Stabilisation mechanism of main paint pigments
Different types of minerals in varying amounts are used in paint formulations depending on the paint characteristic. While titanium dioxide (TiO2) is used as a main pigment to improve the paint properties, some minerals such as calcite and calcined kaolin are used as a filler to decrease the cost of the paint, and in some cases as a substitute for TiO2. An important criterion for developing paint formula, especially for architectural ones, is to load maximum amounts of mineral pigments or fillers as much as possible to satisfy the rheology of the paint. Appropriate type and amount of dispersants is crucial at this stage to get the proper flowability at high amount of pigment and fillers.
Interaction of individual minerals and their mixtures
Polyacrylic acid sodium salt (NaPAA), a well-known dispersant, is generally used as a commercial dispersant in various paint formulations. Interaction of NaPAA with a group of minerals as single or mixture will be rather different. In the case of paint, as a variety of minerals and reagents are available in a mixture, in order to improve the paint formulation, this complex system should be revealed step by step. In a new study, the interaction of single minerals, titanium dioxide (TiO2), calcined kaolin (C.Kaolin), ground calcite (GCC) and their mixtures as TiO2 + GCC, TiO2 + C.Kaolin and TiO2 + GCC + C.Kaolin in the presence of NaPAA was investigated in terms of adsorption, rheology, and electrokinetic phenomena.
Mixture of minerals of different surface properties
The results showed that adsorption plateau, zeta potential and viscosity values of the mixtures were very close to the arithmetic mean of the individual minerals of the mixtures. The most attractive mineral ingredient for NaPAA was TiO2, followed by GCC and C.Kaolin. The mixture of minerals behaved differently at the same dosage of NaPAA compared to the single minerals. It is thus important to adjust the minerals mixtures and dispersant type and dosage to closely tune the paint properties. This study clearly revealed that it is more viable to adjust the desired paint properties using a mixture of minerals of different surface properties than a single mineral.
The study is published in: Progress in Organic Coatings Volume 123, October 2018, Pages 292-298.