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Cocamidopropyl Betaine and Sodium Cocoyl Glycinate
Hello Everyone,
I am currently working on some body wash formulations that are sulfate free. Our current base formulations for this line of body washes have hydroxypropyl starch phosphate at 4%, Cocamidoproyl Betaine at 30% and Sodium Cocoyl Glycinate at 4%. I’ve noticed that these formulations are highly pH dependent in that minor deviations from a pH of 6.2 to 6.4 influence viscosity. pHs above 6.5 result in low viscosities of 17000 and below where pHs closer to 6.1 results in higher viscosities. pH values below 6.0 change the look and feel of the product. Its less smooth and even less foaming. I have tried a formulation where the the concentrations of Betaine and SCG are almost equivalent and have noticed that this behaves much like the SLES and Betaine formulations which are responsive to thickening with salt. The previously mentioned formualations are non responsive to salt. Does anyone know what the chemistry involved in Betaine & SCG formulations and why are said formulations so pH dependent. Anyone who has worked with Betaine & SCG combinations, please let me know about their findings. Cheers everyone. -
3 Replies
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I would definitely wait for a reply from a senior mentor here, though my two pence worth would be charge on micelles which is fluctuating with pH and hence the viscosity variation. And of course which also affects their packing whether it would be spherical or cylindrical at a given pH and concentration.
The other part too is again about micelles which become highly charged at equivalent concentrations and you need salt to ‘pacify’ them and allow the cylindrical packing to have a compact packing as opposed to loose packing.
Hope someone has a better explanation if this sounds less than 2 pence.cheers
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That’s not a bad explanation. Gives me something to think about. I was thinking that the addition of NaOH is somehow affecting the nature of the betaine i.e. higher pH resulting in more anionic characteristics which in turn results in the salt from the betaine (i believe that betaine has about 5-6% salt) thickening the system much like a regular SLES/Betaine/Salt formulation.
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I never saw NaOH coming but yes this is a life of amphoteric, ‘when in Rome, do as Romans do’. It changes on account of pH, cationic in acidic and anionic in alkaline and hence better thickening in presence of salt.
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