How much additive is used in paint formulations?

Paint additives are typically used in concentrations ranging from 0.01% to 5% of the total coating formulation. The exact dosage depends on the additive type and target performance, and choosing the right combination requires testing against the specific resin, pigment, and solvent system.

What are the 4 main types of paint additives?

Paint additives are typically grouped into 4 categories by their function: (1) Coating Production additives such as wetting agents, dispersants, defoamers, and emulsifiers; (2) Storage and Transportation additives such as anti-settling, anti-skinning, anti-freezing agents, and preservatives; (3) Application and Film-Formation additives such as curing agents (PU hardeners), leveling agents, matting agents, and anti-sag agents; and (4) Specialty Performance additives such as UV absorbers, heat stabilizers, scratch-resistance and hydrophobic agents.

Are PU hardeners and curing agents considered paint additives?

Yes. Polyurethane hardeners (polyisocyanate crosslinkers) fall under the Application and Film-Formation additive category. They react with hydroxyl groups in the resin to form the urethane film. Common PU hardeners include aromatic types such as TDI adducts and TDI trimers, aliphatic types such as HDI biuret and HDI trimer, blocked isocyanates for 1K baked systems, and water-dispersible hardeners for waterborne 2K coatings.

What is the difference between paint additives and pigments?

Pigments are solid particles that provide color, opacity, and bulk to the coating, often making up 10–40% of the formulation. Additives are functional ingredients used in much smaller amounts (0.01–5%) to modify specific behaviors such as wetting, leveling, foam control, UV resistance, or curing. Pigments stay visible in the dried film, while additives mainly influence formulation behavior, storage, application, or final film properties.

Paint Additives Guide: 4 Types & Their Role in PU Coatings

Q: What are additives in paint?

Paint additives, also known as coating auxiliary materials, are functional ingredients added in small amounts (0.01–5% of formulation) to enhance specific performance properties of the coating. Unlike solvents, additives remain in the dried film and directly affect storage stability, application behavior, film formation, and final coating properties.

4 Types of Paint Additives & Their Role in PU Coating Formulations

For Coating Manufacturers and Formulators

If you are selecting paint additives for wood coatings, automotive refinish, or industrial coating systems, additive choice should always be reviewed together with resin, solvent, and hardener compatibility. Getting the right combination directly affects film formation, drying speed, gloss, and final coating durability.

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What Are Additives in Paint?

Among coating additives, curing agents and crosslinkers are especially important in polyurethane systems because they directly affect film formation, drying behavior, chemical resistance, and final coating performance.

Coatings include 4 core components: resins (binders), additives (such as PU hardeners), solvents, and pigments. Additives in paints — also called coating auxiliary materials — play a crucial role in enhancing performance and facilitating film formation. They are used in minimal quantities yet remain indispensable in water-based, high-performance, and decorative coatings.

Unlike solvents, which evaporate after film formation, additives remain as integral components within the dried coating film. This means they may give either desired effects or adverse effects on the final coating. For instance, emulsifiers are indispensable in emulsions, yet the migration and hydrophilicity of residual emulsifiers can inevitably impact water resistance and adhesion. Understanding these nuances is crucial for optimizing coating formulations.

How Much Additive Is Used in Paint?

Typically, additives make up 0.01% to 5% of the total paint formulation. Despite the small quantity, their effect is significant. Additives have different structures and physicochemical properties, and many of them are surfactants of various types. They can work either synergistically or antagonistically in the same formulation. Furthermore, additives interact in complex ways with film-forming resins, pigments, and dispersing media. Therefore, choosing the right combination requires close collaboration between additive suppliers and formulators.

The 4 Types of Paint Additives

Paint additives are typically grouped into 4 categories according to their role at different stages of the coating process — from production to the final film performance.

