Common problems in the use of defoamers
During the use of defoamers, you may encounter many different problems. So what are the common problems in the use of defoamers? Let’s take a look together.
Turbidity problem
The main components of defoamers are generally hydrophobic particles, silicone oil and emulsifiers. Hydrophobic particles absorb silicone oil, so that silicone can achieve the maximum effect with as little as possible. Silicone oil, as the main defoaming medium, has a very small surface tension and is neither lipophilic nor hydrophilic. It is suspended in the system. When the defoamer exists in the middle of the foam wall, it displaces the oil and water phase to produce a defoaming effect. At the same time, a small amount of silicone oil is consumed. When the silicone oil outside the hydrophobic particles is completely consumed, the foam system becomes turbid. Therefore, the different amounts and colors of hydrophobic particles, silicone oil, and emulsifiers used in defoamers result in different performances of defoamers. When the defoaming effect of the defoamer is good and the anti-foaming time is long, turbidity generally does not occur in the system.
Floating oil problem
Since the defoamer is not dissolved in the system but dispersed in the system, the uniformity of the dispersion of the defoamer in the system is crucial. When the defoamer is evenly dispersed in the system, it has little effect on the transparency of the system, and it takes a long time to aggregate into larger particles, and it can remain in the system for a long time; when the defoamer is not evenly dispersed in the system, but agglomerated into many small particles, it will affect the transparency of the system on the one hand, and shorten the time for the defoamer to aggregate into large particles on the other hand, which leads to turbidity after the defoamer is added to the system, and floating oil every other day. In order to avoid floating oil, the following methods can be adopted: move the order of adding the defoamer forward; dilute it before adding it to the system, and the diluent can be water or a surfactant in the system.
Foam suppression time problem
The properties of silicone oil in defoamers determine the foam suppression time of defoamers, and the content of silicone oil determines the consumption cycle of defoamers in use. Too little silicone oil will make the defoaming performance of defoamers fail to meet the required value, and too much silicone oil will affect the performance of defoamers and reduce the defoaming property of defoamers; the particle size of defoamers determines the filterability of defoamers. Too large a particle size may cause defoamers to be easily filtered, resulting in floating oil, which affects the foam suppression; stirring time is also an important indicator of the foam suppression ability of defoamers. Insufficient stirring may cause turbidity, floating oil, weakened defoaming ability, and shorter foam suppression time.
Failure problem
Acid and alkali stability. Silicone oil can destroy the surface tension of liquids and play a role in eliminating foam. If the defoamer has poor acid and alkali resistance, it will cause the silicone oil to decompose, thereby reducing the defoaming ability or even failure. Adding silicates to the system generally inhibits its decomposition; defoamer solubility. Certain chemical components make silicone oil dissolve into the system, so that the defoamer no longer has a defoaming effect, but exists in the system as a surfactant, and the foam in the system is higher than when no defoamer is added.
