Adsorption of water in the cell wall of wood is believed to involve the attraction of the sorbed water molecules to the OH groups of the cell wall polymers. These are usually referred to as sorption sites and it is assumed that the sorbed water molecules are immobilized at these sites through hydrogen bonding. It is also assumed that water molecules will gradually occupy the sorption sites until there are no longer any more available and that the water molecules will then begin to form multilayers on the cell wall internal surface. However, it is also possible that water molecules will tend to form clusters around specific sorption sites, leaving other sorption sites free of water until high levels of cell wall hydration are reached. The polymer literature has long considered this behaviour and there has been a model available (the Zimm-Lundberg model) which is very commonly used in the polymer literature to examine whether sorbates form clusters or layers. The purpose of this study was to examine the applicability of the Zimm-Lundberg model to studies of the water sorption of wood. The paper also considers a wider range of materials, including cellulose and plant fibres.
Keywords: water sorption, sorption sites, clustering
Authors
Hill C.A.S.
Visiting researcher, Norwegian Institute of Bioeconomy Research, Ås, Norway
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