Pickering emulsions stabilised via novel fumed silica

 Fumed silica (INCI: Silica, Silica … Silylate) has a long track record in personal care formulations. A novel type of these traditional ingredients has been modified in a way to have both hydrophilic and hydrophobic properties in the same particle. This special feature makes the material that is available as Aerosil® R 816 (INCI: Silica Cetyl Silylate) resemble organic emulsifiers. The material has been tested for its ability to stabilise O/W emulsions. Remarkable stable emulsions have been obtained with a wide range of emollients and oil concentration using only a small dosage of the novel Pickering Stabiliser. The stabilisation of emulsions with Aerosil R 816 as well as its effect on other properties of the emulsions have been investigated.

Emulsions that are stabilised by solid particles are usually referred to as Pickering Emulsions after S.U. Pickering, the first researcher recognising the effect.1 These kinds of emulsions have attracted substantial interest in recent years.2,3,4,5 Although the stabilising effect of particles is thoroughly investigated and the effect is well understood scientifically, the concept has only sporadically been used in personal care formulations. Despite the fact that many personal care formulations are emulsions, these are typically stabilised using organic emulsifiers of many different chemistries. However, Pickering Stabilisation of personal care emulsions has become more popular in the last few years and particles composed of starch (using a high concentration of 12 w.-% in the formulation),6 customised sol-gel materials,7 clays8 and mineral UV absorbers9 have been suggested. 

Fumed silica (e.g. available under the trade name Aerosil®) either in hydrophilic (INCI: Silica) or surface modified hydrophobic form (INCI dependent on modification agent: Silica … Silylate) is a common ingredient in personal care formulations. Mostly, the fine white powders are used to improve texture, stabilise pigments against sedimentation and improve the heat stability of stick formulations. The chemical modification of the reactive surface silanol groups of the hydrophilic silica is a powerful tool to produce materials providing different surface chemistries that enable compatibility with many formulations, which generates a wide range of different effects.