Rheological and textural characterization of cosmetic emulsions containing natural and synthetic polymers: relationships between both data

The objectives of the study were to investigate the effect of various polymers on both the rheological and mechanical properties of cosmetic O/W emulsions on one hand, and to investigate the relationships between rheological and textural parameters of the emulsions on the other hand. For this purpose, eight hydrophilic polymers, either natural (e.g. xanthan gum), or natural modified (e.g. hydroxyethyl cellulose) or synthetic (e.g. carbomer), were incorporated in an O/W emulsion at a concentration of 1% w/w. In addition, a formulation without any polymer was also prepared to be used as a control. The rheological assessment was carried out by analyzing continuous shear flow, creep-recovery and dynamic oscillatory tests, while penetration and compression tests were performed using a texture analyzer under various experimental conditions. This work showed that rheology and texture analysis are useful and complementary tools to allow full understanding of the role of a particular ingredient in an emulsion formulation. It notably allowed establishing that distinct shear thinning behavior induce marked differences for the textural parameters. As an example, the xanthan-based emulsion was the system for which the textural parameters obtained during texture analysis were the less affected by increasing probe speed or container’s diameter, due to its extreme shear thinning behavior as evidenced by flow rheometry.