Electric Field Effect on the Rheology of MWCNT Dispersions in Liquid Crystalline Polymers
A.R. Cameron-Soto, A. Acevedo-Rullán
University Of Puerto Rico Mayaguez, PR
Keywords: LCP, electrorheology, nanocomposite
Abstract:Carbon nanotubes (CNT) are ideal candidates for the development of nanocomposites. Nevertheless, to achieve their potential they should be dispersed and aligned with a specific orientation. Many techniques have been proposed to achieve these requirements based on self-assembly of surfactants or electric and magnetic field assisted alignment of the anisotropic nanotubes. In this research, we combine the self-organizing properties of liquid crystal polymers (LCP) and the fact that the CNT are electronically polarizable to develop novel oriented LCP nanocomposites and study the effect of electric and flow fields. The electrorheological (ER) effect of multiwalled carbon nanotubes (MWCNT) dispersion on LCP matrices was observed and quantified experimentally for the first time. A non electric field responsive, hydroxypropyl cellulose (HPC), was used as the polymeric matrix. The steady-state viscosity was obtained from transient experiments as a function of DC electric fields at constant ambient temperature and shear rate. The effect of particle concentration and shear rate was elucidated. A negative ER effect was observed. Simple mechanisms for homogeneous or heterogeneous electrorheological fluids do not capture the observed behavior. Nevertheless, results are explained in terms of particle aggregation and displacement of the liquid crystalline phase diagram.