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Air entrapment and phase separation
Hi! I’ve been trying to formulate a base lotion for a sunscreen, but i’m having problems with the air entrapments in the final product, then when I tried making the sunscreen there’s a phase separation after 2-3wks. Can anyone help me, it would be much appreciated. Below is the formula and the procedure that I’m following:
(oil Phase)
Cetyl alcohol 1%
Stearic acid 1%
Ceteareth-20 (and) Cetearyl Alcohol 3.5%
Cyclopentasiloxane 2.5%
Caprylic/ Capric Triglyceride 8%
Dimethicone 2.5%
Propylene Glycol 4%
Octocrylene 10%
Avobenzone 2%
Titanium Dioxide, Alumina, Simethicone 4%(water phase)
Water 55.4%
Glycerin 5%
Carbomer 0.2%Preservative 1%
When I do the base lotion formula, I just removed the sunscreen actives(Octocrylene, Avobenzone, TiO2 Alumina Simethicone) and adjust the quantity of water.
Procedure:
1. Disperse well the Carbomer into the water, add the glycerin then heat at 70-80deg C
2. Mix oil phase except for the dimethicone, cyclopentasiloxane (I’ve read that silicones should not be heatedabove 50deg C) and TiO2 sunscreen, heat at 70-80deg C
3. when everything in the oil phase is melted, add TiO2, dispersed well
4. at <50deg C, add dimethicone and cyclopentasiloxane
5. Add the water phase to the oil phase slowly, homogenize.
6. At below 45deg C, add the preservative. homogenizeAnyone who could give me advice and/or suggestions, please help, Thank you in advance.
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8 Replies
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I don’t see that you are neutralize the carbomer.
Add NaOH 10% Solution at step 6- 0.5%
Move the Propylene Glycol to the water phase and lower it to 2% or less, It diluted the end product and effects the carbomer.
Lower the Caprylic/ Capric Triglyceride to 2%.
Add C12-15 alkyl benzoate- 5-7%.
If you still get separation-
use Polyoxyethylene (40) stearate 1-2% and Sorbitan Tristearate 0.2-0.5%
instead of Cetyl alcohol & Stearic acid.
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you’re adding the water phase to your oil phase near the drop point of the solid materials, so it’s likely that the batch is not being mixed properly
I’d suggest adding the water phase at at least 65°C, to ensure everything is fully liquid
also I agree with @ZivBA about the carbomer; it needs to be neutralised
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I agree. Neutralize Carbomer. We always used TEA or AMP to do it.
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Bill is also right about the drop point. You can’t emulsify solids, or even pastes very well. You might lose some of the silicone due to temperature, but your oil phase needs to be completely fluid when you emulsify it and for at least 10 minutes as the emulsion is cooling down.
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Thank you very much for your replies @ZivBA @Bill_Toge @Perry @Bobzchemist I’m so thrilled when I saw that someone replied on my post!!
))There’s just some follow up questions that I want to clear,
First, I usually use TEA as neutralizer for Carbomer ( I add it on the water phase, about 0.1-0.2%) but when I do that I’d get a cottage cheese product after 2-3 days, should I use NaOH instead??Second, should I just add the silicones after emulsification, since it shouldn’t be heated above 50deg C?? so that the oil phase can be heated at around 65 deg??
Lastly, AMP is Acrylates Copolymer right?? is that the same as acrylates/c10-30 alkyl acrylate crosspolymer?? should i use it in combination of carbomer?? (What I have tried before is to use acrylates/c10-30 alkyl acrylate crosspolymer alone in the formulation, about 0.2-0.4%)
Thank you so much!
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I see no problem running this at 70C, my first cream was similar in some ways. Basically it looks like a carbomer cream, the carbomer is acting as emulsifier. Or stabiliser, rather.
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You need to calculate how much TEA you need for your carbomer, and then test to be sure you like the texture. Consider using a Pemulen/carbomer mix, it will help emulsification. “Swiss Cheese” is probably a sign that you’re using too much.
Second, you can add silicones during/a little after emulsification, but then you run the risk of having some of your internal phase only be silicone, so stability MIGHT be not as good. Testing is important.
Lastly, AMP and/or AMPD are neutralizers - aminomethyl propanol or aminomethyl propanediol. Using these avoids the MEA contamination issue that happens with TEA.
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if you get a cottage cheese consistency after neutralising your carbomer, that does suggest, again, that your batch is not fully mixed
what it shows is that some parts of the batch are becoming thicker than others, and the fact that the carbomer has been neutralised means the thin and thick parts can’t mix together (because the water phase has been gelled, and cannot flow except under shear) - if it’s fully emulsified, then any changes in viscosity will occur at the same rate throughout the batch
also, AMP is not a polymer at all, it’s short for aminomethyl propanol
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