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Recycling a carbon fibre reinforced polymer with a supercritical acetone/water solvent mixture: Comprehensive analysis of reaction kinetics
- Keith, Matthew J., Román-Ramírez, Luis A., Leeke, Gary, Ingram, Andrew
- Polymer degradation and stability 2019 v.161 pp. 225-234
- acetone, activation energy, carbon fibers, computed tomography, epoxides, equations, image analysis, mass transfer, models, polymers, reaction kinetics, recycling, solvents, temperature
- The decomposition of a carbon fibre reinforced epoxy resin with an acetone/water solvent supplied in the ratio of 80:20 v/v has been investigated using a non-stirred batch reactor. Temperatures and pressures in the range of 300–380 °C and 16–30 MPa were studied over a reaction time of up to 150 min using an initial reactor loading of 30 gresin Lsolvent−1. The minimum conditions necessary for effective fibre recovery were identified as 320 °C and 20 MPa. After processing for 120 min at this temperature and pressure, up to 95 wt.% of the resin was stripped from the fibre surface and the original weave architecture was retained. Increasing the reactor loading to 90 gresin Lsolvent−1 demonstrates no significant effect on the extent of resin decomposition. This, combined with imaging using X-ray computer tomography, suggests that the solvent is always in excess and that the mass transfer of the solvent into the composite and degradation products away from the surface is fast. A first order reaction rate equation based on the Arrhenius expression and a reaction-rate limited shrinking core model (SCM) have both been successfully fitted to the experimental data. From this, the parameters activation energy and frequency factor have been calculated to be 222.3 kJ mol−1 and 7.64 × 1017 min−1 respectively for the Arrhenius model and 164.3 kJ mol−1 and 1.29 × 1012 min−1 for the SCM. The results presented in this work demonstrate that either approach can be used to predict the resin decomposition to within ±5% which is similar to the margin of experimental error.