John Woodruff highlights examples of silicones and their alternatives and the benefits that they can bring to cosmetic and personal care products
Despite qualms about the use of silicones, they continue to be one of the most commonly used group of materials in hair, skin and sun care products and in colour cosmetics, unique both in terms of their chemistry and in their wide range of useful applications.
Silicone technology can be used to confer wash-off and transfer resistance to colour cosmetics. MQ-1640 Flake Resin and MQ-1600 Solid Resin are two resins from Dow Corning developed for this application. Blends of trimethylsiloxysilicate and polypropylsilsesquioxane, they are designed to give a soft flexible film that resists wear and wash-off while also improving the intensity and shine of colour cosmetics.
Silicones are often used as coatings in pigment technology to aid dispersion and improve application properties, not only for colour cosmetics but also for micronised sunscreens. An example of this application is Solaveil Sensation, a recent introduction from Croda. It is titanium dioxide treated with hydrated silica and coated with aminopropyl triethoxysilane. Croda claims that this coating avoids the need for silicone based dispersions and enables Solaveil Sensation to be dispersed in C12-15 alkyl benzoate, giving the product a light and refreshing skin feel.
Silicone elastomers are used for their unique skin feel of dry smoothness. EL-9240 Silicone Elastomer Blend from Dow Corning is a mixture of high molecular weight silicone elastomer in volatile, low viscosity dimethicone. It is said to provide dry smoothness with a light, silky, non-greasy skin feel. It also acts as a thickening agent for water-in-oil and water-in-silicone formulations and silicone fluids, and is suitable for cold processing.
Bentone Gel 1002-V from Elementis Specialities is a dispersion of an organically modified hectorite in an ultra pure cyclopentasiloxane [INCI: Cyclopentasiloxane, disteardimonium hectorite, propylene carbonate]. Bentone Gel TMF-V is methyl trimethicone, disteardimonium hectorite and triethyl citrate. They provide thermostable viscosity control of an emulsion’s oil phase, impart thixotropic flow, improve application properties and impart a pleasant residual silkiness to the skin.
Chemsil recently introduced a silicone crosspolymer base for the formulation of cold process skin care and cosmetic products, trade-named Gelaid CPE [INCI: Cyclopentasiloxane, dimethicone/vinyl dimethicone crosspolymer, hydroxyethyl acrylate/sodium acryloyldimethyl taurate copolymer]. By adding water, esters, oils and actives it is possible to formulate a stable and elegant emulsion with a silky after feel. Gelaid CPE delivers both water and micronised silicone polymer to the skin surface and as the microemulsion breaks on the skin, the silicone polymer droplets coalesce to form a soft flexible film, sealing in hydrating moisture.
There are various ways of combating the visible signs of ageing, one being that of optical blurring or soft focus effect. By transmitting light between microspheres within wrinkles the depth is disguised. Centerchem produces AuraSphere [INCI: Isododecane, adipic acid/neopentyl glycol crosspolymer, lauryl dimethicone, hydrogenated polyisobutene], which is described as an anhydrous complex dispersed in a moisturising gel base. In addition to line blurring and wrinkle filling it imparts long wearing properties, a novel sensory feel and a silicone cushion to products without the use of cyclomethicone.