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Selecting and Evaluating Emulsifiers for Cosmetics

It takes a lot to develop complex cosmetic formulations that come up to our expectations. Today, we are lucky to have a wide range of different ‘drop-in-and-go’ technologies to help us balance creativity with emulsifiers under tight deadlines.

Get detailed information about emulsions, types of emulsifiers used to create emulsions for cosmetics, factors to be considered in their selection and evaluating them before using in your personal care formulations. Review:


(Let’s start by understanding role of emulsifiers or click to go on specific section of the page)

We would like to acknowledge Amanda Foxon-Hill and Nick Morante for providing technical information needed to develop this guide.

Role of Emulsifiers


Selecting Emulsifiers for CosmeticsEmulsions 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.

When emulsions are made surfactants called emulsifiers are used to slow the process of separation of the immiscible phases. All emulsions are inherently unstable with the exception of some spontaneously forming microemulsions.


Simply put, any combination of unlike phases that are put together can be considered a type of emulsion. Emulsions are classified by:

  • The continuous phase (external)
  • The discontinuous phase (internal)

The use of homogenizers and other equipment to minimize droplet size will improve the stability of an emulsion.

When naming the emulsion type, the first letter is the discontinuous phase.

  • O/W stands for oil-in-water and is classified as an emulsion.
  • W/O stands for water-in-oil and is classified as an invert emulsion.
    • These types of emulsions are much more difficult to stabilize than oil-in-water systems.
    • They also must have much smaller droplets to help them stay together longer.

Making emulsions can sometimes be fun, and sometimes not. When things go well, it certainly is a lot of fun. In all cases, emulsions vary in the size and type of each of the phases and this phase ratio is critical in determining the characteristics and performance of the resulting product.

Changing the phase ratio alters the physical properties of the emulsion. It is the emulsifiers that help keep them together.

 »  View All the Commercially Available Emulsifiers in Market Today!

The cosmetics ingredients database is available to all, free of charge. You can filter down your options by INCI, origin, applications, end consumer benefits and many more dimensions.


Benefits & Limitations of Emulsifiers


Creating cosmetic formulations could be a task without having comprehensive knowledge about the ingredients involved in it. Before adding any ingredient, it becomes necessary for a formulator to know about the strengths and weaknesses it imparts.

Considering these aspects beforehand, a formulator could decide if the additive is actually required or not. If added, would it give an extra edge to the end product? Also, it could help the formulator to engineer his formulation to achieve desired end-use requirements.

Similarly, it is wise to look upon emulsifier benefits and limitations to stumble upon the right emulsifier. The table below discusses emulsifier benefits in cosmetics and some limitations associated with them.

Emulsifiers
Benefits Limitations
Correct use of emulsifiers creates homogenous mixtures, dispersions or emulsions of oily or waxy substances with water. Being physically unstable they get separated into distinctive phases.
Addition of emulsifiers helps solids to be dispersed in liquids or insoluble liquids with other liquids. The dispersed oil droplets can fuse together and rise in o/w emulsion or may get settled down in w/o emulsions.
Greasy anhydrous creams can be modified to washable ones. Permanently irreversible separation and fusion of the dispersed phase may occur. Conversion of w/o to o/w (or vice versa) can be observed.

Emulsifiers can be anionic, cationic or non-ionic depending on the ingredient's chemistry. Let's discuss their chemistry in detail...


Emulsifiers Based on Ingredient's Chemistry


Anionic Emulsifiers


Anionic emulsifiers are, in some ways, the old-fashioned cousins when it comes to emulsifier technology. Soap-based emulsifiers can be extremely useful in cleansing formulations but can also form part of a very elegant high-end anti-aging formulation just as long as your selection of actives is chosen carefully.

  • Anionic emulsifiers carry a net negative charge in solution and because of that they, like the cationics, are sensitive to electrolytes.
  • Anionics benefit from the presence of a little monovalent salt or acid up to a point (as the increased saltiness/ acidity increases the critical micelle concentration and activity of the water phase).

Above that, the formula can critically fail in a similar way like over-salted surfactant blends. Salt content can creep up on you in an active formula as ingredients such as:


As such, freeze/ thaw stability is an essential part of early anionic emulsion stability testing

In terms of skin irritation potential, the old pharmacopeia driven Sodium Lauryl Sulfate and its ‘harsh-on-skin’ reputation has largely been replaced. Anionic emulsifiers, especially elegant phosphate esters renowned for their skin compatibility or gentler surfactants such as the lactylates or glutamates making it entirely possible to make an anionic emulsion that is skin-kind and gentle.

Anionic emulsifiers are the most common used in emulsions. For example, Sodium Laureth Sulfate and PEG-100 Stearate.

The PEG-100 part of the emulsifier is a function of adding Polyethylene Glycol, or PEG. This process is called ethoxylation. This common attribute of anionic emulsifiers is that they are also compounds that have been ethoxylated. This process creates ingredients that have varied amounts of water solubility.

The higher the amount of ethylene oxide (or EtO for short),
the more water solubility the emulsifier has.

The one major issue with ethoxylates is that they can be irritating at high levels. The molecular formula for Polyethylene Glycol is given below, where "n" is the number of moles of ethylene oxide in the molecule.

