Advantages and Selection of Defoamers
Release Time:
2016-06-27
Source:
Advantages and Selection of Defoamers
Defoamers are widely used across various industries, primarily because they offer the following four key advantages during application:
1. Rapid defoaming: After application, it quickly eliminates foam, thereby reducing the environmental impact of harmful substances. During the defoaming process, it delivers swift and effective results, and post-application it also helps to suppress foam formation, enhancing overall performance.
2. Simple to use: It is extremely easy to operate—simply place it in water, and it is ready for use. Moreover, it is widely employed in nonionic surfactants, helping to enhance the efficiency of industrial production.
3. Wide range of applications: During operation, it can be used in a variety of environments without being rendered inoperable due to environmental factors, and is suitable for use in high-temperature and high-pressure conditions.
4. Safe Storage: Even when not in use, the product can be stored safely for extended periods without sustaining damage, effectively eliminating surface foam on items and enhancing overall performance.
Foam formation is usually triggered by external forces, with surfactants in the solution generating foam at the liquid–air interface and causing it to rise, or with colloidal substances such as gelatin and proteins forming films that trap gas and create bubbles. Defoamers are substances added during production processes that reduce surface tension and eliminate foam. To use defoamers effectively: select a defoamer that is specifically suited to the application; understand the operating environment, temperature, pH, and the foaming medium. Conduct small-scale trials first, followed by pilot-scale tests, to determine the optimal product and dosage. If layering occurs, stir thoroughly before use; even when no layering is observed, always stir well prior to application. Do not dilute the defoamer arbitrarily; if dilution is absolutely necessary, do so only under guidance and using a concentrated aqueous solution.
When selecting an antifoam agent, the following criteria must be met:
1. Insoluble or poorly soluble in the foaming liquid
To rupture bubbles, defoaming agents must concentrate and accumulate at the bubble film. For bubble-rupturing agents, this concentration and accumulation should occur instantaneously; for foam-inhibiting agents, such a state should be maintained continuously. Therefore, defoaming agents in the foaming liquid are typically in a supersaturated state, which is readily achieved only when the agent is insoluble or poorly soluble. Only insolubility or poor solubility facilitates aggregation at the gas–liquid interface, promotes enrichment at the bubble film, and enables the agent to exert its effect at low concentrations. For defoamers used in aqueous systems, the active ingredient molecules should exhibit strong hydrophobicity and weak hydrophilicity, with an HLB value in the range of 1.5–3, in order to achieve optimal performance.
2. Surface tension is lower than that of the foaming solution.
Only when the intermolecular forces among defoamer molecules are weak and the surface tension of the defoamer is lower than that of the foaming liquid can the defoamer particles penetrate and spread across the bubble film. It is important to note that the surface tension of the foaming liquid is not the surface tension of the solution itself, but rather the surface tension of the foaming aid solution.
3. Exhibits a certain degree of affinity with the foaming liquid.
Since the defoaming process is essentially a competition between the rate of foam collapse and the rate of foam formation, the defoamer must be able to disperse rapidly in the foaming liquid so that it can quickly exert its effect over a broad area. To ensure rapid diffusion, the active ingredients of the defoamer must exhibit a certain degree of affinity for the foaming liquid. If the active ingredients are too亲 (affine) to the foaming liquid, they will dissolve; if they are too疏 (repellent), they will be difficult to disperse. Only when the affinity is appropriately balanced will the defoamer perform effectively.
4. Does not undergo a chemical reaction with the foaming liquid.
The defoamer reacts with the foaming liquid, resulting in a loss of defoaming efficacy on the one hand and the potential formation of harmful substances that can inhibit microbial growth on the other.
5. Low volatility and long duration of action.
First, it is necessary to determine whether the system requiring an antifoam agent is water-based or oil-based. For example, in the fermentation industry, oil-based antifoams—such as polyether-modified silicones or polyether-type formulations—are appropriate, whereas the water-based coatings industry calls for water-based antifoams, typically silicone-based ones. Once the appropriate antifoam has been selected, its recommended dosage should be compared with the reference price to identify the most suitable and cost-effective product.
