Properties of aqueous foams stabilized by dodecyltrimethylammonium bromide.

Foamability, foam stability and the liquid volume of aqueous foams stabilized by dodecyltrimethylammonium bromide (C(12)TAB) are studied. The foams are generated with a sparging method at different gas flow rates and surfactant concentrations. It is found that at concentrations ccmc drainage dominates foam destruction while at c<cmc additional processes lead to a dramatic decrease in foam stability. Qualitatively similar results are obtained with the Ross-Miles (pouring) method and the winding (shaking) method, respectively. Increasing the gas flow rate of the sparging method at a fixed surfactant concentration, one observes a decrease in the time required for the production of 60 ml foam, while the liquid volume of the generated foam increases. On the other hand, an increase of the surfactant concentration at a fixed gas flow rate leads to an increase in the required foaming time with a plateau at ccmc, while the liquid volume of the generated foam decreases. Finally, the influence of small impurities is also tested and it is found that small amounts of impurities ("as received sample") lead to a significant increase of both the foamability and the stability of foams stabilized by C(12)TAB. The obtained results are discussed in terms of the different processes leading to foam destruction and a comparison between the three different methods is made. Whenever possible and feasible, the correlation between single surfaces, single foam films and foams is addressed.