Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood
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In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 °C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 min prior to adhesive being applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one-third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa, which was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from uncompressed veneer. The findings in this study indicated that compression of birch veneer could be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.
The authors acknowledge COST Action FP1303 “Performance of bio-based building materials” for support of STSM-FP1303-010615-060045. This work was supported by the Slovak Research and Development Agency under the contract no APVV-14-0506 and APVV-15-0235. Special thanks are extended to Ing. B. Lizoň for making microscopic images of veneer samples surfaces before and after densification.
- Bekhta P, Krystofiak T (2016) The influence of short-term thermo-mechanical densification on the surface wettability of wood veneers. Maderas-Cienc Technol 18(1):79–90Google Scholar
- EN 314-1:2004. Plywood. Bonding quality. Part 1: test methods. European Committee for Standardization, BrusselsGoogle Scholar
- EN 314-2 (1993) Plywood. Bonding quality. Part 2: requirements. European Committee for Standardization, BrusselsGoogle Scholar
- EN 315 (2000) Plywood. Tolerances for dimensions. European Committee for Standardization, BrusselsGoogle Scholar
- EN 317 (1993) Particleboards and fibreboards. Determination of swelling in thickness after immersion in water. European Committee for Standardization, BrusselsGoogle Scholar
- Faust TD, Rice JT (1986) Effect of veneer surface roughness on glue-bond quality in Southern pine plywood. For Prod J 36(4):57–62Google Scholar
- ISO 4287 (1997) Geometrical product specification (GPS). Surface texture: profile method. Terms, definitions and surface texture parameters. International Organization for Standartization, GenevaGoogle Scholar
- Rautkari L, Hughes M, Properzi M, Pichelin F (2010) Properties and chemical changes of surface densified wood. In: Proceeding of the 11th World Conference on Timber Engineering, Trees and Timber Institute, National Research Council, Trentino, Italy, 20–24 June 2010, pp. 235–237Google Scholar
- Richter K, Feist WC, Knabe MT (1995) The effect of surface roughness on the performance of finishes. Part 1: roughness characterization and strain performance. For Prod J 45(7/8):91–97Google Scholar
- Sheldon S, Walker J (2006) Wood-based composites: plywood and veneer-based products. In: Walker J (ed) Primary wood processing: principles and practice, 2nd edn. Springer, New York, pp 391–426Google Scholar
- Unsal O, Candan Z, Buyuksari U, Korkut S, Chang Y-S, Yeo H (2011) Effect of thermal compression treatment on the surface hardness, vertical density propile and thickness swelling of eucalyptus wood boards by hot-pressing. Mokchae Konghak 39(2):148–155Google Scholar