Application of a factorial design to the study of the flow behavior, spreadability and transparency of a Carbopol ETD 2020 gel. Part II

Abstract

A factorial design (2 3) is applied to study the influence of three of the components of a cosmetic gel (the concentrations of Carbopol ETD 2020, ethanol and glycerine) on flow parameters (Casson's yield value ( τ c), Casson's viscosity ( η c) and apparent viscosity at 125 s −1 ( η ap. 125 s −1)), spreadability, and transparency. The first-order polynomial equation allowed by the model suitably accounts for the τ c and spreadability. Both depend on the concentrations of Carbopol and ethanol, and τ c also depends on the ethanol–glycerine interaction. The model explains to a certain extent the complex relationships that are established between the components and that influence η c y η ap. 125 s −1. Transparency is independent of the Carbopol concentration and it is also thought to be independent of the ethanol concentration. In addition, a high linear correlation has been found between the τ c and spreadability and other viscoelastic parameters of the gels that were previously determined (Int. J. Pharm. (2001)). The application of the technique of experimental design has been shown to be a very useful tool for formulating gels.