Products undergo shear when one section of the material is imparted with a different velocity through use of a rotating impeller or high speed rotor. The speed of the product while at the tip of the rotor is higher than the speed at the center, creating shear.
High Shear Mixtures are able to combine solids and liquids that usually are unable to mix, like powder and water or oil and water, and emulsify them, meaning the two immiscible materials mix. Like most mixers, high shear mixers are made from metal, specifically stainless steel if used with food products. High shear mixers differ in terms of the diameter of the rotor, its rotational speed, the power of the motor, the number of blades and other variables.
First available only in the rubber industry, high shear mixers are now used widely within the food, cosmetics, chemical, lube oil, pharmaceutical, adhesive and plastics industries. High shear mixers are used to bleach paper pulp, prepare granular products, create emulsions for sauces and dressings and manufacture toiletries, among others; creams, waxes, polishing agents, gelling agents, dyes and polymer emulsions are easily created with the use of a high shear mixer.
During the emulsion process, the high shear mixer is immersed in the two materials. The high speed rotation of the blades creates suction that draws the solid and liquid portions of the mix into the work head, where the blades are.
Centrifugal force drives the materials out the work head and through the blades, where they are finely milled and evenly dispersed. This process is done in circulation until all of the solid material has been sheared and mixed evenly with the liquid, which creates a substance with a totally new viscosity. Unlike other mixers, there is little or no turbulence or splashing at the top.
High shear mixers often have changeable work heads that offer different types of mixing. High shear mixers may be used in a variety of ways. For high shear batch mixers, materials are fed into a mixing tank; this kind of machine can successfully mix twice as much as inline mixers of the same power. They work with one batch at a time.
Inline high shear mixers have a rotor-stator arrangement that handles a continuous stream of components. In an ultra high shear inline mixer, the material is passed through multiple blade arrangements in order to subject the components to a higher shear. High shear granulators consist of a batch or inline high shear mixer and a fluid bed dryer. By combining the two pieces of equipment, particles can be granulated and dried.