Abstract
The problem of climate change, coupled to the propagation of wood diseases (bark beetles for example), is leading to a shortage in softwood supply for the particleboard industries. Furthermore, the recent changes in the German forest policies which promote the conversion of coniferous forest into mixed stands are likely to enhance this phenomenon. There is, therefore, a growing need for research on possibilities of substituting the softwood with hardwood and other alternative material. For the first time, young six to seven years old Black locust (Robinia pseudoaccacia) stems from a short-rotation plantation were used at a laboratory scale with the objective of assessing the suitability of particleboard production. Four different variants were produced using different resin types: UF K350, UF K340, albumin, and PMDI, with a target density and thickness of 650 kg/m3 and 20 mm respectively for each board. The boards were tested regarding their mechanical (modulus of rupture, modulus of elasticity and internal bonding), physical (water absorption and thickness swelling) properties according to the European standard (EN 310, EN 317 and EN 319), and their formaldehyde content and emission following the EN 120 and EN 717. Industrial particles were used as reference material for the purpose of comparison. Promising bending strength was obtained with UF resins-bonded boards. The modulus of elasticity of all four variants fulfilled the EN 2003 requirements. The internal bond of the UF resins-bonded boards also met the general product standard, with values above 0.35 N/mm2. The bending strength and the internal bonding strength properties of the UF-bonded boards were superior to that of the reference boards produced with the industrial particles. Based on these results, black locust is a potential substitute for softwood in particleboard production and can be used in the industry as alternative raw material for panel production.
Highlights
The continuously changing raw material situation has always been one of the major driving forces for constant innovation in the wood-based panel sector and the high variability of the wood raw material in the wood-based panel industry constitutes a challenge not known by many other industries (Thoemen et al, 2010)
The industrial particles-based particleboards bonded with blood albumin had the highest core layer density (913.7 kg/m3), followed by the Robinia particles-based boards bonded with the same resin type (826.0 kg/m3)
The results of the internal bonding (IB) test are presented in figure 4. These results show that the Robinia-based variant bonded with UF resin performed better than those with the industrial-based variant (0.55 N/mm2 with UF K350 and 0.44 N/mm2 with UF K340 for the Robinia-based boards compare to 0.37 N/mm2 with UF K350 and 0.35 N/mm2 with UF K340 for the industrial particle-based boards)
Summary
The continuously changing raw material situation has always been one of the major driving forces for constant innovation in the wood-based panel sector and the high variability of the wood raw material in the wood-based panel industry constitutes a challenge not known by many other industries (Thoemen et al, 2010). According to Mantau (2010), the estimated energy use of wood in Europe is currently equal to that used for material application and will be higher by 2030 (56.5 % of the total wood supply) and the forest woody biomass will decrease from 62 % in 2020 to 59 % in 2030. This means less wood will be available for the industries in the future. The new developments in forest policy advocate the establishment of mixed forest to overcome the effects jmsr.ccsenet.org
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