Surfactants and their Use in Detergents
Surfactants are a category of predominantly organic chemicals that are amphiphilic in nature since they contain both hydrophobic groups (tail group) and hydrophilic groups (head group). Due to these structural features, surfactants have the potential to lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Based on their structural properties, surfactants are of high importance from a technical as well as a commercial viewpoint since they can act as detergents, wetting agents, emulsifiers, foaming agents and dispersants.
Surfactants are an indispensable ingredient of many products used in households for cleaning surfaces, garments, as well as for personal hygiene. They show the ability to dissolve hydrophobic soil (oil, grease), prevent the dissolved soil from redepostion by keeping it in an emulsified form so that it can be removed with the soiled water after use.
Typically, surfactants are classified according to their hydrophilic head group. A non-ionic surfactant is neutral while carrying no charge. If the head group carries a negative charge the surfactant is called anionic. If the charge is positive, it is called a cationic surfactant. If the head group carries a positive as well as a negative charge, it is termed zwitterionic.
Manual dishwashing detergents and liquid laundry detergents (for hand washing as well as for machine washing) are the household products which have the highest surfactant content. Surfactants in manual dishwashing detergents and special laundry detergents typically produce a high amount of foam. Contrary to this, the surfactant concentration in cleansers is rather low. Products for automatic dishwashing as well as professional cleaning have an equally low surfactant content. Since these products are used in machine applications, low foaming surfactants are preferred.