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Selecting the right pigment dispersant is essential for achieving uniform color development, stable viscosity, and reliable storage performance in coating and ink formulations. Different pigments have different surface characteristics, particle structures, and interactions with the surrounding medium. A dispersant that performs well with one pigment may not provide the same results with another.

Polywill develops additives for coating and ink applications, including wetting and dispersing agents for different pigment types and formulation systems. When selecting a pigment dispersing agent, formulators should consider pigment surface chemistry, dispersant adsorption, resin compatibility, and dosage rather than relying on pigment classification alone.

1. Understand the Main Differences Between Pigment Types

Different pigments, including inorganic pigments such as titanium dioxide and iron oxides, organic pigments, and carbon black, exhibit distinct surface characteristics and dispersion behaviors.

These differences influence how easily pigments can be wetted, how effectively dispersants adsorb onto their surfaces, and how well the particles remain separated during storage and application.

Inorganic pigments such as iron oxides generally require attention to surface chemistry and compatibility with the dispersion medium. Titanium dioxide is often evaluated separately because its surface treatment can significantly influence dispersant selection. Organic pigments may require effective adsorption and steric stabilization, while carbon black presents additional challenges related to its specific surface area and aggregate structure.

Therefore, pigment type is a useful starting point, but the specific pigment grade and formulation conditions must also be considered when selecting a pigment dispersing additive.

2. How Does Titanium Dioxide Surface Treatment Affect Dispersant Selection?

Titanium dioxide (TiO₂) is an important inorganic pigment used in coatings because of its contribution to opacity and hiding power. However, different TiO₂ grades may behave differently during dispersion, even when their particle sizes are similar.

For titanium dioxide, surface treatment also plays an important role in dispersant selection. Different inorganic and organic surface treatments can affect surface affinity, wetting behavior, and dispersant adsorption.

Therefore, even titanium dioxide grades with similar particle sizes may require different dispersant technologies or dosage levels to achieve optimal performance.

When evaluating a dispersant for TiO₂, formulators should consider the pigment’s surface treatment, its affinity for the dispersant, and compatibility with the surrounding resin or liquid medium. Laboratory testing can then help determine whether the selected additive provides suitable viscosity, hiding power, and storage stability.

3. Why Do Organic Pigments Require Careful Dispersant Selection?

Organic pigments, particularly high-performance organic pigments with fine particle sizes, often present challenges due to their relatively high specific surface area and complex surface chemistry.

High-molecular-weight polymeric dispersants containing suitable pigment-affinic anchoring groups can help improve adsorption and provide steric stabilization.

However, dispersant performance depends on both pigment surface chemistry and compatibility with the surrounding resin or liquid medium.

These factors explain why a dispersant suitable for one organic pigment may not perform equally well with another. The effectiveness of the anchoring groups depends on the pigment surface, while the polymer chains must remain compatible with the surrounding medium to provide effective stabilization.

During formulation development, the dispersant should therefore be evaluated with the specific organic pigment and resin system. Relevant indicators include color strength, transparency where required, viscosity, and resistance to flocculation during storage.

4. What Makes Carbon Black Dispersion Different?

Carbon black can be challenging to disperse because of its high specific surface area and complex aggregate structures, together with the tendency of these aggregates to form larger agglomerates.

It is important to distinguish between aggregates and agglomerates. Carbon black primary particles are commonly joined into aggregates through strong bonding. These aggregates can associate into larger agglomerates through weaker interactions. Conventional grinding primarily helps break down agglomerates; it does not necessarily separate aggregates into individual primary particles.

The dispersant must therefore provide effective wetting and stabilization while helping prevent undesirable particle association after grinding.

Dosage also depends on the specific carbon black grade. High-color carbon black and conventional grades may differ in specific surface area, structure, and surface chemistry, which can affect dispersant demand. A higher dosage may be required for some grades, but it should not be assumed that every carbon black needs the same amount.

Evaluation should include color development, blackness, blue undertone, viscosity, and storage stability. These results help determine whether the selected dispersant and dosage are suitable for the particular formulation.

