Oil and emulsifier compatibility question

Hi Guys,

I need to pick your brain on separation of oils and emulsifiers. I am trying to create cheap bath blooming oil. The idea is just to mix 20% of an emulsifier with 80% of oil and maybe add some fragrance.

Now the problem: oil and emulsifier separate. I tried following combination:

Polysorbate 80 + Almond oil – separates

PEG-40 HCO + Almond oil - separates

Polysorbate 80 + Olive oil – separates

Polysorbate 80 + Isopropyl Myristate – separates

Polysorbate 80 + Mineral oil – separates

Polysorbate 80 + Sorbitan Oleate + Almond oil (HLB calculated) – works initially, but then separates after a week or so

Polysorbate 80 + C12-15 Alkyl Benzoate – works!

It’s not about matching HLBs. I can see the trend here, polysorbate 80 works the best with oils that have high polarity. Out of all attempts, the only successful one was with the highest polarity ester.

Could you please explain the logic behind it to me?


Comments

  • Can someone with a deeper understanding of chemistry behind it contribute please?
  • PharmaPharma Member, Pharmacist
    You're using something closer to detergents than emulsifiers. A high HLB detergent/emulsifier has a larger part of its molecule being water soluble than oil soluble. Hence, it would have to solubilise in itself which in pure oil means inverse micelles, a state it can not achieve.
    Either you add a "water" phase (glycerol or the like might do as well) and create an "emulsion" or you use an oil soluble emulsifier. Which means something with an HLB of below 4 if only 1 emulsifier is used and to be on the super safe side (and get very re-fattening bath) or below ~8 if a combination of a high and a low HLB emulsifier is preferred (faster "milk" forming without stirring and probably even some foam).
    I made a milk to oil cleanser with 1% Tween 20 (similar to polysorbate 80), 1.5% glyceryl monostearate, and 1.5% sorbitan monostearate in a mix of oils and paraffin and it didn't separate but turns milky and just slightly bubbly (foam could be boosted easily with some tweaking, I'm sure). You certainly have mixed similar things with success: Their behaviour is similar to a bath oil. Not sure what a blooming bath oil is, though.
    If you want to add only a high HLB emulsifier/surfactant: A D-phase might work or add so much emulsifier that you actually have oil-filled micelles swimming in a pool of emulsifier... a stupid thing, because that would be basically a shampoo without water. An oil bath doesn't need to form a stable oil in water emulsion in your hot tub. An oil bath formula just needs to form an emulsion-like or milky state visually stable for 15-30, at most 60 minutes, depending on how long you're soaking before the bath water, by then lukewarm, goes down the drain. Medicinal oil baths here in CH have an emulsion stability of about 5-15 minutes... not enough time for romance but they're made for sick people with skin issues. One sales rep was even VERY proud that their product cracked the 10 (or was it 12?) minutes mark and I was like "Dude, what exactly does your R&D team do? Do they hire cause I've been dreaming of getting paid for doing nothing...." (I did only think that but temptation was nearly overwhelming :smiley: ).
  • @Pharma, as always thank you very much! There is a surfactant called Cithrol 10 GTIS by Croda (but it's expensive and I need to ship it from Italy while poly 80 is like £5 for a lt). It is used specifically to make such products. I noticed that when they mix it with mineral oil (I am referring to Croda's formulas), they always add PG. I thought it was a waste, but now I understand why.

    Funny enough, the conconctions with polysorbate 80 are stable for more than 15 minutes :) but you need to shake them before use. And I don't want to do it because if it separates and you need to shake it I take it as a failure :smiley:

