The study of cellulose derivatives and magnetic field effects on their rheological properties (magnetorheological) is of evident practical importance because its ability to orient under the action of external fields. The orientation process is of great importance owing to the possibility of changes in structure and final products. The aim of this work was to study theoretically the effects of magnetic field on rheological behavior of some cellulose derivatives solutions. The studied samples are Ethyl cellulose (EC), Hydroxyethyl cellulose (HEC), Hydroxypropyl cellulose (HPC) and Carboxymethyl cel-lulose (CMC) dissolved in a suitable solvents. The influence of eight different solvents on solutions viscosity was investi-gated. Vshivkov and his group at the Department of Macromolecular Compounds at the Ural Federal University investi-gated experimentally the changes in magnetorheological properties of these solutions by using a Rheotest RN 4.1 rheome-ter. Their works covered the shear rates and concentration range from to . In this paper, we reconsider Vshivkov et al. works through collecting their experimental data and carry out its theoretical analysis based on Giesekus model for viscoelastic polymers. This model gives more accurate results and takes into account the effects of vis-coelastic shear thinning characteristics, decreasing viscosity with increasing shear rate. The regions of existence of isotropic and anisotropic phases and their concentration dependence were discussed. It is found that a magnetic field increases the viscosities of all solutions under consideration. The study was extended to report the viscosity data of dilute aqueous sus-pension of cellulose nanocrystals (CNC). It has been treated as a dilute fiber suspension whose concentrations ranging from 0.5 to 8 wt% and its rheology are analyzed using Giesekus model. The orientation of CNC nanoparticles are described in terms of the fiber's second– and fourth–order orientation tensors established by Advani and Tucker. Finally, For adequate prediction of viscoelastic shear thinning characteristics of CNC suspensions as a function of both shear rate and concentra-tion, simple correlations were proposed in terms of an exponential function. |
