Effect of aqueous phase composition on the properties of a silica-stabilized W/O emulsion

被引:101
作者
Midmore, BR [1 ]
机构
[1] Univ Reading, Dept Chem, Reading RG6 6AD, Berks, England
关键词
pickering; W/O emulsion; silica; internal phase; hydroxypropyl cellulose;
D O I
10.1006/jcis.1999.6108
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A high volume fraction silica stabilized w/o emulsion with small droplet size (approximate to 3 mu m) has been prepared using a commercially available hydrophobic silica. Addition of hydroxypropyl cellulose to the dispersed aqueous phase was found to improve the monodispersity of the emulsion by suppressing the production of larger droplets. The droplet size distribution showed complex behavior as the silica concentration was varied, which was explained using a simple kinetic argument. The effect of varying the acidity and ionic strength of the internal water phase was investigated. It was found that the presence of strong acid or strong alkali in the internal aqueous phase increased the gelation of the emulsions by promoting flocculation. This could be explained by acid- and alkali-catalyzed cleavage of surface siloxane groups increasing the number of surface silanol groups. If emulsions of strong acid and strong alkali were mixed, substantial additional gelation (again caused by flocculation) occurred. A possible explanation, preferred by the author, was an electrostatic one involving the interaction of dipoles in close proximity in the flocculated emulsion. (C) 1999 Academic Press.
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页码:352 / 359
页数:8
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