    I tried low HLB liquid emulsifiers but they create w/o.. I will continue experimenting now when I have more clarity of the reasons behind the separation. As a default option I have one stable version: 20% Poly 80 and 80% C12-15 Alkyl Benzoate.
  • PharmaPharma Member, Pharmacist
    Yup, that's the job of PG, creating a water phase without water and it has a refractive index similar to oils which turns the droplets in an emulsion "invisible" (the emulsion is not white but transparent).
    I guess there's a small misunderstanding regarding stability: It's not your product which only has to remain stable for 15 minutes but the 200-300 litres of hot water in your bathtub once you added your bath oil into it ;) .
    And you don't need a o/w system. All you need is a transient emulsion in your bathtub, that's the trick. A theoretical w/o emulsifier system will not form a w/o emulsion at a dilution of 1:>10'000 but a semi-stable o/w emulsion and that will do as long as the bath lasts, which is between 10 and 30 minutes, probably 1 hour if you feel like being a mermaid or don't mind soaking in lukewarm water.
    If you're fixed on HLB values: go with an HLB between 7 and 9 (as an example: Eubos uses polyglyceryl-3 palmitate). That's the range of "maybe w/o and maybe o/w". This allows for easier solubilisation of the emulsifier (as pseudo-w/o) and an o/w emulsion in your bathtub.
    Regarding cheap: You might want to add 10-20% octyldodecanol (Eutanol G). It helps keeping oils of different polarities together (or oils and emulsifiers) and, although not an emulsifier per se, it renders the oil easier to emulsify in your bathtub. The advantage is, that it's not turning your oil opaque and it might make it more fluid depending on the oils you use. For example glyceryl stearate, which is used for the same effects, makes the oil more gel-like and imparts opacity. Another "oil binder" (dunno how a substance which helps mixing oils of different polarity is called, hence I call it unprofessionally "oil binder") are ethylhexyl stearate (Cetiol 868) and related esters of branched chain alcohols with straight chain fatty acids. These, however, won't show a benefit regarding easier dispersion of the oil in bath water and aren't as effective in solubilising high HLB emulsifiers in oil. Or stick with alkyl benzoate :smile: .
  • Very useful information! I have both octyldodecanol and ethylhexyl stearate and will experiment with mixing different polarities. Thank you!
  • Bill_TogeBill_Toge Member, Professional Chemist
    you need emulsifiers with a much lower HLB, e.g. Span 20 or polyglyceryl-4 oleate
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • Thank you @Bill_Toge. I tried polyglyceryl-4 oleate and sorbitane oleate in combination with Polysorbate 80 (to bring HLB of an emulsifier to the same as oil). It separates after some time (not right away). I will try it alone and see how it works 
  • PharmaPharma Member, Pharmacist
    Don't go by HLB requirement of the oil. Since you have no water there's no point in considering it ;) . Out of curiosity, what was the HLB you calculated and how much did you add to the oil? Polyglyceryl-4 oleate has a high HLB, no? Mixing that with Twen 80 is obviously too much hydrophilicity. But it just doesn't sound right that sorbitan oleate and Tween 80 wouldn't work... they're supposed to work. Well, another demonstration that cosmetic chemistry is an empirical science and doesn't care too much about theory.
  • Polyglyceryl-4 oleate has an HLB of 5 https://www.makingcosmetics.com/Polyglyceryl-Oleate_p_131.html
    Almond oil is 6 so it was mostly polyglyceryl-4 oleate and small amount of poly 80. Still sinks.
    When I say does not work I don’t mean that the blend fails to create an emulsion in water. They all do (all combinations above) but the emulsifier sinks to the bottom of the bottle and I need to shake it. I agree it’s not an emulsion to calculate HLB but I was looking for a way to stop separation and just tried that to see whether it helps.
  • PharmaPharma Member, Pharmacist
    Dang, my notes said high HLB... re-looked it up and turns out, we're both right (CLICK). Okay, you have a low HLB quality and that really should be fine with Tween 80.
    I know what you mean but I don't understand why it's not working (and I was confused you didn't understand me because you mentioned 15 minutes like I did but in a different context).
    Polyglyceryl-4 oleate alone does work, no? It's cold processable and should do really fine. I'm not sure if Tween 80, although liquid and usually cold processable, might require heating and mixing during cool-down like other PEGs do. Not that it's a problem of preparation rather than incompatibility.
    Oh shuuush, I just re-read your first post: 20% emulsifier and 80% oil? Really? You don't need that much for an oil bath, that's complete overkill and probably the issue of separation!
  • Thank you for the polyglycerol esters doc. I will give it a proper read. 20%... the logic comes from Croda’s formulas. They dump 20-30% of emulsifies in their microemulsion oil cleansers. I figured out in an empirical way that it’s super irritating for eyes (and supplies exaggerate amount of materials in general) but I thought that for bath oil should be ok. Thank you for suggestions. I will run more experiments with low hlb emulsifiers only and see if that works. I have a large bottle of sorbitan oleate for which I have no use. If it works I will kill two birds with one stone.
  • PharmaPharma Member, Pharmacist
    Which emulsifiers do they use and what else do they add? Their product might be what's called a D-phase. This is cool technology but it results, if the name tells the truth, in a microemulsion and that, I can imagine, isn't very much fun in a bath since you won't see that there's actually oil in the water. Microemulsions are transparent/translucent with a bluish shimmering (Tyndall effect) and skin doesn't feel nourished afterwards (the oil droplets penetrate skin way better than common oil drops which remain mostly on the skin).
    BTW since you're going to do a few changes: If you want to combine two emulsifiers, theory has it that you'll get a better stability for o/w emulsions (the final bath) if only one is an oleate ;) . It might no longer be a cold process or use Tween 20 or 60 instead of 80.
  • Hello All,

