Structuring oil phases in personal care products
Cosmetic emulsions are often used to deliver oil soluble actives from aqueous external phases. After these emulsions are applied to the skin or hair, the volatile phase evaporates, leaving behind the actives, surfactants and any other non-volatile component. The aesthetics from this type of emulsion is encountered on application, after evaporation of the water and after spreading out on the skin. Additionally, a major concern that often is overlooked is introduction of water on the skin by sweating, swimming or encountering rain. If not properly selected, the emulsifiers in the formulation can re-emulsify the oil phase and remove the actives or oils off of the skin.
This article will look at two different materials that will structure the oil phase of an emulsion. This structuring of the oil phase will have dramatic effects on the emulsion’s stability and performance. In vivo and in vitro SPF data will be presented to show the effect of these thickeners in sun care products, as well as microscope images and viscosity to demonstrate how these thickeners can be used to decrease the emulsifier concentration.
The challenge to most cosmetic formulations is designing a product that have raw materials that are incompatible with one another (1). The most common way to produce a cosmetic product with two non-compatible materials is to create an emulsion. Emulsions are utilized in many different cosmetic products like: hand moisturizers, make up, hair conditioners, sunscreens, etc.(1). Emulsions by nature are not thermodynamically stable (2), meaning that they will split over time. To produce the most effective emulsions, structuring the oil phases will lead improved performance in: food (3), sun care (4).
STRUCTURING OIL PHASES
There are two main mechanisms for structuring oil phases: conventional crystallization (CC) and oleogelation. Conventional crystallization involves the formation of fat crystals, which thickens or restricts oil movement by physical or chemical bonds (5). Typically, structured oil phases that are gelled by a CC mechanism come out like butters and lack clarity. Oleogelation, on the other hand, are semi-solid structured gels (6, 7). Oleogels are a liquid oil phase that is structured by ...