Viscometric behavior of ternary concentrated solutions of hydroxypropyl cellulose and ethyl cellulose in m-cresol

The shear viscosity of blend solutions of hydroxypropyl cellulose (HPC) and ethyl cellulose (EC) in m-cresol (both HPC/m-cresol and EC/m-cresol systems form lyotropic liquid crystals) was determined by cone-plate-type and capillary-type viscometers. The textures for the same systems at rest and undergoing shear were also observed with a polarized microscope.

At shear rate of 1 s⁻¹, viscosity exhibited a maximum and a minimum with respect to temperature, and this suggested that the phase of the matrix dominated the viscometric behavior of the ternary systems; the blend composition dependence of the viscosity was not additive, and this suggested that HPC and EC were immiscible. At relatively high shear stress, the blend composition dependence of the viscosity greatly depended on the total polymer concentration of the solutions and was quite different from that at low shear rate; the texture of the anisotropic solutions was also different from that at low shear rate. Our findings suggested that the dependence of viscosity on shear and concentration for pure HPC solution was different from that for pure EC solution.