Yielding and flow of concentrated Pickering emulsions
Yielding and flow of concentrated Pickering emulsions
复制标题
DOI：
10.1039/c3sm50889g
复制
发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Clegg, Paul S.
中科院分区：
文献类型：
--
作者：
Hermes, Michiel;Clegg, Paul S.
我们已经使用流变成像研究剪切流动的颗粒稳定（皮克林）乳液与不同的液滴之间的相互作用。为了最大限度地减少乳状液分层，我们使用了被捕获的液滴网络。我们观察到三种不同的屈服机制，以及在高应变剪切增稠。由排斥液滴组成的皮克林乳液最初通过可逆运动响应于小应变，然后，随着应变的增加，通过破笼产生屈服。在大应变下，模量和液滴轨迹之间的相关性都出现峰值，表明剪切增稠和堵塞。由有吸引力的液滴组成的皮克林乳液具有类似的特征，并且另外具有与有吸引力的键的断裂和重排相关的低应变下的损耗模量峰。我们观察到，小的吸引力液滴已经开始在小应变不可逆地移动，即使尚未发生屈服。随着应变的增加，较大液滴的结晶网络最终完全破裂，样品整体屈服。最后，我们探讨了当高度压缩的乳液或双液泡沫受到剪切流动时会发生什么：我们发现，在高应变下，颗粒不能稳定界面，乳液被破坏。
We have used rheo-imaging to investigate the shear flow of particle-stabilized (Pickering) emulsions with different interactions between droplets. To minimize creaming, we have worked with arrested networks of droplets. We observe three different yielding mechanisms as well as shear thickening at high strain. Pickering emulsions comprised of repulsive droplets respond to small strains initially by reversible movement, then, as the strain is increased, yielding occurs via cage breaking. At large strains there is a peak in both moduli and correlations between droplet trajectories indicative of shear thickening and jamming. Pickering emulsions comprised of attractive droplets share similar features and additionally have a loss modulus peak at low strain associated with the breakage and rearrangement of the attractive bonds. We observe that small attractive droplets already start to move irreversibly at small strains even though yielding has not yet occurred. As the strain is increased, the percolating network of larger droplets is eventually completely broken and the sample yields as a whole. Finally, we explore what happens when a highly compressed emulsion or bi-liquid foam is subjected to shear flow: we find that at high strain the particles fail to stabilize the interface and the emulsion is destroyed.