C.2 - Shampoo Formulation

Abstract

While consumers often choose their shampoo based on fragrance or marketing hype/promises, the main reason they use shampoos is to clean their hair. Surfactants (surface active agents) are used to provide this functionality. Although a shampoo often contains a number of surfactants, there is typically a primary surfactant that does most of the foaming and cleaning. In the vast majority of cases, this will be anionic (negatively charged hydrophile) surfactants, in nature/charge. The negative portion/section of the surfactant can be a sulfate, sulfonate, carboxylate, or phosphate. Amphoteric surfactants are characterized by their “ability” to assume a net charge which is dependent on pH. Betaines have been shown to increase the viscosity of shampoos based on anionic surfactants. Hair (and skin) can be thought of as having a net negative charge (anionic) due to the carbonyl group present in proteins. With this in mind, one strategy to achieve hair conditioning is to incorporate a fatty cationic (positively charged) material into the shampoo and have it attach itself to the hair and thus impart conditioning. In addition to the surfactants, conditioning agents and viscosity controlling agents, shampoos are complex formulae that contain many other additives that are intended to provide additional benefits such as anti-dandruff agents, humectants, and preservatives.