Defoamer

Defoamer In our daily lives, in industry and even in nature itself, we frequently encounter foam; sometimes it entertains us, sometimes it troubles us. Have you ever wondered what foam is, why it forms and how it disappears? Foam mechanism consists of a mass of bubbles in which gas is well dispersed in a liquid. These gas bubbles created by the combination of surfactants, water and air appear as cleaning agents in our homes. Liquid detergents, laundry detergents and shampoos that we use for cleaning purposes in our homes work through this mechanism. As we see more foam while using these products, we become convinced that we are cleaning better. However, not every foam that forms makes us so happy. The presence of foam in industrial processes and its inability to be controlled brings serious problems. If the resulting foam cannot be properly controlled, it can cause the processing time to increase, the stability of chemicals to be affected, pump efficiency to decrease, finished product performance to fail to be standardized, equipment capacity to be reduced, and filling processes to be prolonged. Each problem directly affects the costs of facilities. Foam observed in facilities generally forms during blending and mixing processes, in circulating systems, during distillation, filtration, filling and transportation.

How Does Foam Form?

A good scientific theory that explains why some solutions foam excessively, others moderately, and many not at all has yet to be developed. Today, the most important problem with foaming theory is the incomplete explanation of physicochemical factors in different systems. However, two theories related to foam formation have been partially accepted. The first accepted theory regarding this matter is that pure liquids do not foam. The second accepted theory is that there is a connection between the foaming solution and the surface activity of the dissolved substance. Literature classifies foam systems to better explain the resulting foam systems. Non-Foaming Systems: Pure liquids do not form foam. Additionally, solutions with similar chemical structure and surface tension, and solutions of hydrophilic substances are classified as non-foaming systems. Temporary Foaming Systems: Obtained with solutions of substances that moderately reduce surface activity. Temporary foams can best be characterized by dilute solutions of short-chain aliphatic alcohols and acids. The foam lifetime varies depending on solution concentration. Persistent Foaming Systems: Only substances that reduce surface tension when diluted (materials with high surface activity) create persistent foam. Cleaning soaps and detergents used in our homes are examples of these structures.

Defoaming Mechanism

The most important effect of defoamers should be in reducing surface elasticity. Defoamers must exhibit a constant surface tension under stress. To do this, they must eliminate the effects of foaming agents on the surface. For this reason, it must have a very low surface tension coefficient on its own and spread over the film. Generally, silicone compounds with very low surface tension values such as 20 dyn/cm are more effective than other types of defoamers because they are not water soluble. They are used as defoamers in emulsion or solution form. It is known that quantities in the range of 1-60 ppm are extremely effective in defoaming. There are physicochemical properties that must be considered and directly affect defoaming performance in a defoaming mechanism. These are: Solubility: Many defoamers have low solubility in aqueous systems. For a more effective defoaming process, the amount of active substance must dissolve optimally in the solution. Droplet Particle Size: The force that allows the defoamer droplet to pass through the bubble wall increases as the defoamer particle size decreases. Presence of Hydrophobic Solids: Liquid/solid mixtures generally show more effective results than structures used alone. The hydrophobic solid particles contained in the defoamer can easily break the resistance by increasing efficiency. Shear Strength: This property is essentially dependent on the dispersion of solid/liquid particles and defoamer particle size. Repeated Foaming Effect: Repeated foaming effect is generally observed in continuous processes. By fixing the hydrophobic particle size, continuity of the defoaming effect can be achieved. This continuity of the defoaming effect can be measured through multiple agitation methods. Surfactant Concentration: A defoamer system having a high amount of surfactant concentration can weaken the defoaming effect, create an interface, and generate a foaming effect. Dissolved Salt Particles: The presence of a high amount of metal ions in the environment is a characteristic that reduces the efficiency of the defoamer. Counter ions encircle the polar ends in the surfactant molecule, weakening the electrostatic interaction of surfactant molecules.

What Affects Defoaming Performance?

There are areas where defoamers are used and environmental conditions are constantly changing. Defoamer products must be chemically incompatible with the resulting foam. The higher the performance a defoamer shows, the lower its compatibility with the system. The more compatible a defoamer is, the lower its performance. To determine the appropriate defoamer, the characteristics of the application environment must be considered. For this reason, the variety of defoamers is extensive. There are many defoamers with different functional structures and active amounts. The reason for this is that it varies depending on physicochemical conditions, environmental characterization and usage method. With the work of our R&D Center and our technical experience, we need to simply answer some questions to determine which defoamer will work best in your system. • What is the pH in the working environment? • Will temperature be used during application? • What is the determined solution concentration? • Are there mechanical speeds and revolutions in operating conditions? • What is the ionic character of the environment? • What is the viscosity of the system? • Are there volatile compounds in the system? • What class of foam forms in the system?

What Performance is Expected from Defoamers?

This is exactly the question that concerns us most and causes us to minimize our expectations. "What performance should I expect from a defoamer?" The product groups offered by our R&D Center have been developed to provide solutions to different problems. For this reason, your expectation is our solution. General performance criteria expected from a defoamer are: Rapid Instant Defoaming Capability: Classified as the performance of breaking foam instantly when added to the foaming system. This performance is called the "knockdown" effect.   Long-Term Durability: After the defoamer material is added to the foaming system, foam formation is prevented despite any type of mixing and rotation speeds for a long period. High Activity: Defoamers that show high performance despite low dosing. Low Viscosity: A physical property frequently expected in applications involving dosing and pumping systems. Temperature: Defoamers that operate at high and low temperatures are often preferred. Especially in continuous systems, even if the operation starts at 25°C, the system heats up as the temperature increases over time. Defoamers that operate over a wide temperature range are highly preferred for these systems. pH: Considering that the alkalinity of the water used in the facility constantly changes, defoamers that can work over a wide pH range are not affected by possible pH changes affecting the system and do not negatively impact processes. High Salt Concentration: Depending on facility and application differences, not every defoamer exhibits high performance in saline environments. For this reason, defoamer selection should be made based on environmental salt concentration. Solubility: Using defoamers that provide ease of dissolution even in different ionic characters directly affects both your shelf life and stability. Good Deaeration Property: Defoamers that perform air release have high defoaming power. Eda Kamertay Kurttay Researcher Latro Kimya