Influence of the flow field in curtain coating onto a prewet substrate

摘要

The onset of air entrainment for curtain coating onto a surface prewetted with the coating fluid was studied. The substrate used was a polished, scraped steel wheel and coating was performed over ranges of dimensionless parameters observed in commercial coating processes (Reynolds number, 0.14 < Re=rho Q/mu < 33.02; Capillary number, 0.19 < Ca=mu U/sigma < 25.07). The substrate velocity for the onset of air entrainment was obtained as a function of the curtain flow rate per unit width of curtain (1 < Q < 9 cm(2) s(-1)), fluid dynamic viscosity (0.0326