OH–(CH2–CH2–O)n–H

Structure of Polyethylene Glycol


Cationic Emulsifiers


Cationic technology for skin care arose from the wool industry and then transferred to hair care. As hair and skin are both keratin-derived it didn’t take long for the benefits of cationics to be harnessed in moisturizer technology.

Cationics function very well in formulations that are desired to stay on the skin for a long time such as sunscreens, long-wear make-up and barrier creams. This is because they are positive, cationic charge adheres these products strongly to the surface of the skin, resisting wash-off and wear.

A practical example of where cationic emulsifiers has proved very helpful, is in preventing sand from sticking to a freshly-sun-screened body. Thanks to its anti-static capacity.

Like anionics, cationics are also sensitive to what is going on in the water phase and cope best with a relatively quiet external phase rather than one loaded with additives. Due to their natural capacity for skin adhesion, cationic emulsifiers can be more likely to irritate than other chemical families, but that said, in many cases the formulator can work around this – formulating to an acidic pH is advisable.

The new generation of cationic emulsifiers tend to favor long hydrophobic tail(s) as these have the effect of reducing the charge density of the head group and thus minimizing irritation potential. This, of course, must be balanced by the ingredients capacity to form and hold an emulsion.

As with anionic emulsifiers, cationics do benefit from a little monovalent salt as this can boost the CMC and as a consequence of that, the viscosity, but beyond a certain point, the salt becomes detrimental to stability.

It is important to note that, in using a cationic emulsifier system the formulator does rule out the use of pretty much all grades of Carbomer, and even anionic thickening agents such as xanthan, unmodified guar and tragacanth.

Cationic emulsifiers are those that are mostly used in hair care products. These are commonly called quaternium ammonium compounds or "quats". An example is Distearyldimonium Chloride.

  • Apart from having excellent emulsification capabilities, they act as hair conditioners because of their natural electrical charge in association with that of the hair.
  • They also have very good preservative activity such as Quaternium-15 (Hexamethylenetetramine Chloroallyl Chloride or Dowicil™ 100). These ingredients are very substantive and quite functional.

The one downside of cationic emulsifiers is that they can be somewhat irritating at high levels, more so than the anionic emulsifiers with higher levels of ethoxylation.

Cationic emulsifiers exhibit a charge on the molecule with the use of a halogen ion, such as a chloride or bromide. Below is an example of Quaternium-70 (Stearamidopropyl Dimethyl Myristyl Acetate Ammonium Chloride), another ingredient that can act as a cationic emulsifier and anti-static conditioning agent in hair care.

Structure of Quaternium-70
Structure of Quaternium-70

Notice the ammonium groups [-NH-] and the chloride ion, which gives the molecule its negative charge.


Non-ionic Emulsifiers


Non-ionics remain the first choice go-to emulsifiers for most applications due to their flexibility and low potential for chemical interaction. Non-ionic emulsifiers are those that are free from any external electrical charge caused by free ions. Examples of these are:


These are familiarly known as Tweens, a common trade name.

It is often a non-ionic emulsifier blend that is chosen first when creating creams with high activity levels or hard-to-stabilize ingredients such as:


There were ingredients such as Seppic’s MONTANOV™ 68 MB that first got us hooked on the self-emulsifying blend of non-ionic and freed us from the trials of calculating HLB in a complex oil-phase world.

The key benefit of a non-ionic emulsifier is its robust salt tolerance.

In fact, the addition of a little non-ionic is recommended in ionic emulsions as the mixed micelles that will form tend to display a dramatically enhanced salt tolerance over the ionic alone.

While the presence of self-emulsifying blends has made things easier, it doesn’t for a moment mean we shouldn’t consider what is going on inside of our product.

The HLB system is alive and well in the non-ionic world and gives us a great insight into where the emulsifier will orient itself and whether it is able to bring any other features to the product. That said, it is also important to mention the existence of more than one HLB system so that one can compare like with like.

Liquid Crystal Emulsifiers


Liquid Crystal Emulsifiers work on the principle of forming a lamella network in the cream, which most closely mimics the skin barrier, thus facilitating the effective delivery of actives. Lecithin naturally works this way, as does Olivem 100 and various other combinations available to purchase today.

Because of their skin-like structure, liquid crystal emulsifiers are often desired for their beautiful aesthetics.

While it is possible to create a range of textures using almost any emulsifier, depending on what goes into the rest of the formula, it would be reasonable to say that the liquid crystal generating emulsifier is the most foolproof way of creating a beautiful texture without too much additional work.

Polymeric Emulsifiers


Polymeric emulsifiers are a good option for those looking for elegant and quick cold-process solutions. Often sold as liquid polymer suspensions, these emulsifiers can create anything from lightweight sprayable milks through to thicker, richer creams depending on what they are paired with.

While not for the natural market, these can be quite a sustainable option, due to:

  • Their low addition rate
  • The speed with which they can form an emulsion, and
  • Their cold processing capabilities

Polymeric emulsifiers won’t work in every situation. Often these emulsifiers are acrylic acid polymers that tend to form complexes with cationic species.

In addition, the general salt tolerance of acrylates is low (reflecting the overall intolerance of ionic substances).

