Leveling Agents for Paints, Coatings and Inks

Need for Leveling Agents

It is admitted for many paints that a perfect appearance means also a perfect leveling. Poor leveling (like orange peel or ghosting) may not influence significantly the paint parameters in time, as it is more aesthetic orientated. But the leveling agent itself may cause some severe issues.

A correct leveling agent helps in reaching the wanted leveling and final film finish. But a wrong choice may lead to surface defects such as craters, pinholes, loss of gloss or even inter-coat adhesion problems. Therefore, to understand the leveling, it is important to understand the influence of the surface tension on the paint and finding a balance is critical:

Too low surface tension may be good for the substrate wetting but may lead also to a wavy surface.
Too high surface tension can cause adhesion and surface wetting issues.

If you are exploring the factors that govern leveling in any formulation, it might be worth to begin with an in-depth understanding of leveling basics (surface tension, contact angle, test method, etc.) at first.

Importance of Leveling in Paints and Coatings

Which leveling agent is suitable for your formulation?

There are several base chemistries to choose from when selecting a leveling agent & lower the surface tension to the point just that you need for a desired application.

The most common types of leveling agents are listed below.

Silicone-based agents (Polydimethylsiloxane modified - PDMS)
Acrylate-based agents (Polyacrylate)
Fluorocarbon-based agents (Modified Fluorocarbons)
Hydrocarbon-based leveling agents: less efficient than previous families

Understand each chemistry in detail and see which one fits best for your formulation & end-application needs.

Silicone-based Leveling Agents

Silicone-based leveling agents offer good leveling properties due to strong surface tension reduction & controlled tensions at all the interfaces thus improving the paint wetting properties.

Advantages	Disadvantage
Give good flow, reduce orange peel Increase the surface slip, improve scratch and mar resistance Avoid air draft sensitivity Avoid silking	Incompatibility May provoke intercoat adhesion issue May provoke contamination

Key Features of Silicone-based Leveling Agents

Strong surface tension reduction, controlled tensions at all the interfaces: improve the paint wetting properties, recommended to reduce the surface long waves (> 1.2mm)
Reduce the turbulences and rheological currents during the solvent evaporation
Excellent to improve the slip
May have a negative influence on the inter-coat adhesion and may provoke unwanted negative side effects (contamination / craters, migration in the upper layer in case of multi layers systems)
Polyether modifications with various Ethylene Oxide (polar) / Propylene Oxide (unipolar) units will improve the compatibility
Thermal stability can be also enhanced (like with a polyester modification for instance)
To lower the possible negative influence on the inter-coat adhesion, it is possible to use some reactive silicone based leveling agents, which will have a lower migration tendency

Long chain polysiloxanes are the most common leveling agents in the coating industry. Pure polydimethyl siloxanes are not used due to their incompatibility with many resins. Thus, polydimethyl siloxane backbone is further modified with polyethers, polyesters or alkyl side groups to improve recoat ability and inter-coat adhesion.

They are suitable for solvent-, water-borne systems and solvent free applications, depending on the type of side-chain.

Summary of Silicone based Leveling Agent Specificities

Modified PDMS	EO dominant	PO dominant	Short Modification	Long Modification	Long Backbone
Anti-Crater	⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐ ⭐
Leveling	⭐ ⭐	⭐ ⭐	⭐ ⭐	⭐ ⭐	⭐ ⭐
Slip	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐	⭐ ⭐ ⭐ ⭐
Substrate Wetting	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐
Risk of inter layer defects / contamination	low	low	low	medium	high

Polyacrylates Leveling Agents

Polyacrylates and (fluorinated) polyacrylates are a very versatile class of additives used in the coatings as flow and leveling agents. Pure polyacrylate copolymers are highly appreciated for their flow performance, however, do not significantly lower the surface tension of a system to solve problems like cratering or poor substrate wetting. While on the other hand, polyacrylates with fluorinated side chains can lower the surface tension of a formulation. They combine excellent flow and leveling with anti-cratering and good wetting behavior.

For example, in the case of coil coating applications a true surface tension balance is needed to achieve good leveling. Experience shows that fluorocarbon-modified polyacrylates are the most suitable products here. They lower the surface tension to overcome possible defects but not too low to cause bad leveling.

Advantages	Disadvantage
Reduce orange peel, improve the DOI Efficient against ghosting and clouding Efficient against craters and pinholes Temperature resistance	Do not improve the slip effect Incompatibility may cause loss of gloss, loss of DOI, and may increase the haze Can decrease surface hardness for low molecular weight

Key Features of Polyacrylates Leveling Agents

They have a relatively high surface tension: avoid intercoat adhesion issues
They improve the localized harmonization of surface tension by reducing the gradient surface tension, and as a consequence improve the leveling. Excellent to reduce the surface short waves (< 1.2mm)
Limited in the surface tension reduction. But as surface tension agents, they can also have an influence on the air entrapment, especially high molecular weight versions
Due to their low influence on the surface tension, polyacrylates are also recommended in primers!

