Paste viscosity that stays stubbornly high, whiteness that turns gray, and re-agglomeration after just a few days of storage; these seemingly scattered troubles all come down to one link: titanium dioxide dispersion. TiO2 is used in large amounts and has a high specific gravity in white coatings, so once it is not fully dispersed, particle agglomeration directly eats into hiding power and discounts the whiteness and gloss of a film that uses the same formulation. Switch to a waterborne system, where water has high surface tension and wets pigments poorly, and TiO2 is even harder to disperse than in solventborne systems, which is why more and more formulators treat the waterborne dispersant as a key variable.
Where TiO2 Is Difficult
TiO2 surfaces are treated with inorganic coatings, and between particles there is both van der Waals attraction and the influence of surface charge, so they readily re-agglomerate on standing. In industry data, TiO2 has long been one of the pigment types consuming the largest amount of dispersing aids, and the hiding power of white coatings is directly tied to particle spacing. Once particles flocculate, light-scattering efficiency drops, and the same amount of TiO2 does not deliver the expected whiteness, forcing the plant to add more pigment powder and pushing costs up. The rework caused by poor dispersion also slows the pace of the entire production line.
The Viscosity Ceiling of High-Solids Pastes
To cut costs and improve efficiency, production teams generally pursue pastes with higher solids, reducing transport and dilution steps. But as solids go up, paste viscosity soars, grinding and dispersing become more laborious, and pumping and filling also get harder. A good waterborne dispersant can still hold viscosity down at a relatively high pigment solids content, making grinding smooth and discharge stable. According to industry practice, optimizing the dispersant system can raise the solids content of some TiO2 pastes to a considerable level while shortening grinding time and lowering energy consumption, a tangible improvement in a plant's overall output. This is the reason high-solids pastes keep being brought up.
Steric Hindrance of Polymeric Dispersants
Among current waterborne dispersants, the share of polymeric products keeps climbing. They adsorb onto the TiO2 surface through anchoring groups and then use solvated chain segments to prop up steric hindrance, keeping particles from approaching one another. Compared with conventional small-molecule dispersants, polymeric dispersants anchor more firmly, provide stronger steric hindrance, and perform better in anti-flocculation and storage resistance, with a particularly clear stabilizing effect on high-density pigments such as TiO2. When selecting, you should look at compatibility with the resin system and determine the dosage using three indicators: grind fineness, viscosity change, and heat storage stability. More is not always better; an overdose instead brings more foam and reduced water resistance.
For our engineers, dispersing TiO2 is not as simple as pouring in a dispersant and stirring; you have to do full justice to the three links of wetting, de-agglomeration, and stabilization. The trend toward high solids and low VOC continues to intensify, and only by choosing the right waterborne dispersant and using the right dosage can you find a balance among color strength, storage stability, and cost, and avoid being held back by color differences and rework.