Chatzigiannakis Emmanouil, Veenstra Peter, Ten Bosch Dick, Vermant Jan
Department of Materials, ETH Zürich, 8032 Zürich, Switzerland.
Shell Global Solutions International B.V., 38000 Amsterdam, The Netherlands.
Soft Matter. 2020 Oct 28;16(41):9410-9422. doi: 10.1039/d0sm00784f.
The dynamics of thin films containing polymer solutions are studied with a pressure-controlled thin film balance. The setup allows the control of both the magnitude and the sign as well as the duration of the pressure drop across the film. The process of coalescence can be thus studied by mimicking the evolution of pressure during the approach and separation of two bubbles. The drainage dynamics, shape evolution and stability of the films were found to depend non-trivially on the magnitude and the duration of the applied pressure. Film dynamics during the application of the negative pressure step are controlled by an interplay between capillarity and hydrodynamics. A negative hydrodynamic pressure gradient promoted the thickening of the film, while the time-dependent deformation of the Plateau border surrounding it caused its local thinning. Distinct regimes in film break-up were thus observed depending on which of these two effects prevailed. Our study provides new insight into the behaviour of films during bubble separation, allows the determination of the optimum conditions for the occurrence of coalescence, and facilitates the improvement of population balance models.
利用压力控制的薄膜天平研究了含有聚合物溶液的薄膜动力学。该装置能够控制薄膜上压降的大小、正负以及持续时间。通过模拟两个气泡靠近和分离过程中压力的变化，从而可以研究聚并过程。发现薄膜的排水动力学、形状演变和稳定性非平凡地依赖于所施加压力的大小和持续时间。施加负压步骤期间的薄膜动力学由毛细作用和流体动力学之间的相互作用控制。负的流体动力压力梯度促进了薄膜的增厚，而围绕它的 Plateau 边界随时间的变形导致其局部变薄。因此，根据这两种效应中哪一种占主导，观察到了薄膜破裂的不同状态。我们的研究为气泡分离过程中薄膜的行为提供了新的见解，能够确定聚并发生的最佳条件，并有助于改进群体平衡模型。
