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On the effect of electric field application during the curing process on the electrical conductivity of single-walled carbon nanotubes–epoxy composites

Morais, M.V.C., Oliva-Avilés, A.I., Matos, M.A.S., Tagarielli, V.L., Pinho, S.T., Hübner, C., Henning, F.
Carbon 2019 v.150 pp. 153-167
carbon, carbon nanotubes, dielectrophoresis, electric field, electrical conductivity, electrical resistance, finite element analysis, liquids, mechanics, microstructure, models, nanoparticles, polymers, temperature, viscosity
Single-walled carbon nanotube (SWCNT)/epoxy composites were cured under external electric fields and the influence of the processing parameters (electric field magnitude and frequency, SWCNT concentration and curing temperature) on the electrical response of the system was evaluated. A mold for the electric field application was designed and manufactured, allowing in situ measurements of the electrical resistivity of the composite, during and after the curing process. The resulting electrical properties revealed a strong dependence on the processing parameters. By rising the curing temperature, the solid bulk resistivity was decreased by one order of magnitude. Further reduction was observed with electric fields, up to an additional order of magnitude. Such improvements can be related with the decrease in viscosity and improvement of interconnected-nanotube paths within the polymer matrix. The effect of the electric field on the rotation and interconnection of the SWCNTs was investigated using a classical mechanics model based on the dielectrophoretic theory for the liquid state. The influence of inter-nanotube distances on the bulk electrical properties was calculated at different particle concentrations, using finite element models of the microstructure. This processing technique presents promising results for enhancing the electrical conductivity of polymer composites with carbon-based nanoparticles.