The action mechanism of dispersants can be summarized as steric hindrance and electrostatic stabilization. Dispersants have a great characteristic in molecular structure, namely “amphiphilicity”, hydrophilicity and lipophilicity. The lipophilic group of traditional dispersants is generally a hydrocarbon chain structure, and mainly an alkane chain. The molecular structure of superdispersants includes two parts: anchoring group and solvation chain. Dispersants have two action mechanisms: ① Liquid non-water-soluble raw materials are difficult to disperse due to excessive surface tension, such as oils and organic solvents with very weak polarity, which form an oil/water interface in water. The interfacial tension is very large, so the oil/water is divided into two layers. Although the oil can be dispersed into oil droplets under strong mechanical stirring, it will quickly separate under the action of interfacial tension after stopping stirring.

Sulfur becomes liquid after melting at 114°C, and for the same reason, it cannot be mixed with water. However, if a surfactant is added to the oil/water system and the oil is dispersed by mechanical force, a monolayer of surfactant will be immediately formed on the surface of the oil droplets, surrounding the oil droplets so that the oil droplets cannot condense, and the generated oil droplets can be stably dispersed in the water phase.

Adding a dispersant to the suspension can reduce the interfacial tension between the solid and liquid and effectively wet the particles. Taking the aqueous dispersion medium as an example, the lipophilic group of the dispersant is adsorbed on the surface of the solid particles, and the hydrophilic group is solvated by the water medium and expanded into the water phase medium, thereby forming a charged protective barrier around the particles, and the double layer surrounds the particles, generating electrostatic repulsion between the particles, making the dispersion stable; for the non-ionic dispersant, the hydration film formed by the long polymer chain can prevent the flocculation of solid particles and make the dispersion stable.

② There is also water/solid interfacial tension between solid powder particles and aqueous media. At the same time, the air film adsorbed on the surface of solid powder particles also hinders affinity with water, which is conducive to flocculation of powder particles. Surfactants can also remove the air film on the surface of powder particles and reduce the water/solid interfacial tension, thus making the powder particles easy to disperse.

The action mechanism of hyperdispersants can be divided into anchoring mechanism and stabilization mechanism. Its anchoring group is tightly adsorbed on the surface of solid particles through interactions such as ionic bonds, hydrogen bonds and van der Waals forces; its solvation chain has good compatibility with the dispersion medium and adopts a relatively extended conformation in the dispersion medium. When the particles adsorbed with hyperdispersants approach each other, the particles bounce off each other due to the spatial barriers of the solvation chain, thereby achieving stable dispersion of the particles in the medium.