But one large advantage over ionic and, to a certain point the non-ionic emulsifiers is their ability to form highly stable emulsions with a very low level of polymer (with a non-polar or very slightly polar oil phase). This makes them the perfect emulsifier for a silicone-based emulsion, even those containing cyclomethicone.

Solving Cosmetic Emulsion Stability Issues Faster

A few destabilizing and stabilizing factors are mentioned below. Let's understand how critical it is to study the phases before making the right selection of emulsifier(s)…


Chemistry of the Water Phase


As mentioned in the beginning, an emulsion is a combination of two immiscible phases held together by what to many looks and feels like magic! What is really going on is a physical rearrangement of components, all trying to get themselves into a position that means they are exerting the lowest possible amount of energy – those dispersed phase droplets are lazy!

The dispersed and continuous phases are influenced by everything that comes into the formula, and some things are more disruptive than others.

Impact of Surface Tension in Water Phase


The surface tension between oil and water is so high that they don’t mix unless you add a surfactant (emulsifier in this situation). We understand that and have discussed the different types of emulsifiers that we could add, but do we understand what other ingredients do to the product’s surface tension?

Preservatives and solvents can dramatically alter the surface tension between the oil and water droplets. As we see with our emulsifier, some reduction in surface tension is required to facilitate the development of an emulsion, but in other cases, the changes are catastrophic and can result in viscosity and emulsion collapse.

Glycerin, Propylene Glycol and Ethanol are common additives in a cosmetic product and can all impact on surface tension. All of these ingredients decrease the polarity of the water phase, and the influence of that decrease changes depending on the quantity of additive present, although the relationship between dose and effect is not strictly linear.

Reducing water phase polarity loosens the grip the water has on the dispersed phase somewhat by toning down the intramolecular forces that make water behave as it does – Van Der Waals, Dipole-Dipole and hydrogen bonding.

While all emulsifiers depend on these forces to some degree to stabilize the product, the Ionic emulsifiers depend on them more strongly and are therefore most likely to be influenced by their presence.

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Impact of Ions in Water Phase


We often talk about salt and saltiness in formulating, but what we really talk about much of the time is the ionic strength of continuous phase.

The swapping of demineralized water for sea water, might cause formulary issues, we are less likely to accept that the actives we carefully measure into our water phase are doing the same. Be they acids, bases or salts, an ion-rich water phase, can cause havoc, for the stability of a product.

Ionic charge in the water phase can help increase intramolecular bonding and can also help in the formation of an electric double layer around the dispersed phase, which increases stability but things can go too far, especially with:

  • Divalent salts such as zinc
  • Strong acids, and
  • Oxidizing agents such as glycolic and peroxide

Impact of Ions on Continuous Phase

In general, the cosmetic chemist is looking to minimize chemical reactions in their formula, and so any addition of ions should be thought of as fueling the fire of chemical rebellion. Every emulsion has its limits, plus adding too many ions into the continuous phase will give the product a sticky/ tacky/ salty feel when applied.


Tricky Oil Phases


Silicone Oils


When compared to vegetable oils, silicones demonstrate practically no polarity as well as a very different chemical structure – flexible chains vs bulky triglycerides. Because of these differences, silicone fluids such as dimethicone and cyclomethicone tend to mix poorly or not at all with vegetable oils in the same formula.

If the formulator wishes to create a silicone rich emulsion, the influence of this low polarity should be considered.

Steps to reduce the polarity of the continuous phase would increase stability and take some of the pressure off the emulsifier as the surface tension between the two phases would be lessened.

Silicone emulsifiers are available from the major silicone manufacturers should be the first port of call for all those looking to create a silicone-dominant emulsion, especially where the silicone phase will be large or even dominant. Having said that, with careful consideration it is also possible to create a silicone-rich emulsion with non-silicone emulsifiers if the chemistry of the whole product is considered and accounted for.

Solvent Polarity
Solubility Parameter
(A difference of <2 indicates mutual structural solubility)
Based on the theory of ‘like dissolving like’
Water increasing polarity 23.40
Glycerin 16.26
Lactic Acid 14.81
Propylene Glycol 14.00
Ethanol 12.55
Isopropyl Alcohol 11.24
Cetyl Alcohol / Stearyl Alcohol 8.94 – 8.90
Castor Oil 8.90
Isopropyl Myristate 8.02
Olive Oil 7.87
Isopropyl Palmitate 7.78
White Mineral Oil 7.09
Squalene 6.19
Squalane 6.03
Cyclomethicone D5 5.77
Dimethicone 5.92

Is your emulsion going to be salty, acidic, basic, or contains a high proportion of solvents that are less polar than water, or does it contain Hydrogen Peroxide? If so, the best starting point is non-ionic.


Types of Emulsifiers


As water and oil do not mix, emulsifiers in cosmetics assist in forming homogenous mixtures of both. Emulsifiers in cosmetics stabilize the emulsion and influence the consistency of the formulation. Most of the cosmetic products make good use of emulsifiers in their formulations like:

  • Creams
  • Lotions
  • Sprays, and
  • Foams

Some common emulsifiers in cosmetics are:


Key Features of Various Types of Emulsifiers
Oil-in-water (O/W) Water-in-oil (W/O) Natural Silicone
  • Can be synthetic
  • Keeps oil drops packed in water
  • Used for moisturizing effects
  • Can be synthetic
  • Keeps water droplets packed in oil
  • Used for a fatty feel
  • Derived from natural resource
  • They are much into being due to a global emphasis on going green


Oil-in-water Emulsifiers


Oil-in-water EmulsionsOil-in-water emulsifiers create oil-in-water emulsions. In oil-in-water (o/w) emulsion systems, oil droplets are dispersed in water.

