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The modifying effects of Scots pine (Pinus sylvestris L.) wood with the crosslinking agent glutaraldehyde (GA) on the water vapor sorption kinetics were studied by curve fitting the experimental isotherm sorption data obtained using a Dynamic Vapor Sorption apparatus using the parallel exponential kinetics model (PEK model) and the Hailwood-Horrobin model (H-H model) for the isotherm. Both the H-H model and the PEK model provided good fits to the experimental data. Modification of wood with GA reduced both the time to equilibrium and the equilibrium moisture content (EMC). According to the PEK and H-H models, the reduction in EMC was mainly due to the decrease of moisture content (MC) associated with the slow sorption processes and polylayer water. The fast sorption processes and monolayer water were little affected by GA modification. Compared to the untreated control, the estimated total water absorbed by wood treated to a WPG of 20.9% at 100% RH decreased by 52.2%, by extrapolating the fitted curves derived from the H-H model. V

The objective of this study was to examine the water vapour sorption behaviour of three celluloses, which were originally derived from cotton fibers, using a dynamic vapour sorption apparatus, including analyses of the sorption rate and hysteresis occurring in the isotherm run. Cotton linter, a-cellulose, and microcrystalline cellulose (MCC), respectively attained equilibrium moisture contents of 14.2, 20.6, and 16.9% at a relative humidity (RH) of 95%. All three cellulosic materials exhibited sorption hysteresis to varying degrees throughout the full RH range; the MCC and a-cellulose displayed the lowest and highest total hysteresis, respectively. The sorption kinetics were analysed in terms of the parallel exponential kinetics (PEK) model, with excellent fits to the data being obtained. The PEK data is further interpreted on the basis of two Kelvin-Voigt elements operating in series. Clear differences in behaviour were seen between the a-cellulose and the other two celluloses in this study. The relative importance of capillary condensation and matrix viscoelasticity with respect to sorption hysteresis is discussed.

The dynamic vapour sorption behaviour of two Malaysian hardwoods, acacia (Acacia mangium Wild) and sesendok (Endospermum malaccense Bent ex Müll. Arg.) was studied over a narrow temperature range (20–40°C). The rate of sorption or desorption of water into or out of the wood cell wall was considered to be limited by the viscoelastic behaviour of the material and the sorption kinetics was accordingly analysed in terms of a canonical series of Kelvin-Voigt elements. A two series and three series model have been applied to the kinetic data and the results are compared. Characteristic times and moisture contents were obtained from the models. The Arrhenius equation was used in conjunction with the reciprocals of the characteristic times to calculate the activation energy and activation entropy of sorption, and the Gibbs free energy of activation for the sorption process was also determined. This is the first time that entropy of activation and Gibbs free energy of activation for sorption processes with wood have been reported. Interpretation of these data invokes a model describing the polymeric relaxation processes occurring within the cell wall during adsorption or desorption. A possible link between sorption kinetics, polymeric relaxation processes, and sorption hysteresis is discussed.