A new stability index for characterizing the colloidal gas aphrons dispersion

Aphrons are surfactant stabilized microbubbles with thick soapy shells. Stability is a key feature of microbubbles. Colloidal gas aphrons (CGAs), with an average diameter of 50 μm, offer particular advantages where the stability of microbubbles is of interest. Various factors that affect on CGA stability such as surfactant type, concentration, and processing parameters have been extensively studied. However, there is no simple and accurate stability index for characterizing the stability of microbubbles dispersion. In this study, the stability of CGAs dispersion has been examined based on the drainage curve by four stability indexes. The surfactant of choice was nonyl phenol ethoxylate (NPE), a nonionic surfactant. The results show that the one-tenth of drained liquid life (T0.1), the time elapsed when the drained liquid from CGA dispersion reaches ten percent of its final height is the best indicator among the other stability indexes for characterizing the CGAs dispersion.