Rheological transition of concentrated emulsions during successive shearing cycles.

Rheological investigations have identified a shear viscosity transition from shear thinning to Newtonian at low to moderate shear rates for concentrated polydimethylsiloxane emulsions during successive shearing cycles. The viscosity "flattening" behavior is dependent on the maximum shear rate applied and on droplet deformation. Atomic force microscopy measurements indicate attraction between the "repulsive" emulsion droplets under deformation. The results suggest formation of stable droplet layers due to deformation under high shear hydrodynamic compression. Based on these findings, unique methods to control the post-shear rheology of concentrated emulsions can be envisaged.