Xianai Huang

Changes in wettability of heat-treated wood due to artificial weathering

Effect of artificial weathering on the wettability of three heat-treated North American wood species (jack pine, aspen, and birch) is studied from the point of view of the structural and chemical changes taking place on the wood surface. Weathering increases wettability of all three heat-treated woods by water. Changes in wettability during artificial weathering differ according to heat treatment procedure and wood species and are likely due to combination of structural and chemical changes of the surfaces. Scanning electron microscopic analysis indicates that cracks form due to degradation taking place during weathering. As a result, water has easier entry into the cell wall, which consequently increases wettability. IR spectra suggest that the OH/CH2 ratio for heat-treated specimens is inversely proportional to the contact angle regardless of the type of wood species. The presence of cellulose-rich layer on wood surface and increasing amount of amorphous cellulose transformed from crystallized cellulose due to weathering result in increase in hydroxyl; consequently, it increases heat-treated wood wettability.

Effect of surface preparation on the wettability of heat-treated jack pine wood surface by different liquids

The objectives of this study are to quantitatively evaluate, using a wetting model, the wettability of three probe liquids with different properties on heat-treated jack pine surfaces prepared by three different types of machining (sanding, planing and sawing) and to compare with those of untreated wood surfaces. The results indicate that the heat-treated wood is wetted less than the untreated wood due to degradation of wood components (hemicelluloses, lignin and cellulose) during heat treatment and it absorbs less liquid. The heat-treated wood becomes most hydrophobic when wood surfaces are sanded by 180-grit paper compared to those prepared by other machining process. Heat-treated wood surfaces are strongly acidic similar to those of untreated wood. Consequently, the basic probe liquid, formamide, shows the highest spreading and penetration rate (K-value) on wood surfaces.ZusammenfassungZiel dieser Studie war es, die Benetzbarkeit mit drei Versuchsflüssigkeiten mit unterschiedlichen Eigenschaften von thermisch behandeltem Jack Pine Holz, dessen Oberflächen unterschiedlich bearbeitet worden waren (schleifen, hobeln, sägen) quantitativ anhand eines Modells zu bestimmen und mit unbehandelten Holzoberflächen zu vergleichen. Die Ergebnisse zeigen, dass thermisch behandeltes Holz aufgrund des Abbaus von Holzbestandteilen (Hemicellulose, Lignin und Cellulose) bei der thermischen Behandlung weniger stark benetzt wurde als unbehandeltes Holz und dass es weniger Flüssigkeit aufnimmt. Thermisch behandeltes Holz, dessen Oberfläche mit Schleifpapier der Körnung 180 bearbeitet wurde, ist im Vergleich zu anders bearbeitetem Holz am hydrophobsten. Thermisch behandelte Holzoberflächen sind stark acidisch, ähnlich wie unbehandeltes Holz. Folglich weist die basische Testflüssigkeit Formamid die höchste Ausbreitungs- und Eindringrate (K-Wert) auf Holzoberflächen auf.

Dimensional Stabilization of Wood

This paper comprehensively reviews the relevant literature and presents the methods and processes used to investigate the dimensional stabilization of wood using various modification techniques, including (a) hydrophobization of wood surfaces to block the entrance and exit of water; (b) impregnation treatment with bulking agents, such as resin and wax, to maintain wood in a swollen state and diminish dimensional changes caused by moisture; (c) chemical treatment with different chemical agents to reduce the hygroscopicity of the wood; and (d) high temperature heat treatment, which modifies wood components, reducing accessible hydroxyl groups and decreasing the possibility of water absorption. The results of dimensionally stabilizing wood via different treatments are interpreted and compared, and the effects of treating conditions and parameters on the dimensional changes of wood are analyzed.