Capillary Flow Properties of Lyotropic Liquid Crystalline Solution of Hydroxypropyl Cellulose in Acetic Acid

Abstract

Viscoelastic properties of a lyotropic liquid crystal were determined with a capillary rheometer. So-called Bagley end correction was taken into consideration by using three dies which have the same diameter but different lengths. Measurements included the shear rate (γ) and concentration (c) dependences of shear viscosity (η) and three elastic parameters: Bagley end correction (ν), entrance pressure loss (ΔP_ent), and die swell (B). Shear viscosity behavior typical of lyotropic liquid crystal was observed. The shear rate dependence of ν varied greatly with the change of concentration: ν increased with γ at some concentrations, but decreased at other concentrations. η and ν showed the maximum and minimum with respect to concentration. However, the concentration at the minimum was not identical with that for viscosity. ΔP_ent increased with shear rate at all concentrations. The concentration dependence of ΔP_ent was the same as that of viscosity. B increased with shear stress only for isotropic solutions and decreased for anisotropic ones. The following relations have been found:
ν∝Bⁿ
ΔP_ent∝Bⁿ′
where n and n′ are constants which depend on concentration.