PPG is the acronym for "polypropylene glycol", the polymer of propylene glycol (1,2-propanediol), a dihydric alcohol. The number after "PPG" indicates the average number of propylene glycol molecular units, e.g. "PPG-9" has 9 propylene glycol molecular units. "Butyl" generally designates butanol (1-butanol or n-butanol) as the alcoholic component, "ether" the linking product of 2 alcohol molecules via an oxygen bridge. PPG-9-butyl ether is used in cosmetic formulations; the substance acts as an antistatic agent (reduces static charges by neutralizing the electrical charge on the surface, e.g. of hair) and as a combability aid (reduces or prevents tangling of the hair due to changes or damage on the hair surface and thus improves combability).