An experimental study on the shear viscosity of the polymer liquid crystal and the wall effect of a capillary on the viscosity was carried out to examine the flow behavior of poly-p-phenyleneterephthalamide(PPTA) in 100% sulfuric acid at 25 and 50℃. Viscosity was measured by use of five glass capillaries with diameters ranging from 252.6 to 1238.3㎛.
The visible homeotropic orientation of the polymer liquid crystal (PPTA) at the wall surface of the capillary was observed.
This homeotropic orientation resulted in different viscosities measured with different diameter capillaries at the low shear rates. The shear viscosity increased at the same shear rate as the capillary diameter was decreased. This indicates that the fluid near the wall surface behaves like a fluid with a higher viscosity than the fluid near the center of the capillary.
At the low shear rates, the viscosity of PPTA liquid crystal was found to be a unique function of Q/R predicted by Leslie-Ericksen theory.
