silica+silylate

A silica silylate aerogel can absorb more than ten times its weight in low molecular weight oils such as cyclomethicone or fragrance. Absorption of higher molecular weight oils such as vitamins, organic oils or silicone oils can reach seven to eight times the weight of the powder. The aerogels have demonstrated effective and long-lasting sebum absorption properties compared to other sebum-absorbing powders promoted for this purpose. Figure 2 compares this property for five powders after two, four and six hours. When delivered from a formulation, results show the long-term ability of the aerogel to reduce sebum compared to the other powders. Formulation 1 illustrates the use of the aerogel fine particles to absorb sebum from the skin. The silica silylate aerogels are efficient oil phase thickeners at concentrations of 1 to 15%. Figure 3 shows the thickening effect of the silica silylate aerogel (fine particles) and a typical hydrophobic silica with a lower surface area (225m2/g). Dimethicone represents the oil phase in this example. A similar effect is observed with mineral oil and other oils. Another important characteristic of the silica silylate aerogels is their ability to reduce formulation volatility, a property that can aid the delivery of fragrance or active ingredients. Samples of the aerogel fine particles and the silica silylate with lower surface area were loaded with fragrance, overcoated with various siloxane waxes and evaluated for fragrance retention. Figure 4 summarises volatility assessments as recorded by weight loss. Volatility rate decreased when the silica silylate aerogel was encapsulated within a siloxane wax. Materials evaluated included several alkylmethylsiloxane waxes and one polyether functional wax, the latter providing the best performance.



http://www.cosmeticsbusiness.com/technical/article_page/Taking_control/47075