Experimenting with different emulsifiers

I know there are lots of different types of emulsifiers but how do different emulsifiers make my emulsion feel?

After all the reading in my last article: The Secret Life Of The Emulsifier  I feel it is time to bring things back to the lab again as we try out a very simple yet effective experiment to demonstrate how one might answer that very important question ‘This chemistry is all well and good but how do these emulsifiers FEEL?’

I developed a very simple formula based on a common non-ionic emulsifier – Cetearyl Alcohol and Cetearyl Glucoside. 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 idea of this base formula was for it to be stable and easy, I wasn’t too bothered about anything else at that stage.

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 I used a cationic guar at the same level.

 

Formula 1: Cationic (Brassicyl Isoleucinate Esylate (and) Brassica Glycerides (and) Brassica Alcohol)

 

Formula 2: Anionic (Potassium Cetyl Phosphate)

 

Formula 3: Non-Ionic (Cetearyl Alcohol, Cetearyl Glucoside

 

Formula 4: Mixed Anionic/ NonIonic. (Glyceryl Stearate (and) Cetearyl Alcohol (and) Sodium Stearoyl Lactylate)

 

Formula 5: Non-Ionic Synthetic (Cetearyl Alcohol, Ceteareth-20)

 

Formula 6: Polymeric (Acrylates/C10-30 Alkyl Acrylate Crosspolymer)

Formula 7: Liquid Crystal Emulsifier (Cetearyl Olivate, Sorbitan Olivate).

Formula 8: HLB balance (Sorbitan Monooleate, PET-20 Sorbitan Monostearate)

Formula Number	Skin Feel	Viscosity @ 3.0 Spindle
1	Thin, high spreading, slightly tacky to touch at first drying to powdery.	19,380
2	Silky, takes a while to absorb, feels substantive after drying.	90,630
3	Easy to rub in	56,250
4	Easily absorbed	74,690
5	Very thick and creamy, light after feel	160,600
6	Ultra-light, quick break and high spreading. Tacky on drying.	15,310
7	Rich waxy texture, slow spreading	82,190
8	Very light and spreadable	13,440

 

Base formulation used.

 

Phase	Ingredient	%	200g	Function
A. Water Phase	Deionised Water	71.95	143.9	Solvent
	Acacia and Xanthan Gum	0.4	0.8	Thickener/ Stabiliser
	Glycerin	3	6	Humectant
	EDTA	0.1	0.2	Chelating Agent
B. 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	2.5	Emulsion Stabiliser
C. Finishing Touches	Natural Vitamin E	0.5	1	Antioxidant
	Perfume	0.3	0.6	Aroma
	Preservative (Phenoxyethanol, Ethylhexylglycerin)	1	2	Broad Spectrum Preservative
TOTAL		100	200

 

 

Microscope Slides:

As expected the polymeric emulsifier produced the largest dispersed phase droplets.

Top: Formula 6: Polymeric (Acrylates/C10-30 Alkyl Acrylate Crosspolymer) 

Bottom: Formula 5: Non-Ionic Synthetic (Cetearyl Alcohol, Ceteareth-20)

The Cationic emulsifier Vs Anionic Emulsifier.

Stability:

4 weeks in 40C oven pass at time of going to press.

Conclusion.

There really is a lot to take in when developing complex cosmetic formulations including the ionic strength and polarity of your water phase, your marketing departments wishes, the viscosity and feel you are trying to achieve and the packaging you hope to sell in. That said, today we are lucky enough to have at our finger tips a wide range of different ‘drop-in-and-go’ technology to help us balance creativity with tight deadlines. My only hope is that we remain engaged and inspired by the chemistry that underpins this convenience so we can keep on innovating for centuries to come.