PEI is the acronym for polyethyleneimine, a polymerised ethyleneimine, also called aziridine, a cyclic secondary amine (the number after "PEI-" indicates the average number of monomer units - CH2-CH2-NH-), "PEG" denotes a PEG (polyethylene glycol) derivative. The number after "PEG-" (or the first number after "PEG/...-") indicates the average number of molecular units -CH2-CH2-CH2-O-), "PPG" means a polypropylene glycol derivative (the number after "PPG-" indicates the average number of molecular units -CH2-CH2-CH2-O-), "copolymer" means a polymer composed of several different monomers.
This mixture of substances is used in cosmetic formulations. It acts as a surfactant (washing-active substance; improves the even distribution of the products during application).