The reduction in the fibre saturation point of wood due to chemical modification using anhydride reagents: A reappraisal

Abstract

The data from a previous study of the moisture adsorption of Corsican pine modified with linear chain carboxylic acid anhydrides (acetic, propionic, butyric, valeric, hexanoic) has been reanalysed so that moisture content is reported as a percentage of cell wall mass only. As part of this work, the change in fibre saturation point (FSP, determined from fits of the Hailwood-Horrobin model) of the modified wood has been determined as a function of weight percentage gain (WPG). The change in FSP is not determined by the extent of hydroxyl substitution of the cell wall, but is related to WPG only (as reported previously). This is also true for the relationship between monolayer water, polylayer water, molecular weight per sorption site at saturation and WPG. However, there is no simple linear relationship between calculated FSP and WPG. When the FSP was determined by solute exclusion methods, the reduction thereof could be simply explained as due to bulking of the cell wall by the bonded acyl substituents. This is not the case when the FSP is determined from adsorption isotherms. This result is interpreted as an ambiguity of determination of FSP from projections of sorption isotherms. Differences in FSP determined by the two methods (sorption versus solute exclusion) are considered to be due to incomplete wetting of the lignocellulosic material when absorbing moisture from the initial dry state.

Experimental techniques for characterising water in wood covering the range from dry to fully water-saturated

“…However, from a scientific standpoint the concept is problematic (Babiak and Kudela 1995;Feist and Tarkow 1967), and it mischaracterises the wood-water relations. Instead, in this review, FSP is regarded as the maximum cell wall water capacity measured in the fully water-saturated state (Hill 2008). The first part of this definition is in line with the intension behind the original definition by Tiemann (1906), i.e.…”

“…In this review, it is described by water mass divided by dry wood mass. When dealing with physicochemically modified wood materials, it is often necessary to adjust MC for added dry mass due to the modification process (Hill 2008;Thybring 2013) in order to correctly compare a given modified material with untreated or differently modified materials. This is done by multiplying MC of the modified material, MC mod [%], with (1 ?…”

Characterisation of Postia placenta colonisation during 36 weeks in acetylated southern yellow pine sapwood at three acetylation levels including genomic DNA and gene expression quantification of the fungus

“…However, only a few studies focused on the moisture distribution within the cell wall of modified wood (e.g. Hill et al 2005;Hill 2008;Engelund et al 2010;Thygesen et al 2010). Moisture dynamics in the cell wall during decay should be considered in the context of anatomical and chemical changes.…”

Dynamic water vapour sorption properties of wood treated with glutaraldehyde

“…Furthermore, incorporation of glutaraldehyde will locate in the nanopores of the cell wall and pre-swell the cell wall. As a result, the size (free space) of nanopores is reduced, and the cell wall swelling due to water adsorption can also be diminished, which results in less accommodation for water (primary dissolved water and condensed water) in the high RH range (Hill 2008).…”

“…A large decrease in equilibrium moisture content (EMC) has been reported due to wood acetylation treatment (Chang and Chang 2002;Epmeier et al 2007). The decrease has been attributed to the reduced sorption sites due to the deactivation of hydroxyl groups but, more crucially, the deposition of chemicals in the nanopores (bulking) (Chang and Chang 2002;Papadopoulos and Hill 2003;Hill 2006Hill , 2008.…”