Surface Tension Gradients Induced by Spreading Antifoam

2 Surface Tension Gradients Induced by Spreading Antifoam 

Spreading from antifoam particle drags underlying liquid because dSVdy = l(AuylAx)x=o 

FIGURE 4.10 Foam film rupture caused by spreading from antifoam particle— Marangoni 

This mechanism was first proposed by Ewers and Sutherland [38]. These authors identified three categories of antifoam substance, which could, in principle, function by this mechanism. These are 

Here S and are defined for an aqueous foaming liquid by Equations 3.5 and 3.6 respectively. However these definitions can be readily generalised for non-aqueous systems by appropriate substitutions of the relevant surface tensions in those equations. This is exemplified for the case of natural gas-crude oil-antifoam systems in Section 10.4.1. 

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