Experimental study of the effect of surface-absorbed hydrophobic particles on the Landau-Levich law

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Abstract
We study the dip coating of liquids with particles absorbed on the interface under controlled conditions to obtain data on the coating thickness of particle dispersions as a function of coating speed, physical properties, and particle surface concentration. The thickness of the coating film created by the withdrawal of a plate from a bath was measured gravimetrically over a wide range of capillary numbers for two different kinds of particles. It is found that the presence of particles results in a significant thickening of the film relative to that for a clean interface, and in a slightly different power law for the thickness vs. capillary number than the classical Landau-Levich law. The influence of the particle surface concentration is also investigated, and shows a strong dependence of the film thickness on concentration, including a threshold concentration at which the film thickness begins to deviate from that for a clean interface.

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