Home Cosmetic Science Talk Formulating SLAS - Slimy or too thick surfactant system problems

  • SLAS - Slimy or too thick surfactant system problems

    Posted by Paprik on December 20, 2022 at 11:08 pm

    Hey guys,

    I’ve had some SLAS (Sodium Lauryl Sulfoacetate 65% active) for a long time and started to play with it just now . Don’t remember the exact formula now (posting this from work), but it was something like this: 

    7% SLAS
    10% Cocamidopropyl Betaine
    0.3% Guar Hydroxypropyltrimonium Chloride
    Some fragrance and preservative. 

    My question: 
    1. It got super thick. How do you usually cope with that? Do you reduce Coca-Betaine? Or do you add a bit of NaCl so you start to lose the viscosity? 

    Another scenario was to make a face wash and I wanted to know if I can thicken the system with salt if I use 4% of SLAS. 
    So it was just water, 4% SLAS and NaCl. 

    After I dissolved SLAS and brought pH to 5-5.5, I started to add NaCl and at 1% ish it was thickening, but it got kind of slimy. Not like typical nice body-wash flow but like stringy (like ugly XG grade type of stringy/slimy).
    Could be something wrong with the SLAS or some surfactants can thicken this way? 

    My final question - SLAS is salt responsive. What if I add another non-salt responsive anionic and non-ionic surfactant - can those negatively effect the SLAS salt responsiveness? 

    Thank you! :)

    ketchito replied 1 year, 3 months ago 3 Members · 2 Replies
  • 2 Replies
  • LeoCosm

    January 6, 2023 at 1:33 am

    How thick? I had the same problem when thickening sodium cocoyl glutamate’s formula. It was so thick that when I had to squish it out of the bottle it would get back in if I would have stopped squishing.
    I had to add iselux to the formula and it worked for me.

  • ketchito

    January 6, 2023 at 2:05 am

    @Paprik Maybe 10% of CAPB is too much for yoir 1st system. I’d add guar first, 2% of CAPB (just to prevent coacervation), your SLAS and the the remaining CAPB little by little, till you have your desired viscosity.

    The slimy consistency of your face wash, it might have to do with a change in micellar arrangement, you went over the rod-like micelles at that level of salt. Try to add it little by little, till you get the viscosity (and foaming) that you want. 

    Adding a non ionic, cationic surfactant or zwitterionic surfactant can modify the salt response (same as adding a cationic polymer). 

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