Hydrophilic and hydrophobic AEROSIL fumed silica grades are used in many liquid systems for viscosity control, anti-sag and anti-settling behavior, and for general rheological enhancement. To optimize efficiency and consistency of the behavior for all fumed silica grades, the following conditions are important for success.
Whatever the use, loading levels in most coating and ink applications are relatively low. In the final formulation, < 1.0% by weight (based on total system) is usually suggested as a starting point. Loading levels for anti-settling properties may approach 1.5% if the formulation contains high loadings of other pigments and heavy fillers. For adhesive and sealant applications, loading levels are typically higher, in most cases 4-8% by weight (based on total system), because the desired thickening and thixotropy is higher. The actual percentage is dependent on the initial viscosity condition of the system, the desired condition, the desired length of storage stability and the polarity of the final formulation. The optimum loading is determined by trial and error and is very system specific.