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Propanediol Deodorant
I am having problems with “sweating” using propanediol in a deodorant stick. I am not using a pH adjuster because this formula is “natural”. Has anyone else had this “sweating” or condensation problem? Did you find a solution? Thank you.
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33 Replies
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You must have some ingredient that absorbs moisture from the air.
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Belassi,
Would corn starch be the best “natural” solution? -
That’s not what I meant … what I meant was, there must be some hygroscopic material in your formula. Without knowing the formula I can’t say more.
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Kind of ironic that your deodorant sweats
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Propanediol-40%
Water-25%
Glycerin-25%
Sodium Stearate-5%
Stearic Acid-1.5%
Triglycerol Monolaurate-1.5%
Exthylhexylglycerin-1%
Fragrance-1%Mark-the irony is killing me!
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25% glycerin! Will surely absorb water. Isn’t the pH terribly high with the sodium stearate?
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think the free stearic acid will help to lower ph but both propanediol and glycerin are likely at 65% causing the sweat.
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Belassi-It’s a legacy formula from my predecessor. I’m not sure why he added so much glycerin. The pH is about 8.
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With that formula I can’t see how it can possibly be a solid. You’ve got 92% liquids.
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If you’re using sodium stearate, you’re already using a pH adjuster - you can only get sodium stearate by adding sodium hydroxide to stearic acid.
You might want to try a higher pH. At a pH of 8, sodium stearate is skating on the edge of stability.
I once solved a similar problem by using fumed silica - but I’m not sure if that’s “natural” enough for you.
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Belassi-I heat water/glycerin,dissolve sodium stearate and then add propanediol. It cools to a solid.
Bob-I use a silica/corn starch mix in my preferred version of the formula but this was already in production. -
But the melting point of propanediol is -25C. I just don’t see it.
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What is the purpose of the Triglycerol Monolaurate? It is not a common material and I don’t see that is has any advantages over more widely used components. Or should it read glyceryl monolaurate or even glyceryl trilaurate?
Why use stearic acid?
The inclusion of a coupling agent such as ceteareth 20 could help with the syneresis.
Which of the ingredients is the active deodorant material?
I don’t understand the relevance of the comment regarding the melting point of propanediol.
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@Belassi the sodium stearate acts as a gelling agent, and makes the product solidify
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TRUE—The sysneresis is likely coming from high glycerin.You can replace some with/ or all with talc or maltdextrin
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I am curious as to how talc or maltodextrin can replace a polyol in a soap based stick in order to avoid syneresis. I have not seen this done before.
I only ask because I want to know.
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talc in bars makes soap short (similar to excess salt) adding to drying effect-too much causes cracking—maltodextrin plasticizes -balance needed
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Ah! but this is a deo stick, not a soap bar with only a small proportion of soap to act as a stiffening/gelling agent.
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https://patents.google.com/patent/US4322400A/en?q=talc&q=deodarant&q=sticks
see claim 1 part 3 -
I’m going to lower my glycerin level and see what happens.
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Nothing is working. I have changed the amount of filler material, the heating and cooling temperature and reduced the glycerin.
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Try increasing stearic to 10%, monolaurate to 6%, replace sodium stearate with fumed silica, cut propanediol and glycerin by half, heat to 80-90C, neutralize to pH 10-11.
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Have you seen this
https://chemistscorner.com/basic-cosmetic-formulations-deodorant-sticks/
??
Might give an insight to your dilemma - and it’s here all the time.
Also remember that Google is your friend. Do a search using deodorant stick formulation as the keywords.
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Thank you. I read this article before. I understand traditional deodorant formulation. My problem is that my predecessor has combined two propanediol formulations into one to make them work. A water/propanediol/glycerin stick must be pH adjusted before the hardener stearic acid is added. However, my predecessor tried to bypass this step by using sodium stearate and water to neutralize the reaction. In addition, propanediol and water require a solubilizer and higher heating initially for stability. I’m still not sure how to tweak my formulation to eliminate the “sweating”.
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Gazillions of stearate based stick products are produced without problems.
Perhaps it’s time to re-addressthe whole thing and stop trying to patch up the work of someone else.
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