Abstract:The correlation between the phase behavior of aqueous solutions of nonionic surfactants and the removal of oil from fabrics has been determined. Model washing experiments with pure and technical grade nonionic surfactants indicated that, in the dispersion ranges of liquid crystals, oil removal is substantially more temperature-dependent compared to micellar or surfactant liquid phases. In this phase region, interfacial tension does not seem to play a substantial role. The results are discussed in terms of the macroscopic properties of mesophases.
Neutron scattering is used to look at the structure of aggregates made of silica spheres flocculated with cationic surfactants. With single-chain surfactants, the structures show no local order, but on a certain length scale self-similar behavior is observed and is characterized by an apparent fractal dimension. It is not affected by changes in the surfactant's chain length, but it increases as a function of the surfactant concentration. With a double-chain surfactant, reordering to a liquidlike structure and redispersion are observed. We consider the main features of this system, namely, charge neutralization and the heterogeneity of the adsorbed surfactant layer, and discuss the implications for the formation and structure of these aggregates.
Synopsis Oil-in-water emulsions stabilized with nonionic emulsifiers change to water-in-oil emulsions as the temperature rises when the hydrophilic and lipophilic properties of the mixed emulsifier are just balanced. Preparation above the phase inversion temperature followed by rapid cooling yields emulsions that exhibit very fine droplet size and extreme long-term stability. Cosmetic emulsions were prepared by this phase inversion temperature (PIT) method using typical raw materials such as polar oils, e.g. decyl oleate, 2-octyl dodecanol or isopropyl myristate, and nonionic emulsifiers, e.g. ceteareth-12 or polyoxyethylene eicosyl/docosyl ether combined with cetostearyl alcohol as a co-emulsifier. The phase inversion temperature was measured as a function of the oil polarity and the concentration of mixed emulsifier. The relationship between phase inversion temperature, droplet size and emulsion stability was investigated. In addition, self-bodying agents such as cetostearyl alcohol or monoglycerides were added to these thin, fine disperse emulsions to adjust the consistency. The influence of these ingredients on phase inversion temperature, droplet size, yield value and emulsion stability was studied.
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