The effect of particle hydrophobicity, separation distance and packing patterns on the stability of a thin film

Hydrophobic particles attached to bubble films in foams can increase the capillary pressure required to cause coalescence or bursting. Previous studies have considered the effects of changing particle spacing and contact angle in 2 dimensions (2D), but there are limitations to this approach; in 2D when the separation distance is zero and the particles are touching, the critical capillary pressure tends to infinity as there is no exposed film. In 3 dimensions (3D) spherical packing ensures that there are always exposed sections of film between particles even when they are close packed. Using Surface Evolver, the effects of contact angle and particle separation on the stability of a particle laden film were investigated in 2D and 3D. The 2D model was compared and validated with an analytical approach developed by Ali et al. [Ind. Eng. Chem. Res. 39 (2000) 2742-2745] and a 3D model was used to investigate the critical capillary pressures of square and hexagonal packing of monodisperse particles. It was found that when the stability of the film was compared with the area of film per particle both packing patterns have the same stability.