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VOLUME 50, ISSUE 6/2009

Timbers for window constructions Specific values and properties of recently imported timbers; Kennwerte und Eigenschaften neu eingeführter Hölzer

Language: German
Pages: 5 - 9
Authors: Gerald Koch, Mathias Rehbein

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The current market development on import of tropical timbers for window scantlings is characterised by a decreasing availability in volume and quality of the established species, e.g. Dark Red Meranti (from South-East-Asia) or Sipo (from West-Africa). Based on this development, new so-called “lesser known wood species”, e.g., bintangor (Calophyllum spp.), durian (Durio spp.), kasai (Pometia spp.), and merpauh (Swintonia spp.) are currently imported. For establishing these new species on the German scantling market, the wood properties have to be studied individually according to the standards of the VFF Gütegemeinschaft. In the present study, the physical and mechanical standards and wood properties of these lesser-known species are presented which were tested at the Johann Heinrich von Thünen-Institut (vTI).

Energy dispersive X-ray microanalysis and Raman spectroscopy as topochemical research methods in wood science

Language: German
Pages: 10 - 13
Authors: Michael Rosenthal, Ernst Bäucker, Claus-Thomas Bues

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Several techniques of micro area analysis can be used to determine the distribution of chemical components in the μm-scale, e.g. energy dispersive X-ray microanalysis. For understanding this technique its physical basics are explained and an application (steeping in silicon dioxide nanosols) is demonstrated. Energy dispersive X-ray microanalysis determines the elementary composition, e.g. of chemical modified wood, by means of Xradiation which is emitted from a sample due to excitation by an electron beam.

Smoothing of wood-pencils by high-power ultrasonic

Language: German
Pages: 14 - 18
Authors: Michael Peter, Ingris Fuchs

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The Californian cedar (botanical name: Juniperus virginiana) is no longer available in sufficient quantities for the pencil production. Therefore wooden pencils are increasingly produced from other species. These species are, for various reasons, less well processable. The higher roughness obtained during the milling process is unfavourable for the subsequent coating processes. Up to seven layers of varnish are applied depending on the requirements for surface quality of the pencils.

The Institut für Holztechnologie Dresden (IHD) has developed a smoothing procedure using high-performance ultrasound. It revealed to be very beneficial on the further processing of native wood. Together with a manufacturer of machinery for the processing of wooden pencils, an experimental device was designed and implemented, which can be smoothed five wooden pencils contemporaneously. It has been demonstrated, that the ultrasonic smoothing is principally suitable for the finishing of

wooden pencils and can be included in real pencil production lines.

Review: Design principles for windows, doors and facade elements in composite materials and timber

Language: German
Pages: 19 - 24
Authors: Ingo Leuschner

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The briefing for the research work under consideration was to establish design principles for windows, doors and facade elements in composite materials and timber. It was hoped that the use of composite materials would make it possible to improve the following key aspects of windows, facades and doors: suitability for a wider range of applications, improved commercial viability, longer service life, reduced maintenance input and longer maintenance intervals, using the diverse characteristics of Wood for improving aesthetic qualities, reducing heat losses by integrating insulation materials into frames as well as durability and sustainability of the products using renewable raw materials. The briefing of this sub-project 20 was to investigate various materials, types and design details of composites and report on the conditions under which these would be suitable as frame members or panels/boards in external wall applications. In combination with the results gained in sub-project 19 (design principles for window, door and facade elements made from

composites and timber; Future timber construction) as regards the exposure to moisture and the deformation behaviour of composite materials, the findings are a basis for further developments of material composites for window and facade construction.

Analysis of climate conditions in crawl spaces with high insulated wooden floor plates

Language: German
Pages: 25 - 29
Authors: Norman Werther, Stefan Winter

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Highly insulated wooden base plates in combination with crawl space constructions for foundations of residential and functional timber-buildings were more frequently applied in the last years. Missing knowledge of micro-climatological conditions in crawl spaces and the resulting boundary conditions for timber and wooden board materials led to various constructional designs. By long term in-situ measurements and laboratory tests, design principles, which guarantee a durable use of wooden base plates in combination with air-ventilated crawl spaces, were developed. A rating to use class 0 according to DIN 68800 is possible.

