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Why is formula A stable but formula B not?
This is an LGN emulsion <div>
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Formula A
5% cetearyl alcohol
0.95% SLS active (using liquid SLS)
0.2% EDTA
pH 6.
Method: heat water to 60°c, add EDTA, add SLS, melt FA separately and add, homogenize and cold down.
This product is completely stable and no separation.
Formula B
5% cetearyl alcohol
1% SLS powder 95% active
0.8% citric acid
0.2% EDTA
pH 6
Method: heat water to 60°c, add EDTA, SLS & citric acid in this order, melt and add FA, homogenize and cold down.
This product is not stable and does creaming in ~a month.
I don’t know why but SLS powder here needs a lot of citric acid to reduce the pH.
what can be the cause of instability in formula B? because amounts of LGN surfactants and method are the same in both formula.
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5 Replies
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Formula A is also has more viscosity
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Could you make the second one withput the Citric acid (don’t mind about the pH)? I believe alfer sulfation, some amount of base is added to neutralize the free sulfuric acid remaining. There might be more of this in the powder than in the liquid, hence you need to add more acid to lower the pH.
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Made 3 more batches
1% SLS: 5% FA
0.8% SLS: 4% FA
0.6% SLS: 3% FA
pH was 12 for all of them.
Will check the stability
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Can you compare both the pH and free base (maybe sodium hydroxide) of both surfactants?
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Liquid SLS has pH ~6 and no citric acid needed to adjust it’s pH.
1% powder SLS solution in filtered water has pH ~13.
How can i calculate the free base?
1% SLS powder needs 0.8% citric acid to reduce pH to 6 and during this it creates a lot of foam so it may have a lot of free base.
I will make another batch without citric acid and see what happens.
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