A process to recover carbon fibers from polymer matrix composite scrap

Argonne National Laboratory (ANL) has developed and tested a process to separate and recover carbon fibers from a mixture of carbon fiber reinforced polymer matrix composites (PMCs) made with different thermoset or thermoplastic substrates. For most mixtures of PMCs, the process is energy self-sufficient using the polymer substrate as an energy source. ANL's economic analysis of the process showed an expected payback of less than 2 years, assuming a value of only $1.50 per pound of recovered carbon fibers. IM7 12K fibers were also used in this study to make control panels for evaluation. Test results of the mechanical properties for the recovered fibers indicate that the fiber retained 95% of the original stiffness and 50% of the original strength. Recovered fiber would be suitable for short fibers applications such as SMC (sheet molding compound), batteries, and concrete reinforcement. Oak Ridge National Laboratory conducted analysis and characterization of the recovered fibers using electron microscope and X-Ray Photoelectron Spectroscopy (XPS) techniques. There was no observable physical damage to the fibers at magnifications up to 10,000X, and only a small amount of unevenly distributed, residual material was observed on the fiber. This paper describes the process and the characteristics and properties of the recovered fibers.