Effect of colloidal jamming in continuous phase on the elasticity of high internal phase pickering emulsions

Abstract

High internal phase emulsions, which their volume fraction of dispersed phase is over 74%, shows solid like property because of their tremendous interfacial area. Many researches claimed models to explain the rheological properties of HIPEs, however, most of them are for the surfactant emulsions. In the case of Pickering HIPEs, higher G’ values were obtained compared to surfactant HIPEs at identical volume fraction but there is no clear explanation for this yet. In this study, we figured out how colloidal particles attributed to the change of emulsion rheology in terms of interface and bulk respectively. By measuring the rheological properties of interfacial particle layer and continuous phase which is colloidal suspension, we could validate that colloidal suspension in confined geometry between two droplets brought larger G’ of Pickering HIPEs. By reducing gap of parallel plates of rheometer, we could observe the effect of confinement on rheological properties of colloidal suspensions and figured out that liquid to solid transition can occur without changing volume fraction or temperature. In addition, respective theoretical model for interfacial rheology and confined continuous phase supported the experimental results.