Recycling of carbon/epoxy composites

The recycling of carbon fibers from carbon/epoxy composites was attempted with a solvent method in nitric acid solutions. Gel permeation chromatography and gas chromatography/mass spectrometry showed that the epoxy resin could entirely decompose into low-molecular-weight compounds, and the main components of the dissoluble decomposed compounds were 2,4-dinitrophenol and 2-nitro-4-carboxylphenol. Electron probe microscopy showed no damage to the recycled carbon fibers. The single-fiber tension strength loss of the recycled carbon fibers was 1.1% under the following conditions: a decomposition temperature of 90 °C, a nitric acid solution concentration of 8M, and a ratio of the sample weight to the nitric acid solution volume of 6 g:100 mL. Through orthogonal experimentation, the recycling conditions for the carbon/epoxy composites were examined. The best combination was a decomposition temperature of 90°C, a nitric acid solution concentration of 8M, and a ratio of the sample weight to the nitric acid solution volume of 4g:100 mL. This method could liquefy raw materials for rocket engine shells reinforced with carbon fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 1912–1916, 2004