The Surfactants : How does it work ?

Surfactants, have many functions.

That's what we are going to see.

" When used for stabilising an emulsion, surfactants are caracterised with their Hydrophilic - Lipophilic Balance (HLB).

___ 0 _____________________ 18 ___ HLB scale

more lipophilic

more hydrophilic

Surfactant Properties :

The Superficial Tension

Adding a surfactant product dicreases strongly the superficial tension of water with the disposition molecules take inside the liquid.


schema taken from http://images.google.fr/images?hl=fr&q=micelle&ie=UTF-8&oe=UTF-8&um=1&sa=N&tab=wi

It's this disposition which is responsible of the moistening, foaming and emulsioning power.

However reaching a certain concentration in surfactants, called critical micellar concentration (cmc), the surface of the liquid being satured in surfactant molecules, those molecules join theselves together in the liquid forming micelles.

Foaming power :

Surfactants molecules consolidate the thin water layer which forms bubbles.

Cleansing power :

Lipophile parts of surfactants adhere to oily dirt.

The dirt is then captured and carried away inside the micelles, to the washing water.

Emulsifing power


An emulsion is a system constituted by a liquid that is dispersed as thin droplets in an other liquid, both liquid being non miscible.

However, using surfactants, we can have droplets of oil in water or droplets of water into oil.

> A O/W (oil in water) emulsion must have a surfactant with High HLB

schema taken http://images.google.fr/images?q=micelle&ndsp=18&svnum=10&hl=fr&start=54&sa=N

> A W/O (water in oil) emulsion must have a surfactant with low HLB



micelle including a water droplet "






schema taken fromhttp://images.google.fr/images?q=micelle&ndsp=18&svnum=10&hl=fr&start=126&sa=N

> A " human micelle" I found while searching for schemas on the net..nice right? ;-)

photo taken from http://images.google.fr/images?q=micelle&ndsp=18&svnum=10&hl=fr&start=36&sa=N

source : http://www.ac-bordeaux.fr/Etablissement/StLouis/OLYMP/cosmeto/cosmeto.pdf