Insufficient tinting strength, dull gloss, and separation after a period of storage; the root of these problems usually points to poor pigment dispersion. Because water has a high surface tension and wets organic pigments poorly, pigment agglomeration is more pronounced in waterborne systems than in solventborne ones. By adsorbing onto the pigment surface and providing steric hindrance or electrostatic repulsion, dispersants help pigments de-agglomerate and stay suspended, making them an indispensable part of any waterborne formulation.
Wetting, De-agglomeration, Stabilization
The dispersing process usually has three stages. In the wetting stage, the dispersant lowers the interfacial tension between pigment and medium so the medium penetrates the pigment aggregates; in the de-agglomeration stage, the energy of mechanical grinding, with the help of the dispersant, gradually opens up the pigment agglomerates; in the stabilization stage, the adsorbed layer the dispersant forms on the particle surface keeps the particles from re-agglomerating and maintains long-term stability of the system. These three stages are interlinked, and none can be left out.
New Challenges in Nano Dispersion
As pigment particle size moves toward the nanoscale, the specific surface area of the particles increases and their surface energy rises, making the tendency to agglomerate more pronounced and placing higher demands on the steric hindrance capability of the dispersant. A high-performance dispersant can still keep viscosity low at a relatively high pigment solids content. According to industry practice, optimizing the dispersant system can raise the solids content of some pigment pastes to a fairly high level while significantly reducing VOC emissions, which means a great deal for energy saving and emission reduction.
Dosage and Matching Both Take Care
The choice of dispersant must match the pigment type and the resin system. Inorganic and organic pigments differ in surface charge characteristics, and the type of dispersant they need differs accordingly. Moreover, more is not always better: an overdose may increase foaming and reduce water resistance. The optimum dosage is usually determined by measuring grind fineness, viscosity change, and heat storage stability.
For formulators, choosing the right dispersant and optimizing the grinding process can improve production efficiency and storage stability while raising color strength and gloss, making it an important entry point for cutting costs and improving efficiency in waterborne systems.