Real time monitoring of the through thickness moisture profile of thin sheets using NMR

The through-thickness distribution of liquids and liquid migration over time in thin, porous media is highly relevant for the production and product properties of materials such as textiles, membranes, paper, barrier materials, and thin films. We present a 1D NMR profiling method for the analysis of through-thickness liquid distribution during liquid absorption, migration, and drying of thin sheets. The good temporal resolution (1.3 s) and high spatial resolution (10 μm) make it possible to study changes of liquid distribution in sheets of about 100 μm thickness. A key aspect of our method is the simultaneous scanning of a liquid saturated reference sheet. Using a reference, local liquid saturation and absolute amount of liquid present over time can be evaluated. We studied the drying of water-based inkjet ink on paper substrates with differing water absorption behaviors. Differences in z-directional liquid distribution, penetration depth, and drying kinetics over time could be observed.