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Published on: February 7, 2017
Band formation on shearing in phase-separated polymer solutions.
R Hans Tromp1, Els H A De Hoog
1NIZO Food Research, Kernhemseweg 2, 6718 ZB Ede, The Netherlands.
Summary
Shear-induced droplet coalescence in polymer solutions leads to unique band formation. These bands, with distinct compositions and flow properties, emerge from initial wormlike structures under specific shear conditions.
Area of Science:
- Polymer Science
- Fluid Dynamics
- Rheology
Background:
- Phase-separated polymer solutions exhibit complex behavior under shear.
- Understanding droplet dynamics is crucial for predicting material properties.
Purpose of the Study:
- To investigate shear-induced droplet coalescence and band formation in a two-phase polymer solution.
- To analyze the structural evolution and properties of the resulting bands.
Main Methods:
- Microscopic observation of a sheared polymer solution in a cone-plate geometry.
- Analysis of droplet coalescence, structure evolution, and band formation at the zero-velocity plane.
Main Results:
- Observed shear-induced coalescence of droplets, leading to wormlike structures and subsequently doughnut-shaped bands.
- Identified differences in shear rate and composition within the bands compared to the surrounding solution.
- Qualitatively described the preceding shear-shear rate instability using a van der Waals-loop model for droplet deformation.
Conclusions:
- Shear forces drive significant structural changes in phase-separated polymer solutions.
- The formation of distinct bands suggests a shear-induced phase separation or organization.
- Droplet deformation dynamics are key to understanding the instability preceding band formation.
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