Using Mercury Porosimetry to Characterize Coating Pore Structure and its Relations to Coating Optical Performance, 1996 Coating Conference Proceedings

Mercury intrusion porosimetry can provide a quantitative description of paper coating pore structure. Improvements in data handling using computer software allow us to compensate for coating compressibility and permit close examination of specific important regions of the pore spectrum. A method is presented showing how to correct for sample compressibility. This ability is essential to remove instrumental artifacts caused by compressibility, especially in the pore domain below 1 µm, and to increase data accuracy. Also, the ability to overlay pore spectra permits paper mills to understand and optimize pore evolution as a function of coating formula and mill operating parameters. Comparison of the pore distribution data from many samples has demonstrated clear correlations with coating optical performance. This technique therefore can help mills optimize the optical performance of coating formulations and processes, i.e. achieve optical performance at equal or lower cost. Quantitative measurements of the pores important to optical performance will be discussed. Examples of the impact of lab and mill coating formula changes on pore structure and optical performance are presented providing insight on how this technique can be used to optimize mill coating formulations.