Jerzy Majka

Sorption isotherms of thermally modified wood

Abstract The hygroscopic properties of thermally modified wood have been studied in terms of adsorption and desorption processes. Poplar (Populus spp.) and European beech (Fagus sylvatica L.) were in focus. The obtained isotherms were parameterized with the models of Hailwood-Horrobin, Guggenheim-Anderson-deBoer, generalized D’Arcy and Watt, and Yanniotis and Blahovec. The changes in equilibrium moisture content (EMC) were quantified, and the accessibility of water vapor to the sorption sites was determined. The monolayer and multilayer sorption was studied and the sorption isotherms were classified. All sorption isotherms were type II, and the type was not changed after the modification. The monolayer sorption was found to be responsible for the reduction in EMC after thermal modification. The observed increase in the hysteresis coefficient was explained by the reorganization of the wood ultrastructure.

Sorption isotherms of waterlogged subfossil Scots pine wood impregnated with a lactitol and trehalose mixture

Abstract A waterlogged subfossil Scots pine wood, 12 500-years-old, was impregnated with a mixture of lactitol and trehalose as well as with polyethylene glycol (PEG) mixtures, respectively, and the sorption properties of the impregnated samples were determined. All the impregnated wood samples were freeze-dried. The sorption isotherms were parameterized with the Guggenheim-Anderson-deBoer (GAB) and Generalized D’Arcy and Watt (GDW) models. Better hygroscopic properties were found for wood impregnated with the lactitol and trehalose mixture as compared to the PEG treatments. An anomalous increase of equilibrium moisture content (EMC) was found for PEG treated wood at a high relative humidity (RH) as compared to untreated wood at RH<80%. The lactitol and trehalose mixture significantly reduced this effect due to the decreased sorption of polymolecular water. Another positive effect of the alternative method is the ca. 50% reduction of the sorption hysteresis as compared to untreated wood. Moreover, the hysteresis was also much lower in the case of high RH as compared to PEG treated wood. The alternative treatment is also effective in terms of the dimensional stabilization of decayed wood.