Experimental investigation of rheological properties of liquid crystal modified with carbon nanotubes

Abstract

The results of an experimental study of the rheological properties of a nematic liquid crystal MBBA modified with carbon nanotubes depending on the mass concentration of the filler are presented. The measurements were performed on the Physica MCR 501 rheometer (Anton Paar, Austria) by the method of oscillations in the controlled deformation mode. It is shown that the introduction of a modifier into a liquid crystal changes the temperature of the phase transition to the isotropic phase of Ti. The dependence of Ti on the concentration of the filler is constructed. The flow curves and the curves of the complex viscosity of the samples were measured in the concentration range from 0.015 to 0.085 wt.%. It is shown that all flow curves can be approximated by one functional dependence: the rheological Tscheuschner equation. The parameters of the approximating curves are calculated. It is shown that the doped samples, in contrast to the dispersion medium, exhibit viscoelastic properties, the greater the greater the concentration of the filler. The dependences of the phase shift angle between tangential stresses and the strain value δ on the concentration of the modifier are investigated. It is shown that as the shear flow velocity increases, the values of δ →π/2, which corresponds to a purely viscous flow. The values of tangential stresses at which the transition to a viscous flow occurs, depending on the concentration of the modifier, are calculated.