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VOLUME 52, ISSUE 4/2011

Difficulties and prospects in the processing of hardwood; Part 3: Possible uses for hardwood waste

Language: German
Pages: 5 - 10
Authors: Verena Krackler, Peter Niemz

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The processing of wood from stem to an end product is always associated with the appearance of low rate timber and saw mill waste. In contrast to softwood, however, cascade utilization of hardwood has not yet been established. The energetic use dominates, although the production of wood based materials and use as a substance or chemical product is possible. The current amount of hardwood in particle materials and fibre materials (10 % bis 40 %) could rise to 100 % (e.g. Klauditz, 1952; Kehr und Schilling, 1965a, b; Grigoriou, 1981; Vos und Kharazipour, 2008; Krug und Mäbert, 2007). As a substance, hardwood can be used in the food industry, to filter certain heavy metals or to produce plastics, linoleum or biomateials. By applying wood chemistry, cellulose facilitates the extraction of pulp, paper, cellulose ester, cellulose ether, wood sugar and regenerated cellulose. Lignin can be used multifariously as a raw material for example vanillin, binders, fertilizers or bio-materials.

Initial tensioning of a circular saw blade for wood machining; Part 2: The influence of rolling force on the residual stresses

Language: English
Pages: 11 - 16
Authors: Bolesław Porankiewicz, Jari Parantainen, Karolina Ostrowska

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X-ray diffraction, BN and FWHM methods for evaluation of residual stresses inside and outside rolling paths were used. Dependencies of a tangential rolling residual stresses inside rolling paths upon rolling force, and rolling area were evaluated. The rolling force, as large as 14 kN, resulting tangential residual compression stresses inside a rolling path, as large as -648 MPa, was considered to be the largest for the practical use. The BN allows fast, indirect evaluation of rolling stresses inside and outside rolling paths by low saw body hardness dispersion.

Size analysis of not separated OSB strands; Part 1: Results of size measurements and discussion

Language: German
Pages: 17 - 23
Authors: Burkhard Plinke

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Gray value images of mats with OSB strands were evaluated using the method of extended threshold analysis. Length and width of detected objects were measured and characterized by density function, cumulated density function and its quantiles. Size measurements were performed for simulated objects and for strands from laboratory and industrial origin. Different results between size measurements for single strands and for strands in the mat can be traced back to covering effects to a limited extent. The proposed method can be suitable for a continuous monitoring of strand geometry in the OSB mat.

Studies regarding the emission behaviour of cured oak

Language: German
Pages: 24 - 28
Authors: Karsten Aehlig, Sebastian Weidlich, Enrico Zönnchen

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The curing process is a chemical reaction of wood ingredients in the presence of ammonia with the formation of not-wood based compounds. Those can emit from the product and do not fulfil certification criteria. Analytical studies came to the conclusion, that mainly acetamide, acetic acid and ammonia are released. Studies of the emission behaviour have been realised using a solid wood sample and a veneer sample both composed of oak. Immediately after storage the veneer sample shows the highest concentrations, which decrease over time. Regarding time, concentration courses of the oak square plank are different. Concentrations of acetic acid and acetamide initially increase from a comparatively low level and then distinctly decrease within 82 days. The very high release level of ammonia distinctly decreases within 82 days as well. The results show, that the currently existing limits and standards can not be adhered to except for acetic acid of the sliced veneer. Hence, further investigations, especially regarding the technological influence, are essential.

Geometry of characteristic joints; Some findings relevant to the theory of adhesive joints

Language: English
Pages: 29 - 33
Authors: Adolf Musil, Josef Polášek, Marek Polášek, Jirí Zálešák

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This paper deals with theory and practise of surface phenomena in polymers and hard adhesives with respect to their adhesion and tensile strength. It stems from the rheological theory of molecular adhesion, which can also characterize join of various chemical compositions. The relationships between adhesives and substrates are described in examples and they affect in the design and calculation bonded joints, in connection with research, and development of adhesives regarding those currently

available and coating technology. Based on the analysis of geometric shapes of bonded materials, including wood and defects in adhesives, mathematical relations may be derived. Within deformations of individual join, these relationships describe stress distribution in existing details.

Condensate in the rebate of wooden windows

Language: German
Pages: 34 - 40
Authors: Josef Schmid, Michael Stiller

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It is not uncommon that technical advancements in building construction are not coordinated with different specialist departments. This is also true for the energy-saving efforts in combination with demands for air-tight external envelopes of buildings. As a consequence a high humidification load can cause mold formation. Exhaust air can only escape through the remaining leaks like those in the rebates of windows. In combination with centre seals used in wooden windows this leads to an air flow around the rebate space and ultimately to condensate from air when in contact with the cold surface. In wooden windows this means critical stress affecting the use time of those windows. It is therefore essential to reduce the stress by preventing air flow around the rebate space. This can be achieved by user-independent airing and an additional indoor gasket.

Effective DNA extraction methods for molecular diagnostics of building rot fungi

Language: German
Pages: 41 - 46
Authors: Natalya Rangno, Kordula Jacobs

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For the specific remediation of fungus damage, it is important to identify the present species of fungi (DIN 68800-4, 1992). However, a correct identification of fungi in practice using the conventional or molecular diagnostic methods is not always successful. The crucial weakness of the molecular diagnostics is the extraction of analysable fungal DNA from practical samples. Especially in highly degraded or contaminated wood samples, with no visible fungal material, there may be recovered no or very small amounts of DNA and the extract containing inhibitors often prevent the PCR amplification. For the determination of an effective DNA extraction method from practical samples, five commercially available extraction kits and a CTAB (cetyl trimethylammonium bromide) method were tested and evaluated. In result a standard protocol for DNA extraction from practical samples was developed, based on the NucleoSpin® Plant II Kit (Macherey-Nagel) that is favoured for routine diagnosis.

Causes of algal infested buildings

Language: German
Pages: 47 - 50
Authors: Ulf Karsten

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Green discoloration of building surfaces is mainly caused by unicellular green microalgae. These organisms depend on the water availability, i. e. as long as physical and chemical properties of building materials result in holding moisture or restrict drying up of the surfaces, conditions suitable for life are present. But also the direction and environment of buildings, as well as the climatic region and the properties of the algae themselves play an important role for excessive growth. Consequently, besides constructive material protection, the right properties of the building materials should be always selected in relation to the prevailing climatic conditions to minimize or even prevent water availability for settling organisms.

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