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Home Cosmetic Science Talk Formulating 15% Urea cream - Crystals forming in the tube opening

  • 15% Urea cream - Crystals forming in the tube opening

    Posted by Padmavathi on September 15, 2021 at 5:17 am

    Hi

    I developed a 15% urea foot cream 10 days back. Its stable at 40 C 75% RH, and 50 C for now. However, there are crystals formed in the tube orifice.
    Need help on resolving this issue. 

    Formula: 
    LLP 10%
    Butters 4%
    Herbal extract (coconut oil based) 3% - Provided by client
    Cetyl Palmitate 2.5%
    Arlacel 165 3.5%
    Cetyl alcohol 2.5%

    DM Water Qs to 100
    Carbopol 940 0.4%
    Urea 15%

    Preservative Qs
    Perfume Qs
    Color Qs


    Should I be adding something else to stabilise urea? 

    Please help!

    Padmavathi replied 1 year, 4 months ago 5 Members · 10 Replies
  • 10 Replies
  • Pharma

    Member
    September 15, 2021 at 6:20 pm


    Should I be adding something else to stabilise urea? 

    Yes. With 15% urea you should. Adjust pH to around 6.2 (rather lower than higher), use a buffer if possible, and add triethyl citrate or triacetin.
    BTW this only increases shelf life of urea but does not prevent crystal formation. Adding glycerin or another liquid diol/polyol might help with that.

  • Padmavathi

    Member
    September 16, 2021 at 10:11 am

    The pH by itself is 6.28. So, I left it a such. Should I still do something to increase shelf life?

    I will try adding glycerin or polyols. 

    Thanks for the help :)

  • Pharma

    Member
    September 17, 2021 at 4:28 am

    The issue with urea is that once it starts degrading it increases pH and that in turn accelerates degradation. A chemical vicious cycle. And that’s wyh you’re on the safer side with some additives which stop the pH from rising.

  • Juliatrudie

    Member
    September 17, 2021 at 10:42 pm

    Pharma said:


    Should I be adding something else to stabilise urea? 

    Yes. With 15% urea you should. Adjust pH to around 6.2 (rather lower than higher), use a buffer if possible, and add triethyl citrate or triacetin.
    BTW this only increases shelf life of urea but does not prevent crystal formation. Adding glycerin or another liquid diol/polyol might help with that.

    I have a questIon regarding buffers and ph. If I wanted to use a buffer to get say a Urea containing product to a ph of 6.0 should the buffer itself have a ph of 6 or should the buffers ph be lower so as to effectively  reduce the ph of said urea containing product down to say a ph of 6?  

  • Pharma

    Member
    September 18, 2021 at 4:39 pm

    The buffer should be bring the product to the aimd at pH (i.e. 6.2ish). However, a good buffer will have its buffering range around pH 6 to 7 (and not, as an example, an upper limit at 6).

  • em88

    Member
    September 30, 2021 at 2:12 pm

    I’m actually surprised the product is stable at 40 C 75% RH and 50 C. 

  • amitvedakar

    Member
    October 1, 2021 at 6:28 am

    we have 10% urea in foot cream & is stable.

  • Padmavathi

    Member
    October 1, 2021 at 6:34 am

    @em88 Yes it is stable. But still there are crystals forming in the tube opening.
    @amitvedakar We re-formulated with 10% urea and its stable. 

  • amitvedakar

    Member
    October 1, 2021 at 6:48 am

    our is bottle packing

  • em88

    Member
    October 1, 2021 at 7:47 am

    @Padmavathi, Well,  what do you mean by stable? 

  • Padmavathi

    Member
    October 1, 2021 at 10:20 am

    @em88 I meant that there was no separation (probably shouldn’t have said stable?).
    We squeeze the tube to get the cream out and close the cap, and open it again the next day to get more cream.. there are crystals in the opening, which come out along with the cream. Just a tiny bit. This did not happen with 5% or 10% urea. 
    Haven’t had time to work more on the 15% cream.