  • Oil is the internal/ dispersed phase whereas water is the external/continuous phase.
  • O/W emulsifiers are more soluble in water than in oil.
  • O/W emulsifiers have an HLB greater than 15.

The emulsions produced with the help of oil-in-water emulsifiers have certain advantages, disadvantages and applications which are discussed below.

Oil-in-water Emulsifiers
Advantages Applications Disadvantages
  • Oil-in-water emulsions have a good spreadability on skin.
  • They are economical and can be easily manufactured.
  • They have good physical stability.
  • Are stable at temperatures even below 0°C.
  • Oil-in-water emulsions provide a cooling effect to the skin as water constitutes the external phase of these emulsions.
  • Used in personal care products like:
    • Cleansing milks
    • Hair conditioning formulations
    • Shaving creams
    • Moisturizing lotions, and
    • Sprayable emulsions
  • More vulnerable to microbial attack and bacterial contamination.
  • Do not prove to be cost effective as addition of preservatives is required to prevent degradation of the formulation.

Listed below are few oil-in-water emulsifiers along with their main properties and applications.

Product name INCI CAS Applications Main Properties
Emulsynt™ 1055

(Liquid)
PEG-8 PROPYLENE GLYCOL COCOATE

POLYGLYCERYL-4
OLEATE
9007-48-1,
977061-81-6
and
126645-98-5
Skin / Sun care
Hair care
Fragrances
Toiletries/ Make-up
  • Acts as a water-in-oil, water-in-silicone emulsifier as well as auxiliary stabilizer for oil-in-water preparations.
HallStar® EGAS

(Flakes)
STEARAMIDE AMP

GLYCOL STEARATE
111-60-4
and
68951-62-2 or
36284-86-3
Skin / Sun care
Hair care
Fragrances
Toiletries/ Make-up
  • Acts as a bodying agent, co-emulsifying agent, emulsifying agent (o/w), emulsion stabilizing agent and viscosity stabilizer.
  • Is plant derived / vegetal-based and biodegradable.
  • Provides good electrolyte stability for both hair and skin conditioning emulsions.
HallStar® GMS SE

(Flakes)
GLYCERYL STEARATE SE
11099-07-3
and
593-29-3
Skin / Sun care
Hair care
Toiletries/ Make-up 
  • Acts as bodying agent, co emulsifying agent, emulsifying agent (o/w) and emulsion stabilizing agent.
  • Is biodegradable, plant derived / vegetal-based.
HallStar® GMS SE/AS

(Flakes)
PEG-100 STEARATE

GLYCERYL STEARATE

123-94-4,
9004-99-3

Skin / Sun care
Hair care
Toiletries/ Make-up 
  • Acts as a bodying agent, co-emulsifying agent, emulsifying agent (o/w), emulsion stabilizing agent and viscosity stabilizer.
  • Is plant derived / vegetal-based and biodegradable.
  • Provides good electrolyte stability for both hair and skin conditioning emulsions.


Water-in-oil Emulsifiers


Water-in-oil Emulsions Water-in-oil emulsifiers help in producing water-in-oil (w/o) emulsions. In W/O emulsions, water droplets are dispersed in oil (oil encases water).

  • The oil comes in contact with skin first providing more greasiness.
  • These emulsifiers are more soluble in oil than in water.
  • They have HLB between 2.5-6 are non-ionic or polymeric.

Emulsions produced by W/O emulsifiers aid in protecting and nurturing dry and dehydrated skin (moisturizing effect). Thus, these are brought to use in moisturizers, dry skin care, skin-nourishing lotions, etc.

The benefits of water-in-oil emulsifiers are given below along with their disadvantages and applications.

Water-in-oil Emulsifiers
Benefits Applications Limitations
  • Water resistant
  • Lustrous and glossy
  • Opaque and
  • Great skin feel
  • Smooth application
  • Milder than o/w and do not harm the lipid bilayers in the skin
  • Less susceptible to microbiological attack
  • W/O emulsions are used in manufacturing skin care products like:
    • Lotions
    • Sunscreens
    • Cold creams, as they are more water resistant than O/W emulsions
    • Make up products, with all types of oil
  • When applied , these may give a heavy and greasy feeling on the skin
  • Often difficult to obtain stable W/O systems, addition of stabilizers may be required

Some water-in-oil emulsifiers are listed below along with their properties and applications.