    An update for those who will be looking up this topic. Polysorbate 80 mixes well with any ester with very high polarity. Not medium but high. Examples: C12-15 Alkyl Benzoate (as above), Octyldodecanol, Caprylic Capric Triglycerides. Works wonders as oil makeup remover (poly 80 is quite gentle on eyes, and this type of product dissolves waterproof mascara) or blooming bath oil (milky emulsion is created when added to the bathtub, oil doesn't float on the top). 
  • Hello, ngarayeva001! Did you try your formula with Tween 80 and Sorbitan oleate? Do you have an update on that?
  • It works initially but the separate.
  • A lot of my DIY projects are oil cleansing related for example i make cleansing balms and liquid cleansing oil using mostly sunflower oil with polysorbate 80 as the emulsifier.
    For liquid cleansing oil, the oil and polysorbate 80 always separate after a while (polysorbate 80 will sink to the bottom of the bottle and i will need to shake before use). Now i know why... thank you..

    Btw, what if i still wanna keep using polysorbate80 and plant oil (sunflower oil) but dont wanna see polysorbate 80 at the bottom? What should i add? I like polysorbate 80 because it's so easy to find in my country, price is cheap, and yes, i agree with you @ngarayeva001 when you mentioned polysorbate 80 is gentle on eyes to remove waterproof mascara. Love it!


  • Speaking of cleansing oils, there's a product that i've been wanting to copy for a while but simply couldnt find the right available ingredients: Belif: Cleansing Gel Oil Enriched... It's a cleansing oil that has a little bit of body to it but still looks transparent.. i came across sucragel on the internet but it doesnt ship to my country and it's VERY expensive. anyone can suggest an oil thickener that could work? thanks!
  • ngarayeva001ngarayeva001 Member
    edited October 2019
    Polysorbate 80 is very polar on its own and it needs very polar ester to mix properly. You can't achieve the same with vegetable oils because they are  not polar enough. Try to find alkyl benzoate, it's usually very cheap. It's also a very versatile ingredient, so if you find it get a lot (I don't buy less than 1 lt).

    Sucragel is sticky and isn't easy processable. I personally don't like it. Please post ingredients list for that product. There are many ways to thicken oil, it all depends on what you are trying to achieve. From the top of my head without knowing much about your benchmark product - cera bellina.
  • @ngarayeva001 i was just thinking, can we make a 2-phase cleansing oil : about 50% the top part will be a mix of plant oils and 50% the bottom part will be a mix of tween80+ alkyl benzoate/ isopropyl myristate / MCT oil ... it'll definitely be a product where you have to shake before use, but 2-phase products are pretty cool... do you think this is achievable?
  • If you want to have two obvious phases, I would suggest polysorbate 80 with some type of hydrocarbon, say mineral oil. What you suggesting might end up being very cloudy plus partially separated. The layers won't be obvious enough to make it a marketing thing.
  • Pharma said:
    Another "oil binder" (dunno how a substance which helps mixing oils of different polarity is called, hence I call it unprofessionally "oil binder")
    @Pharma I think it’s called a “coupling agent”.
  • PharmaPharma Member, Pharmacist
     @Sponge Hmmm.... that reminds me of coupling reagents aka coupling agents = compounds which react with substrates to speed up or enable a chemical coupling reaction such as esterification or amid bond formation.
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