Investigation through the DSC Measurements

Liquid Cristal Formation and the Mechanism of Fatty Soil Removal by the Surfactant (Part 2)

Abstract

In a previous work, it was recognized that the formation of liquid crystalline phases played an important role in a fatty soil detergent action. In the present work the temperatures, at which liquid crystalline phase appears in the ternary system, surfactant-water-fatty soil, have been determined at various concentrations of the surfactant using a differential scanning calorimeter (DSC). The structures of liquid crystal have been determined by the observation with a polarizing microscope. Samples used are sodium dodecyl sulfate (SDS) as a surfactant and the mixture of palmitic and stearic acids, 4 : 1, as a model soil. The results showed that two kinds of liquid crystals, a middle phase and a neat phase, were formed depending on the concentrations of SDS and temperature. The SDS concentration dependences of T_M and T_N, the temperatures at which the middle phase and neat phase were formed respectively, were investigated together with the conversion ratio of the model soil from a solid state into a liquid crystallin state. It was proved consequently, that for fatty soil removal the formation of the neat phase was preferable but not that of the middle phase.