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VOLUME 51, ISSUE 6/2010

Penetration behaviour of fluids in wood – Influence of surfactant and method of application

Language: German
Pages: 5 - 11
Authors: Peter Niemz, David Mannes, Walter Koch, Yvonne Herbers

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The penetration behaviour of different liquids was tested in radial and tangential direction and additionally along the fibre on samples of Norway spruce (Picea abies) and European beech (Fagus sylvatica). Different types of application were compared: brush impregnation, dip impregnation and pressure impregnation. The penetration depth of the tested systems increased from brush impregnation over dip impregnation to pressure impregnation showing the maximum values. Analogue to previous studies (Niemz et al., 2010) only the outer most layers of the samples could be impregnated. The utilisation of different surfactants and solvents had only little impact on the penetration depth.

Mechanical resistance of specifically modified surfaces on decor finish foils

Language: German
Pages: 12 - 17
Authors: Gerhard Görmar
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Decorative finish foils are usually manufactured by applying prints and varnishes on high-quality special papers (pre-impregnated products). Used on continuous profile-wrapping and laminating plants decorative finish foils excel in their high flexibility and easy process ability. In the development of new surfaces on the basis of decorative finish foils special attention has been paid in recent years on the improvement of the mechanical properties (abrasion resistance, scratch resistance, rub resistance), while different approaches were pursued. Despite having sufficient flexibility the new products were designed to show excellent mechanical lasting properties regarding the quality of finish and, most of all, their applicability. Various new products Titanoflex® with different mechanical property profiles are compared. Furthermore a test method for determination of abrasion shall be put up for discussion, which can be used in particular for surfaces without printed decors (mass-dyed single-colour decors) as well as for comparison of the abrasion characteristics of different surfaces of decor finish foils.

Weather-proof coatings of wood and WPC based on low-grade solvent transparent acrylate-silica-ZnO-nano-composites

Language: German
Pages: 18 - 21
Authors: Mario Beyer, Roman Flyunt, Franziska Weichelt, Rico Emmler,

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Nano-composite UV-coatings with adjustable properties for use on wood substrates in outdoor conditions were developed. The coatings were characterized in terms of elongation at brake, residual photo-initiator content, and double bond conversion as well as of universal hardness, transparency, hydrophobicity, and yellowing. Their suitability for use in outdoor conditions was additionally assured by optimizing the elasticity of the coating and decreasing its water permeability. Coated samples were artificially weathered and studied with regard to their optical and mechanical properties, as well as to changes in brightness, transparency, hydrophobicity and water permeability. Nano-scale ZnO was shown to be an efficient light absorber, particularly when used in combination with a lignin stabilizing wood impregnation. The prepared wood coatings showed an increased weather fastness and improved optical properties. These coatings can also be used for weather protection of WPC façade panels.

Hybrid-adhesives and multiple utilization of wood Basic research initiated by industry

Language: German
Pages: 22 - 27
Authors: Rupert Wimmer, Lars Kloeser, Sarah Himmel

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Wood as a resource is the base for a number of ideas, products or applications, and universities are invited to define their individual role within the entire innovation process. Two basic-research topics are discussed, both initiated during talks with industry. Mixture adhesives with emulsifiable PMDI are so far rarely investigated. In the adhesive mixture pure UF resin was successively replaced by ePMDI to produce lab-based particle boards. Low additions of ePMDI led to significant improvements of mechanical panel properties (bending strength, modulus of elasticity, internal bonding), and thickness swell. Formaldehyde content was not significantly lowered before pure ePMDI was used. For a number of years “biorefinery” has been a heavily discussed topic, which focuses on utilizing wood in multiple ways. In an experimental pre-stage process hot-water extraction was employed to solve hemicelluloses. Boards were made from the extracted particles and technological properties have partly improved. Hardwoods seemed to be better suited for multiple-uses than softwoods. Recovery of hemicelluloses hydrolysates for ethanol production may add up to 20 % d. w. Future research will focus on process development, and on economic evaluation of the entire process.

The influence of extreme inclination angles of wood planing; Part 2: Experimental investigations

Language: German
Pages: 28 - 34
Authors: Christian Gottlöber, Michael Oertel, André Wagenführ

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The principle of drawing cut is a possibility to influence the cutting forces, the work piece surface quality, the noise and dust emissions and the tool wear of wood planing positively. This effect can be achieved by increase of the tool inclination angle λS larger than 0°. In the past only the range of this angle between 0° and 50° – mostly lower – has been investigated on planing tools. Following a new approach by Prof. Dr.-Ing. habil. Dr. h. c. Roland Fischer of adjusting the inclination angle of planing tools in a range between 45° and 85° Institute of Wood and Paper Technology (Technische Universität Dresden) has investigated a promising development. After discussing the state of the art in part 1 of this publication now the experiments with prototype planing tools are in the focus of the article.

Experimental and numerical study on the hygrothermal behaviour of nonventilated wooden flat roof constructions

Language: German
Pages: 35 - 40
Authors: Norman Werther, Claudia Fülle, Stefan Winter

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Highly insulated non-ventilated flat roofs in timber construction were more frequently applied in the last years. According to German standard DIN 4108-3 (2001) an internal tight vapour barrier is required for a verified construction, but also can easily cause moisture damages. At the same time new building products, airtight constructions, dry timber and wood based panels give new opportunities for safe and durable constructions. With the help of long term laboratory examinations, numerical simulations and in-situ measurements for German climate conditions, design principles and recommendations have been developed. These principles can guarantee a durable use of wooden flat roof constructions in combination with high energetic efficiency, including ecological building products and without chemical treated timber according use class 0 of DIN 68800 (1996).

Market opportunities for modified solid wood in German- speaking countries; Part 2: Results

Language: German
Pages: 41 - 45
Authors: Asta Eder, Christian Hansmann, Peter Schwarzbauer

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The focus of this paper is the assessment of market opportunities for modified solid wood in the German-speaking countries, which closes this two-piece article. The results show positive market prospects for modified solid wood in all examined market

segments. The investigation confirms several a-priori assumptions: Market opportunities for modified solid wood exist mainly in areas, where technical properties are improved through modification, which are crucial for decision makers. All examined

groups of manufacturers show interest in modified solid wood, in each case on a different level. The producers generally show willingness to pay a price premium for technically improved solid wood. Several factors indicate that market opportunities

of modified solid wood are highest in the floor industry, in particular because of the willingness of the manufacturers to pay for a price premium.

Minimization of the emission of pentachlorophenol from contaminated wood

Language: German
Pages: 46 - 48
Authors: Karsten Aehlig

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Methods for the substantial reduction of the emissions of PCP from contaminated building elements have been established. Using even small quantities of the active compounds on contaminated wood surfaces the emissions can be reduced over 99 %,

the effect lasting 570 days at least. The good water solubility of the polyimine allows the application of an established vacuum washing procedure. With this method also larger objects can be treated, such as roof structures or ceiling panels. A major

advantage is characterized in that the treatment is practically not visible. The procedure was already successfully tested at a real object under industry-oriented conditions for the treatment.

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