Leveling agents used in coatings are generally classified into mixed solvents, acrylic acid, silicone, fluorocarbon polymers and cellulose acetate. Due to its low surface tension characteristics, leveling agents can not only help the coating to level, but may also cause side effects. During use, the main consideration is the adverse effects of leveling agents on the recoatability and anti-cratering properties of the coating, and the compatibility of the selected leveling agents needs to be tested through experiments.

1. Mixed solvent leveling agent

It is basically composed of high-boiling-point aromatic hydrocarbon solvents, ketones, esters or excellent solvents of various functional groups, and high-boiling-point solvent mixtures. When preparing and using, attention should be paid to its volatilization rate, volatilization balance and solubility, so that the coating has an average solvent volatility rate and solubility during the drying process. If the volatilization rate is too low, it will remain in the paint film for a long time and cannot be released, which will affect the hardness of the paint film.

This type of leveling agent is only suitable for improving the leveling defects (such as shrinkage, whitening, and poor gloss) caused by too fast drying of the coating solvent and poor solubility of the base material. The dosage is generally 2%~7% of the total paint. It will prolong the drying time of the coating. For room temperature drying coatings (such as nitro paint) that are prone to sagging when applied on the facade, it not only helps with leveling, but also helps to improve gloss. During the drying process, it can also prevent solvent bubbles and pinholes caused by too fast evaporation of the solvent. Especially when used under high temperature and high humidity climate conditions, it can prevent the paint film surface from drying out prematurely, provide a uniform solvent volatilization curve, and prevent the occurrence of white fog in nitro paint. This type of leveling agent is generally used in conjunction with other leveling agents.

2. Acrylic leveling agents

This type of leveling agent is mostly a copolymer of acrylic esters. Its characteristics are:

(1) The alkyl ester of acrylic acid provides basic surface activity;

(2) Its −COOH, −OH, and −NR can help adjust the compatibility of the alkyl ester structure;

(3) The relative molecular weight is directly related to the final spreading performance. Critical compatibility and the chain configuration of polyacrylate are necessary conditions for becoming a suitable leveling agent. Its possible leveling mechanism is mainly manifested in the later stage;

(4) It exhibits anti-foaming and defoaming properties in many systems;

(5) As long as there are a small number of active groups (such as -OH, -COOH) in the leveling agent, the impact on recoating is almost unnoticeable, but there is still the possibility of affecting recoating;

(6) There is also the problem of matching polarity and compatibility, which also requires experimental selection.

3. Silicone leveling agent

Silicones are a type of polymer with a silicon-oxygen bond chain (Si-O-Si) as the skeleton and organic groups attached to silicon atoms. Most silicone compounds have side chains with low surface energy, so silicone molecules have very low surface energy and very low surface tension.

The most commonly used polysiloxane additive is polydimethylsiloxane, also known as methyl silicone oil. Its main use is as a defoamer. Low molecular weight models are more effective in promoting leveling, but due to serious compatibility issues, they are often prone to shrinkage or inability to recoat. Therefore, polydimethylsiloxane must be modified before it can be safely and effectively used in coatings.

The main modification methods are: polyether modified silicone, alkyl and other side group modified silicone, polyester modified silicone, polyacrylate modified silicone, fluorine modified silicone. There are many modification methods for polydimethylsiloxane, but all of them are aimed at improving its compatibility with coatings.

This type of leveling agent usually has both leveling and defoaming effects. Its compatibility with the coating should be determined through tests before use.

4.Key points for usage

Choose the right type: Choose the right leveling agent according to the type and functional requirements of the coating. When choosing a leveling agent, its composition and properties as well as its compatibility with the coating itself should be considered; at the same time, various leveling agents or other additives are often used in combination to balance various issues.

Pay attention to the amount added: excessive addition will cause problems such as shrinkage and sagging on the coating surface, while too little addition will not achieve the leveling effect. Usually, the amount added should be determined based on the viscosity and leveling requirements of the coating, follow the instructions for use of the reagent, and combine the actual test results.

Coating method: The leveling performance of the coating is affected by the coating method. When using the leveling agent, you can use brushing, roller coating or spraying to give full play to the role of the leveling agent.

Stirring: When using the leveling agent, the paint should be fully stirred so that the leveling agent is evenly dispersed in the paint. The stirring time should be determined according to the characteristics of the leveling agent, generally not more than 10 minutes.

Nanjing Reborn New Materials provides various leveling agents including Organo Silicone ones and Non-silicon ones for coating. Matching BYK series.