Product name INCI CAS Applications Main Properties
Capmul® MCM C10

(Powder)
GLYCERYL CAPRATE 26402-22-2
Skin care
Fragrances
Toiletries/ Make-up
  • Glyceryl caprylate.
  • Acts as water / oil emulsifier.
  • Recommended for creams, lotions, ointments and lipsticks.
Elfacos® E 200

(Paste)
METHOXY PEG-22/DODECYL GLYCOL COPOLYMER 88507-00-0
Skin care
  • Highly efficient emulsifier for water-in-oil systems.
  • Has a high water retention capacity that allows the formulation of light creams with a very high water content that do not leave the skin feeling greasy.
Cremophor® WO 7

(Liquid)
PEG-7 HYDROGENATED CASTOR OIL
61788-85-0
Skin care
  • Used in W/O emulsions, particularly suitable for liquid and modern, soft preparations that are known as soft creams.
  • Acts as a non-ionic emulsifier.
  • Does not leave a noticeable fatty sheen on the skin but produce a visible cosmetic effect.
Dehymuls® PGPH

(Liquid)
POLYGLYCERYL-2 DIPOLYHYDROXY
STEARATE
144470-58-6
Skin care
  • Acts as a W/O emulsifier.
  • Used in W/O creams containing greater fractions of high molecular oils, like vegetable oils.


Co-emulsifiers in Cosmetics


Co-emulsifiers are added to improve the viscosity and stability of the resultant emulsion. Borax, cetyl alcohol, cetearyl alcohol, etc. are some examples of co-emulsifiers in cosmetics.

Product name INCI CAS Applications Main Properties

Cerasynt® PA ester

(Flakes)

PROPYLENE GLYCOL STEARATE 1323-36-3
Skin care
Hair care
Toiletries
  • Acts as an opacifier, pearlizer and co-emulsifier.
Natrosol® PLUS 330CS CETYL HYDROXYETHYL
CELLULOSE
80455-45-4
Skin care
Hair care
Sun care
Decoratives/ Make-up
Toiletries
  • Cetyl hydroxyethylcellulose, co-emulsifier, lubricant and thickener.
  • Stabilizes O/W emulsions.
  • Used in shampoos, cosmetics, shower gels, foam bath and facial wash.
Pluracare® F127

(Solid)
POLOXAMER 407
9003-11-6 Skin care
Hair care
Sun care
Decoratives/ Make-up
Toiletries
  • Acts as a non ionic surfactant.
  • Possesses solubilizing, bodying and gelling properties.
Hostacerin® DGMS

(Pellets)
POLYGLYCERYL-2 STEARATE
61725-93-7
Skin care
  • Acts as an EO free thickener and co-emulsifier for O/W emulsions.
  • Used in liquid and creamy oil-in-water emulsions.


Silicone Emulsifiers in Cosmetics


Silicone-based emulsifiers are generally liquid at room temperature. There are two general structures for this class of emulsifiers.

  • The first one being a rake silicone polyether in which the polyether segments are attached to a silicone backbone, which allows for the addition of alkyl chains in order to increase their compatibility with organic oils.
  • The other structure is an (AB)n silicone polyether, where the polyether segments are added within the silicone backbone.

These emulsifiers have an affinity for silicone and organic oils which makes the oil phase flexible enough for the addition of other specialty silicones. Silicone emulsifiers help to reduce the cost of the overall formulation by emulsifying up to 80 percent water.

Moreover, water in silicone (W/Si) emulsifiers last longer and are wash resistant when compared to O/W emulsifiers. Silicone emulsifiers find uses in almost all skin care products.


Natural Emulsifiers in Cosmetics


Natural emulsifiers, as their name says, are naturally sourced. Since their introduction to the cosmetic industry, they have received an overwhelming response. Thanks to the "global go-green" emphasis.

Natural emulsifiers in cosmetics are more susceptible to microbial attack, and the formulation needs the addition of a preservative. They are not too effective as emulsifiers which calls for their addition in large quantities. Though a natural emulsifier containing formulation has an extra edge over others, it can have some serious repercussions on the skin of the end-user.

Being naturally sourced, natural emulsifiers in cosmetics can prove potential allergens to some individuals.

  • Lanolin - sheep's water-free wool fat is a natural emulsifier that serves as a bond between water and oil. It is added to skin care creams.
  • Lecithin is a natural emulsifier that can be used alone or in combination with other emulsifiers. They are usually based on chemicals called phospholipids and can be both plant an animal derived.
    • Depending upon the quantity of lecithin added, a formulator can achieve the desired consistency in a lotion.
    • It is majorly used in skin care formulations due to its emollience/ moisturization effect.
    • For hair care applications, in addition to lecithin, pectin and glycerin is also used.
  • Beeswax, another natural emulsifier finds good use in lip balms, lipsticks, ointments, etc.

Product
name
INCI CAS Applications Main Properties
ALKOLAN® CD 80

(Liquid)
PALM KERNELAMIDE DEA 68155-07-7
Skin care
Hair care
Sun care
Fragrances
Toiletries
  • Acts as a thickener, foam stabilizer, re-fatting agent, detergent, emulsifier and solubilizer for fragrances and essential oils in the formulation of personal care products.
  • Exhibits emolliency and neutralizing properties.
Phoenotaine® C-35

(Liquid)
SODIUM COCAMIDOPROPYL PG-DIMONIUM CHLORIDE PHOSPHATE 83682-78-4
Skin care
Hair care
Toiletries
  • Used as extremely mild surfactants, especially in baby products such as shampoos, bath and shower gels, body wash, bath beads, and products used in personal care.
Phytocompo™ -PP

(Powder)
GLYCINE SOJA STEROLS

HYDROGENATED LECITHIN
92128-87-5,
68555-08-8
Skin care
Hair care
  • Acts as a natural emulsifier.
  • Enhances barrier properties, moisturizes skin and provides a unique skin feeling.
  • It can be used in synthetic surfactant-free products.
Lecinol S-PIE

(Powder)
HYDROGENATED LECITHIN
92128-87-5
Skin care
Hair care
Sun care Fragrances
Toiletries
Decorative/
Make-up
  • Used in cosmetics.
  • Possesses good heat and oxidation stability compared to natural lecithin.


