Читать книгу Additives for Water-borne Coatings - Wernfried Heilen - Страница 73

Molecular defoamers or gemini surfactants are a new class of defoamers. Like surfactants, molecular defoamers have pronounced surface active properties and the molecules orientate themselves at the surface of foam lamellas. The foam lamella is destabilised by the molecular defoamer and destroyed. In contrast to all other defoamer active ingredients, molecular defoamers do not act via their incompatibility in the system like an oil droplet. The defoaming mechanisms, described in the previous section, cannot therefore be applied to molecular defoamers.

Molecular defoamers are also very effective at controlling micro-foam because they are able to migrate into bubbles and aid in deaeration.

The use of a molecular defoamer as an antagonistic surfactant or polymer is one answer to today’s needs concerning the formulation of modern water-borne coatings and inks. This type of product boosts the efficiency of the defoaming process and can therefore be used at low dosages, as well as in combination with various classes of defoamers, such as mineral oil-based, silicone-based and water-borne emulsion types.

Molecular defoamers can be used in UV coatings, furniture coatings, automotive coatings, and printing inks [10] [11].