A Washington State University research team for the first time has developed a promising way to recycle the popular carbon fiber plastics that are used in everything from modern airplanes and sporting goods to the wind energy industry. The work, reported in "Polymer Degradation and Stability", provides an efficient way to re-use the expensive carbon fiber and other materials that make up the composites.
Carbon fiber reinforced plastics are popular in many industries, particularly aviation, because they are light and strong. They are, however, very difficult to break down or recycle, and disposing of them has become of increasing concern. While thermoplastics, the type of plastic used in milk bottles, can be melted and easily re-used, most composites used in planes are thermosets. These types of plastics are cured and can't easily be undone and returned to their original materials.
To recycle them, researchers mostly have tried grinding them down mechanically or breaking them down with very high temperatures or harsh chemicals to recover the expensive carbon fiber. Oftentimes, however, the carbon fiber is damaged in the process. The caustic chemicals used are hazardous and difficult to dispose of. They also destroy the matrix resin materials in the composites, creating a messy mixture of chemicals and an additional waste problem.
In their project, Jinwen Zhang, a professor in the School of Mechanical and Materials Engineering, and his team developed a new 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 can penetrate into the composite and break down the complex structure.
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03 May 2017
