As most polymers, epoxy resins are electrical insulators. Air frictions can damage the materials because of charges accumulation. The preparation of composites with conductive fillers allows to solve this problem for a sufficient rate of charge in the matrix. Using carbon nanotubes (CNTs) as a charge offers an attractive way to improve the electrical properties of such composites.
CNTs, mostly single- and double-walled, were synthesized by CCVD [1] and obtained in suspension in HCl after catalytic particles dissolution.
In a first time, an experimental procedure was set up in order to prepare CNTs - epoxy resin composites containing few wt % of CNTs. Scanning electron microscopy pictures (SEM) show an homogeneous dispersion of CNTs bundles. A study of the nanocomposites electrical properties was performed in order to characterize an insulator/conductor transition. The measurements of the complex conductivity were carried out using a broadband dynamic dielectric spectrometer in the frequency range 10^-2 - 10⁶ Hz and above ambient temperature. The dc conductivity σ_dc exhibits a percolation threshold at 0,3 wt % at room temperature with a conductivity about 10^-4 S.cm^-1 above 2 wt % of CNTs. The percolation threshold is found to be independent of temperature.
To improve CNTs dispersion, we added, in a second time, an amphiphilic molecule : the palmitic acid. The hydrophobic part is adsorbed onto the nanotube surface. The hydrophilic head induces electrostatic repulsions between nanotubes and then preventing their aggregation [2]. Electrical measurements displays an percolation threshold decrease and SEM pictures show CNTs essentially individuals. This experimental procedure appears promising for future.

[1] E. Flahaut, A. Peigney, Ch. Laurent, A. Rousset, J. Mater. Chem. 2000, 10, 249.
[2] S. Barrau, P. Demont, E. Perez, A. Peigney, Ch. Laurent, C. Lacabanne, Macromolecules 2003, 36, 9678.

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