Reduce oil syneresis without waxes

JonahRay · May 10

Hi there!

I have a formula with the following ingredients:

squalane, caprylic/capric triglyceride, silica dimethyl silylate, petrolatum, glycerin, polymethylsilsesquioxane, tribehenin, bisabolol

Unfortunately I can't divulge the concentration of each ingredient - I know that may limit me in terms of what help I can get.

I am looking to reduce the amount of syneresis I get with this product.

I am also wondering if there are suggestions other than waxes to achieve this as it is a a gel texture that is very light on the skin - I don't want to mess to much with this.

Any help is appreciated!

Perry · May 10

Not a direct answer to your question but for people who are curious about syneresis and the causes, you'll find this helpful.

Is this a solid or semi solid product?

JonahRay · May 10

It's a semi solid oil-gel.

Image: https://chemistscorner.com/cosmeticsciencetalk/uploads/editor/rk/5qybtk8oe1ka.png

chemicalmatt · May 10

@JonahRay ;Are you sure its oil not glycerin popping out? Switch out the glycerin with dipropylene glycol and see what happens.

JonahRay · May 10

@chemicalmatt I can't be completely sure but the liquid seeping out is thin and greasy, not sticky. I can try your suggestion out though as I have some dipropylene glycol on hand. Would propylene glycol work as well (I keep this in stock in larger quantities)?

chemicalmatt · May 10

Negative, the glycol ether works best. If it is oil creep then perhaps try adding a bit more tribehenin and cooling that gel REALLY SLOWLY. If that crystal structure doesn't form right you will get the syneresis you see there.

Graillotion · May 10

I am no expert...but I use something like a cross linked polymer towards this end:

INCI: Dimethicone (and) Dimethicone/Vinyl Dimethicone Crosspolymer

Not sure if it works.... just don't get syneresis, however I put it in at the inception of the formula...so never tested it without. Other can chime in...if this is a viable option.

MarkBroussard · May 11

@JonahRay

Out of curiosity, are you homogenizing your mixture once melted or are you just mixing using a stirrer? If you are not, you might try homogenizing.

ketchito · May 11

chemicalmatt said:

@JonahRay ;Are you sure its oil not glycerin popping out? Switch out the glycerin with dipropylene glycol and see what happens.

I agree with @chemicalmatt. Glycerin doesn't seem to fit within that mixture. What's the purpose of your product? Perhaps you can remove it without affecting your claims, or replace it with ethylhexylglycerin.

Pharma · May 11

You might try adding a w/si emulsifier (such as DOWSIL ES-5600 or maybe readily available PGPR or PEG-10 dimethicone?) if you have to use glycerin. Depending on the emulsifier, you'll have to tweak your formulation a wee bit.

Alternatively, using a sorbent (such as unmodified silica) for glycerin could work as well... however, there are several drawbacky to that strategy.

JonahRay · May 11

@chemicalmatt I will try increasing the tribehenin and see if there is any improvement. I will also try swapping out glycerin for dipropylene glycol.

@MarkBroussard I heat & homogenize for quite a while once adding in the silica dimethyl silylate. There is not much to indicate when is a good time stop. I tried to look up some more information about homogenizing and silica dimethyl silylate but nothing came up.

@ketchito It is a gelled oil balm that replaces conventional petrolatum or vaseline. The glycerin is just there as a bit of humectancy and for skin feel. I understand that it doesn't seem to fit but I was under the impression that it could be incorporated into the mixture with silica dimethyl silylate but maybe it's more incompatible than I originally thought.

@Pharma I have peg-8 dimethicone that I could try.

I'm not confident the issue is glycerin, the liquid has a dry oil feel. Is it possible that glycerin is contributing to the problem even if its not what is separating out.

The frustrating thing with this product is no matter how many stability tests I've done it always passes with flying colours but then I get customer reports & pictures of it seeping... it doesn't seem to be heat related as I have customers in very hot climates who say theirs are all good (also it always passes test in an incubator).

Of my whole product collection - this is the one that gives me the most grief...

MarkBroussard · May 11

@JonahRay

You might want to consider Isosorbide Dicaprylate or Sunflower Seed Oil Unsaponifiables if you're looking for some sort of moisturizing component. Both are oil soluble. I concur with other posters that the most likely culprit is Glycerin. Do a knock-out w/o glycerin and see if it confirms.

