Home Cosmetic Science Talk Formulating Why so many modern creams contain fatty alcohols instead of the usual stearic acid?

  • Why so many modern creams contain fatty alcohols instead of the usual stearic acid?

    Posted by gunther on April 3, 2019 at 12:00 am

    Is that because fatty alcohols are usually less irritating than fatty acids?
    Fatty acids become soaps at higher pH, while alcohols don’t

    On the other hand, fatty alcohols can become a bit sticky at higher concentrations.

    microformulation replied 4 years, 10 months ago 6 Members · 8 Replies
  • 8 Replies
  • fekher

    Member
    April 3, 2019 at 1:45 pm

    @Gunther according to my experience even in low level stearic acid genearally give waxy and flacking effect wich is not the case of fatty alcohol.

  • ngarayeva001

    Member
    April 4, 2019 at 12:39 pm

    I am pretty sure texture is the answer. Stearic is draggy and causes a lot of soaping (much more that cetearyl alcohol). There are vey few formulas with stearic acid that have good texture (I usually think of the formulator as a magican when I find one). Regarding stickiness, you don’t usually achieve full viscosity by fatty alcohols only, so don’t use it to the point where they become sticky.

  • ngarayeva001

    Member
    April 4, 2019 at 12:42 pm

    I usually think of “granma’s hand cream in an alumimum tube from early 90’s” when feel stearic acid in a product.

  • bill_toge

    Member
    April 7, 2019 at 5:11 pm
    from an extensive series of experiments carried out a few years ago, I’ve found the two are both surface-active (though they are not emulsifiers) and have substantially different effects on the rheology of the product
    fatty alcohols increase the zero-shear viscosity of the product, i.e. make it more solid when at rest, and cause the viscosity to decrease very sharply with applied shear force
    stearic/palmitic acid has very little effect on the zero-shear viscosity, but increases the viscosity at higher shear rates, i.e. makes the product feel more ‘creamy’
  • das

    Member
    April 7, 2019 at 11:33 pm

    @Bill_Toge that’s interesting. And regarding temperature?. In my experience fatty alcohols will decrease viscosity above 35°, even using 1% or less. 

  • bill_toge

    Member
    April 8, 2019 at 8:05 pm

    DAS said:

    @Bill_Toge that’s interesting. And regarding temperature?. In my experience fatty alcohols will decrease viscosity above 35°, even using 1% or less. 

    that depends more on what rheology modifier(s) you have in the water phase - if you use xanthan gum and/or a carbomer, there is little variation of viscosity with temperature, whereas if you use cellulose derivatives the variation is much larger

  • ngarayeva001

    Member
    April 9, 2019 at 6:40 am

    @Bill_Toge, this is a very interesting point.. what about carbomers or addition of small amounts of polymeric emulsifiers (for example Aristoflex) as a rheology modifier? 

  • microformulation

    Member
    April 10, 2019 at 2:20 pm

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