Mechanism and Catalysis of Oxidative Degradation of Fiber-Reinforced Epoxy Composites

  • Carlos A. Navarro
  • Elyse A. Kedzie
  • Yijia Ma
  • Katelyn H. Michael
  • Steven R. Nutt
  • Travis J. Williams
Original Paper
  • 62 Downloads

Abstract

Carbon fiber-reinforced polymer (CFRP) materials are widely used in aerospace and recreational equipment, but there is no efficient procedure for their end-of-life recycling. Ongoing work in the chemistry and engineering communities emphasizes recovering carbon fibers from such waste streams by dissolving or destroying the polymer binding. By contrast, our goal is to depolymerize amine-cured epoxy CFRP composites catalytically, thus enabling not only isolation of high-value carbon fibers, but simultaneously opening an approach to recovery of small molecule monomers that can be used to regenerate precursors to new composite resin. To do so will require understanding of the molecular mechanism(s) of such degradation sequences. Prior work has shown the utility of hydrogen peroxide as a reagent to affect epoxy matrix decomposition. Herein we describe the chemical transformations involved in that sequence: the reaction proceeds by oxygen atom transfer to the polymer’s linking aniline group, forming an N-oxide intermediate. The polymer is then cleaved by an elimination and hydrolysis sequence. We find that elimination is the slower step. Scandium trichloride is an efficient catalyst for this step, reducing reaction time in homogeneous model systems and neat cured matrix blocks. The conditions can be applied to composed composite materials, from which pristine carbon fibers can be recovered.

Keywords

Recycling Epoxy Composites Carbon fiber Depolymerize Catalysis 

Notes

Acknowledgements

Financial support from the USC Zumberge fund, the M.C. Gill Composites Center at USC, the National Science Foundation (CHE-1566167), and George Olah’s Hydrocarbon Research Foundation are gratefully acknowledged. We thank the NSF (DBI-0821671, CHE-0840366) and the NIH (S10 RR25432) for NMR spectrometers.

Supplementary material

11244_2018_917_MOESM1_ESM.docx (6.1 mb)
Supplementary material 1 (DOCX 6227 KB)

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Loker Hydrocarbon Research Institute and Department of ChemistryUniversity of Southern CaliforniaLos AngelesUSA
  2. 2.M.C. Gill Composites Center and Mork Family Department of Chemical Engineering and Materials ScienceUniversity of Southern CaliforniaLos AngelesUSA

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