BEHAVIOR OF SOLID WOOD AND BOUND WATER AS A FUNCTION OF MOISTURE-CONTENT A PROTON MAGNETIC-RESONANCE STUDY

Nuclear magnetic resonance lineshape second moments of the solid wood protons and spin-spin relaxation times, T2, of the bound water in lodgepole pine heartwood have been measured at 30-degrees-C for a range of moisture contents, mainly in the hygroscopic range. The second moment of the solid wood protons for oven dry wood was found to be about 23% lower than the rigid lattice calculation, indicative of a rigid structure with some anisotropic molecular motion of the polymeric constituents. Above 5% M, the second moment decreased by a further 13 to 16% implying a ''loosening'' of the molecules in the solid with increased moisture content. The T2 of the bound water increased with moisture content, and provided no evidence of separate hydration and solution water fractions as predicted by isotherm theories. The NMR measured fibre saturation point of 27% agreed with the value calculated by the Hailwood-Horrobin isotherm model.