Factors for Selecting Emulsifiers


There are four main factors that deserve consideration:

  1. Marketing/ Product Positioning
  2. Performance
  3. Physical Character
  4. Chemistry

As Cosmetic Chemistry is an applied science, it is appropriate to start with the marketing as this is the main reason for us embarking on this formulation work.

Marketing


Emulsifier-Free Claim


emulsifier free cosmeticsAn emerging niche of ‘emulsifier-free’ creams designed around the philosophy that the emulsifier, being a surface-active ingredient, may be a source of irritation for very sensitive skins and that avoiding the use of an emulsifier may make the product more suitable for this demographic.

Now, this may or may not work out to be true, but nevertheless, the concept is of interest as there is some truth in the idea that surface-active ingredients (of which emulsifiers are a part) can contribute to a product’s irritation potential.

So, if you don’t use an emulsifier to hold the oil and water together, what do you use?

Small amounts of oil can be held in suspension with the use of thickeners/ stabilizers such as Carbomer, and even xanthan and sclerotium gums to a lesser degree. These aren’t emulsifiers and neither are they forming an emulsion, more of a suspension, but if the oil phase is light and dispersed well enough, these products can be made stable through steric hindrance – the oil droplets are caught up, as if in a fishing net!

Sometimes bentonite clays can also be used in this way to bring opacity to the formula and to provide an electrical repulsion layer into the structure to help repel agglomeration of the dispersed phase.

Another option in this space is a modified acrylate copolymer such as Acrylates/Beheneth-25 Methacrylate Copolymer.

  • Although this polymer is best suited to surfactant formulations, it does have a role to play in leave-on skin care.
  • As it has the benefit of being tolerant to relatively high level of salt and other water-phase destabilizers making it a versatile choice for the ‘emulsifier-free’ concept developer.

The fact that the polymer can stabilize a reasonably sized oil phase while remaining ‘emulsifier-free’ paired with its low use levels, add to the cost efficiency of this solution. Another interesting feature of these polymeric ‘emulsifier-free’ ingredients is their ability to be sprayed which opens up new doors for the formulator and marketing department.

What if you are looking to create something a bit richer and with an oil phase more typical of a traditional moisturizer?

  • Modified lecithin chemistry has become the accepted technology in the ‘no emulsifier’ space, especially because these lecithin fractions often have lipid enhancing properties and can be sold on their ‘skin compatibility’ and moisture binding powers.
    In addition, the phospholipid structure also lends itself to active delivery given how similar in structure they are to human cell membranes (well at least in terms of their chemical constituents).
  • Lecithin chemistry tends towards forming a liquid crystal network in the continuous phase, which both traps and interacts with the dispersed phase in an ultra-stable and skin compatible three-dimensional structure.

A number of companies are now offering a range of modified lecithins suitable for everything from light hypoallergenic milk formulations through to super-rich balms which should please marketing departments over the world over, but from a chemist's perspective it is hard to see how these ingredients have managed to escape the ‘emulsifier’ tag.

Ingredient Origin and Ethics


Another important consideration for the general public and formulators alike is ingredient sustainability and/or ethics. There is a steady yet growing interest in ‘palm oil-free or sustainable palm’ concepts, the achieving of which is surprisingly difficult. That said, making an emulsion without adding any palm derived ingredients used to be easy – just use petroleum derived chemicals – but these days that is just as unacceptable for a growing number of brands.

The reality is, our enthusiasm for embracing the natural revolution has increased demand for vegetable-based feedstock and those of us who have been in the industry for a while know that means either palm (orang-u-tan habitat) or Rapeseed/ canola (pesticides and bees).

Cosmetic ingredient sustainability

So today while it is still not easy to create palm free emulsion it is not impossible too, given that our previous ‘emulsifier free’ examples are predominantly palm free (lecithin phospholipids are frequently made from Rapeseed, Egg, Soybean and/or Sunflower).

In fact, it would be fair to say that the hardest thing about making a palm free emulsion today is not over which emulsifier to choose, but which supporting ingredients can be used to increase stability, viscosity (without gumminess) and overall skin feel.

INCI Name – It Has To Look Good On The Label!


natural INCI Still under the guise of marketing issues, the issue of INCI names also comes up here. While ingredient manufacturers do have to abide by a ‘truth in marketing’ legislation when they apply for their INCI names (they can’t just make them up). The reality is that a natural sounding INCI will sell more and have better shelf appeal than a more chemical sounding ingredient.

This reality has really hit home and that can be both good and bad. In some cases, we have very average ingredients (in terms of performance) becoming popular because they have a nice name while outstanding ingredients (that are still natural in many cases) are overlooked.

