Webster’s dictionary defines foam as “A light, frothy mass of fine bubbles formed in or on a surface of a liquid.” Foam is further described as “a stabilized froth produced chemically or mechanically.” These descriptions hold true when discussing foam entrapped in coatings. When discussing coatings, foam is further defined as the dispersion of a relatively large volume of gas (air) in a small volume of liquid. In whichever way that foam is defined or described, it is a serious problem in both the wet and dry state of the coating when it is not removed. Foam that remains in the dried coating film leads to detraction in the coating properties, which in turn can result in premature coating failure and catastrophic effects. This article will show how a class of molecular defoamers proves to be a solution to removing foam from coatings in an effective, efficient and persistent manner. We will first review the causes of foam, discuss the typical components in a defoamer, explain how defoamers work in the coating system and then show examples of the effectiveness of defoamers that contain a molecular-containing active compared to control defoamers that do not contain the molecular active in their composition.
There is much literature discussing the differences between antifoams, defoamers and deaerators. Acceptable definitions are that an antifoam is an ingredient that prevents or retards the formation of foam, a defoamer acts on foam after it has been formed and reduces or eliminates it, and a deaerator aids in intensifying bubble coalescence to accelerate foam release. In reality, an additive made to reduce and eliminate foam works in multiple ways and it becomes difficult to classify the additive, therefore in this article, the term defoamer will be used to describe the additives discussed.