Study of syneresis in thin foam layers by creating pressure drops in the liquid phase

The method of creating pressure drops in liquid phases of foams (foam pressure drop technique) is employed to study the influence of Plateau-Gibbs border radius and surface viscosity on the velocity of liquid flows through foams. Sodium dodecyl sulfate-stabilized foams with Newtonian black films and foams stabilized with 9,6-ethoxylated nonylphenol (Triton X-10 0) are investigated. A method is developed for determining the velocities of nonstationary syneresis in local layers of foams. The measured flow velocities correspond to those calculated through the Nguyen equation for sodium dodecyl sulfate solution foams with constant curvature radii and for local layers of foams at curvature radii varying in the range of 20–80 fum and variable pressure drops. In Triton X-100 solution foams, experimentally measured syneresis velocities are higher than those calculated by the Lemlich and Nguyen equations but agree with the velocities calculated via the Koehler equation at permeability K ₀ ⁿ varying in the range of 0.5 × 10^-3-2 × 10^-3 under the assumption that the key factor is the hydrodynamic resistance in foam knots.