Emulsifiers for Skin Care Applications

Emulsifiers for Skin Care Applications
The majority of Skin Care products and a very significant percentage of toiletry products are emulsions. The basic components of
these formulations are emulsifiers, emollients and consistency enhancers. Additional value can be given to these formulations by
including active ingredients with specific dermatological effects. The selection of these components determines the success of a
formulation. The chosen emulsifier is not only crucial for the stability of an emulsion, but has also a large impact on consistency,
skin feel and care properties of a formulation. Emulsifiers have a wide range of applications in cosmetic products. They are used in
creams, lotions, sprays and foams that can be of the oil-in-water (O/W) or the water-in-oil (W/O) type.
This brochure will help facilitate the selection of the Evonik Goldschmidt Personal Care emulsifier that is most suitable for the
desired application.
The HLB System
An emulsion is a dispersion of droplets of a non-miscible liquid in a continuous phase. The polar (hydrophilic) aqueous phase and
the non-polar (lipophilic) oil phase of an emulsion cannot be combined in a stable and homogenous way without a surface-active
additive.
Emulsifiers are interfacially active substances that reduce the interfacial tension between the oil and the water phase. The emulsifier
is adsorbed at the interface, giving a film between both phases, which prevents coalescence of neighbouring droplets. Due to its
amphiphilic structure, the polar part of the emulsifier has an affinity to the water phase and the non-polar part of the emulsifier to
the oil phase.
Emulsifiers can be defined according to their hydrophilic/lipophilic characteristics. In 1949 W.C. Griffin proposed the HLB
(Hydrophile – Lipophile Balance) system in which non-ionic surfactants have been classified on a scale from 0 to 20. Emulsifiers
with a strong lipophilic character have low HLB values between 3 to 8 and tend to form W/O emulsions. Emulsifiers of the HLB
range of 8 to 18 are hydrophilic and prove most suitable for O/W emulsions. HLB values from 12 to 18 are most favourable for
solubilization.
HLB Value
Use as
1.5 – 3 Antifoaming agent
3 – 8 W/O emulsifier
7 – 9 Wetting agent
8 – 18 O/W emulsifier
13 – 15 Wash active substance
12 – 18 Solubilizer for aqueous systems
Figure 1: HLB System according to W. C. Griffin
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