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A New Approach to Understanding Rheological Additives

SpecialChem / Aug 18, 2004

Rheological additives play a major role concerning storage and application properties of liquid systems. In waterborne coatings they have a major influence on such key properties as vertical flow, leveling, gloss, film thickness, covering power, spattering tendency, brush and roll resistance, sedimentation tendency and pigment stabilization. They have always been an important component in the production of paints and lacquers. Even at the beginning of the production process, it is possible to optimize the energy input into the material to be ground, thus leading to a better dispersibility in those systems. At the same time, rheological additives can considerably improve shelf life by reducing the settling tendency of pigments and fillers in a paint or lacquer formulation. Without adequate rheological control, those systems very often show syneresis effects. With spray application, an optimum compromise has to be found between good vertical flow characteristics (to achieve an adequate film thickness) and good leveling (to obtain a smooth finish). For this reason, in the low-shear range, the viscosity must be set just high enough to prevent vertical flow.

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