The effective recovery of wood waste generated in wood processing and also at the end of wood product life is important from environmental and economic points of view. In a laboratory, 16 mm-thick three-layer urea–formaldehyde (UF)-bonded particleboards (PBs) were produced at 5.8 MPa and 240 °C and with an 8 s/mm pressing factor, using wood particles prepared from (1) fresh spruce wood (C), (2) a mixture of several recycled wood products (R1), and (3) recycled faulty PBs bonded with UF resin (R2). Particles from spruce wood were combined with particles from R1 or R2 recyclates in weight ratios of 100:0, 80:20, 50:50 and 0:100. In comparison to the control spruce PB, the PBs containing the R1 recyclate from old wood products were characterized by lower thickness swelling after 2 and 24 h (TS-2h and TS-24h), lower by 18 and 31%; water absorption after 2 and 24 h (WA-2h and WA-24h), lower by 33 and 28%; modulus of rupture in bending (MOR), lower by 28%; modulus of elasticity in bending (MOE), lower by 18%; internal bond (IB), lower by 33%; and resistance to decay determined by the mass loss under the action of the brown-rot fungus Coniophora puteana (Δm), lower by 32%. The PBs containing the R2 recyclate from faulty PBs were also characterized by a lower TS-2h and TS-24h, lower by 45% and 59%; WA-2h and WA-24h, lower by 61% and 51%; MOR, lower by 37%; MOE, lower by 17%; and IB, lower by 33%; however, their biological resistance to C. puteana was more effective, with a decreased Δm in the decay test, lower by 44%.
Special particleboards (PBs) proposed for kitchens, bathrooms, hospitals, and some other specific products for interiors should have a sufficient resistance against bacteria, molds, and decaying fungi. is work deals about effects of zinc oxide nanoparticles (nano-ZnO) added into melamine-urea-formaldehyde (MUF) glue in the amounts of 0, 2, 6, 12, or 24% wt. on selected biological, moisture, and strength properties of laboratory-produced one-layer PBs. e nano-ZnO-treated PBs had a higher biological resistance: (1) against the Gram-positive bacterium Staphylococcus aureus by up to ca. 70% and the Gram-negative bacterium Escherichia coli by up to 50%, since their bacterial activities at using 1.0 McFarland bacterial inoculum decreased from 0.38-0.40 by up to 0.12-0.19 × 10 8 CFU/ml; (2) against the molds Penicillium brevicompactum and Aspergillus niger by up to ca. 50-63%, since their growth intensities (0-4) on the top surfaces of treated PBs decreased according to a modified EN 15457 from 2.33-2.67 by up to 1.17-1.0; (3) against the brown-rot fungus Coniophora puteana by up to 85.7%, since their weight losses reduced according to a modified ENV 12038 from 17.4% by up to 2.5%. e presence of nano-ZnO in PBs uninfluenced their swelling, water absorption, and bending strength; however, it decreased their internal bond strength by up to 38.8%.
The bonding of wood with assembly adhesives is crucial for manufacturing wood composites, such as solid wood panels, glulam, furniture parts, and sport and musical instruments. This work investigates 13 hardwoods—bangkirai, beech, black locust, bubinga, ipé, iroko, maçaranduba, meranti, oak, palisander, sapelli, wengé and zebrano—and analyzes the impact of their selected structural and physical characteristics (e.g., the density, cold water extract, pH value, roughness, and wettability) on the adhesion strength with the polyvinyl acetate (PVAc) adhesive Multibond SK8. The adhesion strength of the bonded hardwoods, determined by the standard EN 205, ranged in the dry state from 9.5 MPa to 17.2 MPa, from 0.6 MPa to 2.6 MPa in the wet state, and from 8.5 MPa to 19.2 MPa in the reconditioned state. The adhesion strength in the dry state of the bonded hardwoods was not influenced by their cold water extracts, pH values, or roughness parallel with the grain. On the contrary, the adhesion strength was significantly with positive tendency influenced by their higher densities, lower roughness parameters perpendicular to the grain, and lower water contact angles.
Bacteria and mould exposures are reported to be associated with allergies, respiratory symptoms and asthma. Wood products with antimicrobial surface would reduce the risk of spreading microbial infections especially in healthcare facilities and public buildings. In future is perspective of their use.In this study, twenty five wooden composites commercially produced in Slovakia having different surfaces were tested both against moulds – microscopic fungi Aspergillus niger and Penicillium spp., and also against bacteria Escherichia coli and Staphylococcus aureus. These organisms are commonly applied as test microbes in laboratory experiments. On the basis of bacteria and mould’s growth on the surfaces of used wooden composites, the tested surfaces have been divided to three groups: (1) wooden composites with high resistant surface, (2) wooden composites with medium resistance surface, (3) and wooden composites with not resistant surface.
In Central Europe, European beech (Fagus sylvatica L.) wood has a high potential for the production of construction and decorative materials, with the aim of replacing Norway spruce, oaks, and other traditionally used tree species. However, the biological resistance of beech wood—to decaying fungi, molds, and insects—is low, and in damp conditions its resistance must be increased with suitable preservatives or modification methods. In the present experiment, beech wood was first treated with water systems of nano-zinc oxide (0.1 to 3.3 wt.% of nano-ZnO) and/or polyethylene glycol 6000 (20 wt.% of PEG 6000), without/with additional thermal modification at 190 °C/2 h. In the presence of nano-ZnO, the decay resistance of beech wood to the brown-rot fungus Rhodonia placenta and the white-rot fungus Trametes versicolor significantly increased, mainly after its additional thermal modification. The presence of nano-ZnO in beech wood—(a) alone, (b) with a subsequent application of PEG 6000, (c) with additional thermal modification—had a more apparent inhibition effect on T. versicolor than on R. placenta. PEG 6000 alone did not improve the resistance of beech wood to rot.
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