Sakai et al. discuss the design of an emulsion film for highly moisturizing and occlusive functions.
Emulsion fi lms: Sakai et al. discuss the design of an emulsion film for highly moisturizing and occlusive functions. Two important functions of emulsion-based cosmetic products are moisturization and occlusion. Both are markedly affected by the ratio of hydrophilic to lipophilic parts in the emulsion. However, due to their confl icting requirements, it is difficult to improve both functions simultaneously. Therefore, these investigators paid attention to emulsion fi lm structure, because an applied emulsion fi lm is in contact with skin directly and performs functions of the emulsion.
The investigators hypothesized that if an emulsion fi lm can be similar to healthy stratum corneum (SC), it would be possible to enhance the moisturizing and occlusive functions simultaneously, because healthy SC contains a large amount of water and the amount of water loss from the skin surface is low.
Using this model in which corneocytes of healthy SC contain a large quantity of water, the investigators dispersed a large quantity of water into the lipophilic part and then focused on the dispersant. Polyglycerin-type surfactants and cetyl alcohol were found to be useful dispersants. For the hydrophilic part, whose intercellular lipids are rigid, the investigators focused on the emulsifi cation method and hydrophilic surfactants. The properties of a polyglycerin-type surfactant generally make it diffi cult to form a liquid crystal structure, but these investigators were able to form that structure by using polyglycerin-13-polyoxybutylene-14- stearyl ether.