-
Why so many modern creams contain fatty alcohols instead of the usual stearic acid?
Is that because fatty alcohols are usually less irritating than fatty acids?
Fatty acids become soaps at higher pH, while alcohols don’tOn the other hand, fatty alcohols can become a bit sticky at higher concentrations.
-
8 Replies
-
@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.
-
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.
-
I usually think of “granma’s hand cream in an alumimum tube from early 90’s” when feel stearic acid in a product.
-
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 productfatty 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 forcestearic/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’ -
@Bill_Toge that’s interesting. And regarding temperature?. In my experience fatty alcohols will decrease viscosity above 35°, even using 1% or less.
-
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
-
@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?
Log in to reply.