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Sedimentation in bidisperse and polydisperse colloids.
Andrew D Watson1, Gary C Barker, Margaret M Robins
1Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK. andrew.watson@bbsrc.ac.uk
Journal of Colloid and Interface Science
|April 26, 2005
Summary
A new model explains particle sedimentation and creaming in concentrated, polydisperse colloidal suspensions. It links particle pressure gradients to sedimentation profile broadening and emulsion interface changes, particularly at short times.
Area of Science:
- Colloidal Science
- Fluid Dynamics
- Materials Science
Background:
- Understanding particle behavior in concentrated suspensions is crucial for various industrial applications.
- Existing models often struggle to accurately predict sedimentation and creaming in polydisperse systems.
Purpose of the Study:
- To develop a simple force and flux balance model for sedimentation and creaming.
- To analyze the behavior of high volume fraction, polydisperse colloidal suspensions.
Main Methods:
- A novel force and flux balance model was introduced.
- The model was validated against experimental data for monodisperse and bidisperse latex spheres.
- Qualitative comparison with real emulsion creaming data was performed.
Main Results:
- The model successfully described sedimentation profiles, linking larger species profile broadening to particle pressure gradients from smaller species.
- It provided a satisfactory qualitative description of emulsion creaming.
- Model discrepancies suggest either an increased effective droplet radius or reduced background viscosity.
Conclusions:
- The proposed model offers a simplified yet effective approach to understanding complex colloidal suspension dynamics.
- Particle pressure gradients significantly influence sedimentation and interface dynamics in polydisperse systems.
- Smallest emulsion droplets appear to play a key role in interface broadening over short timescales.