Summary of Acrylate-based Leveling Agent Specificities

Polyacrylates	Low Molecular Weight	Medium Molecular Weight	High Molecular Weight	Modified
Compatibility	⭐ ⭐ ⭐	⭐ ⭐	⭐ ⭐	⭐ ⭐
Gloss	⭐ ⭐ ⭐	⭐ ⭐	⭐ ⭐	⭐ ⭐ ⭐
Haze	⭐ ⭐ ⭐	⭐ ⭐	⭐	⭐ ⭐
Degassing	⭐	⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐
Hardness	⭐	⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐
Leveling	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐

Fluorocarbon based Leveling Agents

Adding a surfactant to the system will lower the overall surface tension on a microscopic level. It will also equalize local surface tension differences, resulting in improved leveling and smoother surfaces.

Fluorosurfactants are widely used a leveling agent in coatings due to their efficiency at reducing surface tension. Fluorosurfactants easily exist in large amounts near the surface which has an effect that controls the evaporation speed of solvents and achieves excellent uniform & smooth surface. This effect becomes even more prominent in oligomer-based surfactants and it changes by molecular weight, compatibility with matrix resins, and the amount of additive.

Advantages	Disadvantage
Reduce orange peel Improve DOI Efficient against craters and pinholes Relatively polyvalent	Strong surface tension reduction Can decrease surface hardness for low molecular weight May provoke intercoat adhesion issue

Key Features of Fluorosurfactants Leveling Agents

Pure fluorocarbons are too strong and may provoke many defects. That is why this chemistry is often modified
Strong surface tension reduction, even more than silicone-based agents
May resist at higher temperature than standard silicon-based agents (over 150°C)
Usually more expensive than acrylates and silicones modified products
Fluorocarbon chemistry is often acrylate modified. These products can offer a polyvalent action, reducing the orange peel acting both on long waves and short waves, and improve the gloss and DOI

Selecting the Suitable Leveling Additive

Nowadays, you can easily find leveling agent chemistries for solvent-borne-, waterborne- and other coatings systems.

Waterborne paints
Waterborne paints tend to foam, mainly due to the presence of surfactants or other incompatible ingredients. It is beneficial to use defoamers in combination with a leveling additive or leveling agent with good defoaming capabilities. Once the foam bubbles have burst, the surface quickly smooths preventing the formation of dents and pinholes.

If you are struggling with controlling foam while targeting to achieve perfect leveling, then you might need to update the leveling agent with good defoaming or deaerating property.
» Find the suitable grade here offering dual benefit.

Powder Coatings
In case of powder coatings, acrylic-based leveling agents are preferable due to their low contamination tendency. Polyacrylates are added to the molten resin surface. These additives form a monolayer in the curing process to obtain the equilibrium surface chemical potential.

When the acrylate polymer reaches the surface, the polar skeleton is still retained in the molten resin, while the alkyl is escaping into the surrounding environment, providing a more stable equilibrium condition. At this time, the surface tension tends to be balanced due to the large concentration of molecules arranged in the direction of the whole surface.

In the most exigent end-uses, the best solution is often achieved by a combination of technologies, such as modified acrylates with modified silicones. The best leveling agent for your formulation will, of course, improve the leveling, without any influence on the other parameters and will not provoke any unwanted negative side-effect!

You have a large choice in the selection the leveling agent - explore our coatings material selector for tech profile, ask for samples or discuss your case with producer’s tech staff.

In general:

Amphiphilic molecules, derived from hydrocarbon-based hydrophobic groups, can lower aqueous surface tension from pure water’s 72 mN/m into the 30 mN/m range.
Polydimethylsiloxane hydrophobe-based materials lower surface tension into the 20 mN/m range.
Perfluoroalkyl surfactants into the 15-20 mN/m range.

This summary table compares the global tendency of each leveling agent’s chemistry and support you in finding the best leveling agent for your work:

Type of Leveling agent	Modified Acrylates	Modified Silicones	Modified Fluorocarbons
Anti-benard Cell effect	0	⭐ ⭐ ⭐	⭐
Anti crater effect	⭐	⭐ ⭐ ⭐	⭐ ⭐
Flow	⭐ ⭐ ⭐ ⭐ ⭐	⭐ ⭐	⭐ ⭐ ⭐
Leveling / Orange Peel	⭐ ⭐	⭐ ⭐ ⭐	⭐ ⭐
Slip	0	⭐ ⭐ ⭐	⭐
Substrate wetting effect	⭐	⭐ ⭐	⭐ ⭐ ⭐
Surface tension reduction	⭐	⭐ ⭐ ⭐	⭐ ⭐ ⭐
Risk of inter layer defects / contamination	No	High	Low
High temperature resistance	⭐ ⭐ ⭐	⭐ ⭐	⭐ ⭐

Some recommendation:

Always check all parameters when using a leveling agent, and not only the leveling and surface aspect. As surface active material, it can have an influence on the substrate wetting, the haze, the intercoat adhesion, or foam stabilization (especially in waterborne).

Do not hesitate in testing variation of a product: not only in the dosage, but also try different molecular weight, and product modifications (such as EO/PO for PDMS for instance). Some variations may better fit your system and improve the leveling agent compatibility, reducing the loss of gloss and haze negative effects.

Flow/Leveling Agents for Paints, Coatings and Inks

View a wide range of flow/leveling agents available today, analyze technical data of each product, get technical assistance or request samples.

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Optimal Selection of Leveling Agent for Paints and Coatings