Multilamellar Vesicles in a Commercial Surfactant System

The manufacture of concentrated detergent granules in the detergent industry can be achie®ed 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 Na O:2SiO additi®e, and the effect on the formation of shear2 2 ( ) induced multilamellar ®esicle MLV microstructures was studied. Our results suggest that LAS pastes of high hardness and stiffness are always associated with MLV microstructures and ®ice ®ersa these are known as ‘‘ structured’’ pastes in industry, and also appear nonadhesi®e. 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 e®entually re®ert back to being soft and sticky, reflecting the metastable nature of the MLVs.