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, for "PPG-9" this is 9 propylene glycol molecular units; "diethylmonium chloride" refers to a quaternary ammonium salt.
PPG-9 diethylmonium chloride is used in cosmetic formulations. The substance mixture acts as an antistatic agent (reduces static charges by neutralizing the electrical charge on the surface, e.g. of hair), combability aid (reduces or prevents the tangling of hair due to changes or damage on the hair surface and thus improves combability), emulsifier (surface-active substance used in cosmetic preparations as an additive to combine 2 immiscible liquids - e.g. oil and water - to form an emulsion).