Predicting the toplayer coatability of barrier layers
Thursday, 10 November 2011
New study outlines, that the most important aspect for predicting the coatability is the wettability, especially the water contact angle.
Finnish researchers examined in a new study the influence of different surface characteristics of dispersion-coated barrier layers on top layer coatability. 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 was 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 improved the coatability, whereas roughness had only a minor effect. The complete study will appear in the January issue 2012 of "Progress in Organic Coatings".