Viscosity and Rheology Modifiers

Most emulsions are low viscosity liquids. Even with pigments and extenders, the viscosity is still too low for nearly all application methods. Thus, it is necessary to add materials to increase the viscosity of the. finished products and possibly to change its theology. 

Traditionally, hydroxy ethyl cellulose was the most commonly used thickener ( viscosity increaser ) for emulsion systems. The cost was low and delayed action grades were easy to incorporate. Very small additions can produce large changes in viscosity. However, the rheology of these solutions is far from Newtonian and can lead to thixotropic final products. Solvents also have a marked effect on the viscosity of hydroxy ethyl cellulose. 

These synthetic thickeners are much less susceptible to fungal attack than cellulose based ones, and therefore, are less prone to viscosity changes brought about by such degradation. Once dried, tilms thickened with these materials are far less water sensitive than their equivalents thickened with hydroxy ethyl cellulose. They are easier to handle and to incorporate than the cellulosics, as they need no pre-mixing or dissolving, and they can be added at the final stages of production if required. 

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