Three-phase foams drainage

Macroscopic Observations of Three Phase Foam Structure. In Figures 2 and 3 are shown foam drainage results in the presence of Salem crude oil with the surfactants C. OS and C..AOS at 1 wt% NaCl. obtained from the transmitted light microscope. Surfactant chain length is clearly seen to be a significant factor (compare Figure 2 with Figure 3). 

Influence of Emulsion Film Stability. The stability of the emulsion drops inside three-phase foam systems has an influence on the foam stability. When the oil drops collect (flocculate) in the Plateau borders, the drops are compressed and give rise to the formation of emulsion films (Figures 1 and 2). If the emulsion films are stable, drops do not coalesce, and the foam stability is not affected. However, if these emulsion films are unstable, the oil drops coalesce in the Plateau borders and then, on further foam drainage, the large drops relocate, under the action... 

The capillary force will therefore act in a direction to cause enhanced drainage out of the foam film. The process of drainage will continue until the two three-phase contact lines at the particle surface are coincident, whereupon a hole will form in... 

The collapse of foam is attributed to (a) the diffusion of gas molecules from a small bubble with higher internal pressure to a large one with lower internal pressure or into the bulk gas phase surrounding the foam system, (b) coalescence of bubbles due to capillary flow that results in rupture of the lamellar film between the adjacent bubbles (usually slower than (a) and occurring even in stabilized foam system), and (c) rapid hydrodynamic drainage of liquid between bubbles that leads to rapid collapse of bubbles [35], In most nonrigid foam systems, all three mechanisms are operative simultaneously to some extent during the foam collapse process. 

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