1. Coating Production Additives

These additives are added during the manufacturing of the coating to adjust its physical behavior in the wet state:

Wetting Agents — enhance the coating's wetting properties on substrates, ensuring uniform coverage and improved adhesion.
Dispersants — promote uniform dispersion of pigments and solid particles in the liquid phase, preventing settling and ensuring color consistency.
Emulsifiers — crucial in emulsion coatings, stabilize and evenly disperse water and oil-based components.
Defoamers — prevent the formation of bubbles in the coating, ensuring a smooth final surface.

2. Storage and Transportation Additives

These additives keep the coating stable and usable during shelf life, warehousing, and shipping:

Anti-Settling Agents — prevent settling of pigments or solid particles, maintaining uniform dispersion.
Anti-Skinning Agents — prevent skin formation on the coating surface when exposed to air, keeping the container opening clean.
Anti-Floating and Anti-Flocculating Agents — prevent color floating or pigment flocculation, maintaining color consistency.
Anti-Freezing Agents — prevent the coating from freezing in low-temperature storage and transportation.
Preservatives — inhibit microbial contamination during storage, preserving long-term quality.

3. Application and Film-Formation Additives

For polyurethane coating systems, curing agent selection must be considered alongside application method, drying speed, gloss or matte requirements, and final performance targets.

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These additives enhance the coating's behavior during application and final film formation:

Curing Agents (PU Hardeners) — accelerate the curing and cross-linking process, ensuring proper film formation in 2K polyurethane systems.
Leveling Agents — enhance the smoothness of the coating surface, reducing brush or roller marks for an even finish.
Matting Agents — reduce gloss to deliver a matte or satin appearance to the dried film.
Anti-Sag Agents — prevent the coating from sagging or dripping on vertical surfaces during application.
Film-Forming Aids — assist in forming a continuous, uniform film, improving coating integrity (especially important in waterborne systems).

4. Specialty Performance Additives

These additives are added to enhance specific final-film properties for demanding applications:

UV Absorbers — absorb ultraviolet light, protecting the coating from UV-induced degradation and enhancing outdoor durability.
Heat Stabilizers — help the coating withstand high temperatures, preventing thermal degradation.
Scratch-Resistant Agents — improve resistance to surface scratches and abrasion.
Hydrophobic Agents — make the coating water-repellent, enhancing water resistance and outdoor durability.

How Polyurethane Hardeners Fit into the Additive Mix

Among film-formation additives, polyisocyanate hardeners deserve special attention. They are not merely performance modifiers — they are reactive crosslinkers that define the final coating's hardness, durability, gloss retention, and chemical resistance. The right hardener choice depends entirely on your coating system:

Indoor wood & furniture coatings — TDI-based aromatic polyisocyanates (TDI adducts and TDI trimers) offer fast cure, high hardness, and excellent cost-performance. Yellowing is acceptable indoors where UV exposure is minimal.
Automotive refinish & exterior clear coats — Aliphatic HDI-based polyisocyanates (HDI biuret, HDI trimer) provide superior UV resistance and long-term color retention.
Cabinet, kitchen & high-end furniture top coats — TDI+HDI hybrid hardeners balance cost, hardness, and moderate weather resistance for premium indoor surfaces.
Powder coatings, coil coatings & baked 1K systems — Blocked isocyanates remain inert at room temperature and release reactive NCO groups only at elevated cure temperatures (typically 120–180 °C).
Waterborne 2K PU coatings — Hydrophilically modified aliphatic polyisocyanates disperse readily in water-based resin systems while maintaining 2K crosslinking performance and low VOC.

At Dongsen Chemicals, we manufacture this complete polyisocyanate hardener range — no finished paints, only raw materials engineered for formulators and coating manufacturers.

Which Coating System Are You Working On?

If you are working on wood coatings, automotive refinish, industrial coatings, or any 2K polyurethane system, we can help review your application and recommend a suitable hardener direction.

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If you're building a nitrocellulose-based wood finish — or upgrading an NC system with a PU hardener for better hardness, chemical resistance, and durability — Dongsen supplies the TDI adducts, TDI trimers, and HDI biuret hardeners commonly used in NC-PU hybrid lacquers. Tell us your formulation and we'll recommend a starting point.

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