Self-assembly behavior in systems containing surfactants and chelating agents

Abstract

Cleaning products play a crucial role in effectively maintaining a healthy and hygienic living environment. In all cleaning formulations ingredients like chelating agents and surfactants are essential for the products’ performance. This study investigates the self-assembly of surfactants in the presence of chelating agents and their influence on the physicochemical properties and cleaning efficiency of cleaning formulations. The formulations consist of a nonionic surfactant, a chelating agent and a secondary surfactant. Three amine-based secondary surfactants were evaluated, including an amphoteric surfactant, an amine oxide, and a quaternary ammonium compound (quat). The chelating agents evaluated were L-glutamic acid N,N-diacetic acid tetrasodium salt (GLDA), methylglycine N,N-diacetic acid trisodium salt (MGDA), ammonium citrate and citric acid.

The study focuses on how these components affect clouding temperature, viscosity, foaming, wettability, and surface tension. Results show that clouding temperature, viscosity, and foaming are notably impacted by the choice of secondary surfactant and chelating agent, whereas surface tension remains unchanged. Amphoteric surfactants, in particular, reduce the salting-out effect of chelating agents like MGDA and GLDA, likely due to the similarity between their molecular structures. This interaction is hypothesized to lower the critical packing parameter (CPP), leading to smaller, more spherical micelles that increase solubility, raise clouding temperature, decrease viscosity, and improve foaming. These changes could enable higher concentrations of active ingredients, resulting in more concentrated, energy-efficient products with reduced packaging needs.

Cleaning performance tests on model soils revealed that formulations combining amphoteric or amine oxide surfactants with GLDA or MGDA were most effective across various surfaces and soil types, especially at higher concentrations of chelating agents. These findings suggest that combining amphoteric surfactants with GLDA or MGDA could lead to the development of more concentrated, sustainable cleaning products.