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

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 θ_oo, 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.