Relationship of rheological and thermal properties in organogel emulsions (W/O): Influence of temperature, time, and surfactant concentration on thermomechanical behavior

Abstract

Emulsions are thermodynamically unstable systems that, by incorporating more components in their formulation, increase their complexity and make their study challenging. However, a good selection of compounds in the formulation, and suitable methods for their preparation, could result in systems with favorable thermomechanical and microstructural properties for multiple applications. The objective of this research was to evaluate the influence of temperature, time, and surfactant concentration on the microstructural, thermodynamic, and rheological properties of organogel emulsions, and to present in a simple way the relationship between enthalpy of fusion and rheological properties (i.e., viscosity) in organogel emulsions W/O. Canola oil, monoglycerides and polyglyceryl polyricinoleate (PGPR) were used as the oil phase. Microscopy, DSC, and Creep-recovery tests were performed. A molecular organization phenomenon was observed that resulted in systems with a more dispersed and ordered microstructure, delaying the phase separation for 28 days of evaluation. In addition, an increase in the internal viscosity of the organogel emulsions was reflected in higher enthalpy of fusion values at 10 °C. An inverse behavior was also presented in emulsions at 25 °C. The combined activity of stabilizing agents, as well as the three-dimensional network formed in continuous phase, avoided phenomena of coalescence and phase separation by keeping distant the drops of water and the oily liquid phase, while leading to a better organized microstructure over time and retaining good rheological properties.