Progress in the formulation of concentrated ecological emulsions for agrochemical application based on environmentally friendly ingredients

Abstract

Researchers are engaged in exploring new ecological solvents for different applications, in accordance with the current trends in green chemistry and green engineering. This study is focused on the development of stable emulsions using eco-friendly ingredients, such as two green solvents as dispersed phase (N,N-dimethyl decanamide and α-pinene) and a nonionic polyoxyethylene glycerol ester derived from coconut oil as emulsifier. α-Pinene is a renewable essential oil that could find numerous agrochemical applications. In this investigation, we study the influence of dispersed phase concentration on droplet size distribution, physical stability, and rheological properties of highly concentrated eco-friendly emulsions. The laser diffraction technique revealed submicron droplet sizes for all studied emulsions. A coalescence process was detected in the most concentrated emulsions, not only by laser diffraction measurements, but also by rheology. Increasing the dispersed phase concentration from 30 to 45 wt % yielded an increase in the zero shear viscosity and a decrease in the flow index. All samples above 35 wt % dispersed phase displayed clear viscoelastic properties with a predominance of the elastic over the viscous component in the frequency range studied. Flow curves and mechanical spectra were quite sensitive to destabilization by creaming and coalescence. Multiple light scattering demonstrated that the emulsions prepared with a dispersed phase concentration of 35 wt % exhibited the highest physical stability. These emulsions may find applications related to the design of biotechnological complex systems with different uses, such as matrices for agrochemical products or emulsion-based encapsulation and delivery systems.