Double oil-in-oil-in-oil emulsions stabilised solely by particles

Abstract

The stability of vegetable oil-in-100cS silicone oil-in-vegetable oil V/S/V emulsions to sedimentation and coalescence has been studied. The emulsions contained two types of silica particle of different surface silanol content, 70% and 20% SiOH, which prefer to stabilise 100cS silicone oil-in-vegetable oil S/V and vegetable oil-in-100cS silicone oil V/S emulsions respectively, in systems containing equal proportion of the oils. The emulsions were prepared in a two-step process and were characterised using the drop test and optical microscopy. The emulsions were completely stable to coalescence for over a month. However, they underwent sedimentation which decreases as the concentration of 70% SiOH silica particles stabilising the silicone oil globules increases. The gravity-induced sedimentation halted at a relatively high particle concentration (2wt.%) and negligible amount of the vegetable oils was released even after a month. Their average droplet diameter also decreases as the concentration of 70% SiOH silica particles increases. Values of oil-oil-solid particle contact angles θoo, measured on microscope glass slides composed of the particles, are in good agreement with the type of simple emulsions and hence double emulsions formed by the particles.