Do you know the structure, properties and uses of dispersants?

Sep 13,2023


Among the components of the coating, there are film-forming substances, solvents (water), pigment fillers, additives. Among them, additives account for a small proportion of coatings, but they are very important and cannot be ignored. From the principle of action of dispersants, the essence of dispersants is surfactants, which have amphiphilic properties. Therefore, the dispersant will inevitably have a certain hydrophilicity, which has a great impact on water resistance in the paint film.

A dispersant is an interfacial activity additive with two opposite properties of both lipophilic and hydrophilic properties within the molecule. It can uniformly disperse solid and liquid particles of inorganic and organic pigments that are difficult to dissolve in liquids.

Efficient and environmentally friendly water-based dispersants are non-flammable, non-corrosive, infinitely compatible with water, and insoluble in organic solvents such as ethanol, acetone, benzene, etc. It has excellent dispersion effect on kaolin, titanium dioxide, calcium carbonate, barium sulfate, talc, zinc oxide, iron oxide yellow and other pigments, and is also suitable for the dispersion of mixed pigments.

Most dispersants disperse pigments through the process of wetting, grinding and dispersing, coupling and wrapping stabilization. In water-based coatings, most of the wetting and dispersing additives used in the market are anionic and non-ionic.

(1) Anionic surfactants: most of them are composed of non-polar negatively charged lipophilic hydrocarbon chain parts and polar hydrophilic groups. The two groups are located at opposite ends of the molecule, forming an asymmetrical hydrophilic lipophilic molecular structure. Anionic dispersants have good compatibility and are widely used.

(2) Non-ionic type: non-ionizing, no charge. The adsorption on the surface of the pigment is relatively weak, and it is mainly used in aqueous coatings. Their effect is to reduce surface tension and improve wettability. If some organosiloxanes are added, they can prevent flowering and floating, and improve the leveling effect.

The functional characteristics of aqueous dispersants are detailed as follows:

1. Replace ammonia and other alkaline substances as neutralizing agents, reduce the smell of ammonia, and improve the production and construction environment.

2. Waterborne coating dispersant can effectively control the PH value and improve the efficiency and viscosity stability of the thickener.

3. Improve the dispersion effect of pigments, improve the sinking and coarsing phenomenon of pigment particles, and improve the color spread of the color paste and the luster of the paint film.

4. Water-based coating dispersants are volatile, will not stay in the paint film for a long time, can be applied in high-gloss coatings, and have excellent water resistance and scrub resistance.

5. Water-based dispersants can be used as post-additives to effectively reduce shear viscosity and improve the fluidity and leveling of coatings.