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Rheology

 Usually colloidal dispersions have a solid content of about 40-60%. At such high solid concentrations the polymer spheres are not able to move freely. Therefore there are frictions and punches between the particles. This leads to a much higher viscosity of the suspension. For practical use one wants to have a dispersion with a high solid content and a low viscosity. The viscosity of a dispersion does not only depend on the solid content but also on the particle size distribution. A dispersion with a wide  particle size distribution has a much lower viscosity, at the same solid content, than a suspension with a narrow particle size distribution. Today it is possible to get dispersions with a low viscosity and a high solid content (about 70%) by choosing a size distribution so that the small particles can fill the free space between the larger ones.

 

Diagram: Dependency of the viscosity on the solid content and on the particle size distribution.

 


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