The dispersibility and stability of pigment particles are important factors determining the performance of paints and inks. The pigments and fillers in the formula must be ground into small particles and wetted and evenly distributed as much as possible. Only in this case can optimal coloring power, gloss, covering power, light resistance, and weather resistance be achieved.

The pigment dispersion process can be divided into three steps: wetting, dispersion, and stabilization.

1. Wetting

The wetting of pigment particles is a necessary condition for pigment dispersion in liquids. The wetting process completely replaces the air adsorbed in the pigment, so that the pigment particles are completely surrounded by the liquid medium.

In order to wet solids, the surface tension of liquids must be lower than that of solids. Wetting dispersants not only reduce the surface tension of liquids, but also adsorb their own pigment groups, changing the interface. The interfacial tension is no longer between pigments and liquids, but between additives and liquids.

Wetting dispersants can reduce the surface tension of liquids and the interfacial tension between liquids and pigments. Therefore, wetting and dispersing agents can improve the wetting properties of pigments through the above two methods.

2. Dispersion

Nowadays, pigment particles are wetted by the surrounding resin solution and the surface is covered with surfactants. Wetting dispersants reduce the interaction force between pigment particles and lower the viscosity of the grinding slurry, which is particularly important for mechanical dispersion processes as it can achieve higher pigment content. The optimized slurry formula of this method is applicable to all modern grinding equipment such as high-speed dispersers, ball mills, and three roll machines. During the dispersion process, pigment polymers are opened up into smaller pigment polymers and original particles.

3. Stability

During the dispersion process, pigment polymers are opened up into smaller polymers and original particles. The formation of the original particles increases the interfacial area with the liquid medium. The greater the interfacial tension, the greater the driving force to reduce the interfacial area. Therefore, these particles reassemble to form what is known as a flocculant. Coagulants refer to suspended agglomerates. Dispersants can control coagulants.

In order to achieve stable and good particle distribution, wetting and dispersing agents must be firmly adsorbed on the surface of the pigment. This means that the functional groups or segments of wetting and dispersing agent molecules can generate strong forces with the pigment surface through ionic bonds, dipoles, or hydrogen bonds.