On the influence of nanotube properties, processing conditions and shear forces on the electrical conductivity of carbon nanotube epoxy composites.

We analyse statistical and kinetic percolation thresholds and maximum electrical conductivities of carbon nanotube epoxy composites as a function of shear forces, processing conditions, nanotube type and dimensions. Entangled and non-entangled nanotubes of different lengths (15-100 microm) and thicknesses (12-80 nm) have been obtained with three different synthesis methods based on catalytic or plasma enhanced chemical vapour deposition. The dispersions were processed either solely with a dissolver disk or additionally with a three roll calender. Care was taken to prevent unintentional shearing (e.g. through convection) in all samples that were not subject to deliberate shearing. It was found that shear forces have a similar influence on kinetic percolation thresholds and composite conductivities independent of nanotube types and dimensions.