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Gewählte Doctoral Thesis:

Martin Weigl (2011): Veränderung von Holzeigenschaften durch industrielle Prozesse.
Doctoral Thesis - Institut für Holzforschung (IHF), BOKU-Universität für Bodenkultur, pp 193. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
This thesis analyses the variability of wood properties and deals with its reduction due to technological processing of solid wood as well as wood-based panels. With eight scientific publications selected aspects of raw material variability and its impact on processing, subassemblies and final products are presented. Work related to solid wood production mainly focused on colour modification by the use of ammoniation. Besides the shift in colour, effects such as improved colour stability, altered swelling and shrinkage causing increased anisotropy, and increased equilibrium moisture content were observed with this treatment. While wood density was not significantly influenced, mechanical properties have in part decreased. However, these changes are irrelevant with respect to practical applications. Ammoniation seems to be technologically interesting, as the observed alterations suggest that ammonia has reacted with extractives rather than with structural polymers. The altered wood properties have shown also changed variability. It was demonstrated that naturally available formaldehyde within wood depends strongly on the wood species and the cambial age. The formaldehyde content is affected twofold: first by the lignin content, and second by the holocellulose content. Particle board properties as well as particle behaviour during production depended on the wood species, the cambial age class, and the roundwood assortment. Fibre processing has led to chemical alterations in the middle lamella of the wood structure, and to hemicellulose side chain modifications. The degree of degradation depended on process conditions, and on wood species. Thickness swell got affected by the degree of chemical degradation as well. The changed variability went along with altered wood properties. In part even increased variability was observed. Along the wood working process chain a stepwise reduction of material property variability can be anticipated. This reduction has a positive effect on the reliability and the resource efficiency of products showing uniform quality.

Betreuer: Wimmer Rupert

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