 »  Click Here to Get Information on Cosmetic Ingredients from SpecialChem's INCI Database Directory!

Show Me The Money!


Another important factor in the marketing basket is price. Emulsifiers can make quite a dent in the formula budget. When comparing something natural to a stock-standard petroleum-based emulsifier you can be looking at anything from three to five times the price which of course has to be justified.

In many ways this is the acid test – will customers put their money where their ethical mouths are or do we have to sell them another benefit? Blending different technologies together can be a good way to increase performance while managing price. This philosophy has kept many of the older emulsifier’s options such as glyceryl stearate SE alive and selling well.

Performance


Performance benefits of different technology have been looked at more in the chemistry section but as we are starting to see from some of the claims relating to emulsifier free formulations, the ingredient that holds the oil and water together is, in many cases expected to do so much more besides.

When the Olive derived emulsifier Olivem 1000 first came onto the market there was a great deal of interest in its ability to act as an active delivery system as well as the ingredient that just happened to make an emulsion possible. That benefit contributed to the ‘emulsifier-free’ marketing tagline (it isn’t an emulsifier; it is an active delivery system) while also helping the cosmetic chemist deliver oil soluble actives deep into the skin (theoretically).

This important dual functionality contributed to the immediate success of this technology, success that continues today in spite of the ingredients relatively high price point compared with older technology or ingredients like cetearyl alcohol which also form liquid crystal structures for a fraction of the price!

In terms of integrating new emulsifier technology into the laboratory these days the real question isn’t the price but how many benefits one gets for that price? The following benefits are possible thanks to the combination of science and nature:

  • Water resistance
  • Barrier protection
  • Long-wear characteristics
  • Increased dispersion of actives
  • Viscosity boosting, and
  • Rheological benefits

Physical Character


Something that we may overlook when considering price is the emulsifier’s physical form and this is because we often just think of emulsions as hot-process items and so the form of the emulsifier is not really a talking point. But it doesn’t have to be that way.

Electricity prices are rising in many countries and even those with cheap power aren’t in the habit of wasting it so liquid emulsifiers that can be used in cold-process applications can help the formulator to tick a few boxes from sustainability through to the economic benefits of saving time and money.

The range of liquid emulsifiers is steadily growing and is worth a look, especially for markets that demand an ultra-light touch finished product with little to no wax or butter content.

Chemistry


Of course, we couldn’t talk about emulsifier selection without talking about the chemistry. The emulsifier is the heart of the formula and while it may often seem like, today the chemistry has all been done for you, as mentioned in the beginning, there are some very challenging problems that await the professional cosmetic chemist that only an appreciation of the underlying chemistry will help solve!

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Emulsifiers & Surfactant Selection


HLB System in Selecting Emulsifiers


While preparing an emulsion choosing an emulsifier can be cumbersome. HLB system was introduced to save time and stumble upon the right emulsifier/ emulsifiers for an application. HLB stands for Hydrophile-Lipophile Balance (balance between the hydrophilic portion to the lipophilic portion of the non-ionic surfactant).

  • Between 1949-1954 Griffin developed a pretty robust yet simple HLB system and that is the standard upon which the Span and Tween pairings from ICI were arranged.
  • The method produced a scale ranging from 0-20 indicating what percentage of the emulsifier was hydrophilic. The number given was the percentage hydrophilicity / 5 (so the maximum number 20 related to a molecule being 100% hydrophilic).

This simple system was expanded upon by Davie’s in 1957, who thought that some weight should be given to the functionality of the chemical groups on the molecule.

  • This makes sense given the variety of structures available to give a hydrophilic character.
  • This method is widely used today and is one of the reasons that ionic emulsifiers can be assigned an HLB value.
  • It is also the reason that HLB numbers in 30’s is found (the maximum HLB in this system is 40).

While formulating both the emulsifier and the oils to be emulsified have an HLB attached to them – the emulsifiers have a real HLB whereas the oils have a required HLB.

It is widely accepted that the best emulsifier pairings are formed when a high HLB emulsifier is combined with an emulsifier with a low HLB rather than just selecting the emulsifier with the exact HLB you want to achieve. This combination effect serves to best fill the interface surrounding the continuous and dispersed phase, leaving less room for gaps and therefore increasing stability.

Calculating HLB Number of a System


In the HLB system, an ingredient or combinations of ingredients that need to be emulsified are assigned a number and then an emulsifier having the same number is chosen to create an emulsion.

A lipophilic/oil loving/ non-polar emulsifier is assigned a low HLB number (below 9) and a hydrophilic/water loving/ polar emulsifier is assigned a high HLB (above 11.0). The ones that fall in the range of 9-11 are intermediates.

Let's say for example we have a blend of emulsifiers to create an emulsion. To find out the HLB of the blend the following calculations can be carried out:

Values: 70% Emulsifier 1 having an HLB number 15, 30% Emulsifier 2 having HLB number 4.3

HLB Calculation
Emulsifier 1 70% X 15 10.5
+ Emulsifier 2 30% X 4.3 1.3
HLB of Blend   11.8


Evaluating Emulsifiers


How do Emulsifiers feel?


evaluating emulsifiersA very simple formula based on a common non-ionic emulsifier – Cetearyl Alcohol and Cetearyl Glucoside has been developed. This formula was then replicated with different emulsifiers, one from each different class (except silicone). The products were evaluated by an expert panel of five people as well as having their viscosity checked before being evaluated under the microscope.

