The effect of van der Waals force interactions between multi-walled carbon nanotubes and the polymer matrix was examined using three different types of polyamides: polyamide 6, polyamide 11 and polyamide 12. A comparison of the degree of dispersion of multi-walled carbon nanotubes in the polymer and the measured physical properties showed that the hydrophobicity of the polymer matrix is an important factor for determining the properties of the polyamide nanocomposite material. Polyamides with longer hydrophobic methylene groups in the repeating unit had a better dispersion of multi-walled carbon nanotubes and correspondingly lower surface resistivity.