The Hydrophilic-lipophilic balance of a surfactant
is a measure of the degree to which it is hydrophilic
, determined by calculating values for the different regions of the molecule, as described by Griffin in 1949 and 1954. Other methods have been suggested, notably in 1957 by Davies.
Griffin's method for non-ionic surfactants as described in 1954 works as follows:
where Mh is the molecular mass of the hydrophilic portion of the Molecule, and M is the molecular mass of the whole molecule, giving a result on an arbitrary scale of 0 to 20.
An HLB value of 0 corresponds to a completely hydrophobic molecule, and a value of 20 would correspond to a molecule made up completely of hydrophilic components.
The HLB value can be used to predict the surfactant properties of a molecule:
- A value from 0 to 3 indicates an antifoaming agent
- A value from 4 to 6 indicates a W/O emulsifier
- A value from 7 to 9 indicates a wetting agent
- A value from 8 to 18 indicates an O/W emulsifier
- A value from 13 to 15 is typical of detergents
- A value of 10 to 18 indicates a solubiliser or hydrotrope.
In 1957, Davies suggested a method based on calculating a value based on the chemical groups of the molecule. The advantage of this method is that it takes into account the effect of strongly and less strongly hydrophilic groups. The method works as follows:
m - number of hydrophilic groups in the molecule
Hh - Value of the hydrophilic groups
n - Number of lipophilic groups in the molecule
Hl - Value of the lipophilic groups