(767d) Multiscale Approach to Colloidal Systems (emulsions) Design

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.