How To Pick The Right Emulsifier

May 25, 2022

Choosing the right emulsifier for your formulation can be difficult. In an ideal emulsion, the emulsifier is equally attracted to the water phase and the oil phase. If the balance is tipped in either direction, the emulsifier may lose contact with the phase to which it is less attracted, causing the emulsion to break down. Furthermore, it requires trial and errors to get a stable formulation. Emulsifiers do more than ensure stability; they also affect the feel, texture, and properties of an emulsion. It’s therefore important to be well-informed about your options and the effects they will have.

How Emulsions and Emulsifiers Works?

Emulsions are systems composed of two or more immiscible materials, in which one material (the discontinuous or internal phase) is suspended or dispersed throughout another material (the continuous or external phase) in separate droplets. The immiscible phases can be water, oil or silicone.

Emulsifiers are used in creams and lotions to mix water with oils. Since water and oil do not mix but stay separated, an additional agent (emulsifier) is necessary to form a homogenous mixture keeping water and oil together. There are 2 types of emulsifiers. Oil-in-water (o/w) emulsifiers keep oil drops packed in water, while water-in-oil (w/o) emulsifiers keep water drops packed in oil.

Tips In Selecting The Right Emulsifier!

1. Identify The Type Of Emulsion

a. Oil In Water (O/W) Emulsions

Oil droplets are dispersed throughout a continuous water phase
Creamy texture but do not feel greasy
Coloured by water soluble dyes
High electrical conductivities : pH can be measured
Mix readily with water soluble liquids

b. Water In Oil (W/O) Emulsions

Water droplets are dispersed throughout a continuous oil phase
Tend to be greasy except when silicones are used
Coloured by oil soluble dyes
Low electrical conductivities : pH can’t be measured
Mix readily with hydrophobic liquids

2. Choose Suitable HLB Value

HLB system is used to identify the chemical nature of emulsifiers and the type of emulsion formed.

HLB Value	Emulsion formed	Example
< 8 Low HLB	W/O emulsion	Emulri 6GPR ( Polyglycerol-6 Polyricinoleate) HLB value: 3.0
9-15 High HLB	O/W emulsion	Emulri 6GP (Polyglycerol-6 Palmitate) HLB value: 10.5
> 15 High HLB	Solubilizer	Emulri 10GCL (Polyglycerol – 10 Caprylate) HLB value: 17.0

3. Check pH and Charge Compatibility

Types of emulsifiers based on charge:

I. Ionic Emulsifier

Charged; Forms o/w emulsion by electric repulsion
Affected by excess charge, extreme pH and electrolytes
Crystallises at freezing point temperature.
Two types:

a. Anionic Emulsifiers

Negative charge
Not compatible with cationic environment
Example: Stearic acid, sodium stearoyl glutamate, glyceryl stearate

b. Cationic Emulsifiers

Positive charge
Not compatible with anionic environment ; used for conditioners
Example: Cetrimonium chloride, Behentrimonium Chloride

II. Non-ionic Emulsifiers

No charge; Forms o/w or w/o emulsion by physical barrier
Not affected by charge or electrolytes
compatible with both cationic and anionic emulsifiers
Reduces viscosity and stabilization effect at warm to hot climates
Example: Cetearyl alcohol, Stearyl Alcohol, Ceteareth-20

4. Check Product Form and Marketing Concerns

Product Type	Recommended Emulsifier Inputs
Serum (o/w)	•Non ionic waxy emulsifier blend •Use low side of recommended dose •Use polymer to stabilize and build viscosity
Cream gel (o/w)	•Use polymeric emulsifiers •No additional gum/polymer •Non ionic waxy emulsifier: small to mid point of recommended dose for “creaminess”
Crème cleanser (o/w)	•Anionic high HLB waxy emulsifier: use mid-point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Use water compatible polymer/gum to stabilize and build viscosity •Excess emulsifier is desired to ensure good cleansing
Lotion/Cream/ Body Butter (o/w)	•Anionic high HLB waxy emulsifier (if no compatibility issues): mid-point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Add 2-3% low HLB waxy emulsifier to build viscosity and reduce soaping effect •Use water compatible polymer/gum to stabilize and build viscosity
Conditioner	•Cationic waxy or liquid emulsifier: use mid to high point of recommended dose •Non-ionic waxy high HLB emulsifier blend: use high side of recommended dose •Use water compatible polymer/gum to stabilize and build viscosity (not cationic) •No chelating agent
Cream/Lotion (w/o)	•Low HLB waxy emulsifier as primary emulsifier •Low HLB waxy or low liquid emulsifier blend as secondary emulsifier •Add oil compatible polymer •Add NacL or Magnesium sulfate hepta hydrate to water phase to give water charge •Do not use chelating agents.

Additional Formulation Tips!

*According to George Deckner of UL Prospector

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