Abstrakt
The evaporation of thin solution layers is an important process taking place in fields such as distillation, coating, or thin film manufacturing. Under suitable conditions, evaporation can induce convective flow by creating gradients in surface tension (Bénard-Marangoni instability) or density.
These phenomena have been studied by many authors, but detailed and illustrative visualizations of real experiments are surprisingly scarce compared to simulation results and drawn schemes. Therefore, detailed and representative visualizations of regular Bénard-Marangoni convective cell patterns are provided in solution-casted films from acylated hyaluronan.
The visualizations agree with predictions made in the literature, thus providing important experimental validation. Most importantly, structures resulting from both horizontal and vertical convective flow are clearly visible.
In a subsequent parametric study, the effects of selected parameters on the size of the convective cells are elucidated. The results suggest that the cell size increases with increasing solution layer height and increasing polymer concentration, while no statistically significant effect is observed for the degree of hyaluronan substitution.