postemulsifiable

Postemulsifiable is a term used in formulation science to describe materials or formulations that form an emulsion only after a triggering event or activation step, rather than immediately upon mixing. In practice, a postemulsifiable system may be stable as a neat concentrate or pre-dispersion and then emulsify when exposed to a specific medium, energy input, or environmental condition.

Common triggers for postemulsification include dilution with a solvent or water, changes in temperature, pH adjustment, or the application of shear. The emulsification process is governed by interfacial phenomena and the properties of the surfactant system, including the hydrophilic–lipophilic balance (HLB), co-surfactants, and oil-to-water ratio. Some postemulsifiable formulations are designed to minimize premature separation during storage while enabling rapid emulsification at the point of use.

Key considerations for postemulsifiable systems include storage stability, compatibility between components, trigger specificity, and control over droplet size and rheology once emulsified. These formulations can offer advantages such as reduced viscosity in storage, ease of handling, and the ability to tailor release or delivery profiles after activation. Potential drawbacks include sensitivity to environmental conditions that could cause premature or incomplete emulsification and challenges in achieving consistent emulsion quality across batches.

See also: emulsification, emulsifiable concentrate, phase inversion, surfactants, droplet size, in situ emulsification.