Wetting & Dispersing Additives in Coatings

Contents

• What wetting & dispersing additives do
• Where they fit in the process
• Common chemistry families
• Selection matrix by system
• Dosage & incorporation (grind vs letdown)
• Specification & acceptance checks (QC)
• Troubleshooting: symptoms → root causes
• Compatibility & compliance considerations
• RFQ notes (procurement-ready)
• FAQ for technical & purchasing teams

What wetting & dispersing additives do

In coatings, pigments and extenders want to agglomerate. Wetting and dispersing additives help you (1) wet the pigment surface quickly, (2) break down agglomerates under shear, and (3) stabilize the new surface area so it doesn’t re-flocculate. The practical outcomes are measurable:

• Higher color strength and cleaner hue at the same pigment loading.
• Stable viscosity over time (reduced yield stress drift / “creep” in viscosity).
• Lower defect rate: reduced flooding/floating, rub-out, seediness, and microfoam-related craters.
• Faster grind and more reproducible dispersion: fewer passes, less energy per batch.

Mechanism (plain language)

• Wetting: reduces interfacial tension so the binder/solvent displaces air and adsorbed moisture on pigment surfaces.
• Dispersion: improves deagglomeration efficiency under shear (bead mill, high-speed disperser).
• Stabilization: provides electrostatic and/or steric repulsion to keep particles separated.

Where they fit in the process

Most coatings have two mixing stages: grind (high shear) and letdown (lower shear). Wetting and dispersing additives are most effective when they are present at the moment new pigment surface is created—i.e., during grind.

• Grind stage: additive is added early to promote fast wet-out and maximize milling efficiency.
• Letdown stage: small “trim” additions may be used to correct viscosity or stability, but this is not a substitute for proper grind design.
• Post-add (tinting / adjustments): may help tint strength uniformity, but can introduce compatibility issues if overdosed.

Commercial impact (why procurement should care)

• Cost-in-use is more important than price/kg: better dispersion often means lower pigment requirement and fewer defects.
• Risk reduction: selecting a compatible additive reduces rejects, customer complaints, and rework.
• Supply continuity: matching documentation (SDS/COA) and packaging to your plant reduces receiving holds.

Common chemistry families (what you’ll see on datasheets)

Suppliers may describe these products differently, but most wetting & dispersing additives fall into a few functional families. Your resin system, pigment type, and performance targets determine the best fit.

1) Polymeric dispersants (steric stabilization)

• Typical use: high-performance systems, organic pigments, carbon black, high pigment volume concentration (PVC) formulas.
• Strengths: strong long-term stability, high color development, good viscosity control.
• Watch-outs: compatibility in low-polarity systems; can impact water sensitivity if mismatched.

2) Anionic / nonionic surfactants (wetting-focused)

• Typical use: wet-out and flow in waterborne systems; general-purpose wetting for extenders.
• Strengths: fast wetting, improved substrate wetting, helps with crater reduction when used correctly.
• Watch-outs: can increase foam; may reduce water resistance or block resistance if overused.

3) Controlled polarity dispersants (solventborne)

• Typical use: alkyds, acrylics, PU solventborne, industrial enamels, primers.
• Strengths: good balance of wetting and stabilization with reduced side effects.
• Watch-outs: check VOC contribution and odor; ensure compatibility with your solvent blend.

4) Specialty for carbon black / difficult pigments

• Typical use: high-jetness black, deep tinting strength, conductive black dispersions.
• Strengths: improved deagglomeration; reduces viscosity spike common with carbon black.
• Watch-outs: very sensitive to dosage; run a ladder study before scale-up.

Selection matrix by system (practical decision aid)

Use this matrix to shortlist candidates. Final selection should be confirmed with lab dispersion and storage stability tests. If you share your binder type, solvent/water ratio, pigment package, and target performance, we can propose a compliant shortlist and sourcing plan.

Quick matrix

What to match (technical checklist)

• Pigment set: organic pigments and carbon black generally need stronger stabilization than extenders.
• Binder polarity: match dispersant polarity to resin/solvent so the stabilizing chains stay solvated.
• Target rheology: some dispersants lower yield stress (good for pumpability); others can increase structure.
• End-use exposures: chemical resistance, water resistance, outdoor durability, corrosion protection requirements.
• Process constraints: bead mill vs dissolver; batch time; temperature; shear history; filtration requirements.

Dosage & incorporation (grind vs letdown)

There is no universal dosage because pigment surface area and chemistry vary. The best practice is to run a dosage ladder (e.g., low / medium / high) and measure dispersion quality and stability after heat-age. Use these guidelines as a starting point:

Incorporation sequence (reduces defects and variability)

1. Pre-mix: add part of the liquid phase (water/solvent/binder) and start agitation.
2. Add dispersant early: before pigment addition or with the first pigment fraction.
3. Controlled pigment addition: avoid dry “rafts”; maintain vortex and avoid air entrainment.
4. High-shear grind: target fineness-of-grind and stable viscosity; avoid overheating.
5. Letdown: add remaining binder, coalescents/solvents, and other additives (defoamer, flow, thickener) in a verified order.
6. Filter as needed: confirm filterability if the product goes through fine filtration.

