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How much do you know about the characteristics of common antifoaming agents?
Release Date:
2023-02-28
Foam is inherently very unstable; for example, when a liquid is stirred, foam forms but disappears as soon as the agitation ceases. However, in industrial processes, the presence of foam‑stabilizing substances makes it considerably more difficult for the foam to dissipate on its own. The purpose of adding a defoamer is precisely to eliminate the stable foam generated by these stabilizing agents.
Foam is inherently very unstable—just as stirring a liquid creates foam that dissipates once the agitation stops. However, in industrial processes, the presence of foaming agents makes foam remarkably persistent, rendering it difficult for the foam to disappear on its own. To address this, defoamers are added to break down the stable foam generated by these agents. Yet with so many defoamer products available on the market today, choosing the right one can be a daunting task. In this article, we’ll introduce several common types of defoamers and highlight their key characteristics.
Applications of Common Antifoaming Agents
1. Natural oil-based defoamers:
The main components of natural oil-based defoamers include various animal and vegetable oils—such as cottonseed oil, castor oil, and coconut oil—as well as animal fats like lard and tallow from cattle and sheep, and plant and animal waxes, including palm wax, beeswax, and spermaceti.
Advantages of this type of defoamer: it is low-cost and easy to use, effective under both acidic and alkaline conditions, and exhibits excellent heat resistance.
Drawbacks: If not stored properly, it can easily degrade, leading to an increase in acid value. Moreover, this type of defoamer exhibits poor compatibility and delivers suboptimal performance against dense, persistent foam, making it unsuitable for industries with stringent requirements on the appearance of finished parts.
2. Alcohol-based defoamers:
Common branched‑chain alcohols used as defoamers include diethylhexanol, isooctanol, isoamyl alcohol, and diisobutyl methyl alcohol. These defoamers are linear molecules that are strongly hydrophobic and weakly hydrophilic; their defoaming performance depends on their solubility and diffusion rate in the foaming liquid, making them most effective in aqueous systems.
3. Polyether-based defoamers:
These defoamers are prepared by adding propylene oxide, or a mixture of ethylene oxide and propylene oxide, to glycerol as the initiator, followed by addition polymerization. They exhibit poor hydrophilicity and low solubility in foaming media; however, their foam‑suppressing efficacy surpasses their defoaming performance, offering excellent foam‑inhibition properties. As a commonly used antifoam agent, they are well suited for incorporation into the basal medium to curb foam formation throughout the fermentation process.
4. Organic compound defoamer:
Organosilicon compounds used as defoamers are primarily silicone polymers, specifically polydimethylsiloxane, also known as dimethyl silicone oil, methyl silicone oil, or polysiloxane. They exhibit excellent foam‑breaking and foam‑suppressing properties, with low solubility in water and most common oils yet high surface activity. Their backbone consists of siloxane linkages, making them nonpolar molecules that are incompatible with polar solvents such as water and have only limited affinity for typical oils; consequently, they effectively defoam a wide range of gaseous media.
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