替换城市 Principle and influencing factors of special No Foam agents for paints(2)

viscosity-reducing

powder

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 No Foam 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.

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.

wetting

Influencing factors of special defoaming agents for paints:

matte

agent

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.

Defoaming mechanism of hydrophobic solid particles
Hydrophobic solid particles in the foam system will first attract the hydrophobic end of the surfactant, making the hydrophobic solid particles become hydrophilic, thus reducing the concentration of surfactant in the foam film and promoting the foam to burst. This defoaming mechanism cannot explain the action mechanism of other defoaming agents, which is too one-sided. [4] Other reasons for the bursting of foam are the impact caused by the expansion of defoamer, the solubilization of surfactant and the collapse of electrolyte, and the bursting of electric double layer on the liquid film surface. [4] It can be seen from the above defoaming mechanisms that each defoamer has different emphasis on different foam systems, but defoaming is achieved by destroying the stability factors of foam

Effects of other additives

Most surfactants used in coatings tend to be functionally incompatible with No Foam. 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.