Multilamellar vesicles in a commercial surfactant system

Abstract

AbstractThe manufacture of concentrated detergent granules in the detergent industry can be achieved by the incorporation of surfactant pastes, such as linear alkylbenzene sulfonate paste (LAS)—a lamellar liquid crystalline material (surfactant concentration of ca. 78 wt. %). LAS paste was processed at 25°C and 60°C, in both the absence and presence of sodium disilicate (Na2O:2SiO2) additive, and the effect on the formation of shear‐induced multilamellar vesicle (MLV) microstructures was studied. Our results suggest that LAS pastes of high hardness and stiffness are always associated with MLV microstructures and vice versa—these are known as “structured” pastes in industry, and also appear nonadhesive. MLVs are able to form from “pure” LAS at 25°C, although, at 60°C, sodium disilicate is necessary. With increased processing time, the size of the MLVs decreases and becomes more uniform—pastes are also increasingly hard and stiff. When stored, “structured” pastes eventually revert back to being soft and sticky, reflecting the metastable nature of the MLVs.