Film Thickness under Stationary Condition in Dip Coating:Studies on Dip Coating (Part 1)

概要

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A dip coating equipment was prepared for the development of a coating method with water soluble acrylic resin paints on aluminum anodic oxide film. Experiments were conducted by this equipment under the following conditions:Withdrawing speed Vw=0.33-1.67cm/sec., Density of paints ρ=1.00-1.29g/cm3, Viscosity of paints μ=0.19-0.66 poise, Surface tension of paints σ=32.0-36.4dyne/cm.The following results were obtained in the range of 10-3-10-1 of capillary number. (1) The the-oretical thickness of dip-coated film (hth) was in good agreement with the following equation of Landau and Levich: hth=0.944(μVw/σ)1/6(μVw/ρg)1/2 (2) The thickness of film adhered (hov) was expressed by the following equation: hov=K. hth where K is a residual coefficient, which is 0.70-0.84. (3) The film adhered to a vertical plate became thinner with the lapse of time by "running" of the paint, and the "running was continued until the setting of paint occurred by evaporation. The time for setting seemed to be 500-600sec. in these experiments. (4) The residual coefficient of paints used in the experiments was nearly proportional to the value of μ/ρ. (5) The coated surface of test piece showed avery high degree of smoothness. Therefore, the dip coating would be effective in practical application.
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