Defoamer (defoamer, defoamer) of chemicals To understand how it works, we must first examine the foam structure. Foams are systems that consist of the dispersion of gas or liquid vapors in liquids. In foam, gas or vapors are surrounded by a spherical liquid layer. Pure liquids do not foam. In pure liquids (containing no active substance), the gas bubble rises towards the surface at a rate dependent on the bubble diameter and liquid viscosity, in accordance with 'Stoke's laws'. When the gas bubble reaches the surface, the thin liquid film surrounding the bubble flows downwards and the film gradually decreases in thickness and breaks up. This is called the 'Drain Effect'. A bubble of foam on the surface of pure water will explode in a short time like 10-² seconds.
Foam Cutter Types:
- Silicone Based Defoamer
- Oil Based Defoamer
- Organic Defoamer
- Water Based Defoamer
Foam Cutter Usage Areas:
- Antifoaming agents for biological treatments that do not harm aerobic bacteria
- Antifoaming agents for digesters that do not harm anaerobic bacteria
- Anti-foaming agents for biogas plants that do not harm anaerobic bacteria
- Food grade defoamers
- Defoamers for cooling towers
- Defoamers before ultrafiltration systems
- Defoamers for the cosmetics and detergent industry
- Defoamers for evaporation plants
Please get support from our engineers to determine the most suitable defoamer for your process.
In liquids containing active substance, immediately after formation, the bubbles are spherical and these spherical bubbles lead to stable foam and do not deform each other. As the bubbles climb the air interface, they are surrounded by a surface film called the lamella, which contains the active substance. When the bubble reaches the surface, the liquid flows down the surface film, the surface film becomes thinner, the gas bubbles come together more densely to form 'polyhedral' shapes.
The stability of the foam depends on the thickness of the solution film surrounding the air or liquid vapor. The stability of the foam is provided by the elasticity of the liquid film surrounding the foam. When the liquid film expands, this movement causes an intermolecular attraction on the surface and this increases the surface tension. This effect is called 'Gibbs Elasticity'. Another factor contributing to foam stability is the repulsive electrostatic forces between the ionic active substance molecules occupying the lamella. These reasons are the cause of an increase in surface tension. The goal is to achieve the lowest possible surface tension.
How Do Defoamers Work?
Chemical foam control agents (foam breakers) are called antifoam or defoamer. Antifoams prevent or delay the formation of foam. Defoamers are surfactants that destroy foam after forming. The function of degasser is to facilitate the rapid rise of microfoams to the surface.
The purpose of removing the foam is to lower the surface tension of the medium. Defoamers should have low surface tension so that they can reduce the surface tension of the environment and destroy the foam.
Because of these, they usually show the following three characteristics:
- Insolubility in the environment
- positive input coefficient
- positive diffusion coefficient
We can say that the defoamer enters the foaming medium when the input coefficient has a value greater than zero, and likewise, the diffusion coefficient must be greater than zero for diffusion to appear so that it can diffuse to the interface.
This means that for a material to be counted as an Antifoam, both the entry coefficient and the diffusion coefficient must be positive. Input coefficient, diffusion coefficient are factors that vary depending on the surface tension of the foaming medium -interface- defoamer. By calculating the values of these two factors, we can decide the validity of a substance as a defoamer.
Features of Antifoam Chemicals
Defoamers meet all expectations. "additive"and must overcome the foam stabilization mechanism. It must have limited solubility in the coating to be transported to the air interface.
The defoamer mechanism of antifoam chemicals (especially in water systems) can be explained as the addition of well dispersed hydrophobic particles. The defoamer acts as a carrier medium by transporting the particles into the foam lamella. On the one hand, the hydrophobic particles act as foreign particles in the hydrophilic liquid lamella and therefore contribute to the reduction of cohesive forces and, on the other hand, by trapping the active substances on their surface, thereby destabilizing the foam.
Foam stability is impaired by removal of free active substances from the bubble wall. Defoamer products actually do this by attracting the hydrophobic end of the active substance to their hydrophobic surface. As a result of the reduction of cohesive forces, the surface tension drops and the foam explodes on the surface of the coating.
As a result, in the light of the above mentioned features, we can list the features that a defoamer should have as follows:
- The surface tension of the defoamer must be lower than the surface tension of the solution.
- In solution, the solubility of the defoamer should be low.
- The defoamer should be easily dispersed in the solution.
- It should not react with the defoamer solution.
- It should have a high diffusion coefficient.
- It should have a high input coefficient.
- It should leave no residue, which is detrimental to the final product.
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