Surfactant are known as the special chemical that can distinctly change the liquid surface tension or interfacial tension between two phases. It is the class of functional chemicals that are used in plastics, synthetics rubber and synthetic fibers with the development of petrochemical industry. Its molecule contains hydrophilic polar group (such as hydroxyl, sulfate, sulfonate) and hydrophobic or lipophilic, atmophile non-polar group (such as a hydrocarbon group, being a long chain hydrocarbon) two parts. It stays in the interface between the liquid and the other phase, forming a thin layer of molecule membrane, making the concentration of the surface layer of the solution much greater than that of the internal solution, further greatly reducing its surface tension and causing many effects such as wetting, emulsifying, dispersion and bubbling. There are many types of surfactants. They are generally divided into anionic type (e.g., alkylbenzene sulfonate), cationic type (e.g. octadecylamine hydrochloride, etc.), nonionic (e.g. glyceryl stearate, etc.), and amphoteric surfactant.
