Measurement of moisture content profiles during drying of Scots pine using magnetic resonance imaging

• Published in: Holzforschung Vol. 58; no. 2; pp. 138 - 142
• Main Authors: Rosenkilde, A., Gorce, J.-P., Barry, A.
• Format: Journal Article
• Language: English
• Published: Berlin Walter de Gruyter 01.01.2004; New York, NY de Gruyter
• Subjects: Applied sciences; Exact sciences and technology; Mechanical woodworking and drying; Polymer industry, paints, wood; Properties and testing; Wood; Wood. Paper. Non wovens; Scanning electron microscopy; Heartwood; Surface layer; Softwood; Experimental study; Pinus sylvestris; Nuclear magnetic resonance imaging; Image analysis; Gymnospermae; Water content; Coniferales; Spermatophyta; Drying
• ISSN: 0018-3830; 1437-434X; 1437-434X
• DOI: 10.1515/HF.2004.020

Moisture content profiles with high spatial pixel resolution, 21 μm, were measured in Scots pine heartwood while drying from wet conditions to near equilibrium in the surface layer, (0–300 μm). The measuring technique used was Magnetic Resonance Imaging. In order to obtain magnetic resonance profiles with a high pixel resolution at both high and low moisture contents, a highg-radient permanent magnet was used. The results presented show one-dimensional moisture content profiles and mean moisture content development in the surface layer. In Scots pine heartwood, almost flat moisture content profiles were observed when the moisture content was above the fibre saturation level. When the mean moisture content in the surface layer decreases to the fibre saturation level, gradients start to build up from the surface towards the bulk of the sample although the bulk moisture content is far above the fibre saturation. Furthermore, the results presented in this study imply that a dry shell forms in the surface layer shortly after drying has begun. This dry shell controls the drying rate until the mean moisture content in the bulk decreases to the fibre saturation level.