A team of researchers from Washington State University (WSU) has developed a method to recycle carbon fiber reinforced polymer (CFRP) composites that strays from traditional approaches. The researchers’ method does what only a handful have been able to accomplish: recycling epoxy-based thermoset composites. As the researchers explain, thermoplastics are easily recycled, but thermosets are not due to their cured resin.

For the research, Jinwen Zhang, a professor in the WSU School of Mechanical and Materials Engineering, and his team studied a chemical recycling method that used mild acids as catalysts in liquid ethanol at a relatively low temperature to break down the thermosets.  To break down cured materials effectively, the researchers raised the temperature of the material so that the catalyst-containing liquid could penetrate into the composite and break down the complex structure. The approach is similar to Hayward, Calif.-based company Connora Technologies’ approach, which also breaks down thermoset CFRP composites at the chemistry level.

Zhang says the combination of chemicals is what makes the approach effective. The team used ethanol to make the resins expand and zinc chloride to break down critical carbon-nitrogen bonds.

“It is critical to develop efficient catalytic systems that are capable of permeating into the cured resins and breaking down the chemical bonds of cured resins,” Zhang said.

The work was funded by the Joint Center for Aerospace Technology Innovation (JCATI) in collaboration with Global Fiberglass Solutions. The state-funded JCATI works to support Washington’s aerospace industry by pursuing research that is relevant to aerospace companies and by providing industry-focused research opportunities.

The ability to recycle carbon fiber is imperative to the growth of the state’s economy. According to a study by honor society Phi Kappa Phi, Boeing and Airbus each generate as much as a 1 million pounds of cured and uncured carbon fiber prepreg waste each year from Boeing 787 and Airbus A350 XWB production. In the state of Washington alone, 96 composites companies produce 2 million pounds of production waste carbon fiber each year that is sent to a landfill.