Optimum dispersion and stabilization of pigments and fillers are responsible for the characteristics of paints and coatings. Maximum color strength, brilliance and opacity depend on the particle size achieved for the solids to be dispersed.
Solids, like powders, are divided into three types of particles:
- Primary particles - Consist of a single particle or crystal. They can only be grinded and not be dispersed.
- Aggregates - are combinations of primary particles that are fused together at the surfaces. Aggregates can also only be grinded and not be dispersed.
- Agglomerates - are several primary particles and/or aggregates lying next to each other. In contrast to primary particles and aggregates, agglomerates are dispersible.
The aim of dispersion is therefore to break down agglomerated solids (usually powders) into smaller agglomerates and primary particles and to stabilize these in a medium. This is achieved, for example, by using suitable additives. The more compact the agglomerates and aggregates to be dispersed are, the higher the shear forces of the dissolver acting on them must be. Another important function is the wetting of all primary particles with the binding material film. The degree of dispersion influences the physical and optical characteristics of a product.
This distinguishes the dispersing process from the grinding process, since only physical bonds are broken during dispersion. As soon as aggregates, i.e. chemical compounds, are separated, ten times more energy is required for this. This is then referred to as the grinding process.