Prediction of shear and elongational properties of polymeric fluids using
reversible network
with non-interacting dumbbell model
Department of Mechanical Engineering
Graduate School of Engineering , Osaka University
2-1,
Yamadaoka,
Recently, reversible
network with non-interacting dumbbell model has been proposed by Cifre et al. (J. Non-Newtonian Fluid Mech. 113 (2003)
73-96) to model the shear viscosity of associative polymer. It has been shown
that this model is capable to predict the main features of associative polymer,
such as the presence of Newtonian plateau at low shear rates followed by shear
thickening at moderate shear rates and shear thinning at high shear rates.
Although this model was initially derived for associative polymer, the basic
concept of association and disassociation of network junctions can also be
applied to model non-associative polymers such polymer solutions and melts in
general. To use the model in the simulation of flow of polymeric fluids in
complex channel, the prediction capability of the model should be further
investigated. In the present work, we perform a Brownian dynamics simulation
based on the work of Cifre et al. to investigate the
capability of the reversible network with non-interacting dumbbell model in
predicting the shear and elogation properties of
polymer solutions and melts. In order to obtain more realistic prediction of elongational properties, we use a FENE connector force
instead of a Hookean connector force. By adjusting
the parameters controlling the association process of the dumbbells to the
networks, we obtain the correct trend in prediction of rheological properties.
If the association rate is proportional to the dumbbell length, the model
predicts the presence of shear thickening which is typical for associative
polymer, otherwise, with a constant association rate, the model predicts only
shear thinning behavior (without shear thickening),
which is typical for polymer solutions and melts. In the elongational
flow, the increasing association rate results in elongational
viscosity which is characterized by strain thickening at moderate strain rates
followed strain thinning and the second strain thickening at high strain rates.
For the constant association rate, there is no second strain thickening region,
and the maximum extension parameter governs whether the strain thinning region
at high strain rates exists or not exist. The trend in elongational
viscosity in the case of constant shear rate is in agreement with the available
experimental data of elongation viscosity of polymer solutions and melts.