Tönsmann Max, Scharfer Philip, Schabel Wilhelm
Karlsruhe Institute of Technology (KIT), Thin Film Technology (TFT), Kaiserstraße 12, 76131 Karlsruhe, Germany.
Polymers (Basel). 2021 Apr 10;13(8):1223. doi: 10.3390/polym13081223.
Convective Marangoni instabilities in drying polymer films may induce surface deformations, which persist in the dry film, deteriorating product performance. While theoretic stability analyses are abundantly available, experimental data are scarce. We report transient three-dimensional flow field measurements in thin poly(vinyl acetate)-methanol films, drying under ambient conditions with several films exhibiting short-scale Marangoni convection cells. An initial assessment of the upper limit of thermal and solutal Marangoni numbers reveals that the solutal effect is likely to be the dominant cause for the observed instabilities.
干燥聚合物薄膜中的对流马兰戈尼不稳定性可能会引起表面变形，这种变形会在干膜中持续存在，从而降低产品性能。虽然理论稳定性分析有很多，但实验数据却很匮乏。我们报告了在薄聚醋酸乙烯酯 - 甲醇薄膜中进行的瞬态三维流场测量，这些薄膜在环境条件下干燥，有几片薄膜呈现出短尺度的马兰戈尼对流单元。对热马兰戈尼数和溶质马兰戈尼数上限的初步评估表明，溶质效应可能是观察到的不稳定性的主要原因。
