Oscillatory shear induced droplet deformation and breakup in immiscible polymer blends

Abstract

Droplets in polybutadiene/polydimethylsiloxane blends under oscillatory shear flow were observed using an optical flow cell. The apparent major axes, the minor axes, and the deformation of the droplets were measured from the time series of images. These deformation parameters were measured as functions of time, strain, frequency, G' ratio, and G" ratio. From the time series of the deformation parameters, it was possible to define deformation amplitudes, as the difference between the maximum and minimum values divided by two. The amplitudes of the deformation parameters increase linearly with capillary number, the ratio between the viscous force and the interfacial tension force. The amplitudes also increase with decreasing time scale ratio, i.e. within the droplet relaxation time scale and the oscillatory time scale. The effects of viscosity and elasticity are also reported.