Precoat and Topcoat Effect on the Final Printability – Part 1: Using mercury intrusion to analyse the Coating structure

D. Matte, Centre International de Couchage (CIC), Trois-Rivières, QC,, A. Dimmick, Bethlehem, PA, USA, P. Mangin, Centre Intégré en Pâtes et Papiers, Trois-Rivières, QC, C. Daneault, Canada Research Chair in Value-added Paper, Trois-Rivières, QC

Mercury intrusion testing is a well established tool, and has been used extensively within the industry to give a great deal of information to the papermaker about the paper and coating structure.  The test has been invaluable in predicting or troubleshooting many areas such as blister resistance and printing issues.  However, results can vary widely depending on the choice of materials (pigments or binder) used in different formulations.  The main goal of this paper is to explain how to achieve a good analysis of mercury intrusion by good manipulations of the data for double-coated paper. 

It is important to define the point in the data collected where the pore diameter is representative of the area located around the low and high mercury pressure and thus eliminate the occlusion and/or defects effects.  An explanation of the way to identify the point of separation between the coating layers and the base paper and between the pre-coat and top coat together is also provided.  The hexadecane method and the correction (performed with blank correction option) in the Autopore™ program from Micromeritics can be used to achieve these results.  An example of the correction for mercury intrusion method used is also shown using data from a study done for a doctorate begin at University of Québec à Trois-Rivières.