Shampoo with SCI same % different order different viscosity

Hello Chemists!

Currently I am formulating a sulphate free shampoo. During trials, i found out that changing orders can make a different consistency even on the same percentage.

I use:
- Water 
- Sodium Cocoyl Isethionate (powder) 9%
- Cocamide MEA 3%
- Coco Betaine 7%

When i mix water and SCI first the result of my shampoo becomes very runny almost watery. On my 3rd trial i accidentaly mix Coco Betaine & Cocamide MEA and water first, then add SCI. Its really hard to disperse the SCI but when it finally dispersed the consistency is really thick. 

Can someone please explain why this happens? And in which order should i put the surfactants? 

Thank you!

Comments

  • First, you must know the consistency you are expecting at the end of your formulation.

    Secondly, what are the quantities of the various ingredients measured? You may consider reducing the quantity of the SCI to see the effect on the end product, whether it means your expectation.

    Have you tried mixing the SCI with a little of your distilled water before introducing it into the main formulation? and topping up the formulation gradually with water?

    Your list does not contain a preservative, is that intentional? 
  • @rrthae Cocamide MEA and Coco Betaine (or Cocamide DEA and CAPB) have high affinity with a strong viscosity response, regardless of the anionic. I believe that if you add SCI at the start and then one of the other surfactants (especially Betaine), the mixed micelles formed will preferentially have a mixture of SCI and Betaine, which might not give such a strong viscosity response.
  • chemicalmattchemicalmatt Member, Professional Chemist
    @rrthae you are best off heeding advice of @ketchito there. Order of addition - regardless of anionic - is: amphoteric / alkanolamide / anionic. The amphoteric (coco-betaine here) is a hydrotrope. Hydrotropes help materials that don't like water, such as SCI, to like water more than they would without it. Sounds confusing?  No worries, I sometimes confuse myself.


  • rrthaerrthae Member
    Thank you all for your reply!

    @Raychemist I do not mention all of the ingredients, but I do use a preservative. The viscosity that I'm lookin for is 1500-1800.

    @ketchito noted!

    @chemicalmatt confusing but good.. i learn so many things in this discussion. So it is best to mix SCI last. But is it ok tho to mix SCI with a little bit of water like @Raychemist suggested? Since you said SCI doesnt like water? 
  • @chemicalmatt @ketchito what about order of addition of SLES and CAPB?

    I add SLES %70 to water in inline homogenizer to dissolve it, then add CAPB, then add polymer, silicone and etc. 

    Is this the best way of addition or you have another suggestion for SLES+CAPB? 
  • By accident, I purchased SCI powder instead of SCI noodles for making shampoo bars.  If I just make the recipe with the SCI powder, it is too flaky.  Should I double up on the liquids?
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