Polymethylsilsesquioxane

Harm score: 3 (Harmless chemicals)

Polymethylsilsesquioxane, sometimes also referred to as polyisobutylene or butyl rubber, is a synthetic polymer that is formed by a reaction between silicon and carbon. Known for its resistance to temperature, chemicals and weathering, it is found in many products where it plays the role of both a physical property modifier and a protective ingredient.

In cosmetics and skin care, polymethylsilsesquioxane is a popular ingredient in many products due to its ability to form a thin film on the surface of the skin, thus protecting it while giving it a smooth feel. It is also found in make-up products such as powders, which give them a silky, velvety texture and a long-lasting effect. Its popularity extends to the automotive industry, where it can be a component of sealants or adhesives. Furthermore, polymethylsilsesquioxane is included in some building materials, such as silicone compounds, where it increases their temperature and chemical resistance.