TRANSIENT AND STEADY-STATE RHEOLOGY OF A LIQUID-CRYSTALLINE HYDROXYPROPYLCELLULOSE SOLUTION

Cone and plate rheological measurements have been performed on aqueous solutions of hydroxypropylcellulose in the liquid crystalline phase. The time-dependent experiments (start-up of shear and oscillatory shear flow) suggest the presence of a supramolecular structure which is modified by the flow. The characteristic time of structure evolution is estimated, and a tentative explanation of such a process is suggested in terms of polydomain rearrangement. Steady-state measurements confirm some peculiar properties of liquid crystalline polymers, such as the presence of a shear thinning regime at the lowest shear rates and the occurrence of negative values of the first normal stress difference. Finally, an anomalous, yet reproducible, behavior of the dynamical properties is reported and discussed. © 1990, The Society of Rheology. All rights reserved.