PPG-12/SMDI copolymer is a copolymer of saturated methylene diphenyl diisocyanate (SMDI) and PPG-12 monomers. PPG-12 is a polymer consisting of 12 units of propylene oxide. In cosmetics and personal care products, PPG-12/SMDI copolymer functions as a film former, emollient, and hair fixative.

After application to the skin, PPG-12/SMDI copolymer forms a thin film that is neither greasy nor tacky. The film helps to prevent evaporation of the skin’s natural moisture. Over time, this increases skin hydration by causing buildup of water in the stratum corneum (the uppermost layer of skin). These same properties aid in keeping the hair soft, hydrated, and manageable. PPG-12/SMDI copolymer also functions as a hair fixative, which means it helps to hold a hair style in place.