Do you know how to choose the appropriate leveling agent based on the properties of the formula and the desired performance of the leveling agent? If you are unsure or want to delve deeper, then let's take a look with the editor of Jianyi Chemical.
1. Water based coating system:
The water-based coating system is divided into water-soluble system and latex system.
In water-soluble systems, it is necessary to strongly reduce the surface tension of the system. Commonly used leveling agents include fluorocarbon leveling agents and organosilicon leveling agents, which play the same role as their application in solvent based coating systems. Of course, if a truly smooth surface is required, acrylic leveling agents for water-based systems are necessary.
For latex systems, the film-forming mechanism is completely different, and viscosity does not change with solvent evaporation. The coating leveling agent used in the formula may improve the substrate wettability of the coating, while acrylic leveling agent can improve the smoothness of the paint film. However, the main flowability of the coating is mainly controlled and adjusted by adding rheological agents.
2. Solvent coating system
Acrylic leveling agents are commonly used in primer and intermediate coat formulations. If degassing and substrate wetting are required, it is advisable to choose medium or high molecular weight acrylic leveling agents. In primer, if stronger substrate wettability is required, it is recommended to use organic silicon leveling agents and modified acrylic leveling agents that can significantly reduce surface tension (such as fluorine modified acrylic leveling agents and phosphate modified acrylic leveling agents). If organic silicon leveling agents and fluorine modified acrylic leveling agents have side effects such as foam stabilization and affecting interlayer adhesion, phosphate modified acrylic leveling agents should be used.
In the formulation of topcoat and transparent paint, the requirements for the appearance of the paint film are relatively high. Generally, low-molecular-weight acrylic leveling agents can be used to achieve good leveling performance and avoid fogging in the paint film. In cross-linked curing systems, the use of acrylic leveling agents containing reactive functional groups often results in better leveling performance and improves the physical and chemical properties of the paint film. If better fluidity, smoothness, and scratch resistance are required for the paint film, organic silicon leveling agents are necessary. In this case, organic silicon leveling agents are generally used in combination with acrylic leveling agents.
It should be pointed out that during vertical surface construction, the organic silicon leveling agent provides leveling performance while effectively reducing the tendency of coating sagging. In addition, silicone leveling agents should be used with caution in the formulation of metallic glitter paint, as they may cause uneven arrangement of flake aluminum pigments and result in uneven paint film color.
3. Powder coating system
The leveling process of powder coating is divided into two stages. The first stage is the melting of powder particles, and the second stage is when the powder particles melt and flow into a smooth paint film. Powder coatings do not contain solvents and do not generate surface tension gradients during the film-forming process. Leveling is more related to the wettability of the substrate.
Powder coatings generally use acrylic leveling agents. If the leveling agent is in liquid form, it usually needs to be pre made into a masterbatch before use. There are also acrylic leveling agents made into powders, specifically used for powder coatings. These products adsorb liquid acrylic leveling agents onto silica powder, and some low-grade leveling agents are adsorbed with calcium carbonate.
If powder coatings require smoothness and anti scratch properties, organic silicon leveling agents should be used. There are already organic silicon leveling agents specifically used for powder coatings that have been made into powders. Be careful to avoid the formation of shrinkage when using organic silicon leveling agents.
