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Defoamer manufacturers explain: What is the defoaming mechanism of defoamers?
Release Date:
2020-12-24
Typical general‑purpose defoaming mechanisms include the Robinson mechanism and the Ross hypothesis. The Robinson mechanism serves as the foundation for the Ross hypothesis; it emphasizes that defoamers disrupt foam by promoting drainage and by leveraging the Marangoni effect to achieve defoaming. The Ross hypothesis, however, is based on the assumption that defoamer particles are insoluble droplets, whereas in reality some defoamers exert their action in a dissolved state. Consequently, the Ross hypothesis does not provide a comprehensive explanation of the defoaming mechanism.
Related to Defoamer The mechanism of action remains a subject of ongoing debate; based on previously proposed defoaming mechanisms, Defoamer manufacturer Here are the main types:
A generalized defoaming mechanism
Typical general‑purpose defoaming mechanisms include the Robinson mechanism and the Ross hypothesis. The Robinson mechanism serves as the foundation for the Ross hypothesis; it emphasizes that defoamers disrupt foam by promoting drainage and by leveraging the Marangoni effect to achieve defoaming. The Ross hypothesis, however, is based on the assumption that defoamer particles are insoluble droplets, whereas in reality some defoamers exert their action in a dissolved state. Consequently, the Ross hypothesis does not provide a comprehensive explanation of the defoaming mechanism.
The mechanism of action of polysiloxane defoamers
The representative defoaming mechanisms of polysiloxanes include the “bridging–spreading” mechanism, the “bridging–dewetting” mechanism, and the “spreading–liquid entrainment” mechanism. The “bridging–spreading” mechanism is based on the fundamental premise that polysiloxanes have relatively low surface tension and thus readily spread on liquid films; it emphasizes the deformability of defoamer droplets. However, this theory fails to account for the differences in defoaming performance between pure polysiloxanes and mixtures of polysiloxanes with solid particles. The “bridging–dewetting” mechanism focuses on the hydrophobic nature of polysiloxanes, yet it struggles to adequately explain the defoaming efficacy of highly viscous polysiloxanes. As for the “spreading–liquid entrainment” mechanism, it remains unverified, since certain observations indicate that polysiloxanes do not always spread across the bubble film surface, even so they can still effectively break bubbles.
Defoaming mechanism of hydrophobic solid particles
In foam systems, hydrophobic solid particles first adsorb the hydrophobic tails of surfactants, rendering the particles hydrophilic and thereby reducing the surfactant concentration in the bubble film and promoting foam breakdown. However, this defoaming mechanism fails to account for the action of other defoamers and is overly simplistic. Additionally, some foams rupture due to the shock generated by the spreading action of defoamers, the solubilization of surfactants that destabilizes the foam, or the disruption of the electrical double layer at the liquid–film interface by electrolytes. As these defoaming mechanisms illustrate, each defoamer emphasizes different aspects when acting on distinct foam systems; yet all achieve defoaming by undermining the factors that stabilize the foam.
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