Surfactant
A surfactant is a molecule with a water-loving part and a grease-loving part; it lowers surface tension and helps wet, emulsify and disperse soil.
It is the basic component of almost all detergents. In water, its molecules concentrate at surfaces and interfaces: they reduce the surface tension, so that water wets better; they adsorb onto greasy soil and lift it off; and, above a certain concentration (the critical micelle concentration), they form micelles that keep the grease emulsified until rinsing. They also influence foam.
They are classified according to the charge of their hydrophilic part in solution:
- Anionic: negative charge (sulphonates, sulphates, soaps). Good detergency and foam; sensitive to water hardness.
- Non-ionic: no charge (ethoxylated fatty alcohols). Little affected by hardness and often low-foaming.
- Cationic: positive charge, such as quaternary ammonium compounds. Used as softeners and, some of them, as disinfectants. They are neutralised by anionics.
- Amphoteric: their charge depends on the pH. They usually accompany anionics to improve foam and mildness.
Examples of Instaquim products with cationic and amphoteric surfactants, according to their technical data sheet:
- Suau (pH 2.5; 5–10 g/kg of dry laundry): softener for the final rinse; cationic surfactants.
- Brillnet (pH 9.5; 20–40 g/l): surface cleaner with 5–15 % anionic surfactants and amphoteric surfactants; rinsed off with water.