Cationic & viscosity troubles
Dear chemists, I desperately need your guidance 🙂
I have been playing with cationic emulsifiers and trying to make a fancy hair mask, but there is some weird hocus-pocus going on in my concoctions. I have tried a gazillion of knock-outs and formula variations, but been facing more or less the same viscosity issue - my product goes from thick cream to fluffy milk as soon as I add anything that contains sodium benzoate. At least that is the only repetitive pattern so far. Here is the last formula variation:
4% Oil (tried several)
5% Isopropyl myristate
3% Behentrimonium chloride
2% Stearamidopropyl dimethylamine
7% Cetyl alcohol
5% Propylene glycol
1% Polyquaternium 7
0.5% Hydrolized keratin
0.25% Cetrimonium chloride
1% Citric acid
0.2% Sodium phytate
0.9% Euxyl PE9010 (Phenoxyethanol&Ethylhexylglycerin)
0.8% Geogard 221 (Dehydroacetic Acid & Benzyl Alcohol & Water)
I started at 3% fatty alcohol and tried cetearyl, both together and brassica alcohol. Brassica was a complete watery fail. With cetyl alone at 7% the viscosity change is from thick cream to fluffy cream. I was initially going to use P. Sorbate and S. Benzoate blend instead of Geogard, but, upon addition the cream first becomes thicker and grainy, then goes fluffy and runny within seconds. I tried adding citric acid to the water phase and in cool down and I found the texture much thicker and nicer with the latter (pH 4.5-5). Silk proteins turn it watery, rice proteins too but to significantly lower extent, whereas Polyquaternium 7 slightly kind of softens it. These three only have sodium benzoate in common. Red algae extract (preserved with Naticide) turns a perfectly shiny cream to a grainy pile of c*ap and all mixers of this world are helpless.
I see these ingredients on LOIs all the time and sodium benzoate is almost always there. Fragrance addition also affects viscosity in a similar manner. Tried with polysorbate 20, even worse. I have been measuring pH between every addition and the change was +-0.5. What is wrong with this formula?
Obviously, I can eliminate all the culprits, and will probably end up doing so, but why is this happening?
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