Premium
Limiting shear dependence of the intrinsic viscosity of deformable polymer molecules
Author(s) -
Van Oene H.
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.1965.070090721
Subject(s) - thermodynamics , rheology , intrinsic viscosity , polymer , viscosity , polystyrene , materials science , elasticity (physics) , chemistry , physics , composite material
Previous theories of the shear dependence of the intrinsic viscosity of deformable polymer molecules are reviewed. Most of these theories, except those of Cerf and Kuhn and Kuhn, predict that for a polymer homologous series the shear dependence [η]/[η] 0 can be expressed in terms of the reduced parameter ( M [η] 0 / RT )η s q . Such a representation is not in agreement with experimental findings. In this paper a phenomenological model is presented in terms of the Oldroyd rheological equations of state. This model allows one to take into account the finite deformation of the molecule. In terms of this model finite deformation leads to a retarded elasticity, which can be described in terms of the recoverable shear but which does not influence the shear viscosity. The retarded elasticity results, however, in a shift of the [η]/[η] 0 versus ( M ‐[η] 0 / RT )η s q . curve along the reduced stress coordinate. This shift is proportional to the molecular weight and independent of the solvent viscosity. Comparison with experiment shows the existence of the predicted shift factor for series of measurements on fractions of polystyrene in a good solvent. The one series of measurements in a theta solvent reveal that in such a solvent the shift vanishes. The implications of this finding are discussed. The shift factor is also shown to have many properties in common with the inner viscosity as defined by Cerf and experimentally evaluated by Leray from the velocity‐gradient dependence of the extinction angle.