Polymethylsilsesquioxane
Polymethylsilsesquioxane is the INCI name for a silicone resin formed by hydrolysis and condensation of methyltrimethoxysilane. CAS number 68554-70-1. Functions as a film former in cosmetic formulations, delivering matte finish, oil control, water resistance, and long-wear performance. Used extensively in longwear color cosmetics and water-resistant sunscreens.