Effect of quantity and size distribution of calcite filler on the quality of water borne paints

Calcite is the most widely used mineral filler in paint formulations. It provides not only a decrease in the cost of paint but also modifies some physical paint properties. Although some properties of calcite such as particle size distribution and refractive index are not comparable in quality to TiO2, calcite can improve the distribution of TiO2 via its interaction with TiO2 particles. In this study, calcites of different size distributions are used as filler in the architectural waterborne, acrylic based paint recipes. The quality of paints was compared to properties based on both wet and dry paint such as viscosity, density, opacity, gloss, scrub resistance and Buchholz hardness. Examination of the results identified an optimum quantity and size distribution of calcite for the paint recipe. The second series of this study involved substitution possibilities of TiO2 with calcite using seven different paint formulations. Phase images of the dry paint films obtained using “Atomic Force Microscopy” (AFM) showed the extent of distribution and aggregation of particles for each formulation on the paint surface. The overall experimental results revealed that the use of TiO2 can be decreased up to 4% by replacement of calcite with an optimum size distribution that was also supported by AFM measurements.

► Calcite particles with optimized size distribution improve the stability of paint.
► Calcite particles hinder agglomeration of TiO2 particles in paint.
► Part of TiO2 can be replaced by calcite without any appreciable change in service properties of paint.
► AFM is successfully used to investigate the distribution of particles on dry paint film surfaces.