Flow‐induced particle orientation and rheological properties of suspensions of organoclays in thermoplastic resins

Abstract

The influence of nano‐scale particles on the viscoelastic properties of polymer suspensions is investigated. We have developed a simulation technique for the particle orientation and polymer conformation tensors to study various features of the suspensions. The nano‐particles are modeled as thin rigid oblate spheroid particles and the polymers as FENE‐P type viscoelastic and Newtonian fluid. Both interparticle and polymer‐particle interactions have been taken into account in our numerical computations. The nonlinear viscoelastic properties of nanocomposites of layered silicate particles in non‐Newtonian fluids are examined at the start‐up of shear flow and are interpreted using the model to examine the effects of model parameters as well as flow conditions on particle orientation, viscosity, and first normal stress difference of the suspensions. We have studied the microstructure of polymer‐clay nanocomposites using X‐ray diffraction (XRD) scattering and transmission electron microscopy (TEM). The rheology of these nanocomposites in step‐shear is shown to be fairly well predicted by the model. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2003–2011, 2010

Orientation of Anisometric Layered Silicate Particles in Uncompatibilized and Compatibilized Polymer Melts Under Shear Flow: A Dissipative Particle Dynamics Study

“…However, the orientation gets more prominent with an increase in shear‐rate and the distorted orientation of the layers is suppressed to a great deal. The shear‐rate dependency of orientation is also observed experimentally for anisometric particles such as fibers, carbon nanotubes, clays, etc. It should be noted that the semiflexible nature of the simulated layered silicate is reflected in the trajectory data.…”

Dissipative Particle Dynamics Models of Orientation of Weakly‐Interacting Anisometric Silicate Particles in Polymer Melts under Shear Flow: Comparison with the Standard Orientation Models

“…In order to highlight this issue, the MM model is incorporated to evaluate accurate estimations of the evolutions of orientation parameters with time in Cloisite/polypropylene nanocomposites. Rajabian et al performed startup of simple shear flow experiments on such nanocomposites containing 3–7 vol% of nanoparticles. They proposed the following set of parameters to best fit the experimental data: , , , b = 1, , , , , and T = 473.2 K. Utilizing these values and benefiting from the proposed mixing strategy, one can compare the large cell orientation data with the MM model predictions of Cloisite/polypropylene nanocomposites (see Figure ).…”

“…On a mesoscopic level, Rajabian et al developed a rheological model for ellipsoid particles in viscoelastic polymeric fluids by adding a dissipation function to the Jeffery's model. They described such dissipations as a function of the overall free energy with respect to the conformation tensors and Φ C .…”

“…The resulting model has been utilized to predict the flow‐induced orientation of various anisometric particles including short fibers, layered silicates, and carbon nanotubes . Other authors have also investigated different approaches such as nonequilibrium thermodynamics in order to derive constitutive equations that could describe polymer nanocomposites with nanofibers and nanosheets …”

“…[ 20 ] Other authors have also investigated different approaches such as nonequilibrium thermodynamics in order to derive constitutive equations that could describe polymer nanocomposites with nanofi bers and nanosheets. [21][22][23][24] The Folgar-Tucker (FT) model has been later modifi ed by Huynh [ 25 ] to account for the reduced strain in concentrated suspensions by the introduction of a strain reduction factor (SRF). The slower orientation kinetics was also manifested by Sepehr et al [ 26 ] who introduced a slip coeffi cient to slow down the rate of particle orientation.…”