Acrylates/Stearyl Acrylate/Dimethicone Methacrylate Copolymer is an inorganic chemical compound, a Dimethicone by-product.

Safety
Dimethicone is a chemical compound, derived from silicone, a mixture of linear methylated siloxane polymers, a chemically inert silicone-based polymer. It is considered safe when formulated to be non-irritating in cosmetic products.
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What it is used for and where
Cosmetics
Film-forming agent. It produces a continuous ultra-thin film with an optimal balance of cohesion, adhesion and stickiness on the skin or hair to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.
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