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VOLUME 57, ISSUE 5/2016

Beech wood fibre MDF-compound with lignin containing phenolic-resin binder

Language: German
Pages: 5 - 11
Authors: Nicole Eversmann, Torsten Theumer, Veronika Däumlich, Andreas Weber, Andreas Krombholz

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The development of a composite material made of beech wood fibres and a thermosetting resin system containing lignin enables the production of MDF.HLS. The medium density fibreboards (MDF) are amongst others suitable for applications in construction and architecture. The digestion of beech wood to sulfur-free, low molecular organosolv-lignin synthesis utilizes the power of nature optimally. The organosolv-lignin has an aromatic structure and can be covalently incorporated into phenolic resins up to a weight of 20 %. This admixture will not change the process properties of the phenolic resin system compared to the unmodified basic system and can therefore be processed and used analogously.

Rework-free and low-formaldehyde 3D high performance wood chip-plastic composites (HWPC)

Language: German
Pages: 12 - 15
Authors: Robert Hartmann, Jürgen Kreiter, Michael Koch

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The paper describes the approach to combine thermoplastic as well as thermosetting plastics with wood chips for the production of 3D mouldings. Challenging is the purposeful particle and matrix material insertion into the mould so that directional properties can be specifically used. The wood chips must be distributed application-oriented in the mould. Long chips are similar to fibres in conventional FRP components and can be used for load transmission and may be placed suitable to load paths. Short chips and wood dust can be homogeneously distributed between the long chips to increase the wood volume fraction and to allow rework-free border areas. The matrix material insertion process determines the filling of the cavity and the impregnation of the chips. By controlling the subsequent pressing process of the aligned and impregnated wood chips the density and wall thickness of the moulding can be influenced.

Antimicrobial coatings on wood by use of atmospheric pressure chemical vapour deposition (APCVD)

Language: German
Pages: 16 - 25
Authors: Sven Gerullis, Andreas Pfuch, Sebastian Spange, Florian Kettner, Katharina Plaschkies, Pavel Vladimirovich Kosmachev, Gennadi Georgevich Volokitin, Bernd Grünler

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In this work, an atmospheric pressure plasma chemical vapour deposition (APCVD) technology was used to create thin amorphous silicon dioxide films with bactericidal properties on beech wood veneer. Furthermore, the active agents Ag, Cu and Zn were incorporated in the matrices of these films to obtain antimicrobial properties. SiOx-film-matrices were created by use of hexamethyldisiloxane (HMDSO) as a precursor material, the active agents were embedded into the growing film matrix by use of AgNO3, Zn(NO3)2 or Cu(NO3)2 as secondary precursor materials. The structure of the fabricated layers was investigated by SEM, the chemical composition was determined by XPS. The antibacterial effect was evaluated by BacTiter-Glo® and agar diffusion method. The fabricated films showed a strong antibacterial effect against the bacteria strains Escherichia coli (gram-) and Staphylococcus aureus (gram+). However, a significant effect against mould (mould test) could not be achieved. Moreover, resistance of the antimicrobial coating against abrasion and leaching were tested, and the results demonstrated a good wear resistance of the coatings.

Bundle tests; Simple alternatives to standard above ground testing of wood durability

Language: English
Pages: 26 - 30
Authors: Linda Meyer-Veltrup, Christian Brischke

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Within this study different new above ground test set ups to untreated Norway spruce (Picea abies Karst.) and Scots pine sapwood (Pinus sylvestris L.) which are frequently used as reference or control species in wood durability field tests were applied. The overall aim of this study was to find a simple alternative method to the few standardized above ground field test methods, such as the L-joint and the lap-joint methods, and to overcome some of their shortcomings (e. g. costly and time-consuming specimen preparation, occurrence of hardly detectable interior rot behind sealants or coatings). Therefore, different bundle type specimens were exposed above ground and monitored in terms of moisture content (MC) for one year and fungal decay for up to eight years. Both wood species decayed rather fast and all four different bundle compositions accelerated decay compared to single stake shaped specimens. Brown rot was the dominating rot type independent of the set up and the wood species. The global MC of the specimens was not extremely high, but obviously wetting close to the contact faces was sufficient to allow fungal infestation and decay. Also from a practical point of view the set ups performed in a promising way: specimen preparation was simple and inexpensive, decay assessments were easy, and decay progress sufficiently fast, partly faster than expected from a moderate moisture induced risk as determined for all four bundle type specimens.

Parameter study on assessment of base coatings for digital printing on derived timber products

Language: German
Pages: 31 - 37
Authors: Malgorzata Anna Adamska-Reiche, Ingrid Fuchs, Rico Emmler, Anissa Ghozzi, Bernd Brendler

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For base coatings of digitally printed derived timber products such as high density fibreboard (HDF), no normalised properties, characteristic parameters and testing methods exist at the time being. In addition, no parameters or critical values have been defined for characterisation of the printed test images or for prediction of the printing quality. The current development of base coatings and coating-printing-systems follows the trial-and-error procedure. The aim of the project was to derive characteristic properties of base coatings that influence the quality of a digitally printed image. Furthermore, suitable test methods for the printing quality and significant properties were to be developed or modified. As the result of the investigations, the surface quality (roughness) was found to be the most important basecoat property influencing the image quality. Also crucial are the surface energy, the whiteness and the L*-, a*- and b*-values of the base coat. LED-pinning directly after the printing heads has a positive influence on the final result.

Wood materials – Research approaches for a wider utilization

Language: German
Pages: 38 - 43
Authors: Ingo Burgert, Vivian Merk, Tobias Keplinger

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Wood is a material with an enormous potential for the future, in view of its properties and relevance for the transition towards sustainable societies. An approach to better tap the full potential, is to use the hierarchical structure of wood as a sophisticated scaffold for the development of wood-mineral hybrid materials and wood-polymer composites. For this purpose one may use modular modification approaches which allow for improving wood in its given applications but can also fetch novel functionalities for new fields of application. This requires interdisciplinary research activities with links to other research communities, which can raise the needed acceptance and interest for wood in materials science.

Review: Wood dusts and allergies

Language: German
Pages: 44 - 49
Authors: Sabine Kespohl, Monika Raulf

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Wood dust exposure at workplaces can cause health problems involving skin and respiratory tract as well as inducing allergies. About 700,000 workers were occupationally exposed to wood dust in Germany (2000-2003). To minimize health risk by wood dust exposure, an occupational exposure limit (OEL) of 2 mg/m³ inhalable dust was regularized. More than 40 wood species are actually known to induce IgE-mediated allergic reactions. These are tropical as well as non-tropical wood species, hard and soft woods. Diagnosis of wood dust sensitization in exposed workers is often difficult because the commercially available wood allergen test panel is rare. Next to standardized diagnosis it is important to assess actual wood dust exposure e. g. to monitor allergen exposure at different workplaces. Using wood allergen specific immunological test systems it would be possible not only to assess gravimetrical wood dust load but real allergen exposure at workplaces. With these systems wood allergen concentration in airborne samples from workplaces were measured and the transfer of wood allergens in adjacent rooms as well as in private houses was demonstrated.

The collection of wood pieces of Eberswalde's Forest Academy, its origin, use, liquidation and availability

Language: German
Pages: 50 - 52
Authors: Günter Schultze-Dewitz

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This contribution deals with the necessity of an authentical wood col-lection being indispensable for an aimed research on sciences of forestry as well as on wood science.

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