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Advisor(s)
Abstract(s)
first normal-stress difference Ni(+) and the shear viscosity V(?) have been measured for liquid crystalline solutions of HFC in acetic acid (AA) as functions of the shear rate i. and the molecu lar mass of HPC. The measurements were done over four decades in +, for two samples of HPC with M, =6O,OOO and 100,OOO (Klucel E and L, respectively) and solution concentration c = 37% (c > c*). N1(+) is observed to change from positive to negative and again to positive, as the shear rate + increases. The 7 values at which N, changes sign depend on M,. The viscosity q(+) shows a small Newtonian plateau at low shear rates and a strong shear-thinning at higher values of +, includ ing an “hesitation” similar to one previously observed in LC solutions of PBUj [2]. All these obser vations are rationalized within the framework of the constitutive equations for liquid crystalline polymers recently proposed by one of us [l]. Expressions for q(+) and Nl(+) derived from this
theory fit very well (quantitatively) to the experimental data and some fundamental viscoelastic parameters of the system are thereby obtained for the first time.
Description
Keywords
normal-stress difference shear viscosity liquid crystalline solutions of HFC acetic acid (AA)
Citation
Martins AF, Leal CR, Godinho MH, Fried F – The influence of polymer molecular weight on the first normal-stress difference and shear-viscosity of LC solutions of hydroxypropylcellulose. Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals. ISSN 1058-725X. 2001, 362(1): 305-312. https://doi.org/10.1080/10587250108025777
Publisher
Taylor & Francis