Tuesday, December 14, 2010
Surfactants: Disodium cocoamphodiacetate
Disodium cocoamphodiacetate is a mild amphoteric surfactant, much like cocamidopropyl betaine. The "ampho" part in the name indicates it's amphoteric, meaning it carries a different charge in different pH levels. If it's acidic (below 6), it behaves as a cationic surfactant that will be substantive to our hair and skin, offering moisturizing and conditioning properties. If it's alkaline (above 8), it behaves as an anionic surfactant with good foaming and detergency properties. (Click on the link for cocamidopropyl betaine if you want more information on the chemistry!)
It's generally used as a secondary surfactant to boost foam and viscosity, and it can be used as a very gentle cleanser for sensitive skin, babies, and facial products. It has a pH of 8.5 to 9.5 (which is higher than cocamidopropyl betaine), so I'll have to make sure I alter the pH if I'm using a lot of in my products with citric acid (just a titch). It comes as about 38% active in our products, and the suggested usage rate is up to 50%!
You will likely see this surfactant used as a primary surfactant for baby products as it's non-irritating to eyes at up to 5% and because it's very mild. And you'll likely see it combined with decyl glucoside in a lot of natural products or cleansers for sensitive skin as this combination creates a very gentle cleanser that won't strip a ton of oil off your skin! If you want to use this combination, you will have to test the pH and alter it slightly with citric acid.
If you want to use it as a secondary surfactant, it works with any combination of anionic or non-ionic surfactants, much like cocamidopropyl betaine. It will increase the mildness of your surfactant blend and it will increase the viscosity of your product. It does have a slightly yellow tinge, so if you want a completely crystal clear product with no colour, it might not work for those applications. But really, when you have a very gentle cleanser that offers moisturizing and conditioning, increases the mildness and viscosity, and doesn't strip the oils from our hair and skin, is a hint of yellow really going to make that a big a difference?
Click here for the data sheet from Stepan.
Join me tomorrow for fun formulating with this new surfactant!