Predictions of the behavior of a single droplet and blends composed of Newtonian/viscoelastic minor phase and viscous major phase subjected to oscillatory shear flow

Abstract

The oscillatory behavior of Newtonian and viscoelastic droplets in a Newtonian phase and blends composed of viscoelastic minor phase in a Newtonian major phase are theoretically investigated in this work. The non-Newtonian constrained volume model predictions are compared to experimental oscillatory shearing flow data of droplet and blends that are available in the literature. For a Newtonian droplet in a Newtonian phase, the model describes experimental droplet behavior well at high viscosity ratio and high strain amplitude. For viscoelastic droplet in a Newtonian phase, the model predicts less deformation for viscoelastic droplet than a comparable Newtonian droplet. For large amplitude oscillatory shear rheological data of blends composed of Boger fluid minor phase in a Newtonian major phase, the model shows improvement in prediction of the elastic modulus at high viscosity ratio, compared to the Newtonian model. The model also shows good agreement with large and minimum strain elastic moduli and large and minimum rate dynamic viscosities for small and large viscosity ratio viscoelastic polymer blends. For the blend of Boger fluid minor phase in a Newtonian major phase at viscosity ratio larger than one, we find that elasticity contributes to total stress from small to large strain amplitude values. For the blend of Boger fluid minor phase in a Newtonian major phase at viscosity ratio smaller than one, we find that elasticity is important only at large values of strain amplitude. Moreover, for the aforementioned blend at viscosity ratio larger than one, the predicted Lissajous Bowditch plots of excess stress do not reflect droplet shape/droplet orientation, and the opposite is true for the small viscosity ratio blend. Investigation of droplet long semi axis for the large viscosity ratio blend at LAOS conditions reveals oscillations at two to three times the imposed frequency.