Surface Tension Gradients Induced by Antifoamers

Many soHd particles with some degree of hydrophobicity have been shown to cause the destabilisation of foams, including hydrophobic sihca and poly(tetrafluoroethylene) (PTFE) particles. The PTFE particles exhibit a finite contact angle when adhering to the aqueous interface, and it has been suggested that many such hydrophobic particles can deplete the stabilising surfactant film by rapid adsorption, causing weak spots in the film. 

With particles containing rough edges, the situation is more complex, as demonstrated by Johansson and Pugh [32], using finely ground quartz particles of different size fractions, the surfaces of which had been hydrophobised by methylation. The results of these studies and others confirmed the importance of the size, shape and hydrophobicity of the particles on foam stability. 

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