College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, PR China.
College of Pipeline and Civil Engineering, China University of Petroleum, Qingdao 266580, PR China.
J Colloid Interface Sci. 2017 Nov 1;505:460-466. doi: 10.1016/j.jcis.2017.06.042. Epub 2017 Jun 13.
The breakup process of aqueous droplet with surfactant suspended in oil under direct current (DC) electric field is investigated in this paper. The characteristics of the breakup process, stretching, necking and breakup, are discussed quantitatively with the electric capillary number Ca and the dimensionless surfactant concentration C which is the ratio of surfactant concentration to the critical micelle concentration. The results show that the presence of surfactant reduces the steady deformation of droplet and significantly decelerates the stretching process, resulting from the redistribution of surfactant molecules within the oil/water interface. The law of droplet stretching process when C≥1 indicates that the exchange of surfactant molecules between the bulk phase and the interface could not catch up with the increase of oil/water interfacial area. Ca and C count a great deal to the necking position and the daughter droplet size. The daughter droplet size decreases with the increase of surfactant concentration. These results provide a mechanistic framework to promote the electrocoalescence efficiency of oil/water emulsion and to the application of electric emulsification.
本文研究了在直流（DC）电场下含有表面活性剂的油滴的破裂过程。通过电毛细数 Ca 和无量纲表面活性剂浓度 C（即表面活性剂浓度与临界胶束浓度之比）定量讨论了破裂过程、拉伸、颈缩和破裂的特征。结果表明，表面活性剂的存在降低了液滴的稳定变形，并显著减缓了拉伸过程，这是由于表面活性剂分子在油/水界面内的重新分布所致。当 C≥1 时，液滴拉伸过程的规律表明，在油/水界面处，表面活性剂分子在本体相与界面之间的交换无法跟上油/水界面面积的增加。Ca 和 C 对颈缩位置和子液滴尺寸有很大影响。子液滴尺寸随表面活性剂浓度的增加而减小。这些结果为提高油/水乳液的电聚结效率和电乳化的应用提供了一个机械框架。
