Abstract
High moisture content western hemlock veneer was modified using viscoelastic thermal compression (VTC) technology with an integrated drying stage. VTC is a type of thermo-hydro-mechanical treatment. This project determined the influence of five processing parameters on properties of VTC lamina. VTC processing significantly increased the mechanical properties of veneer, which mainly depended on the degree of compression. However, moisture-induced thickness swell increased substantially depending on the degree of compression and venting time. Increasing process temperature increased mass loss. Integrating the drying step improved process efficiency and eliminated drying defects. Process optimization was different depending on the desire to increase mechanical properties or increase dimensional stability. Statistical models were developed to predict properties of VTC treated products and drying time. This project will reduce the cost of VTC technology and provide guidance to design commercial manufacturing processes.
Zusammenfassung
Western Hemlock Furnier mit hohem Feuchtegehalt wurde mittels viskoelastisch-thermischem Verdichtungsverfahren (VTC), eine Art thermo-hydromechanischer Prozess, und mit integrierter Trocknungsstufe behandelt. In dieser Studie wurde der Einfluss von fünf Prozessparametern auf die Eigenschaften von VTC modifizierten Furnieren untersucht. Durch das VTC-Verfahren wurden die mechanischen Eigenschaften von Furnier im Wesentlichen als Folge der Verdichtung signifikant verbessert. Jedoch nahm die feuchtebedingte Dickenquellung in Abhängigkeit des Verdichtungsgrades und der Freisetzungsdauer des Dampfdrucks erheblich zu. Eine Erhöhung der Prozesstemperatur führte zu erhöhtem Masseverlust. Durch Einbindung der Trocknungsstufe konnte die Prozesseffizienz verbessert und Trocknungsfehler ausgeschlossen werden. Prozessoptimierung unterschied sich je nachdem ob die mechanischen Eigenschaften oder die Dimensionsstabilität verbessert werden sollten. Es wurden statistische Modelle zur Vorhersage der Eigenschaften von VTC-behandelten Produkten und der Trocknungszeit entwickelt. Diese Studie senkt die Kosten des VTC-Verfahrens und liefert eine Anleitung zur Entwicklung kommerzieller Produktionsprozesse.
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Acknowledgments
The authors are grateful for the funding support from Oregon Built Environment and Sustainable Technology Center, Oregon State University (Corvallis, OR, USA), and the State Scholarship Fund from China Scholarship Council (CSC). Technical assistance from Chuan Li, Josef Weissensteiner, Darrell Lowe, Junhui Zhao, Jesse Paris and Adam Scouse is appreciated.
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Liu, H., Kamke, F.A. & Guo, K. Integrated drying and thermo-hydro-mechanical modification of western hemlock veneer. Eur. J. Wood Prod. 71, 173–181 (2013). https://doi.org/10.1007/s00107-012-0660-5
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DOI: https://doi.org/10.1007/s00107-012-0660-5