A. Nieto, D. Pradilla, N. Murcia, O. Alvarez
Group of Process and Product Design (GDPP)
Department of Chemical Engineering
Universidad de los Andes, Bogotá-Colombia
Preparation of emulsions (generally mixing of immiscible liquids, water and oil) involves several variables (emulsification conditions, system formulation and composition), being the final properties a consequence of the established level for each of these variables. To analyze separately the effect of a given process condition, formulation or composition on emulsion's properties, facilitates the establishment of a relation between the study variable and the changes in measured properties. However, the statement above limits the comprehension of the existent interactions between formulation, composition and process.
In this paper, molecular interactions of the system water/mineral oil/non ionic surfactant used in the preparation of inverse and direct emulsions were studied, evaluating the effect on the microscopic (particle size) and macroscopic (apparent viscosity, elastic and loss moduli) properties of the system. To achieve this, different agitation geometries and emulsification processes were used in order to establish the influence of the amount of energy added during emulsion preparation. The molecular scale behavior is evaluated using near-infrared spectroscopy NIR (FOSS 5000 Smartprobe Analyzer), size distribution and particle size are settled using dynamic light scattering technique (Zetasizer nano ZS), and finally the rheological behavior is measured from steady state and oscillatory tests using a controlled stress rheometer (TA Instruments AR-G2).
The study of the phenomena that occur during the preparation of these emulsions at three different scales: macroscopic, microscopic and molecular, simultaneously with the effect of the amount of energy added, results in the understanding of the relations between process (emulsification conditions), product (formulation and composition) and properties (rheology), allowing us to design emulsions with specific characteristics. For instance, it has been established for concentrated inverse emulsions (volumetric fraction of dispersed phase > 0.9) that elastic modulus is independent of impeller type used during emulsification.