Formulation and Stability Evaluation of a Water-In-(Highly Volatile) Oil Emulsion
Microencapsulaton is a process where active ingredients are packaged into particles to achieve desirable effects such as control on the release of the core materials, reduction of reactivity and volatility of the core materials or promotion of easier handling. Emulsification is a critical step in the microencapsulation process as it strongly influences not only the quality of the microcapsules produced from the emulsions but also the encapsulation efficiency of the dispersed phase. In this study, a series of experiments have been conducted to investigate the effect of process parameters on the stability of a water-in-oil type of emulsion, which was used for the production of microcapsules containing the water phase in a subsequent step by the break up of a flow-focused laminar emulsion jet and solvent removal by evaporation. To facilitate the solvent removal, a volatile solvent, namely, dichloromethane, mixed with ethyl acetate for density adjustment, was used as the continuous organic phase. Poly(ε-caprolactone) (PCL) was used as the capsule wall-forming polymer as well as the viscosity modifier in the emulsification process. Results show that, in addition to the usual factors such as the density and viscosity ratios of the two phases and the volume fraction of the water phase in the emulsion, the manner in which the PCL was added to the system also has a strong effect on the stability of the emulsion.