Micellization and Foamability of Sodium Laureth Sulfate and Polysorbate Surfactant Mixtures

Abstract

The micellization behavior and foamability of a mixture of anionic surfactant sodium laureth sulfate (SLES) and nonionic polysorbate surfactants commercially available as Tween series were investigated. The mole fraction and the structure of the hydrophobic part of various polysorbates affect the critical micellar concentration (CMC) and foam height and stability of anionic surfactant. Experimental values of CMC were determined by measuring specific conductivity at 25°C and foam height and stability by modified Ross–Miles method at 23°C. The negative deviation of the experimentally determined CMC from theoretical values for ideal mixed micelle indicate non-ideal mixing behavior due to synergism as a consequence of attractive interactions between the individual surfactants in formed micelles. Thus synergism increase with increasing of both the mole fraction and length of hydrophobic tail of examined Tween in SLES/Tween mixtures. Foam height and stability significantly decrease with increasing length of the hydrophobic tail of Tween surfactants and their mole fractions in the binary mixture.