Nuclear magnetic resonance lineshape second moments of the solid wood protons and spin-spin relaxation times, ?2, of the bound water in lodgepole pine heartwood have been measured at 30°C for a ränge of moisture Contents, mainly in the hygroscopic ränge. 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 struclure 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 7*2 of the bound water increased with moisture content, and provided no evidence of separate hydration and solution water fractions äs predicted by isotherm theories. The NMR measured fibre Saturation point of 27% agreed with the value calculated by the Hailwood-Horrobin isotherm model.

No abstract

No abstract

No abstract

The origin of sorption hysteresis in the wood-water system is still under debate. In nanoporous-fluid systems, in general, hysteresis is explained as the manifestation of metastable states in a single pore-fluid system and that is further complicated by the pore connectivity. Cell walls are considered as micro-mesoporous materials and capillary condensation in the entire hygroscopic region is proposed as an alternative sorption mechanism. In the present work, the woods of Douglas-fir, aspen and western red cedar were in focus and the pore connectivity has been investigated by observing five experimentally generated hysteresis patterns comprised by up to 4th scanning curves at 25 and 40°C. Special attention was given to the congruency property from one pattern as it is known from the literature that deviation from this property can reveal the extent of pore connectivity. Consistent patterns were found for the species-temperature combinations. Further, the high extent of congruency property indicated the dominance of independent cell wall pores.