Effects of acetylation and formalization on the dynamic water vapor sorption behavior of wood

Abstract

The dynamic water vapor sorption of untreated, acetylated (W ac ), and formaldehyde-treated (W FA ) Scots pine ( Pinus sylvestris L.) sapwood was studied in a dynamic vapor sorption apparatus to assess the effects of cell wall bulking and cross-linking. Both modifications resulted in a considerable reduction of reduced equilibrium moisture content (EMC R ), the corresponding equilibrium times, and hysteresis in the hydroscopic range of wood. Acetylation reduced the adsorption and desorption of water at each given relative humidity (RH) step from 0% to 95% RH, whereas formalization affected the sorption behavior of wood solely above 20% RH. From 20% to 95% RH, the EMC ratio of W FA to its control steadily decreased, whereas the EMC ratio of W ac was still constant in this RH range. Below 20% RH, the sorption behavior of W ac was governed by hydroxyl blocking, whereas that of W FA was hardly influenced compared with the control. Above 20% RH, the sorption behavior of W ac was solely determined by cell wall bulking, whereas that of W FA was governed by the increased matrix stiffness due to the cross-linking of cell wall polymers.

Scanning or desorption isotherms? Characterising sorption hysteresis of wood

“…In literature, desorption is most often initiated from 95% RH and a peak in absolute hysteresis is observed around 75% RH (Cordin et al 2017;Hill et al 2009Hill et al , 2012bHimmel and Mai 2015;Hosseinpourpia et al 2016;Jalaludin et al 2010;Kymäläinen et al 2015;Okubayashi et al 2005a, b;Popescu et al 2014;Popescu and Hill 2013;Shi and Avramidis 2017;Simón et al 2017;Vahtikari et al 2017;Xie et al 2011) in accordance with the present study. This is also clear from Fig.…”

“…In recent years, when the use of automated sorption balances has become more widespread, the high RH from which desorption is initiated is typically between 90 and 96% (Ceylan et al 2014(Ceylan et al , 2012Cordin et al 2017;Hill et al 2009Hill et al , 2012bHimmel and Mai 2015;Hosseinpourpia et al 2016;Jalaludin et al 2010;Kymäläinen et al 2015;Okubayashi et al 2005a, b;Popescu et al 2014;Popescu and Hill 2013;Shi and Avramidis 2017;Simón et al 2017;Xie et al 2011). However, using this measurement procedure, it is not hysteresis between desorption and absorption isotherms that is evaluated, but hysteresis between a scanning isotherm and the absorption isotherm.…”

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

“…While the low sample mass makes possible detailed studies of differences in water sorption between earlywood and latewood (Fredriksson and Thygesen 2017), even at the growth ring level (Hill et al 2015;Song et al 2014), it also requires the user to consider how to collect representative samples for the study in question. For generating representative samples of larger wood volumes, several studies have used milled wood Himmel and Mai 2015;Xie et al 2010;Zaihan et al 2009Zaihan et al , 2011, but it could be speculated if this gives a representative material or might produce unwanted side effects, for example a change in sample chemistry. Milling is not as intense a method for subdividing wood as ball milling which has been shown to change the material chemistry (Mao et al 2006) and internal chemical bonding (Schwanninger et al 2004).…”

“…Automated sorption balances are useful for studies of sorption hysteresis, and several published studies have focused on this phenomenon. In most studies, absolute sorption hysteresis has a maximum around 70-75% RH and decreases for higher RH (Hill et al , 2012bHimmel and Mai 2015;Hosseinpourpia et al 2016;Popescu et al 2014;Simon et al 2017;Xie et al 2011). The decreasing sorption hysteresis at high RH might, however, be an artefact due to desorption being initiated from a non-saturated state (often by conditioning to 95% RH).…”

ANATOMICAL, ULTRASTRUCTURAL, PHYSICAL AND MECHANICAL WOOD PROPERTIES OF TWO-YEAR-OLD Eucalyptus grandis × Eucalyptus urophylla CLONES

“…The highest value for the anisotropy in clone D indicates that its wood has restricted use in places with high humidity variation. However, treatments such as acetylation (Xie et al, 2013;Himmel et al, 2015) and heat treatment (Korkut, 2012;Zanuncio et al, 2014b) can reduce the variation in the wood dimensions and allow its use in such places.…”