A new method for studying foam stability

Direct measurement of the transversal elasticity modulus of foam films

“…The results are presented in Figures 1 and 2, where well pronounced maxima can be seen near the CMC, as predicted by the above theory. It is of interest that the maxima are located approximately at the same place on the concentration axis as the maxima of foaminess and foam stability, [1][2][3] although the mechanism of elasticity is different for closed and completely open (as in this work) films. These similar locations of the maxima are explained by the leading role of the CMC in both the cases.…”

“…Earlier, [1][2][3] we reported experimental evidences for the sharp maxima of foaminess and foam stability near a critical micelle concentration (CMC). The explanation was given only recently 4 by analysing the behaviour of the film elasticity modulus as a function of concentration.…”

“…The foam film thickness was measured optically as described elsewhere. 2 To evaluate the transversal elasticity modulus, the film thickness was measured in the foam column at heights H 1 = 50 mm and H 2 = 79 mm, and the following equation was used:…”

Elasticity modulus of multicomponent thin liquid films

“…As the film elasticity modulus is responsible for the foam stability, one can expect a maximum of foaminess and the foam stability near the critical micelle concentration. Observations of this kind were reported previously, [7][8][9][10][11] but no explanation of this phenomenon was given until now. We can see that the above theory satisfactorily explains the existence of maxima for foaminess and foam stability.…”

“…Considering a film as an incompressible condensed system, volumes n i are assumed to be constant. In this approximation, concentration c j can be excluded from independent variables, and, accounting for (7), the known thermodynamic expression for the chemical potential differential can be written as Putting (12) in (10) leads to the expression where is evident to be the total film thickness (including adsorbed layers at the two equimolecular surfaces). In the above approximation, the total film volume Ah t is constant, which yields the additional [to equation (3)] relationship…”