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cetyl alcohol or stearyl alcohol in w/o!!
I wonder if we can use fatty alcohols in w/o concept? I believe it will solve stability and viscosity problems,
Anybody can guide me in this point?
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7 Replies
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What do you mean? Fatty alcohols have been used for ages in o/w emulsions as structuring agents.
Edit: Sorry, I misread, you mean w/o…
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This reply was modified 1 year, 1 month ago by fareloz.
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yes I mean water in oil,
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This reply was modified 1 year, 1 month ago by
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There are some theoretical considerations where I don’t know if and when, how, they might contribute to (in-)stability of w/o emulsions.
What we know is the following:
- Fatty alcohols ‘structure’ the water phase by forming lamellar structures. This increases stability and viscosity because these structures are in the outer phase. In case of w/o, they would be in the inner phase.
- Mixed phases are possible but due to the low stability of w/o emulsions and ‘inverse lamellae’ (unlike the other lyotropic phases, lamellar structures can’t be inverted but the oil and water content will be different and hence their performance and effects will differ), coexistance of w/o and lamellar structures are unlikely to work IMHO.
- Fatty alcohols are, as of yet, unpredictable in their effect on w/o emulsions (and also on o/w) because they behave as surfactants and high polarity oils at the same time. The net effect depends on ratios of fatty alcohol to surfactant and fatty alcohol to oil as well as all their absolute amounts and the type of surfactants and oils… If you’re interested in some recent scientific literature on the topic: CLICK
What this publication means is, on one hand. that the effect as emulsifier is not as strongly pushing the emulsion towards w/o but, not very astonishingly, is in the range where the lamellar structure forming emulsifiers are. On the other, the effect as oil is highly favouring w/o (but for that, you’d have to add considerable amounts of fatty alcohol). This still seems promising but then there’s the fact that ‘nobody uses fatty alcohols in w/o because they’re said to kill stability’.
We’ve had that topic last year or so, I think…
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thank you for the detailed answer, it is really helpful. lets discuss this point if I consider adding more than 2% of fatty alcohol and adding very little amount of like a tween in a very little percentage besides high percentages of low HLB emulsifiers of w/o I think we will get something very similar to w/o cream in performance and more stable as o/w emulsion but you can consider it a new type as a mixed emulsion, do you agree with me in this point?!🙂
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..lets discuss
this point if I consider adding more than 2% of fatty alcohol and adding
very little amount of like a tween in a very little percentage besides
high percentages of low HLB emulsifiers of w/o I think we will get
something very similar to w/o cream in performance and more stable as
o/w emulsion but you can consider it a new type as a mixed emulsion, do
you agree with me in this point?Over 2% would be what’s used for lamellar structures. This is likely going to interfere with standard w/o emulsions.
Why a Tween? What good does that do in a w/o emulsion? You mean as ‘hydratation promoter’? Very risky, because this will likely raise HLB too much.
A w/o emulsion is usually never more stable than an o/w one. You can get them stable (in the yar) by gelling the oil phase heavily enough (thinking of traditional cold cream) but this would impart feeling.
I don’t think you’ll get a mixed type emulsion. Feel free to try it out! What you should do then is to prepare the lamellar structure within the water phase (i.e. fatty alcohol plus high HLB emulsifier) and let it settle (which may take up to a few days). Opt for a crystallinisation temp (the melting point of the fatty acid chains) at least 10°C above the temp you use to prepare the w/o emulsion (which, by preference, isn’t of a cold process type). This means that the fatty alcohol of choice is behenyl alcohol. Behenyl alcohol is best mixed with some low HLB co-emulsifier such as glyceryl monostearate, sorbitan behenate, sucrose distearate, or the like to ensure sufficient swelling. To that blend, you’d have to add roughly 10-20% (relative to behenyl alcohol + GMS or similar… best to try the lower % first) of a salt tolerant and non-water soluble high HLB emulsifier (meaning that anionic ones sound great but are usually water soluble, cationic ones don’t play well with w/o, and and PEG-based ones may not work properly due to salt reducing water binding capacity… maybe polyglyceryl-6 distearate or polyglyceryl-10 pentastearate? They also tend to form lamellar structures on their own).
Once you’ve prepared this ‘gelled’ water phase, slowly and under low to medium sheer, add it to an oil phase which contains a fair amount of oil gellant, quickly cool down, and hope that the emulsifiers within the two oil phases don’t diffuse to the other one because else, the system will crash.
Good luck and keep us posted!
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@Pharma is mainly right on here, lamellar liquid crystal (LLC) formation stabilizes oil-in-water emulsions pretty much exclusively and the builders fatty alcohols and glyceryl esters accommodate this as we all know. Invert emulsions like w/o and w/Si are an entirely different story: its upside down world like that Stranger Things TV series. Those same builders will destabilize these, and your o/w nemesis salt will stabilize them, as will having a high internal (disperse) phase. Upside down, right? Also pays to remember that virtually all invert emulsions are intrinsically unstable thermodynamically. Place the sample in an incubator for ACC testing and you’ll rarely see 60 days intact without a rheology additive in there.
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as I mention in my reply above Can we consider it as a new form of emulsion combining performance of w/o and stability of o/w?
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