SURFACE ELASTIC EFFECTS IN PREMETERED COATING TECHNIQUES

The effect of the dilational surface elasticity epsilon on coating was investigated in two-layer slide coatings and single-layer slot and cu rtain coating experiments, respectively, up to 2 m/s. In the slide exp eriments both the surfactant concentration and epsilon were varied in the lower layer. While the position of the static contact line (SCL) i s a function of the elasticity modulus epsilon, the dynamic contact li ne (DCL) position is insensitive to this variable. Also, the vacuum ra nge increases with increasing the modulus E. Best correlations were ob tained when epsilon was measured at 1-2 Hz with a longitudinal wave ge nerator. In curtain coating, the curtain edges can be stabilized and t he wet thickness decreased by increasing the elasticity E. Also, in sl ot coating experiments the minimum wet thickness correlates with epsil on as well. The modulus that best characterizes these coating techniqu es was determined at 0.1-0.2 Hz by means of a Langmuir trough.