Gerd Wegener

Chemical changes during the production of thermo-treated beech wood

Thermal treatments of beech wood with different temperature loads on the wood cause characteristic changes in the chemical composition. The determination of specific changes was carried out by means of suitable methods, both wet chemical and instrumental analyses. It could be confirmed that in addition to the degradation of polyoses, lignin, known as the thermally most stable compound, shows significant thermal alterations too.

Relations between chemical changes and mechanical properties of thermally treated wood 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract Thermal treatments of wood (Fagus sylvatica and Fraxinus excelsior) were examined. The temperature load on wood causes characteristic changes in the chemical composition, which were determined by means of several defined methods. The results confirm that in addition to the degradation of polyoses lignin, known as the thermally most stable compound, also shows significant thermal alterations. In addition, mechanical properties of the specimens were examined in order to correlate these results with the effects of chemical changes of thermally treated wood. It was shown, e.g., that the decomposition of the polyoses can affect the strength properties both positively and negatively.

Evaluation of thermally modified beech and spruce wood and their properties by FT-NIR spectroscopy

Quality assessment of thermally modified spruce (Picea abies (L.) Karst) and beech (Fagus sylvatica L.) wood and of the corresponding reference samples was carried out by means of non-destructive FT-NIR spectroscopic measurements and PLS regression. Oven-dry and basic density as well as MOE and MOR determined by 3-point bending tests were evaluated. The focus was put on specimens produced from material that had been thermally modified in an industrial scale kiln. Modelling results range from poor to very good. The results of the spectra taken from the spruce samples resulted in better prediction results than the spectra of the beech samples. This could be due to different proveniences or variation in the industrial modification process. The results indicate that FT-NIR surface measurements of sound thermally modified wood samples could be applied to evaluate several characteristics before and after the modification process. The method could be used for screening during pre-sorting of thermally modified wood.

Investigation of the correlation between extractives content and natural durability in 20 cultivated larch trees

Material and methods Investigations were carried out on 20 cultivated larch trees (hybrid test area ‘‘Bomigrain’’ forestry district Rothenbuch) selected according to phenotypic criteria. These trees formed the basis of a new breeding program to improve the growth, stem shape and especially the wood quality of larch trees. Two parts of a stem disc taken from each of the 20 larch trees (trunk height 1⁄4 1 m) were analysed: a) inner heartwood (IH); b) outer heartwood (OH, 3 cm within the sapwood/ heartwood border). To determine the extractives, the wood was first ground, adding solid CO2, sieved, and then successively extracted in a Soxhlet apparatus for 6 h and 4 h, using cyclohexane – ethanol (2:1) and ethanol respectively. Together, both extraction steps yield the total amount of extractives related to wood meal (oven-dry). In analogy to EN 113 (1996), the natural durability tests were carried out using the Kolle-flask method. Determination of mass loss after 12 weeks’ exposure to fungi was carried out using three different test fungi, choosing one representative of each decay type for each test: Coniophora puteana (brown rot), Trametes versicolor (white rot), Chaetomium globosum (soft rot). For each fungus and tree, 20 specimens were used. All decay tests were carried out simultaneously. Small pine sapwood blocks served as controls.

Basic properties of specific wood-based materials carbonised in a nitrogen atmosphere

The purpose of this study is to develop new porous carbon materials by carbonising wood-based materials. One of the advantages of wood-based materials used as precursors for porous carbon materials is the simple and cost-effective production technique. Moreover, it is possible to make adjustments for a wide range of macro- and micro-structures by selecting different densities and particle sizes. Compared with solid wood, wood-based materials possess much greater homogeneity, isotropy and reproducible characteristics. Another great advantage is the fact that carbon materials can thus be produced from a renewable resource. A broad variety of specifically developed wood-based materials were carbonised to produce porous carbon materials for which characteristics such as density, yield, dimensional changes and surface area were determined. Light microscopy and mechanical testing were applied for further characterisation. The results showed how density and particle size affect the structure of the carbon materials; dimensional changes and mass loss are influenced by the carbonisation temperature, adhesive content and apparent density; increasing particle size decreases flexural strength and increasing apparent density or adhesive content raises flexural strength super-proportionally; and specific surface area increases with rising carbonisation temperatures.

On the chemical characterisation of plantation teakwood from Panama

The purpose of this study was to compare teakwood (Tectona grandis) from two plantations with regard to chemical composition, especially the quantity of extractives and their qualitative analysis, focussing on the derivatives of anthraquinone and lapachol as biologically active compounds.

Thermal behaviour of polysaccharides in wood during friction welding

Reference IBOIS-ARTICLE-2005-003View record in Web of Science Record created on 2007-10-30, modified on 2016-08-08

Analytical pyrolysis and FTIR spectroscopy of fossil Sequoiadendron giganteum (Lindl.) wood and MWLs isolated hereof

Recent and fossil woods from the genus of Sequoiadendron, as well as their milled wood lignins were investigated by means of FTIR spectroscopy and pyrolysis GC/MS technique. Though almost same in appearance the differences in band intensities of FTIR-spectra reveals the distinctly increased aromatic character and the oxidation in fossil specimens. More detailed information about the changes in old wood were obtained by analytical pyrolysis, which delivers degradation products with shortened side chains and more saturated units relating to fossil lignin.ZusammenfassungRecentes und fossiles Holz der Gattung Seqoiadendron giganteum, sowie daraus isoliertes Björkman-Lignin wurden mittels FTIR Spektroskopie und GC/MS Pyrolyse-Technik untersucht. Obwohl sich die Holzarten äußerlich sehr ähneln, zeigen die Unterschiede der Bandenintensität in den FTIR Spektren einen deutlich erhöhten, aromatischen Charakter und Oxidationsgrad in den fossilen Proben. Detailliertere Information über Veränderungen in den alten Holzarten wurden durch pyrolytische Analyse gewonnen, welche Abbauprodukte mit kürzeren Seitenketten und gesättigtere Einheiten des fossilen Lignin aufweisen.

Investigating the combustion behaviour of various wood species via their fire gases

For the first time, fire gases were extracted directly from the combustion boundary within various wood species subjected to fire and were subsequently analysed by means of GC/MS. Variations in the composition of the fire gases under increasing thermal load were continuously monitored and comparisons were made between the different wood species. Relatively high contents of acetic acid and methanol in the fire gases and a comparatively extensive splitting off of acetyl and methoxy groups proved to be concomitant with a high mass burning rate. Heartwood extractives were found to have no accelerating effect on the combustion process.

Classification of thermally modified wood by FT-NIR spectroscopy and SIMCA

Quality assessment of thermally modified wood has evolved as one of the major fields in the research on thermal modification of wood. This study investigates NIR spectroscopy in combination with the pattern recognition method of soft independent modeling of class analogies (SIMCA). Focus is put on identifying different treatment intensities of thermally modified samples of beech, ash, and Norway spruce. The results indicate that SIMCA classification based on NIR spectroscopy could be used for quality control of thermally modified wood. The method might be applicable for producers (pre-delivery checks) and customers (reception control). However, transfer from laboratory to industrial conditions needs further investigation.