Extensional Viscosity and Stability of Oil-in-water Emulsions with Addition Poly(ethylene oxide)

The main objective of this study was to investigate how polymer used as auxiliary emulsifier improves the stability of oil-in-water emulsions. Two kinds of polymeric emulsifier were used: poly(ethylene oxide) (PEO) and carboxymethylcellulose sodium salt (Na-CMC) with various average molecular mass weight. Therefore, the influence of PEO and Na-CMC on the creaming of oil-in-water emulsions has been investigated. Moreover, studies of extensional viscosity of emulsions and pure polymer solutions were made on the opposed-nozzle rheometer. In the case of emulsions stabilized with PEO the creaming of emulsion progressed slower in the case of polymer having an average molecular weight Mw = 2á106, and faster for addition of PEO with the molecular mass Mw=8 106. However, for emulsions stabilized with Na-CMC the fastest creaming has been observed for polymer with a lowest molecular weight (Mw=2.5 105). The study reveals that there is no direct connection between the extensional viscosity of the continuous phase of emulsions and rate of creaming. This is mainly due to the fact that preparation of emulsion stabilized by addition of PEO with different average molecular weights and similar shear viscosity of the continuous phase was unfortunate.