The Krafft temperature of three anionic surfactants, that is, sodium lauryl sulfate (NaLS), potassium lauryl sulfate (KLS), and calcium lauryl sulfate (CaLS), have been determined in the presence of foam boosters such as lauric diethanolamide (LDEA), cocoamidopropylbetaine (CAPB), monoethoxylated cocomonoethanolamide (CMEA(EO)1), and cocomonoethanolamide (CMEA). The Krafft temperatures were depressed with the increase in the concentration of the foam boosters. The decrease in Krafft temperature was greater for the surfactant with bivalent counterions compared to the surfactant with monovalent counterions. CAPB was found to be the most efficient among the foam boosters in reducing the Krafft temperature of the surfactants studied.

The interactions between the anionic surfactant sodium dodecyl sulfate and various foam boosters such as cocodiethanolamide, cocoamidopropylbetaine, and monoethoxylated cocomonoethanolamide are investigated. Interfacial interactions between sodium dodecyl sulfate and foam boosters were assessed by the surface tension method. An increase in the mole fraction of foam boosters reduced the critical micelle concentration (CMC) of anionic surfactant. The strength of interaction for micellization (βM) and adsorption (β40) are calculated from surface tension studies. The zwitterionic foam booster cocoamidopropylbetaine showed strong synergistic interaction with sodium dodecyl sulfate for both adsorption and micellization.

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