Surfactant Interactions in Formulations
*Part 2 Amphoteric / Anionic Interactions
*Part 1 was published in H&PC Today, Vol. 11(4) July/August 2016, pag. 32-35
This is the second of a series of review articles on the interactions that occur in our formulations as a simple consequence of combining the raw materials used in the formulation of personal care products. These interactions are largely ignored but the functionality of the formulation is the sum of the properties and ratios of each of the raw materials added. There are a number of interactions, which include formation of self-assembling complexes. These complexes can either enhance or detract from the functional attributes of the formulation. Since most of today’s high performance formulations are very complex containing a plethora of ingredients, it is difficult to predict the effect of changes in those formulations. In an attempt to understand these interactions we have gone back to simple systems. The results of these interactions can then be used to help formulate more effective products.
The first article investigated the interaction between anionic and cationic surfactants in aqueous systems1. This article will investigate the interaction between amphoteric surfactants and anionic surfactants. Viscosity when combined, foam and salt curve will all be evaluated. Choice of amphoteric is very important to determine the best combination for optimizing properties (2).
The interaction between ingredients in a formulation is almost always the most important factor in determining the properties of the formulation. Simply put, the formulator adds a number of ingredients to a formulation with the intention of altering viscosity (that include salt, alkanolamid and others), increasing or stabilizing foam, or altering foam structure, and altering rinse off are but a few. This article will show data that indicates that the selection of amphoteric type and concentration in a formulation is a very powerful technique to alter formulations.
It is recommended that the formulator look at a basic formulation, leaving out the ingredients with the exception of the anionic and amphoteric components. By looking at variation in the ratio of these two ingredients and varying the ratio, very important differences in this simple formulation can be determined. One of these is irritation, which is an important concern as lower and lower irritation scores are highly prized in formulations.
The surfactants chosen were the most traditional surfactants in the cosm ...