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Thermal modification of OSB-strands by a one-step heat pre-treatment – Influence of temperature on weight loss, hygroscopicity and improved fungal resistance

Thermisch modifizierte OSB-Strands durch einstufige Hitze-Vorbehandlung – Einfluss der Temperatur auf Masseabnahme, Hygroskopizität und erhöhte Pilzresistenz

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Abstract

Thermal modification of wood leads to improved resistance against fungal decay and decreased moisture uptake. Polyoses contribute most to the sorption behaviour of wood and act as main nutrition source for fungi. Thus, especially the conversion of polyoses has major impact on the degree of improvement. Thermal decomposition of wood is accompanied by weight loss. In this work the influence of temperature on weight loss, resulting equilibrium moisture content (EMC) and fungal resistance of OSB-strands is shown. It was found that EMC reaches a constant level, indicating completed reduction of free accessible hydroxyl groups. The levelling was ascertained to be irrespective of the temperature and duration of the pre-treatment. An improved fungal resistance according to durability class 3 and better was found for samples pre-treated above 200 °C. The presented correlation between reduced EMC and improved fungal resistance provides a tool for efficient determination of the durability of thermally modified wood.

Zusammenfassung

Die thermische Modifizierung von Holz resultiert in erhöhter Pilzresistenz und reduzierter Feuchteaufnahme. Die Polyosen sind die sorptiv wirksamste Holzkomponente und gleichzeitig Hauptnahrungsquelle Holz zerstörender Pilze. Daher hat insbesondere die Modifikation der Polyosen entscheidenden Einfluss auf eine Eigenschaftsoptimierung. Die thermische Zersetzung von Holz geht mit einer Masseabnahme einher. In dieser Arbeit wird der Zusammenhang zwischen temperaturabhängiger Masseabnahme, reduzierter Ausgleichsfeuchte und erhöhter Pilzresistenz dargestellt. Die Untersuchung hat gezeigt, dass die Ausgleichsfeuchte ein konstantes Niveau erreicht, welches den Abbau frei zugänglicher Hydroxylgruppen markiert. Das erreichte Niveau bleibt unabhängig von Temperatur und Dauer der Behandlung konstant. Eine erhöhte Pilzresistenz gemäß Dauerhaftigkeitsklasse 3 und besser konnte für Proben, die bei Temperaturen über 200 °C vorbehandelt worden waren, bestimmt werden. Der dargestellte Zusammenhang zwischen reduzierter Ausgleichsfeuchte und verbesserter Pilzresistenz bietet eine praktikable Methode zur schnellen Abschätzung der Dauerhaftigkeit thermisch modifizierten Holzes.

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Authors and Affiliations

  1. Federal Research Centre for Forestry and Forest Products (BFH), Leuschnerstrasse 91, 21031, Hamburg, Germany

    W. Paul & M. Ohlmeyer

  2. Janssen Pharmaceutica NV, Turnhoutseweg 30, 2340, Beerse, Belgium

    H. Leithoff

Authors
  1. W. Paul
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  2. M. Ohlmeyer
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  3. H. Leithoff
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Correspondence to M. Ohlmeyer.

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Paul, W., Ohlmeyer, M. & Leithoff, H. Thermal modification of OSB-strands by a one-step heat pre-treatment – Influence of temperature on weight loss, hygroscopicity and improved fungal resistance . Holz Roh Werkst 65, 57–63 (2007). https://doi.org/10.1007/s00107-006-0146-4

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