Film Thickness in Transient State in Dip Coating:Studies on Dip Coating (Part 2)

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In case of coating with water soluble acrylic resin paints on aluminum anodic oxide film, dip-coating method was applied to investigate the film in transition state under the following conditions: Withdrawal velocity Ww=1.17-100cm/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 by the above experiments: (1) When a vertical plate was lifted at a constant velocity from the stationary liquid, the film thickness on the plate was approximately equal to the theoretical value, hth=Cthx1/2 when the withdrawal velocity was 100cm/sec., which was the maximum during experiments. (where Cth=√ρg/μ·1/t, t: time for solidification, g: gravitational acceleration, x: distance from the upper edge). (2) The relation between Vw (withdrawal velocity) and Cov/Cth was approximately expressed by an exponential function: when Vw=100cm/Cth, Cov/Cth=1.0, Vw=1.17, Cov/Cth=2.5. (3) The relation between μ/ρ (viscosity/density of paint) and n was approximately expressed by an exponential function: when μ/ρ=0.51, n=0.31, μ/ρ=0.21, n=0.51. (4) The states of film adhered to the plate were divided into two kinds: transition and stationary states. When the withdrawal velocity was as low as 1.17-2.5cm/sec., the relation between the two states was discontinuous.
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