Abstract
The objective of this study was to characterize the flow and rheological behaviour of model wax-stabilized water-in-oil (W/O) emulsions consisting of light mineral oil, paraffin wax and glycerol monooleate as the oil phase and water as the dispersed aqueous phase. An[sic] laboratory-scale benchtop flowloop system was used to explore the flow behaviour of the emulsions' oil phase (oil, paraffin wax and surfactant). The key contribution from this work was that the higher initial temperature gradient (40°C compared to 19°C) experienced by the rapidly-cooled oil led to more initial deposition on the flowloop inner wall. The rheological properties of W/O emulsions with different water cuts (10-50wt%) were also studied. Rotational, oscillatory rheology and creep compliance and recovery were characterized on emulsions aged up to 28 days. Overall, the results demonstrated that emulsion composition, and age could significantly influence an emulsion's flow behaviour and rheological properties.
Highlights
Introduction and literature review1.1 Basic emulsion principlesAn emulsion consists of two immiscible liquids where one is dispersed as micron-sized droplets within the other (McClements 1999)
Stable emulsions were obtained for all water cuts with an average droplet size of 30 μm, except for the 50% W/O emulsion which started to destabilize after 21 days
It was concluded that the higher water cut emulsions were more rigid and showed more elastic behaviour for both fresh and aged samples when compared to lower water cut emulsions (10 – 30 wt%)
Summary
Introduction and literature review1.1 Basic emulsion principlesAn emulsion consists of two immiscible liquids where one is dispersed as micron-sized droplets within the other (McClements 1999). In a W/O/W emulsion, water droplets are dispersed in larger oil droplets, which are themselves dispersed in an aqueous continuous phase. W/O/W emulsions are more commonly used than O/W/O and many have been developed for use in food, pharmaceutical and cosmetic applications. Water-in-oil emulsions stabilized by particles such as triglyceride or paraffin wax crystals naturally exist or are an added ingredient in many products including crude oil, butter, ice cream and cosmetic hand creams. There currently remains a dearth of information on the combined contribution of water cut and continuous phase crystals on stability, flow behaviour and rheological properties of colloidstabilized emulsions. The study focused on the impact of different water cuts (10-50 wt%) on emulsions prepared with an oil phase containing 5 wt% wax and various amount of surfactant (GMO), where all the emulsions had similar average droplet diameter of ~30 μm
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