Mechanism of Action of Paint Defoamers
Release Time:
2016-08-19
Source:
Mechanism of Action of Paint Defoamers
Coatings are a crucial surface finish in modern home decoration and furniture manufacturing, making their quality of paramount importance. During production and application, stirring can introduce air into the coating, leading to bubble formation. Defoamers for coatings are specifically formulated based on the mechanisms that cause foaming in coatings, and they effectively eliminate these bubbles. Below is a detailed introduction to coating defoamers.
1. Bubble formation and the mechanism of foam stabilization: During paint production, air can be entrained, leading to bubble formation; moreover, certain raw materials—such as surfactants and dispersants—can stabilize these bubbles.
Bubbles can also form during the application of coatings, primarily depending on the application method. For example, curtain coating can continuously entrain air into the coating film, and airless spraying is likewise prone to air entrapment; moreover, spraying under relatively low-humidity or high-temperature conditions readily leads to bubble formation.
Stable Foam Principle:
Marangoni effect (surface-active agents induce liquid flow that can counteract gravitational forces)
Electrostatic effect: The electrostatic repulsion generated by surfactants thickens the liquid film surrounding gas bubbles, thereby stabilizing them.
2. Mechanism of Action of Paint Defoamers
Antifoams can be added either before foam formation or after it has already formed: once added, the uniformly dispersed antifoam penetrates the elastic foam film and distributes throughout it, reducing surface tension and thereby causing the thin film to rupture.
A uniformly dispersed defoamer penetrates the foam lamella and forms a monomolecular film, reducing its adhesion and facilitating the rupture of the lamella.
Foam suppressants containing hydrophobic particles operate via a third mechanism. These hydrophobic particles, upon reaching the surface of the foam film, begin to adsorb surfactants at the film’s top. As the surfactant concentration gradually decreases, the foam collapses and ruptures.
