Influence of the concentration of a polyoxyethylene glycerol ester on the physical stability of submicron emulsions

• The combination of techniques provides relevant information of physical stability.
• Emulsions in the range 2–3 wt% surfactant were highly stable.
• Emulsion with 1.5 wt% surfactant showed creaming as a predominant mechanism.
• Emulsions with 3.5–4 wt% surfactant showed flocculation, creaming and coalescence.

The chemistry and technology of agrochemical products has undergone extensive changes over the last 20 years. The new formulations and ingredients should meet the needs of the agrochemical industry for products having greater safety to the user and much lower environmentally impact maintaining the same performance targets. A recent trend involves the use of the emulsion format for agrochemicals, which provides a more efficient performance than those conventionally used. Furthermore, the production of submicron stable emulsion is a key achievement especially for this product.This study has been focused on the development of fine emulsions containing ecofriendly ingredients, such as surfactants and green solvents. It has been proven that the optimal surfactant concentration not only may lead to emulsions with submicron droplet sizes but also may prevent the typical destabilization process occurring in these formulations. In this particular case, it has been demonstrated that 3 wt% surfactant concentration is adequate for three reasons: (a) allowing the lowest droplet size to be achieved, (b) providing the sufficient viscosity to prevent creaming and (c) not being an excess of surfactant that leads to depletion flocculation.