Aqueous foams stabilized with particles and nonionic surfactants

The aqueous foams prepared by mixtures of Laponite particle and nonionic surfactant (C12E4, tetraethylene glycol monododecyl ether) were studied in detail. A synergistic effect on foam stability occurs and becomes more obvious with increasing C12E4 concentration. The synergistic effect mainly comes from the adsorption of particles on the bubble surface and the formation of a three-dimensional network in the coherent phase. The enhancement of the synergistic effect is attributed to the increased adsorption density of the particles. In addition, foams prepared by silica/C12E4 and Laponite/C12E23 dispersions were compared with Laponite/C12E4 foams for better understanding. For silica/C12E4 dispersions, the synergistic effect on foam stability is found at high surfactant concentrations and just results from the increased viscosity of the dispersions. No silica particles are adsorbed at the air–water interface within the synergistic range. For Laponite/C12E23 dispersions, no synergistic effect on foam stability is found. The modified Laponite particles cannot be adsorbed on the bubble surface because of their hydrophilicity. It is assumed that the differences in the foam stability of the three systems arise from the different adsorption of surfactants on the particles.