VOLUME 52, ISSUE 6/2011

Part one of this article deals with the different color features of beech wood and the influence of these features on automated wood grading (Ruminski et al., 2011). Part two tries to evaluate different possibilities to optimize the accuracy of color based grading systems. Therefore these preliminary studies analyzed different wood samples with laser induced fluorescence (LIF). The main goal is to identify which possibilities optimize colour based wood grading systems by implementation of LIF in addition to colour based methods which are conceivable

Thermal conductivity of Populus alba, Carpinus betulus, Acer laetum, Ulmus glabra, Pinus radiata and Alnus subcordata woods at various average temperatures are measured experimentally using ASTM C177 (2010) device. Two samples of each species with 200 × 200 mm² areas and 10 mm thicknesses which have been obtained from the northern part of Iran were utilized to test their thermal conductivity. The results show that thermal conductivity of the species varies linearly with temperature. Furthermore, a relationship is recommended for the prediction of thermal conductivity of each species in the temperature range between 40 °C to 80 °C. Finally, thermal conductivity of these six species has been compared and it has been concluded that Carpinus betulus thermal conductivity is higher than the other.

The effect of temperature on mechanical wood properties is crucial for a number of applications, whereat wood moisture plays a particular role in it. Interactions between temperature and moisture content were investigated for different bending properties. Further, the influence of temperature of dry and wet wood, and the role of ice formation for bending stiffness and for the resulting fracture surfaces was assessed as well. Significant interactions existed between moisture and temperature; the effects explained 74 % of the bending strength variation, and 54 % of the bending stiffness variation. Fracture energy absorption turned out to be independent from temperature and moisture. While fracture failure of wet and frozen samples occurred in the tension zone of the bending samples, the non-frozen bending samples showed the initial rupture primarily in the compression zone. Using the “rules of mixture” from composite theory the experimental data for the role of frozen water in cell lumina could be confirmed.

Thermo-mechanical and chemo-thermo-mechanical pulps from pine and beech wood chips were in part washed by water and urea solution, respectively. MDF were prepared from unwashed and washed fibres with urea formaldehyde resin (UF-resin), phenol formaldehyde resin (UF-resin) and polymeric diisocyanate (PMDI). The technological properties of the boards as well as the formaldehyde release and emission of further volatile organic compounds were measured. Depending on wood species, pulping conditions and the resin washing of fibres influenced the properties of the MDF significantly. In general, the mechanical properties of UF-bonded MDF prepared from washed TMP were lower than from unwashed fibres. In contrast, washing of the CTMP had a less pronounced negative effect on the mechanical properties of UF-bonded MDF. The mechanical properties of PF-bonded MDF produced from washed CTMP were higher than from unwashed fibres. The technological properties of PMDI-bonded MDF made from unwashed or washed fibres were similar. Furthermore, washing of the fibres with water and especially with the urea solution reduced the emission of formaldehyde and the release of volatile organic acids of the boards.

The article presents fundamental research and material properties of solid wood, impregnated with hot melting waxes. The article is based on a dissertation, whose fundamental results were already published in scientific journals. The hydrophobic waxes decrease the uptake of gaseous or liquid water. Furthermore, the mechanical strengths as well as hardness are partly increased significantly. In contrast to several wood modification processes, the treated wood does not become brittle. Wax impregnated wood greys and shows massive infestation by blue stain. But these effects stay limited on the surface. Generally, the resistance against basidiomycetes, soft rot and termites is improved. It has shown, that some strength properties, the impregnation process or the durability vs. xylobiont insects depends on a specific influence of the different wax types.

The application of the Dynstat-procedure for testing timber gives the opportunity, to perform tests on timber with relatively mean cost of material. For the application of this procedure it is essential, to know the relation between the Dynstat-procedure and the three point bending procedure. In the last years comparative studies were conducted at the Hochschule für nachhaltige Entwicklung (FH) Eberswalde for this purpose. In the following the results of these researches are presented summarized.

The paper summarises the results of the effective cross-sections of studs of timber frame elements completely insulated with stone wool of an extensive Austrian research project. Based on the results of the full-scale tests it could be shown, that the post-protection factor k3 according to ÖNORM EN 1995-1-2 (2007) results in conservative cross sections. A proposal for the post-protection factor k3 has been determined. The research project was part of the European wood-wisdom project “Fire in Timber”.

Within a joint industrial research project it was highlighted, how far seat upholsteries are exposed to the risk of microbial activity by the intended use or by introducing larger quantities of liquid. Common physiological studies were combined with microbiological and chemical analytical testing to define correlations between these two. It has been demonstrated that both in the intended use or misuse of upholstery moisture transport and accumulation processes can occur on a relevant level to foster microbiological activity. In this context the single components have different susceptibilities to infection by microorganisms. Basing on series of measurements carried out appropriate opportunities were shown to influence these processes in a positive way, for example by draining moisture in additional horizontal layers.