Related Experiment Videos
Effect of Particle Size Distribution on the Rheology of Dispersed Systems
1Department of Chemical Engineering, Imperial College of Science, Technology and Medicine, Prince Consort Road, London, SW7 2BY, United Kingdom
Journal of Colloid and Interface Science
|December 23, 1999
Summary
Polystyrene latex dispersions with varying particle size distributions show shear-thinning behavior. Broader distributions result in lower viscosity and elastic modulus, with the Krieger-Dougherty equation providing good theoretical agreement.
Area of Science:
- Colloid and Surface Chemistry
- Rheology
- Polymer Science
Background:
- Understanding the rheological properties of colloidal dispersions is crucial for various industrial applications.
- Polystyrene latex dispersions stabilized by triblock copolymers are model systems for studying colloidal behavior.
- Particle size distribution significantly influences the macroscopic properties of dispersions.
Purpose of the Study:
- To investigate the impact of varying polydispersity on the steady-state and oscillatory shear rheological properties of polystyrene latex dispersions.
- To compare experimental rheological data with theoretical models, including the Herschel-Bulkley and Krieger-Dougherty equations.
- To analyze the role of the adsorbed polymer layer and interparticle forces in the observed rheological behavior.
Main Methods:
- Synthesis of three polystyrene latex batches with similar particle sizes but different polydispersity indices.
- Characterization of particle size using photon correlation spectroscopy and transmission electron microscopy.
- Rheological measurements including steady-state shear and oscillatory shear tests.
Main Results:
- Dispersions exhibited shear-thinning behavior at high solid fractions, with narrower distributions showing more pronounced shear thinning.
- The broadest particle size distribution resulted in the lowest viscosity and elastic modulus at a given volume fraction.
- The Krieger-Dougherty equation showed good agreement with experimental data, especially when considering the adsorbed polymer layer and experimental maximum packing fractions.
Conclusions:
- Polydispersity significantly affects the rheological response of polystyrene latex dispersions.
- Interparticle forces, influenced by polymer chain compression and interpenetration, govern the transition from viscous to elastic behavior.
- The study provides valuable insights into the relationship between particle size distribution and the macroscopic rheological properties of colloidal systems.