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Silicone elastomers are a broad class of cross-linked dimethicone polymers that form three-dimensional polymeric structures and provide a beneficial texture and appearance to cosmetics. They are generally formulated into products to enhance consumer appeal by yielding a preferred sensory profile, while functioning for example as anti-aging ingredients such as that of a line filler and soft-focus particle. They also can act as sebum absorbers to reduce excess oil on the surface of the skin and act as mattifying agents, which is just another way to say they make the skin less shiny. Further, these cross-linked dimethicone polymers are capable of delivering actives by acting as controlled-release polymers and can also reduce the oily texture of high-oil-content formulas. Several formula examples are provided to show how silicone elastomers may be co-formulated with common ingredients such as sun protection actives and pigments in order to provide elegant daily wear cosmetics or lotions.
Having described in great detail the varying structural types of silicone-based elastomers and gels in a previous section of this book; we come now to a description of their usefulness in cosmetic and personal care products.
There is always opportunity to offer products that make people say “wow” (sensory elegance) while enhancing the delivery of actives that promote skin health, beauty, and the perception of ageless elegance. As described previously, silicone elastomers are a broad class of cross-linked dimethicone polymers that form a three-dimensional structure and can provide a sought-after texture and appearance to cosmetics. The key to achieving the optimal structure is to create an interstitial pore volume, defined by the cross-link density of the silicones. This elastic volume can be swollen (filled) with a solvent or even a small active material for obtaining enhanced delivery attributes. Depending on the chemistry and process to make them, silicone elastomers may be called silicone crosspolymers, dimethicone crosspolymers, dimethicone/vinyl dimethicone crosspolymers, or Polysilicone-11 (CTFA designation). Altogether, this class of cosmetic ingredients provides a wide range of elegant textures and promotes compatibility with other commodity ingredients. They are generally formulated into products to enhance consumer appeal by yielding a preferred sensory profile, while functioning as a line filler, sebum absorber, soft-focus particle, and mattifying agent. Higher-end cosmetic creams and lotions may contain a significant percentage of silicone elastomer, as this type of formulation helps create a positive consumer feedback loop that reinforces the performance and value associated with a brand. Silicone elastomers (in all their wide varieties) are available as loose powders, as swollen mixtures in cosmetic solvents, and as dispersions in water. The basic polymers can be further compounded into anhydrous and aqueous “formula bases” to help remove the need for later homogenization and/or to help take the guesswork out of the correct emulsifier blend required for stabilizing silicones in a formula.