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 TiO ₂, calcite can improve the distribution of TiO ₂ via its interaction with TiO ₂ 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 TiO ₂ 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 TiO ₂ can be decreased up to 4% by replacement of calcite with an optimum size distribution that was also supported by AFM measurements.