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The Microstructure and Rheology ofFlowing Polymer Dispersions |
The phenomena of deformation and breakup of liquid droplets is of importance in a number of chemical processes and unit operations (Karam and Bellinger, 1968) such as the commercial mixing and dispersion of polymers (see for example Flumerfelt, 1972). Most commercial immiscible blend systems are complex and a starting point is to consider the deformation and breakup behaviour of single droplets in a well-defined flow field. Research on this subject dates back to the pioneering work of G. I. Taylor (1932, 1934) whose interest in this topic arose from the problem of emulsion mixing.
This project was concerned with the microstructure and rheology of flowing polymer dispersions. The objective was to study the way immiscible liquid droplets deformed in both a Newtonian and viscoelastic matrix where the dispersed phase was either Newtonian or viscoelastic. Key variables were the viscosity ratio between the dispersed phase and the matrix phase, the surface tension between the dispersed phase and the matrix phase, the phase volume of the dispersed phase and the flow type that induced deformation. The observation on flow-induced microstructure was performed using a micro-optic apparatus, the Cambridge Shearing System, (Fig. 1 and 2) and the rheological measurements were carried out using a Rheometrics Dynamic Spectrometer. The aim of the project was to observe optical behaviour and predict and model the correlation between microstructure and rheology.
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| Fig. 1: The Cambridge Shearing System (CSS) |
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| Fig. 2: Principle of the CSS |
References
- Mackley, M.R., Wannaborworn, S., Gao, P. and Zhao, F., The optical microscopy of sheared liquids using a newly developed optical stage. J. of Microscopy and Analysis, 69, 25-27 (1999)
- Karam, H. J. and Bellinger, J. C., Deformation and breakup of liquid droplets in a simple shear field. I&EC Fund. 7 (4), 576-581 (1968)
- Flumerfelt, R. W., Drop breakup in simple shear fields of viscoelastic fluids. Ind. Eng. Chem. Fund. 11, 312-318 (1972)
- Taylor, G. I., The viscosity of a fluid containing small drops of another fluid. Pro. Roy. Soc. (London). 138A, 41-48 (1932)
- Taylor, G. I., The formation of emulsions in definable fields of flow. Pro. Roy. Soc. (London). 146A, 501-523 (1934)