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Cocamidopropyl betaine has two structures based upon pH: cationic and zwitterionic.
Cocamidopropyl betaine (CAPB) is an important surfactant used in the personal care market. Amido betaine products are mild, foaming detergents that complex with anionics. They are used extensively in shampoos, bubble baths and in other cleansing products. CAPB has two structures based upon pH, as shown in Figure 1.
CAPB can be made from two different processes, one with coconut oil and the other with fatty acid, which create two potential differences that affect how the product works in formulation. The salient difference is the by-product produced by the reaction. If the acid raw material is used to produce the amidoamine, water is the by-product and water is removed during the reaction. However, if coconut oil, a triglyceride, is used, the by-product glycerin remains and acts as a diluent that is counted as a solid. The presence of glycerin in the final product can result in less active per gram added and ultimately can affect the functionality in formulation.
The second difference is that products made from fatty acid may have a different fatty distribution than those made from coconut oil. When coconut oil is used as a raw material, the alkyl groups on the betaine are fixed by the oil. Fatty acids are sold in many grades including: those that have been stripped to remove lower molecular weight fractions, those that are hydrogenated to remove unsaturation, and even those blended with other fatty acids. Differences caused by this alteration will cause marked differences in the performance of the product in formulation, despite the same INCI name.