Characterization of silicone oil emulsions stabilized by TiO2 suspensions pre-adsorbed SDS

To study the effects of pre-adsorbed emulsifier on Pickering emulsion stability, the preparation of silicone oil emulsions by TiO2 suspensions pre-adsorbed sodium dodecyl sulfate (SDS) at the fixed TiO2 concentration of 0.15 g was carried out below a fiftieth of critical micelle concentration (cmc) of SDS, where all added amounts of SDS are adsorbed on the TiO2 particles. The stability of the Pickering emulsions incorporating TiO2 suspensions pre-adsorbed SDS was investigated by measuring the volume fraction of emulsified silicone oil, adsorbed amounts of TiO2 suspensions pre-adsorbed SDS, oil droplet size, and some rheological responses such as the stress–strain sweep curve and strain and frequency dependences of dynamic viscoelastic moduli. The silicone oil was almost emulsified by TiO2 suspensions pre-adsorbed SDS above cmc/103. Increasing in the adsorbed amount of SDS on the TiO2 particles leads to an increase in the adsorbed amounts of TiO2 suspensions pre-adsorbed SDS. Such silicone oil emulsions for the first time showed two yield stresses in the stress–strain sweep curve as well as the oscillatory stress–strain curve. The respective yield stresses also increase with an increase in the adsorbed amounts of TiO2 suspensions pre-adsorbed SDS. From such characteristic rheological properties and a partial sedimentation of some TiO2 particles remained in the dispersion medium, we proposed the formation of a three dimensional network of the flocculated TiO2 particles pre-adsorbed SDS on the silicone oil droplets.

Shear stress (left) and oscillatory stress (right) as a function of strain for the cmc/103 (open circle), cmc/102 (open square), and cmc/50 emulsions (filled circle).Figure optionsDownload as PowerPoint slideHighlights
► TiO2 particles pre-adsorbed SDS can completely emulsify silicone oil.
► Emulsions show two yield stresses in the stress–strain sweep curve.
► The respective yield stresses increase with an increase in the SDS concentration.