VOLUME 54, ISSUE 5/2013

This report opposes the first time mechanical properties of clear wood and construction timber of the Tree-of-Heaven (Ailanthus altissima) of provenience Central Europe. The results base on a research project which aimed on demonstrating the economical use of Ailanthus, which in China, its country of origin, constitutes the second most important timber species. In terms of its appearance, processing and mechanical properties a strong affinity to the European ash (Fraxinus excelsior) was verified. It points out a notable mechanical potential which is in particular of interest for load-bearing purposes. Utilising the experiences and knowledge gained from ash a dynamical integration of Ailanthus in existing production processes seems to be possible so far we succeed in securing a controlled forest management and thus the acceptance of the Tree-of-Heaven.

Oak wood (Quercus robur) from a bridge was investigated in view of fungal degradation. The outer layer of the wood was attacked by soft-rot fungi and the middle part by white-rot species. Fruit-bodies of the white-rot basidiomycetes Hymenochaete rubiginosa and Stereum hirsutum were identified. Presence of Fuscoporia ferrea and Mycena galericulata was demonstrated by rDNA-ITS sequencing. Light microscopy showed hyphae of blue-stain fungi and white- and softrot decay. Field emission scanning electron microscopy (FE-SEM) exhibited white-rot in vessels, fibres and ray cells. transmission electron microscopy (TEM) revealed soft-rot with cavity formation in the S2-layer of the fibre cell walls.

The results of an investigation of the ageing of multi-layer parquets and of the corresponding adhesives revealed that, for a use on floor heating systems, constructive aspects are the most important prerequisites for a durable product. The parquet construction should meet the requirements of heat transition resistance and the adhesive bond must be carried out thoroughly. In some cases, the ageing of the adhesive led to a decrease of its fastness parameters. However, no failure caused by an aged adhesive could be approved.

This work describes the possibility of processing spruce bark to pallet blocks. When machining roundwood, high quantities of bark are generated, which are mostly used for heat generation. By producing pallet blocks out of bark, it is possible to refine the raw material and consequently achieve a higher value added. The author and his supervisor determined during the two years master course project how it is possible to develop a pallet block made of spruce bark, which meets the requirements according to the specific standard. This research describes in detail which tests and scientific methods were used. Different samples of bark based pallet blocks were produced and tested according to specific standards. The experimental results have been extensively analysed and scientifically interpreted. It was able to work out relationships between several basic parameters to the later properties of the blocks. This enables to optimise the samples with the result that several of these reached the properties required by the specific standards. The authors take the view that such potentials of achieving a higher added value should be forced, especially against the background of today’s scarcity of raw materials.

The thermo mechanical pulping process (TMP) of wood chips is an important stage in the production of wood fibre boards and wood based paper, but the energy consumption for the pulping process is very high, especially for the TMP production in paper industry. An electron beam treatment of wood chips before TMP (ETMP) is able to reduce this milling energy consumption for approximately 25 to 40 %. The irradiation of the wood chips leads also to a significant improvement of strength and water resistance of MDF and offers possibilities for the reduction of the board density.

For direct printing, the quality of the printing substrate is crucial. At present standardised criteria for evaluating quality of woodbased surfaces do not exist. The present paper discusses methods for characterisation of surfaces of wood-based materials such as NIR, roughness measurement and SEM. On the base of these methods consolidated parameters are determined to describe printability of surfaces of wood-based materials. Therefore various laboratory and industrial wood panels were sanded, coated and printed by indirect gravure printing. Their surfaces were analysed before and after printing. As a result, procedures have been developed that allow a realtime assessment of the surface quality of wood surfaces with respect to their suitability for the indirect gravure printing. First, changes of roughness of the wood surface due to a defined humidification are analysed; the so determined difference of roughness parameters describes the suitability of wood surfaces for direct printing. Secondly, primed surfaces are scanned using NIR; the measured values are consolidated to parameters, which can be used to describe the printability of these materials.

With the help of nano-technology it is possible to create very thin, nearly invisible but high efficient coatings. In many different economic sectors silica bonding has been used for two decades now (Böttcher, 2001). The application of this approach in the wood sector seems sensible, as silica is placed in the wood cells naturally and it changes the structure and characteristics of the wood in a positive way. More about this was discussed in part one of this publication (Eisbein, 2013). While the first part focused on modification of the wood by a preferably deep and even dispensation of silica particles including other composites, the second part aims on functional layers which are active near the surface of the wood. This area also belongs to key technologies from which special innovative approaches (developments) are expected. Many projects were carried out in cooperation with different scientific and economic institutes together with the Landesamt für Denkmalpflege Sachsen. Furthermore some student projects at different universities has increased the level of knowledge. Nevertheless, an implementation of the products to the general practice of wood preservation was not successful so far.