Dispersants in Waterborne Coatings

Effective pigment dispersion determines final coating quality — gloss, hiding power, color consistency, and shelf life. Dispersants reduce the energy required to break pigment agglomerates and provide steric or electrostatic stabilization to prevent re-flocculation.

Wetting vs Dispersing

Wetting agents (low-MW surfactants) reduce the surface tension of the aqueous phase, enabling the liquid to displace air from pigment surfaces during grinding. Typically used at 0.1–0.5%.

Dispersants (polymeric or oligomeric) anchor to pigment surfaces via anchor groups (amine, phosphate, carboxyl) and provide a stabilizing shell through the tail group.

Dosage Guidelines

Pigment	Surface Area	Typical Loading (on pigment)
TiO2 (rutile)	6–8 m²/g	1.5–3%
Carbon black	50–300 m²/g	10–25%
Organic pigments	20–100 m²/g	5–20%
Talc / CaCO3	2–5 m²/g	0.5–1.5%

Troubleshooting

• Flooding/floating: Insufficient dispersant; increase loading or switch anchor chemistry.
• Viscosity rise on storage: Under-dispersed system; re-grind with higher dispersant dose.
• Foam during dispersion: Add defoamer after dispersion step, not before.

HMEChem supplies polymeric dispersants compatible with all major waterborne binder systems.