Contact Persons: A. Zamanis [agzamanis@yahoo.gr]

The present project (Figure 1) is related to a novel method for the determination of liquid surface tension and of stability of gas / liquid interfaces encountered in foams. The method is based on accurate measurements of electrical conductivity of liquid bridges created between two vertical electrodes. This double determination (surface tension and layer stability) allows the evaluation of foam forming ability and stability in time, with significantly lower costs (over existing techniques) and remarkable ease.

Figure 1: Device for the determination of liquid surface tension and stability of gas / liquid interfaces in foam applications.

Surface tension measurement (Figure 2): At first, the electrical conductivity of the liquid bridge is measured during the increase of the distance between electrodes. Then, the surface tension of the liquid is calculated accurately by solving the Young-Laplace and Laplace equations. The lower the surface tension, the more easily the foam would be formed and the more stable it would be over time.

Figure 2: Surface tension measurements.

Study of the stability of liquid / gas interfaces in foam (Figure 3): An air bubble is created inside the liquid bridge and the electrical conductivity of the bridge is measured during the reduction of the volume of liquid. The stability of the film is directly related to certain characteristics of the curve of the electrical conductivity over time, allowing the evaluation of foam stability.

Figure 3: Study of the stability of liquid / gas interfaces in foam.