This white paper introduces four advanced rotor/stator technologies for ultra-high shear mixing of fine dispersions, emulsions, and other applications that exceed the capabilities of traditional single-stage and multi-stage rotor/stator equipment. These ultra-high shear mixers have proven to be an effective alternative to expensive high-pressure homogenization and colloidal milling operations, while providing comparable levels of dispersion and particle size reduction.

Any high-shear, high-speed mixing operation—whether the process goal is direct dispersion, particle size reduction, or emulsification—will produce Gaussian distribution results. The bottom line goal is usually to achieve the narrowest distribution possible through equipment solutions that meet process and business needs. In some applications, engineers and scientists are more concerned with the average particle size, while other applications have strict standards for the largest particles that may be present in the suspension (for example, all particles must be smaller than 2 microns). In fact, particle size distribution is just one of many indicators of high-quality products. Depending on the end use, other properties such as conductivity, stability, viscosity, thixotropy, yield stress, color, gloss, etc. should also be considered during equipment testing and selection, whether directly or indirectly related to particle size.

The greatest reduction in particle or droplet size occurs during the first few passes through the in-line rotor/stator mixer or the first few tank turns in a batch mixer setting. This phenomenon applies to almost any dispersion or emulsion. After this stage where the particle size decreases sharply, the distribution hovered in equilibrium. Additional processing will gradually shrink the distribution curve, but expanding the process for this purpose almost always wastes a lot of time and energy.

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