Moisture Relationships of Anhydride-modified Wood

Popper and Bariska (1972) studied the moisture sorption properties of wood chemically modified with acetic (or phthalic) anhydride and analysed the results using Brunauer-Emmett-Teller (BET) theory and the H-H model. Acetylation was found to reduce the number of sorption sites, whereas little effect was noted with phthaloylation. By dividing the sorption isotherm into a monolayer component and a multilayer component using the H-H model, it was shown that there was a large reduction in the 

Rowell and Rowell (1989) acetylated Scandinavian spruce Picea abies) wood chips, then subsequently reduced these to fibres in a laboratory disc refiner, fibre production did not result in loss of acetyl content, but it was found that new water sorption sites were produced as a consequence of the refining process. In addition, these workers modified a variety of lignocellulosic materials and found that all of the materials studied exhibited the same reduction in EMC at comparable WPGs. 

In measurements of the dielectric relaxation of water adsorbed on acetylated wood, a large change in the activation enthalpy and entropy of dielectric relaxation was found to occur at 6 % moisture content (Zhao etal., 1994), this presumably being attributable to the onset of formation of capillary water in the cell wall. 

A recent study of wood modified with a variety of anhydride reagents has questioned the validity of the use of the H-H model when interpreting the moisture sorption isotherms of modified wood (Papadopoulos and Hill, 2003). This has shown that although modification with anhydride reagents leads to a reduction in both monolayer and 

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