Correlation of water vapor adsorption behavior of wood with surface thermodynamic properties

Abstract

ABSTRACT:To improve the overall performance of wood-plastic composites, appropriate technologies are needed to control moisture sorption and to improve the interaction of wood fiber with selected hydrophobic matrices. The objective of this study was to determine the surface thermodynamic characteristics of a wood fiber and to correlate those characteristics with the fiber's water vapor adsorption behavior. The surface thermodynamic properties, determined by inverse gas chromatography at infinite dilution or near zero surface coverage, were the dispersive component of the surface energy, surface acid-base free energy and enthalpy of desorption of acid-base probes, and surface acid-base acceptor and donor parameters (K A and K D ). Water vapor adsorption was expressed in terms of the percentage of weight gain (⌬W%) resulting from water vapor adsorption on the wood particles, calculated relative to their initial weight after preconditioning in a vacuum dessicator at room temperature. The results showed a strong correlation between ⌬W% and K A , and between ⌬W% and surface acid-base free energy of water desorption (⌬H AB water ), calculated from experimental K A and K D and values in the literature for acceptor and donor values of water. These results suggest that for substrates such as wood, whose surface Lewis acid-base properties are characterized by a relatively stronger tendency to accept electrons, the key to controlling water vapor adsorption is to manipulate the magnitude of ⌬H AB water , primarily via K A , and to a lesser extent via K D .

Creation of superhydrophobic wood surfaces by plasma etching and thin-film deposition

“…Furthermore, wood has a high strength-to-weight ratio and requires less energy during manufacturing than steel or cement-based materials. The greatest disadvantage of wood in these applications is its hygroscopicity [5]; hydroxyl groups on the porous surface readily form hydrogen bonds with sorbed water molecules [6,7]. As a result of water uptake, wood suffers from dimensional instability [8] and accelerated biological (fungi, bacteria, insects) and photochemical degradation during the natural weathering process that occurs both outdoors and indoors [9].…”

Surface chemistry and moisture sorption properties of wood coated with multifunctional alkoxysilanes by sol‐gel process

“…In the case of lignocellulosic polymers such as wood, the surface hydroxyls on the wood polysaccharides or lignin form hydrogen bonds with sorbed water molecules. 1,2 Water molecules sorbed on the wood surface affect its rate of photochemical degradation during the natural weathering process outdoors. 3 However, the presence of a sorbed layer of water molecules on a wood surface can also be used to good advantage to promote bonding of water-repellent multifunctional alkoxysilanes to the wood surface.…”

Analysis of the topochemical effects of dielectric-barrier discharge on cellulosic fibers

“…The dispersive surface energies for dielectric-barrier discharge treated kraft and mechanical pulp fibers are summarized in Figure 5. This data has been calculated to 25°C as in the work of Walinder and Gardner (2000) and Tshabalala et al (1999). This analysis indicates that the dispersive surface energy of the fibers is maximized at low treatment, suggesting an increase in the polarizability of probe molecules by the fiber surface.…”