentler environmental impact. The main ingredient responsible for these improvements is lignin, a compound that is essential for most plants but considered a waste product by industry.

The researchers found that the key to opening up lignin’s potential was chemically altering some of its properties. The resulting High Molecular Weight Esterified Linkage Lignin (HiMWELL) was designed by the group of Joshua Yuan, professor and chair of the Department of Energy, Environmental & Chemical Engineering at Washington University in St. Louis’ McKelvey School of Engineering. Yuan and his group report their work in a paper in Matter.

According to the researchers, the newly designed HiMWELL lignin, when combined with polyacrylonitrile (PAN), could become a precursor to a better carbon fiber and also lead to the development of recyclable plastics with better properties.

Already, carbon fiber is known for being a strong and stiff, yet light and premium, material. It is used as structural reinforcement in everything from tennis rackets to airplanes, and carbon fiber frames also reduce weight and improve safety in high-end vehicles. It has been incorporated anywhere possible in some of the fastest super- and hypercars.

Yuan’s previous work identified three main roadblocks to turning lignin into carbon fiber. Neither lignin’s chemical structure nor its molecular weight is uniform, which makes it difficult to combine with other polymers. And it has a high number of hydroxide groups, a reactive pairing of oxygen and hydrogen that attracts water – not ideal for building a rigid material like carbon fiber. These discoveries inspired Yuan and Jinghao Li, a senior scientist at Washington University in St. Louis, to redesign lignin structures.

By developing a technique to chemically alter its properties, Yuan said, “We’ve really created a type of lignin that is very unique.”

When the researchers combined HiMWELL lignin with PAN, they were able to produce carbon fiber with a record tensile strength and better mechanical properties than standard carbon fiber. When it was added to recyclable polymer blends, the HiMWELL-based fiber improved both their mechanical properties and UV protection.

“Finally, we have a technological path for lignin to be used for carbon fibers,” Yuan said. And perhaps one day, “You’ll turn this waste into the shell of a car.”

This story is adapted from material from Washington University in St. Louis, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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