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Oil-in-oil emulsions stabilised solely by solid particles

Binks, Bernard P.; Tyowua, Andrew T.

Authors

Andrew T. Tyowua



Abstract

A brief review of the stabilisation of emulsions of two immiscible oils is given. We then describe the use of fumed silica particles coated with either hydrocarbon or fluorocarbon groups in acting as sole stabilisers of emulsions of various vegetable oils with linear silicone oils (PDMS) of different viscosity. Transitional phase inversion of emulsions, containing equal volumes of the two oils, from silicone-invegetable (S/V) to vegetable-in-silicone (V/S) occurs upon increasing the hydrophobicity of the particles. Close to inversion, emulsions are stable to coalescence and gravity-induced separation for at least one year. Increasing the viscosity of the silicone oil enables stable S/V emulsions to be prepared even with relatively hydrophilic particles. Predictions of emulsion type from calculated contact angles of a silica particle at the oil–oil interface are in agreement with experiment provided a small polar contribution to the surface energy of the oils is included. We also show that stable multiple emulsions of V/S/V can be prepared in a two-step procedure using two particle types of different hydrophobicity. At fixed particle concentration, catastrophic phase inversion of emulsions from V/S to S/V can be effected by increasing the volume fraction of vegetable oil. Finally, in the case of sunflower oil + 20 cS PDMS, the study is extended to particles other than silica which differ in chemical type, particle size and particle shape. Consistent with the above findings, we find that only sufficiently hydrophobic particles (clay, zinc oxide, silicone, calcium carbonate) can act as efficient V/S emulsion stabilisers.

Journal Article Type Article
Publication Date Jan 1, 2016
Journal Soft matter
Print ISSN 1744-683X
Electronic ISSN 1744-6848
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 12
Issue 3
Pages 876-887
Institution Citation Binks, B. P., & Tyowua, A. T. (2016). Oil-in-oil emulsions stabilised solely by solid particles. Soft matter, 12(3), 876-887. doi:10.1039/c5sm02438b
DOI https://doi.org/10.1039/c5sm02438b
Keywords Emulsions; Hydrophobic particles
Publisher URL http://pubs.rsc.org/en/Content/ArticleLanding/2016/SM/C5SM02438B#!divAbstract
Copyright Statement This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
Additional Information Copy of article published in: Soft matter, 2016.

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Copyright Statement
This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.





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