Measuring moisture gradients in cellulose fibre networks: An application of the magnetic resonance imaging method

A magnetic resonance imaging method was employed to measure moisture distributions in pulp samples. A calibration experiment shows that, in the range of moisture contents up to 1.4 g water/g dry substance, the MRI signal is linearly proportional to the mass of moisture of the pulp sample. The in-situ drying of a pulp sheet approximately 4 mm thick was them studied. The resolution in the thickness direction was 0.39 mm. It was found that, even at the very low drying rates employed in the present study (the average drying rate was 0.3 kg/m(2)/h), a gradient in moisture developed across the sheet as drying progressed.