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Home Cosmetic Science Talk General Is there problem with my lactic acid or the information about SPDMA neutralization from supplier?

  • Is there problem with my lactic acid or the information about SPDMA neutralization from supplier?

    Posted by Abdullah on July 19, 2022 at 6:16 am

    Suppliers like Evonik  say that stearamidopropyl dimethylamine needs 0.27g lactic acid(88% solid) to neutralize 1g SPDMA to pH 3.5-4.5 but in my experience 5g lactic acid (80% solid) is required to neutralize SPDMA to pH 4.3. does it means my lactic acid is more diluted and doesn’t have 80% solid as supplier says or there is something else i am messing?

    First added 70% of water water 80°c 
    Then added SPDMA 1%
    Then added lactic acid 5% until pH down to 4.3
    Then added fatty alcohol 2%
    Then added other water And preservative. 

    Abdullah replied 6 months, 2 weeks ago 3 Members · 5 Replies
  • 5 Replies
  • ketchito

    July 19, 2022 at 1:43 pm

    @Abdullah I usually add the acid first to the water, so it’s fully dissolved. Then heat, and add the SAPDMA.

  • Abdullah

    July 19, 2022 at 2:35 pm

    @ketchito how much lactic acid solid do you use to neutralize 1% SPDMA? 

  • ketchito

    July 20, 2022 at 11:41 am

    @Abdullah I usually add the 88% solution. If you have the powder version, you just need to make the conversion. By the way, what’s the composition of your actic acid? You mention 80% and yet, you have a solid ingredient. 

  • Abdullah

    July 20, 2022 at 3:19 pm

    @ketchito i use 80% lactic acid solution that has 80% lactic acid solids & 20% water. By solid i mean actual lactic acid. 

    Do you also need 4.5% lactic acid 88% solution to neutralize 1% SPDMA to pH 4-4.5?

  • chemicalmatt

    July 22, 2022 at 2:38 pm

    Lactic acid 88% is the Standard grade supplied by industrial firms. The solid and 80% you only see in lab source catalogs. This is why Evonik used that assay. My own experience has been 3.5 SPDA : 1.0 LA 88% resulting in pH 5.0 the sweet spot for emulsion stability. If you are also adding alkyl quats - and most hair conditioners will - that pH drops down to 3.5 - 4.5. That’s OK too.

  • Abdullah

    July 23, 2022 at 7:39 am

    @chemicalmatt thanks

    For me 1% SPDMA needed 5% lactic acid that supplier said is 80%. That is very big difference.

    Does it mean this lactic acid is not really 80% and supplier is lying? 

    Supplier is a wholesaler, not manufacturer and i purchase salicylic acid & citric acid from them too. They have good quality. 

    Is there any way to check if this lactic solution really has 80% lactic acid or not?