Common mistakes that look like “bad dispersant”

• Too late addition: dispersant added after agglomerates are already locked in.
• Wrong shear history: insufficient grind time / media selection / tip speed.
• Overdosing wetting surfactant: foam, water sensitivity, craters, and intercoat issues.
• Incompatible additive stack: dispersant + thickener or dispersant + defoamer interactions.

Specification & acceptance checks (QC)

Procurement and QC should align on what is verifiable at receipt and what is verified in production trials. Below is a practical checklist. Adjust it to your site standards.

On-receipt checks (incoming QC)

• Identity & traceability: product name, grade, manufacturer, batch/lot, manufacturing date, and document revision control.
• COA typical items: appearance, active content/assay, solids %, acid value/amine value (if applicable), density, viscosity, pH (waterborne), water content (solventborne/UV).
• Packaging integrity: drum/IBC seal, liner compatibility, labeling completeness, and tamper evidence (where required).
• Shelf life & storage: storage temperature range, freeze–thaw notes (waterborne), and re-homogenization guidance.
• Safety: current SDS, hazard classification, transport status, recommended PPE, and spill handling notes.

Performance qualification tests (lab / pilot)

Troubleshooting: symptoms → root causes

Many coating issues are multi-factor. Use this table as a first diagnostic pass. If you share the system type, pigment package, and your current mill/dispersion process, we can help narrow down the likely cause quickly.

Compatibility & compliance considerations

For industrial coatings, selection is rarely “performance only.” Many sites have compliance constraints that must be checked early to avoid delays in qualification and purchasing.

• Low-VOC requirements: verify solvent contribution and whether the additive is supplied in a carrier solvent.
• Waterborne restrictions: APEO-free or specific surfactant restrictions; verify if the additive contains free surfactant.
• Silicone-sensitive applications: some plants require silicone-free additive stacks for recoating or contamination control.
• Food-contact / sensitive end uses: confirm suitability requirements early (documentation and regulatory position statements may be needed).
• Migration / low-odor: critical for interior applications, packaging-related uses, or UV systems.
• EHS: check handling class, ventilation needs, and storage temperature limits (especially for waterborne dispersions).

Packaging & logistics (how to avoid receiving holds)

• Common pack sizes: pails, drums, IBCs, and bulk (depending on product form and carrier).
• Storage: verify temperature window, freeze sensitivity, and mixing instructions before use.
• Compatibility: confirm container liner / gasket compatibility for long storage periods.
• Documentation at shipment: SDS, COA, packing list, and certificate statements if your site requires them.

RFQ notes (procurement-ready)

To source efficiently, RFQs should include both technical targets and commercial constraints. Use the list below to minimize back-and-forth and shorten lead time.

Technical details to include

• Coating type: waterborne / solventborne / UV; resin family; solids %; VOC targets.
• Pigment package: TiO₂ grade, extenders, organic pigments, carbon black (and approximate loadings).
• Process: dissolver vs bead mill; batch size; target fineness-of-grind; typical shear/time/temperature.
• Performance KPI: color strength, viscosity stability, rub-out resistance, gloss/DOI, filterability, storage stability.
• Constraints: silicone-free, APEO-free, low-odor/low-migration, specific site EHS requirements.

Commercial details to include

• Estimated monthly / annual volume: and whether you need safety stock or dual sourcing.
• Packaging preference: pail/drum/IBC/bulk; pallet requirements if relevant.
• Delivery location: country/city/Incoterms preference; any special receiving windows.
• Required documents: SDS/COA, batch traceability, statements (e.g., silicone-free / APEO-free) if needed.
• Target lead time: and whether samples are required for lab trials before purchase.

FAQ for technical & purchasing teams

How do we compare two dispersants fairly?

Run the same pigment concentrate recipe, same mill settings, and the same dosage ladder. Compare fineness-of-grind, color strength, rub-out difference, initial viscosity, and heat-aged viscosity. The “best” option is the one that meets your KPI with the lowest side effects and stable supply documentation.

Why did our viscosity improve initially but drift after a week?

That usually indicates partial stabilization: the dispersion looks fine at day 1 but slowly re-flocculates (often seen as viscosity rise or gloss drop). Verify aged rub-out, check polarity match, and confirm the additive was present during grind (not only added in letdown).

Can we fix flocculation by adding more dispersant in letdown?

Sometimes you can reduce symptoms, but it’s not reliable. If the pigment was not fully wetted or properly stabilized during grind, late additions may not access the pigment surface effectively. It’s better to correct the grind recipe and process.

What is the biggest procurement risk with these additives?

The two most common issues are (1) receiving holds because of missing/incorrect SDS/COA versions and (2) unexpected performance changes from unannounced formulation updates or substituting “equivalent” grades. Require batch traceability and consistent documentation, and qualify alternatives with controlled tests.

Educational content only. Always follow site EHS rules and the supplier SDS for safe use.