Acetic acid breaks down carbon fiber–reinforced polymers

Lightweight yet strong and resistant to corrosion and weathering, carbon fiber–reinforced polymers (CFRPs) are used in aircraft, shipping containers, natural gas storage tanks, wind turbine blades, high-end sporting goods, and other applications. Their manufacture, though, is expensive and emission heavy, which means that efficient recycling strategies are important.

While the carbon fiber is relatively easy to recycle, the epoxy-amine resins—such as bisphenol A polymers cross-linked with amines—used to give these materials durability are trickier. A new study reports that immersing the material in acetic acid, a biologically derivable compound, and heating it can break down the resins into monomers and keep the carbon fibers intact. The reaction takes just a couple of hours (Nature 2025, DOI: 10.1038/s41586-025-09067-y).

Study coauthor Stephen Dempsey, a chemical engineer at the National Renewable Energy Laboratory (NREL), says, “Much of the trouble comes from just how complex the material you put in your reactor is.” Aerospace materials, for instance, use thermoplastic tougheners that require clever engineering to remove. “We want to get the fibers as clean as possible because that makes them more useful, gives a broader application pool.”

He describes their technique as “pretty straightforward.” Once the acid-material mixture reaches about 220 °C, the reaction starts. But it goes much faster at 280 °C.

The researchers demonstrated the method on model epoxy-amine cubes, carbon fiber composites with epoxy amines they made themselves, and multiple postindustrial, postconsumer materials for different carbon fiber composites. “We [also] modeled what a process would look like at scale, that it could be both economically viable and extremely energy efficient relative to primary production of virgin carbon fiber–based composites,” says coauthor Gregg Beckham, also a chemical engineer at NREL. Their techno-economic analysis indicated that the price of recycled carbon was much lower than that of virgin carbon fiber, and greenhouse gas emissions were around 99% less.

The researchers’ process recovered almost all the carbon fiber from a sample. The recycled fibers were about 1 to 3 cm long. While this size is not suitable for high-end applications, the recycled fibers could be used to replace structural parts of automobiles with lightweight composite alternatives, although the researchers are looking at other possible applications.

The amine and epoxy monomers can be converted back to the starting materials through chemical transformations, and then new epoxy resins created with the same formulation as the original. The researchers are still working on the separations with the goal of getting acetic acid off the amines and the epoxy units recovered in an optimal yield.

Dempsey, Beckham, and colleagues are also attempting to work out the mechanisms of the solvolytic process that breaks down the CFRPs in acetic acid. “From that we hope to be able to design catalytic strategies that let us run the reaction at lower temperatures,” Beckham says.

Bhavik Bakshi, a chemical and biomolecular engineer at Arizona State University, writes in an email that this solvent-based method is likely to make recycling CFRPs easier.

But, he adds, it would have been nice to test the method on more types of fibers and that “there are many other recycling methods out there under development, and the study would be stronger if the comparison had been done against them.”