New surfactant mixtures for fine foams with slowed drainage
We form and investigate foams stabilized by a triple surfactant mixture containing a nonionic alkyl polyglucoside (APG) in addition to the combination of ionic sodium lauryl-dioxyethylene sulphate (SLES) and zwitterionic cocamidopropyl betaine (CAPB) surfactants. APG improves the surfactants compatibility at alkaline pH. The addition of a readily biodegradable chelating agent methylglycinediacetic acid (MGDA) in the mixture contributes further for the excellent performance even in very hard water. Foam properties are analyzed and compared to those of the single components and to the binary mixture without APG. Foam drainage is successfully controlled by introducing additives suitable for the alkaline conditions: fatty alcohol and/or hydrophobically modified starch. Systematic model experiments are performed to characterize the surface tension and dilatational rheology, and thin films drainage. Slowed foam and thin films drainage is confirmed to correlate with the increased surface visco-elasticity in the presence of fatty alcohols. Temperature impact on the surface properties is used for fine tuning of the foam drainage.