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Advisor(s)
Abstract(s)
We apply the recently developed continuum theory of liquid crystalline polymers1 to interpret the behavior of the shear viscosity η(γ.) and the first normal-stress difference N1(γ.) measured for liquid crystalline solutions (c = 37%, c > c*) of HPC (Aldrich, Mw = 100,000) in acetic acid (AA) with different ages: 1 day, 1 month and 2 years. η(γ.) and N1(γ.) were measured over four decades in γ. N1(γ.) is observed to change from positive to negative and again to positive, as the shear rate γ. increases. η(γ.) shows a small newtonian plateau at low shear rates and a strong shear-thinning at higher values of γ. The rate of decrease of η(γ.) in this region is not monotonous, as usual, but shows an “hesitation” similar to one previously observed in a different system2. The aging effect promotes a “depolymerization”3 of HPC. This, in turn, should have a strong influence on the behavior of Nl(γ.) and η(γ.) which is indeed observed4. All these observations can be rationalized within the framework of the theory1.
Description
Keywords
liquid crystalline polymers shear viscosity normal-stress difference acetic acid
Citation
Leal CR, Godinho MH, Martins AF, Fried F – Aging effects on the rheology of LC solutions of hydroxypropylcellulose. Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, 261(1), 87-93. https://doi.org/10.1080/10587259508033455
Publisher
Taylor & Francis