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Rheopexy in some polar fluids and in their concentrated solutions in slightly polar solvents
Author(s) -
Steg I.,
Katz D.
Publication year - 1965
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1965.070090922
Subject(s) - thixotropy , shearing (physics) , shear rate , rheology , shear (geology) , viscometer , materials science , polar , polyester , composite material , intermolecular force , polymer chemistry , thermodynamics , chemical physics , mechanics , chemistry , viscosity , organic chemistry , molecule , physics , astronomy
Abstract Several medium and high molecular weight polar fluids, when subjected to shearing forces above a certain rate of shear, showed a rheopectic behavior. The observation was made on some polyesters, an epoxy compound, and on concentrated solutions of these materials in nonpolar solvents. The experiments were carried out in a rotating type viscometer with cone‐and‐plate arrangements. The following explanation for the observed rheopexy is proposed: above a critical rate of shear, the polar macromolecules after alignment in the field of shear are forming quasicrystallites and a rheological network structure due to intermolecular forces. Because of the simultaneously occurring process of the breaking of structures in the field of shear, a state of pseudoequilibrium is reached. It was found that when the experiments were interrupted at the stage of such a pseudo‐equilibrium for a short time, a thixotropic strengthening of the existing structure occurred; under renewed shear the stress decreased to its value before the interruption. After interruption of shear for longer periods (hours, days), a breakdown of the rheopectic structure was observed.