Effect of [CTAB]–[SiO2] ratio on the formation and stability of hexadecane/water emulsions in the presence of NaCl

The formation and stability of hexadecane (H)/water (W) emulsions stabilized by mixtures of cetyltrimethylammonium bromide (CTAB) and SiO2 particles in decreasing ratios (R1, R2 and R3) in presence of NaCl at constant ionic strength as a co-stabilizer was investigated. Interfacial creep compliance-time studies of the CTAB–SiO2 films at the H–W interface were carried out in order to understand the mechanisms of the CTAB–SiO2 aggregates adsorption and their interactions at the H–W interface. The characterization and stability of H-in-W emulsions (E-R1, E-R2, E-R3) was determined by the combination of light scattering diffraction, DSC and optical microscopy techniques. The emulsions displayed polydisperse droplet size and the average droplet size of the emulsions decreased as the CTAB–SiO2 ratio diminished. DSC aging tests indicated that only emulsions made with R3 presented changes in the average droplet size probably due to slower reorganization of the clusters at the droplet interface until a well structured film was developed. Despite that E-R1 and E-R2 presented a relatively large non-spherical droplets they were highly stable against coalescence due to the formation of a solid-like interfacial layer.