Rheological study of new dispersions of carbon nanotubes in the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide

Abstract Dispersions of three different types of carbon nanotubes in a 1 wt% proportion in the low viscosity 1-ethyl-3-methylimidazolium ([EMIM][DCA]) ionic liquid have been obtained. The neat ionic liquid presents Newtonian behavior, but the addition of carbon nanotubes increases the viscosity with respect to [EMIM][DCA] in the following order: Single-Walled Carbon Nanotubes (SWCNTs) > aligned Multi-Walled Carbon Nanotubes (aligned-MWCNTs) > Multi-Walled Carbon Nanotubes (MWCNTs), and the resulting fluids show non-Newtonian behavior. SWCNTs and MWCNTs dispersions present shear thinning with increasing shear rate, but a shear thickening effect for aligned-MWCNTs at intermediate shear rate values at room temperature has been observed. This effect disappears at 100 °C. The thermal response of the viscosity of [EMIM][DCA] and the CNTs-IL dispersions can be fitted to the Arrhenius model. For [EMIM][DCA] and the dispersion with MWCNTs the viscous behavior prevails at low frequencies, with a cross point at a critical frequency value which decreases with increasing temperature. However, the dispersions of SWCNTs and aligned-MWCNTs present storage modulus values higher than loss modulus in the whole range of frequency.