Researchers at Rice University have published a study in the journal Carbon that demonstrates how carbon nanotube (CNT) fibers can be fully recycled without any loss in their structure or properties.

The discovery shows that CNT fibers could be used as a sustainable alternative to traditional materials like metals, polymers and the larger, harder-to-recycle carbon fibers, which the team hopes can pave the way for more sustainable and efficient recycling efforts.

“Recycling has long been a challenge in the materials industry — metals recycling is often inefficient and energy intensive, polymers tend to lose their properties after reprocessing and carbon fibers cannot be recycled at all, only downcycled by chopping them up into short pieces,” corresponding author Matteo Pasquali, director of Rice’s Carbon Hub and the A.J. Hartsook Professor of Chemical and Biomolecular Engineering, Materials Science and NanoEngineering and Chemistry, explained in a news release. “As CNT fibers are being scaled up, we asked whether and how these new materials could be recycled in the future .... We expected that recycling would be difficult and would lead to significant loss of properties. Surprisingly, we found that carbon nanotube fibers far exceed the recyclability potential of existing engineered materials, offering a solution to a major environmental issue.”

Rice researchers used a solution-spun CNT fiber that was created by dissolving fiber-grade commercial CNTs in chlorosulfonic acid, according to Rice. Mixing the two fibers led to complete redissolution and no sign of separation of the two source materials into different liquid phases. This redissolved material was spun into a mixed-source recycled fiber that retained the same structure and alignment, which was unprecedented.

Pasquali explained in a video release that the new material has properties that overlap with and could be a replacement for carbon fibers, kevlar, steel, copper and aluminum.

“This preservation of quality means CNT fibers can be used and reused in demanding applications without compromising performance, thus extending their lifecycle and reducing the need for new raw materials,” co-first author Ivan R. Siqueira, a recent doctoral graduate in Rice’s Department of Chemical and Biomolecular Engineering, said in a news release.

Other co-authors of the paper are Rice graduate alumni Oliver Dewey, now of DexMat; Steven Williams; Cedric Ginestra, now of LyondellBasell; Yingru Song, now a postdoctoral fellow at Purdue University; Rice undergraduate alumnus Juan De La Garza, now of Axiom Space; and Geoff Wehmeyer, assistant professor of mechanical engineering.

The research is part of the broader program of the Rice-led Carbon Hub, an initiative to develop a zero-emissions future. The work was also supported by the Department of Energy’s Advanced Research Project Agency, the Air Force Office of Scientific Research and a number of other organizations.

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