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  • End effect  (1)
  • polyelectrolyte  (1)
  • simple shear flow  (1)
  • 1985-1989  (3)
  • 1
    Electronic Resource
    Electronic Resource
    A rheological equation of state for dilute polymer solutions with applications to polyelectrolytes (1988)
    Springer
    Rheologica acta 27 (1988), S. 241-254 
    Details
    ISSN: 1435-1528
    Keywords: Rheological equation ; dilute polymersolution ; polyelectrolyte ; shear thickening ; polyacrylamide solution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A mathematical model based on the diffusion-convection equations is used to describe the rheological properties of dilute polymer solutions. The model uses a second-order conformation tensor as a measure of the internal strain; this avoids the mathematical complexity resulting from the use of a more detailed description of the macromolecules and also avoids the necessity of introducing additional ad-hoc assumptions (closure approximations) commonly used in other molecular theories. The rheological equation is obtained in terms of the rate-of-deformation tensor $$\dot \gamma $$ and a scalar functionf(σ) relating the extra stress tensorσ to the internal strain tensorc. The functionf(σ) depends on the physical insight introduced in the Helmholtz free energyA(c) of the solvent-polymer system. This approach is illustrated for an intra-molecular potential of a “FENE-charged” type. The concept of an isotropic, but conformation-dependent, friction coefficient, is also introduced to account for the “coil-stretch” transformation of macromolecules in solution. Viscosity and first normal-stress data, of partially hydrolyzed polyacrylamide solutions, (polyelectrolytes) are analyzed and compared to the model predictions in steady shear and elongational flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01329740
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  • 2
    Electronic Resource
    Electronic Resource
    End effects for highly elastic-constant viscosity fluids (1986)
    Springer
    Rheologica acta 25 (1986), S. 95-101 
    Details
    ISSN: 1435-1528
    Keywords: End effect ; elastic-constant viscosity fluid ; Boger fluid ; primary normalstress difference ; shear-thinning properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract In the light of a new interpretation, we have studied the end effects for highly elastic-constant viscosity fluids commonly called Boger fluids. In terms of entrance effect only, the presence of primary normal-stress differences in absence of shear-thinning properties results in a decrease of the entrance correction below the Couette (Newtonian) value, whereas the total end correction can be substantially increased by an amount which is strongly dependent on the Weissenberg number or recoverable shear.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332128
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  • 3
    Electronic Resource
    Electronic Resource
    Selection of kernel functions used in a new constitutive equation for viscoelastic fluids (1986)
    Springer
    Rheologica acta 25 (1986), S. 214-224 
    Details
    ISSN: 1435-1528
    Keywords: Constitutive equation ; viscoelastic fluid ; kernel function ; simple shear flow ; uniaxial extension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A selection of kernel functions is given to be used in a new integral constitutive equation proposed by Piau whereby the deviatoric stress is calculated from the integral of the history of the past intrinsic rate of rotation and rate of deformation tensors through a representation theorem. Piau has demonstrated the objectivity of a frame moving with a given particle whose axis are directed along the eigenvectors of the rate of deformation tensor. The use of such a framework provides a new approach in the attempt to reduce the computational difficulties associated with conventional constitutive equations written in co-deformational or co-rotational reference frames. The shear and primary normal-stress material functions and the extensional (elongational) stress growth function are defined for the proposed integral constitutive equation. These material functions are used to calculate the kernel functions using steady state, stress relaxation and stress growth data of Attané in simple shear flow for monodisperse polystyrene solutions. The shear and extensional stress growth data of Meissner for a polyethylene melt are also used to show the flexibility of the rheological model. The material functions are first written in terms of five monotonically decreasing functions of the time lag between the past and the present time. Then kernel functions are chosen such that when substituted in the new integral constitutive equation they yield the functions used to describe the data. A further condition imposed on the normalized kernel functions is that they be decreasing functions of time lag.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357949
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