Microscopic investigation of defects in thermally compressed poplar wood panels

The combined effects of temperature and compression on the microstructure of solid-wood panels produced by Aspen (Populus tremula) wood were evaluated. Thermal compression was applied on aspen wood to increase the density for improving its physical and mechanical properties. The solid wood panels with dimensions of 100 mm by 500 mm by 25 mm were hot-pressed by using a laboratory hot press at a temperature of either 150 °C or 170 °C and pressure of either 1MPa or 2 MPa, respectively, for 45 min. Changes in the microstructure were detected by using a light microscope. The microscopic investigations revealed that the wood exhibited much defects in the process conditions of 170 ºC / 2 MPa, and the distribution of defects were not uniform in the growth rings of the wood specimens in the two treatment groups. All defects in cell structure were quite distinct in the beginning and the last parts of the growth rings and the largest damages occurred in the fibers and vessels for the two process conditions. The results indicate that growth ring structure, vessel porosity, and cell wall thickness have a strong effect on wood behavior in various process conditions

A staining method for determining severity of tension wood

Tension wood is considered to be an important defect by the wood processing industries. A considerable amount of research has been done to determine the presence and structure of tension wood; however, there is a need to find a quick, practical, and applicable method to evaluate the severity of tension wood. This study investigated whether zinc-chlorine-iodide (Herzberg reagent) could be applied in determination of tension wood severity. Fagus sylvatica L. (beech wood), Populus alba L. (poplar wood), and Quercus robur L. and Quercus rubra L. (oak wood) species were used in this study. The results were compared with safranin/astra blue and acridine orange to verify the accuracy of the classification of the severity of tension wood. The results showed that the severity of tension wood was incorrect, and in particular the color reaction obtained with zinc-chlorine-iodide was weak; on the other hand, it was reliable for beech and poplar woods, where the color reaction was strong

Ethylene and diethyl-ether production by dehydration reaction of ethanol over different heteropolyacid catalysts

Dehydration reaction of ethanol was investigated in a temperature range of 140-250 degrees C with three different heteropolyacid catalysts, namely tungstophosphoricacid (TPA), silicotungsticacid (STA) and molybdophosphoricacid (NIPA). Very high ethylene yields over 0.75 obtained at 250 degrees C with TPA was highly promising. At temperatures lower than 180 degrees C the main product was diethyl-ether. Presence of water vapor was shown to cause some decrease of catalyst activity. Results showing that product selectivities did not change much with the space time in the reactor indicated two parallel routes for the production of ethylene and DEE. Among the three HPA catalysts, the activity trend was obtained as STA > TPA > MPA

Effects of heat treatment on some macroscopic and physical properties of Scots pine sapwood and heartwood

Impact of heat treatment (ThermoWood) on the macro structure and physical properties of Scots pine sapwood and heartwood were studied by visual examinations, using the following relevant standard test methods: ASTM D2244 and TS 2472, respectively. In the study, two processes-Thermo-S (190 V) and Thermo-D (212V)-were employed for heat treatment.To compare the effect of different types of heat treatment, kiln dried wood samples were used for reference. Macroscopic investigation showed that superficial cracks occurred in all samples, and as the temperature increased, the severity and number of cracks increased. In the Thermo-D process, internal cracks and cupping were seen only in heartwood samples. Physical examination showed that as the temperature increased, color of the samples darkened, the density of the samples decreased, dimensional stability was enhanced.The Anti Swelling-Efficiency (ASE) in the Thermo-S and Thermo-D processes evaluated in sapwood samples was 17.04% and 24,77%, respectively; however, values in the heartwood samples were 11.97% and 3045%, respectively. The highest reduction ratio of air dried density was 14.04% in the thermo-D process applied to the heartwood samples. Thus, it can be concluded that this reduction due to the increased temperature is related to the formation of internal cracks

ANATOMICAL INVESTIGATION OF THERMALLY COMPRESSED WOOD PANELS

Effects of temperature and press pressure on the anatomical structure of solid-wood panels produced by using Pinus sylvestris L. (Scotch pine) wood were evaluated. Solid wood panels with dimensions of 250 by 500 by 18 mm were hot-pressed using a laboratory hot press at a temperature of either 120 degrees C or 150 degrees C and pressure of either 5 or 7 MPa for 1 h. Microscopic investigations conducted by Light Microscopy (LM) and Scanning Electron Microscopy (SEM) showed that the highest deformation occurred in earlywood regions of all growth rings for each process condition and the distribution of deformation was not uniform in growth rings. Cell-wall thickness was observed to be an important factor in wood behavior during thermal compressing processes. The results showed clearly that the impact of pressure in wood structure is promoted by increased temperature. Significant densification was observed at the maximum temperature and maximum pressure condition employed in the study, and almost all earlywood layers showed cell collapse. The study revealed that a homogenous structure of growth rings with the uniform earlywood and latewood widths throughout the wood samples plays a major role in prevention of cell collapse. The results indicated that both process conditions and anatomical structure of the wood have an interaction

Structural Evaluation of a Timber Construction Element Originating from the Great Metéoron Monastery in Greece

This study identified the wood species and evaluated the degree of weathering and biological degradation of a historical timber construction element originating from the Great Metéoron monastery in Metéora, Greece. The wood material was provided from the interior side of a balcony that was fully covered with a roof and exposed to outdoor conditions for more than 400 years. The species was identified as Quercus spp. of the white oak group. In the timber element, the physical, morphological, and chemical changes were studied to assess the type and extent of degradation using light microscopy and Fourier transform infrared (FT-IR) spectroscopy. To examine the degree of biological degradation and weathering, the surface layer and inner parts of the specimen were studied separately and compared with a recent wood specimen of the same species. The FT-IR analysis revealed remarkable differences between the surface layer and the inner parts of the historical wooden element. Macroscopic and microscopic investigation indicated that multiple types of degradation caused by weathering, fungi, and insect attacks had occurred in the wood structure. It was finally concluded that the historical timber construction element was in better condition than was expected before the study

WOOD IDENTIFICATION OF WOODEN MARINE PILES FROM THE ANCIENT BYZANTINE PORT OF ELEUTHERIUS/THEODOSIUS

The purpose of this study was to identify the wood species of the marine and filling piles obtained from the ancient Byzantine port of Eleutherius/ Theodosius, Istanbul, Turkey. Anatomical descriptions and identifications of 12 marine and 4 filling piles were performed by microscopic evaluations. In the study, Castanea sativa Mill., Quercus ithaburensis Decne., Quercus pontica C. Koch., and Cupressus sempervirens L. species were identified. No precise identifications were completed for only six samples at the species level; however, those samples showed significant similarity to Quercus spp. and Fagus spp. It was concluded that the economically viable supply of wood was more appropriate than obtaining it from nearby regions. The people living in ancient times had solid knowledge and experience on the utilization of wood species