Vorticity banding in biphasic polymer blends.

Area of Science:

• Rheology
• Materials Science
• Fluid Dynamics

Background:

• Pattern formation under flow is crucial in microfluidics and granular materials.
• Biphasic liquid-liquid systems exhibit complex behaviors when subjected to shear.
• Understanding shear-induced phenomena is key to controlling material properties.

Purpose of the Study:

• To systematically investigate shear-induced banding in confined biphasic liquid-liquid systems.
• To explore the relationship between band formation, system parameters, and rheological properties.
• To elucidate the underlying mechanisms of shear banding in immiscible polymer blends.

Main Methods:

• Utilizing a sliding parallel plate flow cell to shear immiscible polymer blends.
• Observing pattern formation from a spatially uniform droplet distribution.
• Conducting rheological measurements to correlate microstructure evolution with viscosity.

Main Results:

• Observed formation of shear bands aligned with the flow direction.
• Initial band size correlated with the confinement gap dimension.
• Shear banding occurred only when dispersed phase viscosity was lower than the continuous phase and within a specific shear rate range.
• Band formation led to a decrease in overall system viscosity.

Conclusions:

• Shear-induced banding in confined biphasic systems leads to microstructural evolution.
• The phenomenon is dependent on relative phase viscosity and applied shear rate.
• Observed viscosity reduction suggests a transition towards reduced viscous dissipation within the system.