Characterization of silicone oil emulsions stabilized by TiO 2 suspensions pre-adsorbed SDS

Abstract

To study the effects of pre-adsorbed emulsifier on Pickering emulsion stability, the preparation of silicone oil emulsions by TiO 2 suspensions pre-adsorbed sodium dodecyl sulfate (SDS) at the fixed TiO 2 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 TiO 2 particles. The stability of the Pickering emulsions incorporating TiO 2 suspensions pre-adsorbed SDS was investigated by measuring the volume fraction of emulsified silicone oil, adsorbed amounts of TiO 2 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 TiO 2 suspensions pre-adsorbed SDS above cmc/10 3. Increasing in the adsorbed amount of SDS on the TiO 2 particles leads to an increase in the adsorbed amounts of TiO 2 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 TiO 2 suspensions pre-adsorbed SDS. From such characteristic rheological properties and a partial sedimentation of some TiO 2 particles remained in the dispersion medium, we proposed the formation of a three dimensional network of the flocculated TiO 2 particles pre-adsorbed SDS on the silicone oil droplets.