The Rheology of Oil-In-Water Emulsions

Abstract

Abstract A microscope cell has been made to examine semi-solid oil-in-water emulsions while flowing in a thin layer. Unautoclaved and autoclaved emulsions from cetyl alcohol, sodium lauryl sulphate, liquid paraffin with and without bentonite show differences in the dispersion of the globules. Those in the unautoclaved emulsions are mainly associated, “flocculated”, into loose clusters in which each globule is free to move independently of its neighbours. Composite masses of disperse phase, called agglomerates, are formed in emulsions prepared from a preformed “emulsifying wax” which are absent from emulsions formed by adding sodium lauryl sulphate to the aqueous phase. A compact type of floccule occurs in the autoclaved emulsions containing bentonite. The globules are surrounded by a hydrated layer of bentonite which restricts their movement and provides a mechanical barrier against deformation. Rigidity is supplied by association of the hydrated bentonite particles in a network to form a gel. The globules in the autoclaved emulsions without bentonite are readily deformed and show complete freedom of movement with no association into clusters.