Effects of short-term thermomechanical densification on the structure and properties of wood veneers |
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| Authors: | Pavlo Bekhta Stanis?aw Proszyk Tomasz Krystofiak Jan Sedliacik Igor Novak Miroslava Mamonova |
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| Institution: | 1. Department of Wood-Based Composites, National University of Forestry and Wood Technology of Ukraine, Lviv, Ukrainebekhta@ukr.net;3. Department of Gluing and Finishing of Wood, Poznan University of Life Sciences, Poznan, Poland;4. Department of Furniture and Wood Products, Technical University in Zvolen, Zvolen, Slovakia;5. Department of Composite Materials, Polymer Institute, Slovak Academy of Sciences, Bratislava, Slovakia;6. Department of Wood Science, Technical University in Zvolen, Zvolen, Slovakia |
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| Abstract: | The effects of short-term thermomechanical (STTM) densification temperature and pressure on the changes in surface roughness, wettability, mass loss (ML), thickness and density of alder, beech, birch, and pine wood veneer with low moisture content (~5%) were investigated. The anatomical structure of veneers was also observed. Veneer sheets were densified using pressure levels of 4, 8 and 12 MPa at three temperatures: 100°C, 150°C and 200°C for 4 min. The results were compared with those of the non-densified veneers. The obtained results show that STTM densification of veneers similarly to long-term densification of solid wood causes irreversible changes in their properties. The STTM-densified veneer surfaces became smoother and more hydrophobic, ML increased slightly while roughness and thickness values decreased significantly, the cell lumens collapsed and a certain amount of fractures in cell walls developed with increasing densification temperature and pressure. All of the investigated wood species showed higher density values after densification. It was found that an even STTM densification of veneers provides stable properties under normal atmosphere conditions; in particular, the thickness and contact angle values were stable for 24 hours after densification, which is an important consideration for industrial applications. |
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| Keywords: | Compression ratio mass loss short-term thermomechanical densification surface roughness wettability wood veneer |
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