Effect of pamlitic acid on carbon nanotubes - epoxy resin composites

Sophie Barrau 1Philippe Demont 1Emile Perez 2Alain Peigney 1Christophe Laurent 1Colette Lacabanne 1

1. CIRIMAT, UMR CNRS 5085 (L2P-LCMIE), Toulouse, France
2. IMRCP, UMR CNRS 5623, Toulouse, France

Abstract

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 σdc 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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Presentation: poster at E-MRS Fall Meeting 2004, Symposium G, by Sophie Barrau
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 09:39
Revised:   2009-06-08 12:55