Lightweight particleboards for the furniture industry made of agricultural residues Part 4: Production and testing of domestic and kitchen wall cabinets

Language: German
Pages: 30 - 35
Authors: Brigitte Dix, Peter Meinlschmidt, Anja van de Flierdt, Volker Thole, Marie-Lise Roux, Gilbert Prieur

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In the third part of this publication series three-layer particleboards are described with core layers made from particles of Topinambur stalks while the surface layers consist of spruce particles. The mechanical properties of these particleboards are comparable

with industrial manufactured wood particleboards. The three-layer particleboards were coated with HPL before being processed into small living room and kitchen wall-cabinets. While the pivoted doors and horizontal storage shelves are liable to static and dynamic strength testing, the shelves additionally had to withstand a static overload. All wall-cupboards made from panels with a density of 580 kg/m3 and 620 kg/m3 perform to the standards of this norm. The wall-cabinets of lower density in general did not match the dynamic strength testing their mounting elements are demolished. A possible solution for this problem is a special dowel.

Molecular diagnosis and characterization of wooddestroying basidiomycetes – Review Part 1: DNA-based techniques

Language: German
Pages: 36 - 40
Authors: Olaf Schmidt

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For diagnosis and characterization of indoor wood-decay basidiomycetes,

the review describes DNA-based techniques, RAPD, ITS-RFPL, Species-specific PCR, rDNA sequencing, Microsatellites, AFLP, and DNA-chips.

Parquet analysis

Language: German
Pages: 41 - 43
Authors: Martina Broege

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In the context of a study promoted by the Deutsches Institut für Bautechnik (DIBt) the actual situation in the parquet industry has to be determined on the basis of researches and analyses. In the main focus were information about kinds of parquet, parquet assembly, market situation, parquet materials, kinds of wood, coating materials for on-site coating, production techniques, process parameters with effects on the emission particularly. The results of the study serve continuatively the implementing of DIN EN 14342 – Parquet and wood floorings - Characteristics, evaluation of conformity and marking. In future they provide the basis for the definition of special test conditions for prefinished parquets and for the development of a procedure and/or method for the test of wood floorings, that are coated after laying.

On the formation of free urea by thermal treatment of fibres bonded with UF-resins

Language: German
Pages: 44 - 46
Authors: Edmone Roffael, Mahmood Hameed, Redelf Kraft

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UF-resin of a molar ratio U:F (1:1) was thermally treated at 120 °C, 160 °C and 180°C for different periods of time, the water extractives of the thermally treated resin were evaluated regarding the pH-values, the water soluble contents and the amounts of free urea in the extractives. As it becomes glaringly obvious from the results, the pH-value of the resin elevates with increasing curing temperature from 120 °C to 180 °C; analogously the content of water soluble extractives and that of free urea increased. More or less the same trend was established in case of fibres blended with the same resin and thermally treated. At very high temperature (180 °C) the amount of free urea in the extracts decreases, this has been attributed to its possible thermal

degradation.

Review: Relevance of hardwoods in gluelam production

Language: German
Pages: 47 - 49
Authors: Maximilian Henning, Gero Becker, Denny Ohnesorge

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The share of softwoods on current production volume of glued laminated solid wood products is almost 100 % whereof mainly spruce timber is used. This was confirmed by a survey among glued laminated timber producers in 2007 in Germany, Austria and Switzerland. The total amount of hardwood glulam products manufactured in 2005 by the respondent’s was 90 m3 only. Besides, less than half of the queried companies indicated themselves as already experienced in gluing hardwoods. Preferentially

a higher pressure and a lower lamellae thickness were recommended when using hardwood instead of softwood lamellae for glulam. Manufacturers experienced in processing hardwoods pointed out the positive effect of an extension of assembly, pressing and post cure times.

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