Anionic Surfactant
An anionic surfactant is a surfactant whose hydrophilic part carries a negative charge in solution, such as sulphonates, sulphates and soaps.
The molecule combines a grease-loving tail with a negatively charged polar head. In water it lowers surface tension, adsorbs onto greasy soil and forms micelles that keep it dispersed until rinsing. The most common families are alkylbenzene sulphonates, alkyl sulphates and alkyl ether sulphates, and soaps (fatty acid salts). They usually give good detergency and plenty of foam, so they are common in manual dishwashing detergents, foam cleaning and vehicle washing.
They have two well-known limitations. In hard water, calcium and magnesium form poorly soluble salts with some of these surfactants (especially soaps), which reduces their effectiveness; that is why they are combined with sequestrants or chelants. And because they carry the opposite charge, they are neutralised by cationic surfactants, such as quaternary ammonium compounds, so products of both types should not be mixed.
Some Instaquim products containing anionic surfactants, according to their technical data sheets:
- Eco Top (pH 5.3; 4–8 g per 5 l of water): manual washing of tableware and glassware; anionic surfactants 5–15 % and amphoteric surfactants; EU Ecolabel ES-CAT/019/014.
- Neutro Foam (pH 5.5; 1–5 %): neutral foaming detergent for food industry surfaces, by foam projection or by hand; anionic surfactants 5–15 % and amphoteric surfactants.
- Carfoam (pH 8.5; 3–8 g/l): washing of car bodywork in automatic tunnels with high foam formation; anionic surfactants 5–15 %.
- Atom (pH 1 %: 11.0; 10–20 g/kg of dry laundry): powder detergent for all types of laundry, in water of up to 30 ºHF; phosphates 5–15 % and anionic surfactants.