Why Use Wetting Agent

Aug 18, 2021

Floating and blooming, vertical surface construction will cause silk lines. During the drying process of the paint film, some insoluble colloidal particles are sometimes produced. The production of insoluble colloidal particles will lead to the formation of a surface tension gradient, which often leads to the generation of shrinkage holes in the paint film. For example, in a cross-linking curing system, the formula contains more than one resin. During the drying process of the paint film, as the solvent volatilizes, the resin with poor solubility may form insoluble colloidal particles. In addition, in formulations containing surfactants, if the surfactant is incompatible with the system, or as the solvent volatilizes during the drying process, its concentration changes, resulting in a change in solubility and the formation of incompatible droplets. There will also be a difference in surface tension. These may cause shrinkage.

In the process of coating construction and film formation, if there are external contaminants, it may also cause levelling defects such as shrinkage holes and fish eyes. These pollutants are usually oil, dust, paint mist, water vapor, etc. from the air, construction tools and substrates. The properties of the paint itself, such as construction viscosity, drying time, etc., will also have a significant impact on the final leveling of the paint film. Too high application viscosity and too short drying time usually produce a poorly leveled surface. Therefore, it is necessary to add a leveling agent to help the paint obtain a good leveling by adjusting some changes and the properties of the paint during the construction and film forming process. Types of leveling agents Leveling agents are roughly divided into two categories. One works by adjusting the viscosity of the paint film and the leveling time. Most of these leveling agents are high-boiling organic solvents or their mixtures. The other one works by adjusting the surface properties of the paint film. Generally speaking, the leveling agent refers to this type of leveling agent. This type of leveling agent migrates to the surface of the paint film through limited compatibility, which affects the surface properties such as the interfacial tension of the paint film, and enables the paint film to achieve good leveling.

According to the different chemical structure, there are three main types of this type of leveling agent: acrylic, silicone and fluorocarbon. ●Acrylic leveling agent Acrylic leveling agent includes pure acrylic leveling agent and modified acrylic leveling agent. Pure acrylic leveling agents include traditional non-reactive acrylic leveling agents and new reactive acrylic leveling agents containing tube energy groups. This is a type of acrylic homopolymer or copolymer with different molecular weights. This type of leveling agent only slightly reduces the surface tension of the paint, but it can balance the difference in the surface tension of the paint film to obtain a truly flat, mirror-like paint film surface. If the molecular weight is high enough, this type of leveling agent also has the effect of degassing and defoaming. The disadvantage of traditional non-reactive acrylic leveling agents is that high molecular weight products may produce haze in the paint film, and low molecular weight products may reduce the surface hardness of the paint film. Acrylic leveling agents containing reactive functional groups can well solve this contradiction. While providing good leveling properties, they will not produce haze nor reduce surface hardness, and sometimes increase surface hardness. The main varieties of modified acrylic leveling agents are fluorine modified acrylic leveling agents and phosphate modified acrylic leveling agents. Different from pure acrylic leveling agent, modified acrylic leveling agent can significantly reduce the surface tension of the coating, so that it will be used in a leveling condition, but it also has a tendency to stabilize the foam and affect the adhesion between layers.