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Is there problem with my lactic acid or the information about SPDMA neutralization from supplier?
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?
method
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.
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6 Replies
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@Abdullah I usually add the acid first to the water, so it’s fully dissolved. Then heat, and add the SAPDMA.
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@ketchito how much lactic acid solid do you use to neutralize 1% SPDMA?
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@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.
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@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?
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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.
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@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?
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