Topography and gloss of paper coating layers

The aim of the work is to study the correlations of topog., morphol. and optical properties between a coating substrate and different coating layers. Pptd. calcium carbonate (PCC) pigments were coated on a model substrate and various coating thicknesses (coating amts.) were compared. A versatile roughness anal. was carried out for the measured AFM topog. 3D images in three different length scales: 3,10, and 50 $μ$m. The results give novel detailed information about different topog. features of pigment coatings, e.g., surface porosity, effective surface area, kurtosis, and d. of local summits. Even a relatively low coating thickness was found to be enough to cover and smooth the surface on large scale (50 $μ$m) but was obsd. to increase the root-mean-square (RMS) roughness at small scale (3 $μ$m). The gloss was obsd. to be quite linearly dependent on RMS roughness. Interestingly the gloss was also found to increase with decreasing skewness, i.e. increasing surface porosity. The results give promise for enhanced control of coating amt. and prepn. of surfaces with desired topog. and optical features. [on SciFinder(R)]