The formula and feedback is not presented to help sway a decision towards or away from a particular type of emulsifier, merely it is to illustrate a point, that the emulsifier can impact everything from viscosity to feel, efficacy to stability. It also demonstrates the importance of optimizing the whole formula so as to get the most out of the emulsifier of choice. Plus there is always room for pairing up on technologies or trying something new!

So the only difference between these formulations is the emulsifier except for the cationic version which was incompatible with the thickener Acacia and Xanthan gum blend. In the cationic, a cationic guar has been used at the same level. This could be seen from the table below:

Formula
Skin Feel
Viscosity @ 3.0
Spindle
Cationic (Brassicyl Isoleucinate Esylate (and) Brassica Glycerides (and) Brassica Alcohol) Thin, high spreading, slightly tacky to touch at first drying to
powdery
19,380
Anionic (Potassium Cetyl Phosphate) Silky, takes a while to absorb, feels substantive after drying. 90,630
Non-Ionic (Cetearyl Alcohol, Cetearyl Glucoside) Easy to rub in 56,250
Mixed Anionic/ Non-ionic. (Glyceryl Stearate (and) Cetearyl Alcohol (and) Sodium Stearoyl Lactylate) Easily absorbed 74,690
Non-Ionic Synthetic (Cetearyl Alcohol, Ceteareth-20) Very thick and creamy, light after feel 160,600
Polymeric (Acrylates/C10-30 Alkyl Acrylate Crosspolymer) Ultra-light, quick break and high spreading. Tacky on drying. 15,310
Liquid Crystal Emulsifier (Cetearyl Olivate, Sorbitan Olivate) Rich waxy texture, slow spreading 82,190
HLB balance (Sorbitan Monooleate, PET-20 Sorbitan Monostearate) Very light and spreadable 13,440

Base formulation used could be observed from the table shown below:

Phase
Ingredient
%
200g
Function
Water Phase Deionized Water 71.95 143.9 Solvent
 Acacia and Xanthan Gum  0.4 0.8  Thickener/ Stabilizer 
Glycerin 3 6 Humectant
EDTA 0.1 0.2 Chelating Agent
Oil Phase Jojoba Oil 8 16 Emollient
Shea Butter 8 16 Barrier Protection
Squalane 2.5 5 Emollient
 Emulsifier of choice  3 6 Emulsifier
Cetearyl Alcohol 1.25 1.25 Emulsion Stabilizer
Finishing Touches Natural Vitamin E 0.5 1 Antioxidant
Perfume 0.3 0.6 Aroma
Preservative
1 2 Broad Spectrum
Preservative
TOTAL 100 200


Suitable Emulsifiers Used in Cosmetic Formulations






Polymer Application Check Latest News on Emulsifiers for Cosmetics

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About Amanda Foxon-Hill

Amanda Foxon HillAmanda Foxon-Hill is a consultant Chemist and Science Communicator with over 14 years of experience in the global cosmetics industry. She is a writer, after dinner speaker, strategist and lecturer in all aspects of cosmetic science and runs a successful consultancy practice under the name of Realize Beauty.

Amanda’s key skills are in networking and communicating ideas and opportunities both on a business to business and business to market level. She is an advocate for green science and through her team funds research into the development of more sustainable manufacturing practices.


About Nick Morante

Nick MoranteNick Morante is currently a Senior Chemist at IFC Solutions (formerly International Foodcraft) in New Jersey where he works with many types of colors and additives for both the food and cosmetics industries.

He has over 40 years of experience in the formulation of cosmetics, personal care products and makeup products. Prior to joining IFC, Nick was a consultant to the cosmetics industry for over 10 years providing custom formulations for clients as well as giving presentations and seminars to various companies and organizations within the cosmetics industry providing guidance in the practical use of color in consumer products.

He is current an adjunct faculty member at Fairleigh Dickinson University’s School of Natural Sciences in Hackensack, NJ where he is an instructor in the Master of Science Program in Cosmetic Science.

Nick also spent over 30 years in Research and Development at The Estée Lauder Companies where he was both a formulator and laboratory manager in the corporate makeup and hair care departments. He was also in charge of the Color Science Laboratory where he was responsible for color measurement and spectrophotometric analysis of finished products, ingredients and human skin as it relates to color that is used in various cosmetic products, as well as developing testing protocols and methodologies for many color applications.

Nick holds a Bachelor of Science degree from The New York Institute of Technology. He has taken numerous continuing education courses in the area of cosmetic science. He is a long time member of U.S. The Society of Cosmetic Chemists and has been active both on the local and national levels having served on the executive committee for the Long Island Chapter and on the National Board, serving as Area Director and National Secretary. He has been elected a Fellow of the Society and is an instructor for the Society’s Continuing Education Program (CEP) Program in the area of color and makeup formulation problem solving and troubleshooting.

He has given many seminars and presentations worldwide as well as to the SCC, CTFA and HBA. He has been awarded numerous patents and has contributed many articles and papers and authored chapters in numerous cosmetic, technical and beauty publications and texts.

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