Pharma · May 12

I suspect that it's a mixture of glycerin and bisabolol

.

JonahRay · May 12

Pharma said:

I suspect that it's a mixture of glycerin and bisabolol .

Why bisabolol? Isn't it oil soluble?

MarkBroussard · May 12

@JonahRay

You can get syneresis even with a completely anhydrous formula if the polarity of the oils are substantially different.

JonahRay · May 13

MarkBroussard said:

@JonahRay

You can get syneresis even with a completely anhydrous formula if the polarity of the oils are substantially different.

I was told once that I could add c12-15 alkyl benzoate to balance the polarity disparity between CCT and squalane for better stability. Do you have any thoughts on that as an option?

MarkBroussard · May 13

@JonahRay

I honestly don't know, but you might give it a try. 2% Rice Bran Wax would probably solve your problem.

Pharma · May 13

JonahRay said:

Why bisabolol? Isn't it oil soluble?

It is, but it's also glycerin soluble. And this could explain the greasy/oily appearence of the 'exudate'.

BTW w/o emulsifiers wouldn't just emulsify glycerin in oil but can also help dissolving different polarity oils in each other (like in your case three: triglycerides, hydrocarbons, and silicones). However, it doesn't always work...

JonahRay · May 13

Okay so, this is what I'm going to try. Several knock out experiments... but I have a feeling replacing some squalane & CCT with C12-15 alkyl benzoate, increasing the amount of tribehenin, replacing the glycerin with dipropylene glycol and reduce the amount as well, could lead to a satisfactory upgrade to the formula. Thanks for everyone's help!

Pharma · May 13

Just as a 'nice to know': Alkyl benzoate is like a HLB emulsifier with a negative value, so to speak. It's so lipophilic that it does not interact with a water phase but only with the interphase. Meaning, it acts like an emulsifier for different polarity oils and quasi-oils

.

JonahRay · May 13

Pharma said:

Just as a 'nice to know': Alkyl benzoate is like a HLB emulsifier with a negative value, so to speak. It's so lipophilic that it does not interact with a water phase but only with the interphase. Meaning, it acts like an emulsifier for different polarity oils and quasi-oils .

That is a very good 'nice to know' haha, thank you!

evchem2 · May 20

@Pharma do you have any literature on the alkyl benzoate interphase interaction? Is that just based on the structure? I'm a little confused since most sites I've seen say it has a 'required HLB' near 13.

Pharma · May 20

@evchem2

A: Correct, it's the benzyl ring which dictates this.

B: Stop using/thinking HLB. It's a system which is only suitable for pure PEG-based emulsifiers in very simple mixtures. Start using HLD.

C: True, it has a 'required HLB' or, in HLD language, an EACN and not a Cc value.

But, as said in point A, alkyl benzoates behave differently to standard oils. For those who like the HLB system more, benzyl rings behave similar to PPG moieties as found in extended surfactants (obviously, alkyl benzoates would correspond to one without the PEG end chain). Back in the day, you could find the benzyl ring in nonylphenol surfactants too and it was that aromatic ring which gave it the extra kick (and the toxicity which led to its ban). Alkyl benzoate are like such an 'interface-active' surfactant but with a hydrophilic head group which tends to zero in lenght = HLB becomes negative. I know, it's counterintuitive and true surfactancy is obviously completely lost.

JonahRay · May 26

Okay after a plethora of trials - peg-8 dimethicone helps to retain to glycerin in the formula. After knockouts it seems it's actually the squalane that is separating - likely due to polarity I would think. I have tried multiple ratios of cct, c12-15 alkyl benzoate and squalane but eventually the squalane just separates out in the incubator. Does silica dimethyl silylate not thicken squalane or is the polarity disparity pushing squalane out of the gel? Removing squalane altogether is not the BEST option considering its a marketing point... but maybe I should be swapping cct out for an emollient with the same polarity of squalane?

mindyourmolecules · May 26

I had a project years ago where I was trying to gel squalane using silica dimethyl silylate, and it does thicken, but I was never able to achieve stability, even with very high levels of the gellant. If you were able to get the glycerin into formulation, you could try swapping it out for Dermanet Squalane - the squalane is 'encapsulated' inside of glycerin. If I recall, it's only about 1% squalane, so you wouldn't be able to incorporate a high amount, but if it's mainly for the marketing story it could be worth a try!

Reduce oil syneresis without waxes

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