Improvement of mechanical properties of thermally modified hardwood through melamine treatment |
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| Authors: | Georg Behr Susanne Bollmus Antje Gellerich Holger Militz |
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| Institution: | 1. Department of Wood Biology and Wood Products, Burckhardt Institute, University of Goettingen, G?ttingen, Germanygbehr@gwdg.de;3. Department of Wood Biology and Wood Products, Burckhardt Institute, University of Goettingen, G?ttingen, Germany |
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| Abstract: | Specimens of beech, ash, lime and poplar were thermally modified (T) and treated with an aqueous solution of melamine (M) resin to investigate the mechanical changes after combined (double) modification (TM). Density, solution uptake, weight percent gain, bulking and equilibrium moisture content were recorded to ensure proper treatment. Samples for Brinell hardness and three-point bending were cured at 120°C under dry conditions. The WPGs of the two treatment groups M and TM were similar, but bulking of TM specimens was negative. This might indicate an incomplete penetration into the thermally modified cell wall in combination with a potential leaching of soluble hemicellulose components by the alkaline impregnation solution. The decreased hardness of heat-treated wood was substantially increased by melamine treatment (combined modification). Both modifications and their combination slightly increased the modulus of elasticity. The modulus of rupture was increased after melamine treatment, decreased after thermal modification and combined modification. The work in bending was severely reduced for all treatments. Melamine treatment of thermally modified wood was carried out successfully and some mechanical properties were improved. Double-modified wood with increased modulus of rupture (MOR) and extraordinary surface hardness would be suitable for non-structural outdoor applications such as decking and cladding. Abbreviations: ANOVA: Analysis of variance; EMC: Equilibrium moisture content; EMCR: Reduced (corrected) equilibrium moisture content; IB: Impact bending strength; M: Melamine treated; MOE: Modulus of elasticity; MOR: Modulus of rupture; MUF: melamine-urea-formaldehyde resin; OD: Oven dry density; R: Untreated references; RH: relative humidity; SC: Solid content; SU: Solution uptake; T: Thermally modified; TM: Thermally modified and melamine treated (double modification); WB: Work in bending; WPG: Weight percent gain |
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| Keywords: | European hardwoods mechanical properties melamine formaldehyde resin thermal modification double modification |
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