Formation of Pickering Emulsion with Cellulose Nanofibers for Cosmetics

Abstract

Cellulose nanofiber (CNF), which is used in various cosmetics as a rheology control agent, has various functions such as thickening effects. One of the functions of CNF is to form Pickering emulsion. However, it has been unclear under what conditions CNF can emulsify in cosmetic formulations that contain a wide variety of ingredients. In the present study, we investigated the relationship between the emulsifying ability of CNF and the type of oil and the ingredients added to the aqueous phase, and searched for the emulsifiable range of CNF. First, we investigated the emulsifiable oils. The possibility of emulsification was plotted on an organic conceptual diagram based on the structure of the oils. The results showed that CNF could emulsify relatively low polarity oils with a ratio of inorganic to organic values of less than 0.25. Next, we investigated the effects of the addition of ethanol or polyols into the aqueous phase on interfacial tension and emulsification. As a result, the higher the additive concentration, the lower the interfacial tension. Furthermore, it was found that the decrease in the interfacial tension due to the additives made emulsification difficult even for the oils that were originally emulsifiable. In other words, the emulsification ability of CNF was reduced by the addition of water-soluble additives.