Application of defoamers in coatings: Popular science analysis
In the production and application of coatings, the foam problem has always been one of the
key factors affecting the quality and construction effect of coatings.
In order to effectively solve this problem, defoamers came into being as an important additive.
1. Definition and mechanism of action of defoamers
Defoamers, also known as antifoaming agents, are chemical additives used to reduce the surface
tension of liquids, inhibit the generation of foam or eliminate the generated foam.
In the field of coatings, the main function of defoamers is to prevent the generation of foam during
the production, storage and construction of coatings,
which may affect the fluidity, uniformity and final film quality of the coating.
The mechanism of action of defoamers mainly includes the following aspects:
Destroy foam stability: Defoamers can quickly destroy the film structure of foam, causing it to lose
stability and break.
Reduce surface tension: By reducing the surface tension of the coating, defoamers make bubbles
easier to break and dissipate.
Inhibit foam regeneration: Some defoamers can also form a protective film on the surface of the
coating to prevent new foam from forming.
2. Types of defoamers
There are many types of defoamers, which can be divided into the following categories according to
their chemical composition and mechanism of action:
Silicone oil defoamers: the most common type of defoamer, with excellent defoaming effect and
temperature resistance. Its main component is polysiloxane,
which can form a thin film in the coating and quickly destroy the surface tension of the bubbles.
Polyether defoamers: made of polyether compounds, with good compatibility, suitable for water-based
and oil-based coatings. Its defoaming effect is relatively mild
and suitable for use in coating systems with high requirements for foam control.
Fatty alcohol defoamers: made of natural or synthetic fatty alcohols, with good defoaming performance,
suitable for a variety of coating systems, especially solvent-based coatings.
The cost is relatively low, but the defoaming speed may not be as good as silicone oil and polyether defoamers.
Surfactant defoamers: eliminate bubbles by reducing the surface tension of the liquid. There are many types
and they need to be selected according to the specific coating formula.
Although the defoaming effect is good, it may cause foam recurrence in some cases.
Natural vegetable oil defoamer: extracted from vegetable oil, it is environmentally friendly and low in toxicity.
It performs well in water-based paints,
but the defoaming effect may not be as rapid as that of synthetic defoamers.
3. Application of defoamers in paints
Defoamers are widely used in paints, covering almost all types of paints, including water-based paints, latex paints,
powder paints and wood paints.
Water-based paints: Adding defoamers to water-based paints can effectively prevent the generation of foam,
protect the beauty of the paint, high temperature resistance and
other characteristics, and avoid environmental pollution.
Latex paint: Defoamers can not only eliminate foam in latex paints, but also inhibit the generation of new foams,
improve the dispersibility and film-forming quality of latex paints,
and enhance their scrub resistance, water resistance and other properties.
Powder coatings: Powder coatings dissolve each other due to heating during use, and are prone to foaming.
The addition of defoamers can effectively prevent the generation of foam and maintain
the beauty of the coating.
Wood coating: Defoamers can make wood coatings better reflect the texture of the wood surface, prevent foam
from affecting the construction effect of wood coatings,
and improve the gloss and strength of the paint film.
4. Precautions for using defoamers
When using defoamers, you need to pay attention to the following points to ensure its effectiveness and safety:
Read the product instructions carefully: understand the properties, uses and dosage of defoamers.
Stir well: Stir the defoamer well before use to ensure that its components are fully mixed.
Determine the dosage reasonably: According to the type of coating and the need for use, reasonably determine
the amount of defoamer input. In general,
the amount of defoamer is 1%~2% of the total
amount of coating, and the specific amount can be adjusted according to the actual situation.
Choose the right defoamer variety: Different types of coatings require defoamers of different types and performances.
Control the stirring speed and time: prevent excessive foaming.
Keep good ventilation: Defoamers generally have a certain volatility, and good ventilation should be maintained
during use to avoid inhaling their volatiles.
