Anomalous Viscous Flow at Very Low Rate of Shear and Small Shearing Stress
作者:
J. T. Bergen,
W. Patterson,
期刊:
Journal of Applied Physics
(AIP Available online 1953)
卷期:
Volume 24,
issue 6
页码: 712-719
ISSN:0021-8979
年代: 1953
DOI:10.1063/1.1721364
出版商: AIP
数据来源: AIP
摘要:
Fluid suspensions of a solid phase in a liquid, for example, paints and printing inks, have been presumed to exhibit anomaly of flow at very low rate of shear. The consistency characteristics of such materials require an experimental shear rate and shear stress much lower than has heretofore been reported.This paper describes a translated cylinder, or translational, viscometer of a modified Pochettino type, which possesses a shear stress sensitivity of 5×10−3dyne/cm2, and a shear rate sensitivity of 1×10−4sec−1. A rubber Latex of high solids content exhibited no anomaly of flow within this range of sensitivity. A rubber dissolved in organic solvent was observed to approximate a Bingham material of 0.05‐dyne/cm2yield value, while a gum tragacanth suspension in water exhibited a yield value of 0.4 dyne/cm2with marked post‐yield anomalous flow. Household paints exhibited yield value ranging from zero to 6 dyne/cm2. These yield values were related to leveling‐out of brushmarks, and to sagging or ``curtain,'' except for examples exhibiting marked thixotropic behavior. Industrial organosol coatings likewise possessed yield values ranging up to 5 dyne/cm2which were related to leveling characteristics. These yield values agree with those postulated by Waring from consideration of the forces of leveling of brushmarks. They are considerably smaller than those reported in the literature from extrapolation of flow curves from much higher rate of shear.
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