Aqueous foams stabilized by n-dodecyl-β-d-maltoside, hexaethyleneglycol monododecyl ether, and their 1 : 1 mixture

Abstract

Aqueous foams stabilized by the non-ionic surfactants n-dodecyl-β-D-maltoside (β-C₁₂G₂) and hexaethyleneglycol monododecyl ether (C₁₂E₆) as well as by their 1 : 1 mixture were studied as a function of the total surfactant concentration from 0.1 to 10 cmc. Foamability and foam stability were measured with home-built winding equipment, the commercially available FoamScan, and a home-built foam conductivity apparatus (FCA), respectively. It was found that the foamability increases with increasing surfactant concentration for both the single and the mixed surfactant systems. On the other hand, at a fixed relative surfactant concentration (c/cmc) the foamability of β-C₁₂G₂ solutions was found to be much higher than that of C₁₂E₆ solutions, while the 1 : 1 mixture behaves like the pure C₁₂E₆. Measurements at different gas (N₂) flow rates have shown that the foamability decreases non-linearly with decreasing N₂ flow rate, which shows that foam generation and foam breakdown occur simultaneously. Regarding foam stability it was found that it also increases with increasing surfactant concentration. As was the case for the foamability, the stability of foams stabilized by β-C₁₂G₂ was much higher than that of foams stabilized by C₁₂E₆, while the foam stability of the 1 : 1 mixture was comparable to that of the pure C₁₂E₆. The foam results are discussed in the light of static surface tensions, dynamic surface tensions, and surface elasticities, which were measured for the single and the mixed surfactant systems.