Complete list of defoamers and foam suppressants for coatings

Curtain coating can continuously draw air into the coating, and airless spraying can also easily draw air in. Spraying construction under relatively low humidity conditions or high temperature conditions can easily generate bubbles.

1. Why do water-based coatings bubble?

Answer: Because surfactants, dispersants, solvents, and resins themselves all have the ability to form and stabilize bubbles; Pure water (or any pure liquid) will not produce foam.

2. How to conduct a test to control foaming?

Answer: Although theoretical calculation methods can be used to determine the effectiveness of controlling bubbles in a certain chemical mixture, they cannot be used to predict its persistence, side effects, difficulty of mixing, etc. Therefore, it is recommended to use the "post addition method", which involves selecting coatings without defoamers as control samples, subjecting them to shear, oscillation, and thermal aging, and evaluating them after coating. Using this method may yield more specific data.

3. What are the adverse side effects of defoamers?

Answer: Although the amount of defoamer used in coatings is very small, usually added at 0.1% to 1% of the total weight of the formula, improper use of defoamers can lead to shrinkage, shrinkage, fish eyes, poor pigment acceptance, blooming, floating color, silk lines, moon shadow stripes, and other adverse effects. The so-called improper use refers to the incorrect selection of defoamer type, insufficient or excessive dosage.

4. How to deal with coating defects?

Answer: Correct it by adjusting its formula. Generally, other additives should not be used to control side effects. For example, if fish eyes (sometimes considered shrinkage) appear, the variable factors in the formula should be carefully examined, and the types, concentrations, and addition methods of each component in the formula should be adjusted, rather than using anti shrinkage agents without consideration. Following the correct manufacturing steps and using appropriate concentrations of suitable defoamers should not result in these coating defects.

5. Why is it recommended to use more than one defoamer in the formula?

Answer: A single type of defoamer can either control the foam more effectively in the manufacturing process or control the foam more effectively in the coating construction. This is a general rule. Occasionally, the same defoamer is used in both grinding and painting stages, but to achieve the best results, the method of using silicone defoamers in grinding and non silicone defoamers in painting is always adopted. The synergistic effect plays a role here.

6. Why should we recommend using defoamer products containing organic silicon?

Answer: Defoamer products containing organic silicon are the most persistent (referring to modified organosilicon, not simply dimethyl polysiloxane liquid). Proper selection and addition have almost no adverse effect on the acceptability of pigments, at least less than the impact of most non organic silicon products. Throughout the manufacturing process, durability may be required during storage, high shear flow, or roll coating construction.

7. What is the recoating adaptability of defoamers containing organic silicon?

Answer: If the product containing organic silicon is selected appropriately and the dosage and addition method are correct, its recoating adaptability is not a problem.

8. Why aren't laboratory screening results always correct for factory applications?

Answer: The most important reason is that it is not possible to fully simulate actual manufacturing conditions in laboratory experiments. The laboratory screening process should be as close as possible to the manufacturing process, and strict adherence to process requirements and quality control should be implemented during the manufacturing process.

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