In the use of paint, people often encounter problems such as flocculation, insufficient color or transparency, poor rheology or stability. These problems are closely related to the insufficient dispersion of the pigment.
Purely speaking, "good dispersion" means that each pigment particle in the system is completely deflocculated, that is, each pigment particle is surrounded by a thin layer of paint base or solvent. However, this is actually difficult to achieve. So, what effect does the pigment dispersion have on the performance of the coating?
1. Gloss: If the pigment is optimally dispersed, this can directly increase the gloss. In principle, gloss is determined by the performance of the paint base. Adding the necessary pigments can only adversely affect the gloss: if the pigments are not optimally dispersed, some pigment agglomerates will adversely affect the surface smoothness, thus reducing the gloss due to diffuse light scattering.
2. Resistance: Weather resistance and chemical resistance will mainly be determined by the selected paint base. Insufficient dispersion of the pigment particles here also reduces the resistance. The pigment particles protruding from the surface provide an attack point for chemicals and climatic factors. Conversely, if the correct choice of pigment is optimally dispersed, it can only improve the resistance of the coating system, for example, by reflecting (TiO2) or absorbing ultraviolet radiation (iron oxide red) to improve weather resistance. Proper pigments or extender pigments can also improve the chemical resistance of the paint base if they are optimally dispersed.
3. Storage period: The storage period of the coating system depends largely on the quality of the pigment dispersion. When there are excessive ratios of coarse pigment particles in the system, the adverse effects caused by the precipitation of coarse pigment particles are easy to understand. Such stability problems are caused either by so-called "post-wetting" of the pigments, or by re-flocculation of the opposite pigments. If the pigment is not completely re-flocculated at the beginning of dispersion to complete dispersion, post-wetting can be imparted. The reason for the re-flocculation of the previously dispersed pigment dispersion is that the stability of the pigment paste is good enough. This largely depends on the stability of the dispersed paint base during the dispersion process or the ratio of paint base to solvent. Solvents generally have excellent wetting properties, and paint bases are beneficial to stability. The problem is that wetting (= solvent) and stability (= lacquer base) should achieve the ideal combination.
4. Color, color intensity, transparency, and hiding power: All these properties depend to a large extent on the pigment surface used, that is, the "optimal dispersion". The complete dispersion of the pigment in the case of covering pigments can lead to increased hiding power, making the color strength of the color paste greater (without flocculation); and in the case of transparent pigments, it can make transparency better. For all pigments, the complete dispersion of the pigment can lead to the full development of the hue and "color purity" of the color.