Researchers find efficient way to fully recycle carbon-fiber composites into new, equally strong material

Strong and light carbon-fiber composites can be easily and cost-effectively recycled into new material just as strong as the originals, a team of researchers led by the University of Colorado Boulder has found.

Additionally, both the fabrication and the recycling are energy-efficient and comparatively fast, potentially addressing barriers to wider use in manufacturing. For these reasons, the team’s carbon-fiber composites are “unprecedented,” said Wei Zhang, CU-Boulder associate professor of chemistry and biochemistry.

The findings, published in the journal Advanced Materials, address a growing issue with carbon-fiber composites, used in components ranging from jetliners to fishing poles. The composites are popular because they are lighter than aluminum and stronger than steel.

Unlike metal, however, carbon-fiber composite is generally not recyclable.

The glue that binds the fiber in most carbon-fiber composites can be broken down with expensive, energy-intensive processes that may yield toxic waste. Carbon-fiber composites can also be crushed into a fine powder, but composites made with short fibers are weak.

Millions of pounds of carbon-fiber composites are therefore destined for landfills.

However, “we can achieve complete recyclability” of both the glue and the carbon fiber, Zhang said.

Philip Taynton, who earned his PhD in Zhang’s laboratory last year, is lead author on the paper in Advanced Materials and co-founder of a start-up company working to bring the novel carbon-fiber composites to market.

The company’s name — Mallinda — is itself a composite of the words “malleable” and “industries.” Taynton and Zhang have also discovered a way to make hard but malleable plastics that can be refashioned into new, equally strong plastic using just heat or water.

Recycling the team’s carbon-fiber composites is also simple, Zhang said: “at room temperature, soaking in an organic solution for some time, that’s it. It’s really energy-efficient and eco-friendly.”

Taynton added, “We reuse all of the stuff that we recycle, that we reclaim. … There’s nothing we have to throw away.”

In its recycled incarnation, the new carbon-fiber composite contains 25 percent to 30 percent of original material. The recycled carbon-fiber composite is just as strong as the original.

Carbon fibers have high tensile strength but are brittle. Adding a strong glue to the carbon filaments holds the fibers in place, yielding a composite that’s stronger than either of its components. “It’s like soaking your T-shirt in glue and letting it dry,” Taynton said.

Zhang and Taynton noted that the team’s carbon-fiber composite, for which the university’s Technology Transfer Office has filed a U.S. patent application, is more quickly fabricated than most carbon-fiber composites, which can take an hour to cure. CU’s tech-transfer office has licensed the technology to Mallinda.

The CU-Boulder team’s composites can be formed in 60 seconds.

Increasingly, automakers are using carbon-fiber composites, which help save fuel because they are light. Without a means of recycling carbon-fiber composites, “we’re going to solve the short-term fuel-efficiency problem, but we’re going to create a long-term landfill problem,” Taynton said.

Mallinda LLC, which Zhang and Taynton co-founded with CU-Boulder alumnus Chris Kaffer, has gotten $150,000 in support from an NSF Small Business Innovative Research Grant. Kaffer holds an MBA from CU-Boulder and a PhD in immunology from the University of California, Berkeley.

The company’s first marketing target will be sporting gear such as shin guards. “You can mold it directly to your body, but it will take whatever impact you can throw at it,” Taynton said.

Customized sporting goods are popular with the “YouTube generation,” Taynton said. “Nobody wants a size ‘small’; everybody wants a size ‘Philip.’”

Co-authors on the Advanced Materials paper are Chengpu Zhu, Samuel Loob and Yinghua Jin at CU-Boulder; Huagang Ni at Zhejiang Sci-Tech University in Hangzhou, China; and Kai Yu and H. Jerry Qi at the Georgia Institute of Technology.

The research was funded by the National Science Foundation and the Colorado Advanced Industries Accelerator Grant program.

Clint Talbott is director of communications and external relations for the College of Arts and Sciences and editor of the College of Arts and Sciences Magazine.