Influence of mixing conditions on the rheological properties and structure of capillary suspensions.
Influence of mixing conditions on the rheological properties and structure of capillary suspensions.
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DOI：
10.1016/j.colsurfa.2017.01.026
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发表时间：
2017-04-05
期刊：
影响因子：
--
通讯作者：
Koos E
中科院分区：
文献类型：
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作者：
Bossler F;Weyrauch L;Schmidt R;Koos E
悬浮液的流变特性可以通过添加少量的与主体液体不混溶的第二流体而显著改变。这些毛细悬浮液存在于摆动状态或毛细状态，在摆动状态下，次级流体优先润湿颗粒，在毛细状态下，主体流体优先润湿。屈服应力，以及存储和损耗模量，取决于在样品制备过程中产生的第二相液滴的大小和分布。增强的液滴破碎导致更强的样品结构。在毛细管状态系统中，这可以通过使用溶解器搅拌器增加湍流混合的混合速度和时间来实现。在摆动状态下，增加的混合速度也会导致更好的液滴破碎，但球形团聚是有利的，在较长的时间降低屈服应力。额外的混合与球磨机被证明是有益的样品强度。通过用粘度匹配的流体进行实验，排除了本体和第二流体之间的粘度变化对液滴破碎的影响。这些实验表明，毛细状态与皮克林乳液液滴的形成竞争，并且通常比摆动状态更难实现。
The rheological properties of a suspension can be dramatically altered by adding a small amount of a secondary fluid that is immiscible with the bulk liquid. These capillary suspensions exist either in the pendular state where the secondary fluid preferentially wets the particles or the capillary state where the bulk fluid is preferentially wetting. The yield stress, as well as storage and loss moduli, depends on the size and distribution of secondary phase droplets created during sample preparation. Enhanced droplet breakup leads to stronger sample structures. In capillary state systems, this can be achieved by increasing the mixing speed and time of turbulent mixing using a dissolver stirrer. In the pendular state, increased mixing speed also leads to better droplet breakup, but spherical agglomeration is favored at longer times decreasing the yield stress. Additional mixing with a ball mill is shown to be beneficial to sample strength. The influence of viscosity variance between the bulk and second fluid on the droplet breakup is excluded by performing experiments with viscosity-matched fluids. These experiments show that the capillary state competes with the formation of Pickering emulsion droplets and is often more difficult to achieve than the pendular state.