films (CBF), and Newton black foam films (NBF). Foaming prop-
These different types possess significantly different kinetic erties were investigated at 20 and 28ΠC where DMPG is in the (e.g., drainage) and thermodynamic (e.g., stability) propergel and liquid-crystalline states. Higher conductivity signals were ties (5-8, 14, 43).
observed at the higher temperature where DMPG was in the liquid-The principal differences in properties of the different crystalline state, which is indicative of wetter or more stable foams under these conditions. This effect was observed independent of foam film types may be summarized as follows. It is estabfoam film type. However, for a given phase state, the type of lished that the DLVO theory of colloid stability is also valid foam films formed significantly influenced the stability and rate for TFFs and describes their stability (4, 5, 9) in terms of drainage of the foam. Indeed, the water content of the foams, of a balance between the Van der Waals attractive forces, obtained under conditions for formation of different foam films, electrostatic repulsion forces between the two foam film suris ranked in the order TFF ΓΊ CBF ΓΊ NBF. When the temperature faces, and the external pressure that promotes foam film was increased to 28ΠC (i.e., in the liquid-crystalline state), CBF drainage. However, the film thickness-electrolyte concenand NBF showed a slight decrease in film thickness and an intration dependence deviates from that predicted from DLVO crease in film lifetime and surface molecular diffusion coefficient theory for the thinner, black foam films, where additional in the adsorbed layer. It is likely that the fluidity of the interfacial components of the disjoining pressure (e.g., steric, hydralayer is an important factor contributing to DMPG foam stabilization) can appear.
tion.