Properties of SLS powder surfactant.

This is my first time to work with SLS. 
It is in powder form. When i dissolve it 5.4% in water the pH is 11-12. And it needs around 3% citric acid powder to bring pH down to 5. Also when i add CAPB %10 to it the viscosity increases more than enough.

Are all these normal for sodium lauryl sulfate or it has something mixed with it? 
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Comments

  • Bax65Bax65 Member
    What you describe is normal for these surfactants / surfactant mixtures.
    No need to worry.
  • @Bax65 thanks 
    Is there a way to prevent SLS from too much foaming when reducing it's pH? 
    For 100g sample it produces like 500ml foam when i add citric acid to it. 

    I don't know how to handle that amount of foam in large batch. 
  • Bax65Bax65 Member
    edited July 2021
    @Abdullah - that's an unavoidable issue linked to the manufacturing of the SLS granulate.
    To make this easier to deal with a first pH adjustment should be done right at the beginning with only the SLS in water. Then you will have the lowest possible viscosity.
    Once you have added a co-surfatant and/or any kind of thickener the foam will stay even longer.
    Final pH adjustment can and probably still needs to be done when the formulation is completed.
    Do you have the chance to apply vacuum and have a propeller stirrer running on top of the liquid? Idea is that the rotating propeller will destroy the rising foam when vacuum is applied.  
  • Bax65 said:
    @Abdullah - that's an unavoidable issue linked to the manufacturing of the SLS granulate.
    To make this easier to deal with a first pH adjustment should be done right at the beginning with only the SLS in water. Then you will have the lowest possible viscosity.
    Once you have added a co-surfatant and/or any kind of thickener the foam will stay even longer.
    Final pH adjustment can and probably still needs to be done when the formulation is completed.
    Do you have the chance to apply vacuum and have a propeller stirrer running on top of the liquid? Idea is that the rotating propeller will destroy the rising foam when vacuum is applied.  
    Unfortunately i don't have vacuum available
  • Bax65Bax65 Member
    edited July 2021
    If I am not mistaken in such case a SLS solution should be the better choice. Because the "gas release" is linked to the drying of the SLS.
    But SLS solutions are not the easiest to deal with. You need to protect them from too cold temperatures to avoid that they start forming SLS crystals.
    Because it can be a pain to get the crystals back into solution (at least in IBCs).
  • @Bax65 thanks, very good information. 

    At what temperature will it form criatals?
    Will heating it reverse that? 
    I am purchasing in 180kg drums not IBC. That is easier to use. 

    And how about ALS 
    Does it have powder form? 
    Does liquid ALS also form crystals? 
  • @Abdullah - crystallization temperature depends on the c-chain cut of the product. Normally it is mentioned in the product specification or technical data.
    The higher the C12 content the higher the crystallization temp. Common grades with a share of C14 shall be kept above 20°C.
    Crystallization is reversible but product needs to be carefully heated to ~40°C while gently stirring. Local overheating needs to be avoided, because normally at temp 50°C and higher the products can start degrading and once this process started it can speeds itself up (pH decrease is a good measure for this).

    Anyway, ALS can also form crystalls below 15 - 20°C and needs to be reworked in the same way as SLS.
    I am not aware that powders are available. I only know of 70% pastes but they are not too easy to dilute.

    But as mentioned supplieres information normally describes all this for their grades.
  • @Bax65 thanks a lot
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