Home Cosmetic Science Talk Formulating Skin Long Term Heat Stability

  • Long Term Heat Stability

    Posted by rubzilla on April 30, 2015 at 9:47 pm

    Hello I am new to the forum. I am hoping to gain stability advice. For years we have been successful with a stearic acid cetyl alcohol structure in heat age testing. We have recently created a new product with cetearyl and cetyl as our stucture to create a lighter feel with better glide and less whitening upon application. Our room temp stability is excellent even in the oldest samples from 2013 but our 40C oven samples loose half viscosity after 1 month But no separation. Due to regulatory constraints we are limited on emulsification systems we can employ And our standard emulsifier is a jojoba based product Which works well in other cetearyl based products we make So I know the emulsifier is effective. However, when looking at brand competitors i see that they are creating similar products with no clear emulsifier listed. I currently heat and hold in the kettle at 80C for 60 min to create my emulsion. Is there a production trick anyone knows to tighten my emulsion and improve my heat stability? I have a ross. Or is is our problem that we are misunderstanding pass/fail criteria for heat age testing? Again there is no separation just loss of viscosity. Any opinion is welcomed. Thank you.

    Chemist77 replied 9 years, 1 month ago 7 Members · 8 Replies
  • 8 Replies
  • billichemist

    May 1, 2015 at 1:09 am

    yes i get this too!! :( :(

  • Bill_Toge

    May 1, 2015 at 6:43 am

    have you run freeze/thaw tests on it? and if so, does the same thing happen after several freeze/thaw cycles?

    if it can’t be reproduced in freeze/thaw tests, it’s most likely a side effect of being stored at high temperature, rather than a sign of intrinsic instability
  • OldPerry

    May 1, 2015 at 1:18 pm

    Can you give us the full ingredient list?  Do you have something in the formula that works as a suspending agent?

  • rubzilla

    May 1, 2015 at 1:39 pm

    The suspension agent is Xanthan gum and the oil phase is 20% largely comprised of shea with about 2% oils and 4% cetyl/cetearyl. My pH is 7. The formulation does pass 3 cycles of freeze thaw. I can improve oven stability by increasing my cetyl cetearyl but then i move into a formula with an unappealing waxy feel.

  • manstra

    May 1, 2015 at 7:26 pm

    Is there any pH shift in your receipe over this month? After the new emulsification system do you use higher temperatures to emulsify it or have you made any changes in the shear force?

  • Bobzchemist

    May 1, 2015 at 8:48 pm

    Sounds to me like you’re getting a good portion of your viscosity from the crystalline wax network formed by the cetearyl/cetyl, which typically breaks down at 40C. Your only option to fix this, aside from increasing the cetyl alcohol, would be to increase your viscosity through another mechanism, using gums, for example.

    Viscosity from cetearyl/cetyl is built up the most by slow cooling, which allows the wax crystals the maximum amount of time to grow. It is minimized by rapid cooling, so once you build up your viscosity with other ingredients, you’ll be able to get similar viscosities at RT and at 40C by cooling your batch as rapidly as possible.
  • rubzilla

    May 2, 2015 at 1:14 am

    Thank you Bobzchemist. I’ll get started on Monday. Our lab and our production floor do not have equal cooling capabilities. My stability results are based on rapid lab cooling but I do have access to production material that was cooled based on our equipment limitations which is much slower and produces a thicker final product. I can re-evaluate for stability to determine if my problem is actually lab samples.

  • Chemist77

    May 2, 2015 at 12:59 pm

    @Bobzchemist Brilliant dissection!!!!!!!

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