Calenderability of Coating Grit Lines, 1996 Coating Conference Proceedings

The objective of the study was to determine characteristics of grit lines (coater scratches, blade lines, etc.) that could be identified which would allow prediction of which grit lines may be rendered undetectable after supercalendering. Samples of thirty two grit lines which varied in severity were collected for the analysis. The severity of the grit lines was determined before and after calendering via profilometry, and visually with the aid of low angle and transmitted light. The calenderability of grit lines did not correlate with grit line width, depth, or combinations of width and depth. Calenderability appeared to depend on the amount of coating which remained in the valleys of the grit lines (as determined by transmitted light) and the steepness of the valley walls. The calenderability of grit lines was enhanced with increasing calendering temperature or pressure. The combination of increased calendering temperature and pressure may have had additive effects on the calenderability of grit lines.