Navegando por Palavras-chave "Coalescence"

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    Interfacial Tension
    (Springer Heidelberg, 2016) Leonardi, Gislaine Ricci [UNIFESP]; Monteiro e Silva, Silas A. [UNIFESP]; Guimaraes, Carina M. [UNIFESP]; Perrechil, Fabiana A. [UNIFESP]; Landgraf, Richardt G. [UNIFESP]; Friberg, Stig E.
    The destabilization process was investigated for a Janus emulsion of silicone and Bixa Orellana oils stabilized by polyoxyethylene sorbitan monooleate (Tw 80) and carboxymethyl cellulose. The emulsion stabilized with Tw 80 showed significant and fast creaming, a process that was prevented by the addition of the polymer. During the extensive coalescence of the emulsions stabilized by Tw 80, the Janus topology was retained for months of storage until, finally, separation of the oils occurred. This result strongly indicates an unexpected stabilizing action of the i nterfacial free energy. This conclusion was supported by a calculation for a realistic model system of the interfacial energy difference between two cases of coalescence. In the first case, the two coalescing Janus drops united into a larger Janus drop, while in the second case two drops formed, each with only one oil. The first case gave a spontaneous reaction (reduced interfacial energy), while the second one meant an increase of energy, i.e. it cannot happen without adding energy. The authors are aware that this stabilization is a new phenomenon in emulsion science with potential ramifications in future emulsion technology. However, it is essential to realize that the stabilization is of temporary occurrence in the destabilization process, and the free energy to give a final emulsion state with separated oils is overwhelmingly dominant. In short, Janus emulsions will, in the end, separate into layers of the liquids, like all emulsions.
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    Janus emulsions of bixa orellana oil
    (Taylor & francis inc, 2016) Leonardi, Gislaine Ricci; Silva, Marina Martines [UNIFESP]; Guimaraes, Carina Moreira [UNIFESP]; Perrechil, Fabiana de Assis [UNIFESP]; Friberg, Stig
    Janus emulsions of the oil from the Bixa orellana (BO) nut, silicone oil (SO), and an aqueous solution of Tween 80 were prepared by intense mixing and optical microscopy images were obtained of the drops. The results showed the expected disordered emulsion of large SO drops with a number of attached smaller drops of the vegetable oil, whose images were transformed to regular Janus drops by the shear, when the cover glass was applied. The drops with a large BO/SO volume ratio did not immediately form well-defined and topologically equal Janus drops due to kinetic factors. The microscopy image was used to evaluate the correct angles and radii by a mathematical rotation to form an image with a straight-line contact line.