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Olivem 1000 liquid crystal emulsifier - how to emulsify properly & avoid excessive gelling?
Using 3% Olivem 1000 (Cetearyl Olivate (and) Sorbitan Olivate) and 2% Glyceryl Sterate to emulsify a ~10% oil phase.
In a 250 ml beaker at stir speeds above 600 rpm with a 75mm sawtooth impeller invariable leads to the formula gelling excessively between 75 - 40C, going under 40C it turns into a liquid pourable and I assume lamellar emulsion again. This happens regardless if I add oil to water or vice versa.
What’s likely the best solution here that will allow me to make larger e.g. 500 ml test batches?
1. Do very slow < 600 rpm stirring above 40C?
2. And/or get a paddle impeller? E.g. http://www.ebay.com/itm/Propeller-PTFE-Paddle-A-Type-Used-at-low-speeds-Impeller-64mm-/192100167545?hash=item2cba0fef79:g:w5kAAOSw-itXraz3
3. Add oil to water phase EXTREMELY slowly over several minutes?It’s has great skin feel and stability, but it’s tricky to work with. Let me know if you have any protips.
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7 Replies
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This effect is very common when making emulsions by phase inversion (that is adding the major phase to the minor phase during emulsification).
The phase inversion method is a very good way of making “fine grained” emulsions but does need careful mixing. You may find a paddle impeller better than the saw blade and it is definitely worth trying.
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Your first problem is that you are not using enough Olivem 1000 … You’ll need 6% to 8%. It also is best if you include 0.3% Xanthan Gum when formulating with Olivem 1000. In addition to the Glyceryl Stearate, you’re going to need approximately 1% to 2% Cetyl Alcohol to thicken it up. It can be a tricky emulsifier to work with.
If you used a homogenizer, that would be much better. Just stir continuously … when the temp reaches 50C or so, it will form a stable cream. I think your thinning under 40C is due to either not enough Olive 1000, that you don’t have a thickener (Cetyl Alcohol or Cetearyl Alcohol) to begin with or perhaps you are adding heat sensitive ingredients at that point that thin the emulsion … something with Caprylyl Glycol in it, for instance.
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If you do not already have a paddle and/or anchor impeller, you should definitely get at least one of them. They are invaluable for emulsion making, particularly for scale-up uses. Homogenizing/sawtooth mixing during cooldown can disrupt the structure of a cream/lotion.
The ebay impeller you linked to does not have straight sides. This is bad for mixing/heat transfer. I wouldn’t recommend it.
Also, cooling in an ice/water bath after emulsification can dramatically improve stability and texture of lab batches. Unfortunately, rapid cooling like that isn’t a very scaleable technique over 10 liters or so, and has been the source of a great deal of embarrassment over the years when formulating chemists try to get manufacturing facilities to replicate their wonderful lab formula at a much larger scale. (This, by the way, is why you should always insist on making a pilot batch. In the long run, it saves a lot of trouble)
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Thanks for the thoughtful replies
I decided to design and 3D print my own anchor impeller last night in ABS plastic, which I believe should work fine for sample making with most formulas. It definitely works well and looks pretty funky in bright orange.
50 mm diameter, 50 mm tall, for 8 mm shaft with bolt on end.
Freecad file: http://www.filedropper.com/50mmabsimpeller2
STL file for printing: http://www.filedropper.com/impeller10001@MarkBroussard I’m not sure that’s true, it’s a small oil phase and the formula is stable for 1 month at 45C, but I can always give it a shot, just concerned it’ll ruin the watery skin feel. I previously went down from 4% Olivem to improve sensory properties. But could give it another shot going up to 6%.
@Bobzchemist good to know about scaling up! When would you go paddle over anchor? They also have a 50mm anchor which would be perfect for small scale 250ml samples.
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Well, when I talk about scale up, I talking about going from 1 kilo to a couple of hundred. If you’re making a kilo or two, it doesn’t matter hugely which one you use. The differences are minor.
Unless, of course, you’re making something very thick, like mascara. In that case, you need the paddle, because the stress on the anchor configuration will break the impeller.
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@Bobzchemist I see. I was referring to the cooling, but you’re saying paddle and anchor impellers perform similarly on the sub 200 kg scale?
I tried the new impeller at 400 rpm, and what I got adding the oil to the water phase was some gelling under 50C for it to revert to liquid again under 40C. Maybe gelling can be prevented with 200 rpm stirring, or maybe it’s not preventable with this formula and maybe it doesn’t matter.
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not quite at this scale yet
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