The formation of a stable dispersion system, in addition to using electrostatic repulsion, that is, the negative charges adsorbed on the surface of the particles repel each other, to prevent the adsorption/aggregation between particles and finally form large particles and stratify/settlement, but also use. The theory of the steric hindrance effect, whereby particles that have adsorbed negative charges slide away from each other as they approach each other.

Such sterically hindered surfactants are generally nonionic surfactants. Using the theory of electrostatic repulsion and steric hindrance flexibly, a highly stable dispersion system can be formed. The polymer adsorption layer has a certain thickness, which can effectively block the mutual adsorption of particles, mainly relying on the solvation layer of the polymer.

The mechanism of the dispersant:
1. Adsorbed on the surface of solid particles to reduce the interfacial tension between liquid-liquid or solid-liquid. Make the surface of agglomerated solid particles easy to wet.
2. The polymer type dispersant forms an adsorption layer on the surface of the solid particles, increases the charge on the surface of the solid particles, and improves the reaction force between the particles that form a three-dimensional barrier.
3. The surface of the solid particles forms a bilayer structure, and the polar end of the outer dispersant has a strong affinity with water, which increases the degree of the solid particles being wetted by water. The solid particles are separated by electrostatic repulsion.
4. Make the system uniform, increase the suspension performance, do not precipitate, and make the physical and chemical properties of the whole system the same.

In summary, the use of dispersants can stably disperse solid particles in liquids.


The dispersants used in water-based coatings must be water-soluble, and they are selectively adsorbed on the powder-water interface. Commonly used are anions, which are ionized in water to form anions, and have a certain surface activity, which is adsorbed on the surface of the powder. After adsorbing the dispersant on the surface of the powder particles, an electric double layer is formed, and the anions are tightly adsorbed by the surface of the particles, which are called surface ions.