5. Match the Dispersant to the Formulation System

Pigment selection is only one part of dispersant evaluation. The surrounding formulation also affects adsorption and stabilization.

Water-borne, solvent-borne, and solvent-free systems can differ in polarity, resin compatibility, and the way polymer chains interact with the liquid medium. A dispersant that performs effectively in one system may not provide equivalent performance in another.

For polymeric dispersants, suitable anchoring groups help the additive adsorb onto the pigment surface, while compatible polymer chains extend into the surrounding medium and contribute to steric stabilization. Electrostatic repulsion may also contribute to particle stability, depending on the dispersant chemistry and formulation conditions.

When evaluating a pigment dispersant, formulators should consider:

• Pigment surface chemistry and surface treatment
• Dispersant adsorption and anchoring groups
• Compatibility with the resin and liquid medium
• Viscosity and color development during dispersion
• Stability during storage and subsequent processing

These factors help narrow the options before laboratory trials and reduce the risk of choosing an additive based only on its general product category.

6. How Much Dispersant Should Be Added?

Dispersant dosage depends on the pigment type, specific pigment grade, surface characteristics, and formulation system. Too little dispersant may result in insufficient surface coverage and poor stabilization, while an unsuitable dosage may affect viscosity, color development, or overall formulation performance.

For example, Coadd™ D-6075B, a high-molecular-weight polymeric dispersant for water-borne coatings, has different recommended dosage ranges depending on the pigment type.

Typical starting ranges, based on pigment weight, include 1.5–3.0% for titanium dioxide, 15–40% for organic pigments, and 20–50% for carbon black. These values are general guidelines rather than fixed formulation requirements. The optimal dosage should be confirmed through laboratory testing with the specific pigment grade and coating formulation.

The manufacturer’s published dosage ranges for Coadd™ D-6075B are summarized below.

These ranges are product-specific recommendations, not universal requirements for all dispersants or pigments. In particular, the carbon black range should not be interpreted as meaning that every carbon black grade requires a dosage of 20% or more. The appropriate amount should be established through testing and checked against the latest product technical data sheet.

7. Practical Dispersant Selection Guide

The following table summarizes the main factors to consider when evaluating a pigment dispersing agent for different pigment types.

This guide provides a starting point for selecting and testing a dispersant. Actual performance depends on the specific pigment grade, additive chemistry, resin system, and processing conditions.

8. How Can Laboratory Testing Confirm the Selection?

Laboratory testing is essential for confirming whether a selected dispersant works in the intended formulation. Product descriptions and recommended dosage ranges help narrow the options, but they cannot replace application testing.

A practical evaluation should examine several aspects:

• Dispersion efficiency: Assess whether the dispersant supports effective pigment wetting and grinding under the selected processing conditions.
• Viscosity: Measure viscosity during preparation and after storage to identify undesirable changes.
• Color performance: Evaluate color strength, blackness, blue undertone, gloss, or transparency as appropriate for the pigment and application.
• Storage stability: Check for sedimentation, flocculation, or other changes after storage.
• Formulation compatibility: Confirm that the dispersant performs appropriately with the selected resin and liquid medium.

Comparing several dosage levels can help identify a suitable operating range rather than assuming that increasing the dispersant concentration will always improve performance.

Conclusion

Choosing a suitable pigment dispersant requires an understanding of pigment surface characteristics, dispersant adsorption, formulation compatibility, and dosage. Titanium dioxide surface treatment can influence dispersant selection, organic pigments may require effective polymeric anchoring and steric stabilization, and carbon black requires attention to its aggregate structure and grade-specific properties.

Polywill offers dispersing additives for different pigment types and formulation systems. Its Coadd™ D-6075B product provides published dosage recommendations for titanium dioxide, other inorganic pigments, organic pigments, and carbon black. By combining these product guidelines with laboratory testing, formulators can identify a suitable dispersant and dosage for their specific coating or ink application.

Polywill has more than 30 years of industry experience and an R&D center spanning over 5,000 m². The company holds 32 patents, including 17 international patents, supporting its ongoing work in additive development and technical solutions for industrial customers.