替换城市 Principle and influencing factors of special Free of silicone defoamers agents for paints(2)

surface

agent

UV

The larger the molecular weight, the stronger the control ability of its surface state, and the better its skid resistance and adhesion resistance, such as the 1070 and 1071 series products of the friction chemical industry.
There are two methods for bonding modified polyester or polyether to siloxanes: one is a silicon oxygen bond; The other is silicon carbon chains, which generally have less thermal stability and water resistance than the latter.
The compatibility of polyether and polyester modified siloxanes with resins has been greatly improved, reducing surface tension, controlling surface flow, increasing slip resistance, anti shrinkage, and anti adhesion. Some products also have interlayer adhesion issues. In particular, polyether modified polysiloxanes have poor thermal stability and are prone to foam stabilization. It is important to pay attention to the negative effects of these products when applying them.

chemical

powder

dispersant

Good paint defoamers not only have a good defoaming effect in paint systems, but also maintain defoaming ability at room temperature and under heating environments. In addition, it cannot be compatible with foam system. If the compatibility is good, it will help to produce foam. While the paint Free of silicone defoamers has good dispersibility in the foaming system, specifically refers to the uniform and smooth diffusion of the defoamer on the surface, which can cover the foam to achieve the elimination effect. Its working principle is to reduce the surface tension of the liquid around the foam, so that small foam can gather into large foam, and finally foam will burst.

Influencing factors of special defoaming agents for paints:

Elimination of foam
(1) Physical methods
From the physical point of view, the methods to eliminate foam mainly include placing baffle or filter screen, mechanical agitation, static electricity, freezing, heating, steam, radiation, high-speed centrifugation, pressure reduction, high-frequency vibration, instantaneous discharge and ultrasound (acoustic liquid control). These methods promote the gas transmission rate at both ends of the liquid film and the liquid discharge of the bubble film to varying degrees, making the stability factor of foam less than the attenuation factor, As a result, the number of foam gradually decreased. However, the common disadvantage of these methods is that their use is strongly restricted by environmental factors, and the defoaming rate is not high. The advantages are environmental protection and high reuse rate.

surface tension

替换城市  The level of coating surface tension has a significant impact on defoaming agents. The surface tension of defoaming agents is lower than that of coatings, otherwise they cannot have defoaming and antifoaming effects. The surface tension of a coating is a variable factor, so when selecting defoamers, it is necessary to maintain a constant surface tension, taking into account the surface tension variation factor.

Effects of other additives

Most surfactants used in coatings tend to be functionally incompatible with Free of silicone defoamers. In particular, emulsifiers, wetting and dispersing agents, leveling agents, thickeners, etc. can have an impact on the effectiveness of defoamers. Therefore, when coordinating various additives, it is necessary to pay attention to the relationship between different additives and select a good balance point.