Achieving optimum viscosity on challenging surfactant compositions by understanding the thickening mechanism
Podium 57
Presented by: Núria Marimon
Achieving viscosity in today’s personal cleansing products while accomplishing green trends is not an easy requisite to fulfill for cosmetic formulators. Moving away from sulfate-based surfactants and at the same time avoiding PEG-derivative thickeners opens a world of new possibilities and challenges. In order to succeed in achieving the desired viscosity in each formulation, we believe that understanding the mechanism behind a thickener is the best way to proceed, at the same time than predicting good stability and nice sensory feelings.
In this work, we present a study to understand how different associative thickeners interact with surfactant aggregates to make viscosity increase. By understanding the thickening mechanism, we can clarify which are the main factors that can be modified in order to achieve the target viscosity in each formulation.
The techniques that have been used in this study are Dynamic Light Scattering (DLS) to characterize the size distribution profile of surfactant aggregates, Z-potential to determine the surface charge of the aggregates, Small-Angle X-Ray Scattering (SAXS) to determine the shape and structure of the aggregates, and finally Cryo Transmission Electron Microscope (cryoTEM). The compositions that have been evaluated during this study include most of the sulfate-free anionic surfactants used in personal care combined with amphoteric surfactant. The associative thickeners that have been evaluated are non-ionic surfactants. The factors that have been modified during the study are the ratio of anionic/amphoteric surfactant, the addition of electrolytes, and the pH of the formulation.
Results show that non-ionic thickener surfactants have a strong dependance on the charge of the aggregates, meaning that an appropriate charge balance between aggregates is necessary for the thickener to increase viscosity. As a consequence, the nature of the anionic surfactant plays a crucial role in achieving viscosity, as the polar head group will have a big impact on the surface charge of the aggregates. In addition, a very good correlation has been observed between the increase of viscosity and the increase of the aggregate size, indicating an evolution of the aggregates from spherical micelles into bigger structures like rod-like or worm-like micelles.
As a whole, this study represents a progress on understanding the thickening mechanism in a wide frame of sulfate-free personal cleansing formulations which can lead to the design of more effective formulations at the same time than fulfilling green market requirements.
In this work, we present a study to understand how different associative thickeners interact with surfactant aggregates to make viscosity increase. By understanding the thickening mechanism, we can clarify which are the main factors that can be modified in order to achieve the target viscosity in each formulation.
The techniques that have been used in this study are Dynamic Light Scattering (DLS) to characterize the size distribution profile of surfactant aggregates, Z-potential to determine the surface charge of the aggregates, Small-Angle X-Ray Scattering (SAXS) to determine the shape and structure of the aggregates, and finally Cryo Transmission Electron Microscope (cryoTEM). The compositions that have been evaluated during this study include most of the sulfate-free anionic surfactants used in personal care combined with amphoteric surfactant. The associative thickeners that have been evaluated are non-ionic surfactants. The factors that have been modified during the study are the ratio of anionic/amphoteric surfactant, the addition of electrolytes, and the pH of the formulation.
Results show that non-ionic thickener surfactants have a strong dependance on the charge of the aggregates, meaning that an appropriate charge balance between aggregates is necessary for the thickener to increase viscosity. As a consequence, the nature of the anionic surfactant plays a crucial role in achieving viscosity, as the polar head group will have a big impact on the surface charge of the aggregates. In addition, a very good correlation has been observed between the increase of viscosity and the increase of the aggregate size, indicating an evolution of the aggregates from spherical micelles into bigger structures like rod-like or worm-like micelles.
As a whole, this study represents a progress on understanding the thickening mechanism in a wide frame of sulfate-free personal cleansing formulations which can lead to the design of more effective formulations at the same time than fulfilling green market requirements.