Concentration Dependence of Rheology for Poly(vinyl Acetate) Solutions
作者:
S. H. Agarwal,
Roger S. Porter,
期刊:
Journal of Rheology
(AIP Available online 1981)
卷期:
Volume 25,
issue 2
页码: 171-191
ISSN:0148-6055
年代: 1981
DOI:10.1122/1.549643
出版商: The Society of Rheology
数据来源: AIP
摘要:
The rheology of a poly(vinyl acetate) (PVAc) ofM̄w=1.75×106,M̄w/M̄n=6.0,andB̄n(long branches/molecule)=3.2in diethyl phthalate and benzyl alcohol solutions has been investigated at concentration of 0.01–0.20 g/ml. The low shear‐rate viscosities, first normal stress differences, dynamic viscosities and moduli were measured by a mechanical spectrometer and the high shear values were obtained by a concentric‐cylinder viscometer. Consistent with the stress trend, it was observed that at lower concentration and higher temperature, non‐Newtonian effects occurred at higher shear rate and that the variation in viscosity with shear rate was greater at higher concentration. Solvent effects were found important even in concentrated solutions with the increase in viscosity with concentration more in diethyl phthalate than in a better solvent, benzyl alcohol. The critical concentration at which “entanglement” occurs was estimated to be ∼0.05 g/ml in both solvents. The viscosity data superimposed on a Graeasley viscosity‐shear‐rate master curve forM̄w/M̄n=1.65at lower shear rates for all concentrations, but not at higher shear rates. At low shear rates and frequencies, steady shear viscosity and dynamic viscosity coincided giving the so‐called zero‐shear viscosity. The applicability of several relationships which correlate steady‐flow and dynamic oscillatory behavior was examined. It was found that they are intercorrelated by a constant shift factor.
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