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In-treatment cooling during thermal modification of wood in soy oil medium: soy oil uptake, wettability, water uptake and swelling properties

Wärmebehandlung von Holz mit anschließender Abkühlung in Sojaöl: Sojaölaufnahme, Benetzbarkeit, Wasseraufnahme und Quelleigenschaften

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Abstract

Thermal modification of wood is a process which has gained wider acceptability as an alternative to chemical treatment in wood preservation. In order to maximize the benefits of this technique several options have been adopted including the use of soy oil in transferring the heat to the wood. Available information on thermal treatment in general and the oil method in particular show that there is need for further investigations on the possibilities of improving the available options in order to evolve new techniques.

Thermal treatment of ponderosa pine (Pinus ponderosa P Laws ex C Laws) and black spruce (Picea mariana (Mill) BSP) in soy bean oil was carried out at 220 °C for 2 hours followed by cooling inside the hot oil 180 °C and 135 °C. The surface wettability, (contact angle), amount of oil uptake, water absorption and thickness swelling were determined thereafter.

The oil uptake ranged from 88 to 93.3% in the permeable ponderosa pine sapwood and from 6.1 to 11.3% in the refractory black spruce with the uptake increasing with cooling time but decreasing with increasing depth of wood in both species. Thermal modification in soybean oil increased the wettability of the surface to water (reduced contact angle). However, there were no significant changes to the surface energies due to in-treatment cooling, as determined by contact angles of water, glycerol, ethylene glycol, and formamide.

There were reductions in the hydrophilic behaviour and swelling of wood as a result of the thermal treatment; in-oil cooling resulted in greater hydrophobicity and dimensional stability in the wood. In both species, there were greater reductions in water uptake and swelling with increasing cooling time.

Zusammenfassung

Die Wärmebehandlung von Holz stößt als Alternative zum chemischen Holzschutz auf immer größere Akzeptanz. Um ein möglichst wirtschaftliches Holzschutzverfahren zu entwickeln, wurden zahlreiche Möglichkeiten untersucht, einschließlich der Verwendung von Sojaöl zur Übertragung der Wärme zum Holz. Der Stand der Informationen zur Wärmebehandlung im Allgemeinen und zum Ölverfahren im Besonderen zeigt, dass zur Weiterentwicklung dieser neuen Verfahren weitere Untersuchungen notwendig sind.

Gelbkiefer- (Pinus ponderosa P Laws ex C Laws) und Schwarzfichteproben (Picea mariana (Mill) BSP) wurden in Sojaöl bei 220 °C einer zweistündigen Wärmebehandlung unterzogen und danach im heißen Öl bei 180 und 135 °C abgekühlt. Anschließend wurden die Oberflächenbenetzbarkeit (Kontaktwinkel), die Ölaufnahme, die Wasseraufnahme und die Dickenquellung bestimmt.

Die Ölaufnahme lag bei dem gut tränkbaren Gelbkiefernsplintholz zwischen 88 und 93.3% und bei den schwer tränkbaren Schwarzfichtenproben zwischen 6,1 und 11.3%, wobei die Aufnahme mit steigender Abkühlzeit zunahm und mit zunehmender Holztiefe bei beiden Holzarten abnahm.

Durch die Wärmebehandlung in Sojaöl erhöhte sich die Oberflächenbenetzbarkeit (kleinerer Kontaktwinkel), jedoch zeigte die Bestimmung der Kontaktwinkel von Wasser, Glycerol, Äthylenglykol und Formamid, dass sich durch die Abkühlung die Oberflächenenergien nicht signifikant veränderten.

Die hydrophilen Eigenschaften und die Dickenquellung von Holz nahmen aufgrund der Wärmebehandlung ab. Die Abkühlung in Öl führte zu einer stärkeren Hydrophobierung und größeren Dimensionsstabilität. Bei beiden Holzarten nahm die Wasseraufnahme und Dickenquellung mit zunehmender Abkühlzeit ab.

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Authors and Affiliations

  1. Forestry, Wildlife and Fisheries, University of Ado-Ekiti, Ado-Ekiti, Nigeria

    L. Awoyemi

  2. Forestry, University of Toronto, Toronto, ON, Canada

    P. A. Cooper & T. Y. Ung

Authors
  1. L. Awoyemi
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  2. P. A. Cooper
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  3. T. Y. Ung
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Correspondence to L. Awoyemi.

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Awoyemi, L., Cooper, P.A. & Ung, T.Y. In-treatment cooling during thermal modification of wood in soy oil medium: soy oil uptake, wettability, water uptake and swelling properties . Eur. J. Wood Prod. 67, 465–470 (2009). https://doi.org/10.1007/s00107-009-0346-9

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  • DOI: https://doi.org/10.1007/s00107-009-0346-9

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