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Imparting Thermal Stability
In more of a general sense, what are some approaches that you as a formulator have taken to specifically add thermal stability to a lotion? I am trouble shooting a lotion right now and I am considering my options. Currently it has a very non-polar oil phase and I am concerned that perhaps that is contributing towards a lack of heat stability, but I’m not really sure (lotion is not falling apart, but loosing about 50% viscosity). Please keep in mind that I am still fairly new to the field; I was planning on either increasing the amount of Xanthan Gum or adding methyl hydroxyethylcellulose to address this issue. Alternatively would simply adding some stearyl alcohol or petrolatum help?
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4 Replies
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I have had this issue with a cream that uses Olivem 1000 as the emulsifier. I have added Stearic Acid and Cetyl Alcohol and increased my gum level a little to help improve heat stability and it seems to be considerably improved. Interested to hear if others have had the same problem.
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Increasing waxes I suppose won’t be of as much help as increasing the percentage of the polymer in the formula.
@ gfeldman Try heating a carbopol gel to 70°C or above and you would see it for yourself the strength of the gel network. Accordingly you can make your decision.Cheers
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@milliachemist I would love to increase the amount of polymer, but that will increase my initial thickness which is not something that I would desire. What other alternatives would you suggest?
@Jeannie Thank you for the suggestion. That is roughly what I was considering doing, but I am afraid of introducing too much drag to the lotion if I start adding all these long chain alcohols to increase the heat stability. Right now it spreads like crazy, which is what I want. I will start with increasing the level of gum, but do you have any additional suggestions? Also, with regards to the Olivem1000 (which I like), I’m sure you already know this, but it is a bit hard to completely dissolve that stuff. I always heat it to 80C and keep it there for a while with some stirring before adding it to my water phase.
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How about optimizing the increase of both the polymer and waxes, strike a balance and I am sure you can reach there.
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