| The spreading of a fluid drop on a smooth horizontal surface is an often studied phenomenon from both, the experimental and theoretical point of view. Depending on the drop radius, the main driving force is either capillary or gravity and the drop shape is assumed to be spherical or pancake-like. The transition is commonly characterized by the capillary length.[1] The current models in the literature typically neglect either capillary or gravity contributions in the respective drop radius regime. However, for an accurate description of the spreading process in the transition zone, it is necessary to take into account the two driving forces simultaneously. Therefore, we derive novel physical models to describe the spreading kinetics for the complete and partial wetting scenario detailed and consider capillary, gravity and viscose friction contributions. The manageable equations enable the analytical description of the drop radius as a function of time with only physical quantities.[2] The theoretical models are experimentally verified with silicon oils varying in viscosity and spreading volume over two orders of magnitude. The fluids are initiated as drops on solid substrates, e.g. polyolefins, polyamide and fluoropolymers, and the diameter of wetted area is measured as a function of time. The experimental data are consistent to the suggested models.[2] [1] P.G. de Gennes, F. Brochard-Wyart, D. Quéré, Capillarity and Wetting Phenomena. Drops, Bubbles, Pearls, Waves, Springer, New York, USA, 2004 [2] M. Härth, D.W. Schubert, Macromol. Chem. Phys., 2012, 213, 654 |
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