The beginning and end of HIPE
Surprisingly, it is straightforward to create emulsions with significantly more than 70% volume of droplets by mixing alone. This can be achieved when the emulsion droplets are stabilized by an interfacial layer of colloidal particles which have a significant preference for the minority phase. The resulting soft solids are called high internal-phase emulsions (HIPE) or gel emulsions. Since these samples scarcely flow the normal picture of emulsification via the deformation and breakup of droplets may not be relevant. Under shear, the densely packed emulsions jam and fracture; they may well create new droplets in the contact region as the fractured granules collide. For low concentrations of particles (below 1%) and long emulsification times (several minutes) the emulsions eventually turns inside out (invert) and then readily flow. I will suggest how this comes about.
This is a weekly series of informal talks given primarily by members of the soft condensed matter and statistical mechanics groups, but is also open to members of other groups and external visitors. The aim of the series is to promote discussion and learning of various topics at a level suitable to the broad background of the group. Everyone is welcome to attend..