(361b) Multi-Scale Approach in Mixing for Colloidal Systems Design: Concentrated and Highly Concentrated Inverse/Direct Emulsions

Emulsions are found in many fields of science: they can be found in cosmetics, pharmaceuticals, oil extraction and food industry. An emulsion is a type of colloid in which there are two phases, normally one is dispersed as droplets in other one. This dispersion is thermodynamically and kinetically unstable, reason why an agent that reduces the interfacial tension is needed (i.e surfactant). Energy consumed, concentration, type of mixing system, droplet size distribution and stability, are some of the key variables in emulsion design.   

During an emulsification process, several variables related to process and formulation must be taken into account because the final properties of the product depend on the condition at which each one of them is set. Relationships in such mixing systems are usually established by analyzing the effect of one variable on a property of the final product; however, this does not allow the observation of other interactions that might arise at different levels.

In this paper, the coupled effect between molecular interactions, the microscopic structure, the macroscopic level response and the energy consumed by direct oil-in-water and inverse water-in-oil emulsions was studied. A semi-batch emulsification process was used changing the type of impeller in the mixing system and the concentration of the dispersed phase. Near-infrared spectroscopy (NIR) was used to study the molecular response, laser diffraction (Mastersizer 3000) was used to obtain the particle size distribution, the rheological behavior was measured through steady state and oscillatory tests using a controlled stress rheometer (ARG2 TA Instruments) and the energy consumed was obtained through torque measurement from the mixing system (Lightnin LabMaster Mixer).

Using the multi-scale approach to analyze the final properties and characteristics of a product, different parameters can be evaluated simultaneously at the molecular, microscopic and macroscopic level and its relationship with emulsification variables.

For instance, the change in the microscopic structure of the water droplets influences a macroscopic response of the emulsion and a relationship between these two levels can be established through the pumping capacity of the mixing system.