Investigation of foam drainage using foam pressure drop technique

In the present work we have investigated the influence of surface shear viscosity and Plateau borders (PBs) radii (R) on drainage rate of foam, stabilized with SDS (producing Newton black films) or Triton X-100. In the foam generated with SDS the measured drainage rate agrees with that one calculated with Nguyenʹs equation [A.V. Nguyen, Liquid drainage in single Plateau border of foam, J. Colloid Interface Sci. 249 (2002) 194], when PBs radii varied from 20 × 10−6 to 85 × 10−6 m. In the foam produced with Triton X-100 the experimental foam drainage rate exceeded the calculated one in the range of R = (20–80) × 10−6 m. We also investigated the influence of foam column height and bubbles sizes on the inner collapse of foam, which increase the foam drainage rate. No influence of the pressure gradient on the PBs surface mobility was found when the gradient was varied 2–5 times. The foam drainage rate exceeds the calculated one from the Lemlich’ equation (i.e. experimental results contradict the channel-dominated regime). It was shown that the standard theories of Lemlich and Nguyen predict values of the volumetric velocity same as our model of independent channels does.