Top layer coatability on barrier coatings

In this study, the influence of different surface characteristics of dispersion-coated barrier layers on top layer coatability is examined. The barrier layer consisted of platy pigments, such as talc and kaolin, combined with different amounts and types of latexes. Coating of the top coat was carried out using the reverse gravure technique in which a dispersion consisting of mineral pigments and latex is applied under slight pressure onto the barrier-coated substrate. Wettability and coatability were measured as a function of surface energy and surface roughness of the barrier layer and the surface tension of the top coat dispersion. Plasma and corona surface treatments were used to increase the surface energy and wettability without affecting the surface topography. The most important aspect for predicting the coatability was the wettability, especially the water contact angle, because the top coat is an aqueous suspension. Decreasing the surface tension of the top coat dispersion also improved the coatability, whereas roughness had only a minor effect.

► Water contact angle the most important predictor for toplayer coatability on barrier layers.
► Influence of roughness is minimal.
► Plasma or corona treatment improves coatability.