Birch Samples Research Articles

Исследование внутреннего трения натуральной и модифицированной прессованием древесины березы повислой (Betula pendula Roth)

A method is proposed for approximating of the internal friction of wood based on the Boltzmann superposition principle, which describes the complex viscoelastic behavior of the system by a linear combination of components. Prepared samples of natural and modified wood, sawn from the stem part of drooping birch (Betula pendula ROTH) trees growing in the Khlevensky Forestry (52.184130, 39.110463, ASL 157m), were exposed to radial and tangential directions with ultrasound (frequency 24.5 kHz, exposure 0 -20 minutes, step 5 minutes) and pulsed magnetic field (strength - 0.3 T, exposure 0-2 minutes, step 0.5 minutes). Next, the internal friction of the samples was studied on an experimental setup using the logarithmic damping decrement based on free-bending vibrations. The absolute values of the dimensionless viscosity coefficient κ included in the model as the main structural parameter for samples of natural and modified wood were obtained at a significance level of p=0.95: for moisture content from 4.3 to 15; for ultrasound 4.6 to 20; for a pulsed magnetic field from 3.6 to 7.7. The absolute values of the dimensionless scaling factors μ for natural and modified wood samples range from 1.92 to 3.91. The highest approximation value was achieved when testing natural wood samples of silver birch (Betula pendula ROTH): R2=0.98 for the radial direction, the influence of the humidity factor, and R2=0.85 for the tangential direction, the influence of the ultrasonic factor, as well as for a sample of modified wood brand "Destam" in the radial direction R2=0.96, the influence of the factor of the pulsed magnetic field.

Expression of juvenility related microRNAs and target genes during micropropagation of silver birch (Betula pendula Roth.)

Silver birch (Betula pendula Roth.) is an ecologically and economically important deciduous tree species in Northern Europe. In vitro culture initiation and shoot rejuvenation from birches in their reproductive phase is difficult and often unsuccessful. Currently, markers to evaluate the degree of juvenility of birch in vitro shoots, which could be used to track the rejuvenation process and to determine factors affecting it, have not been developed. The aims of this study were to assess expression of juvenility related microRNAs and target genes during micropropagation of silver birch, and to investigate factors affecting juvenility of birch genotypes with different in vitro morphogenic ability. Potential precursor sequences and target genes of the microRNAs miR156 and miR172 were determined by alignment to the birch unigene set. Ten potential miR156 and miR172 precursor sequences were identified, and were tested for the ability to form the required stem-loop structure. Based on precursor sequences, primers were designed for real time PCR analysis of precursor miRNA expression. Expression patterns of two miR156 family precursors (miR156_511 and miR156_789) and one miR172 precursor (miR172_1931) and two target genes (BpSPL1 and BpAP2) had the best correlation with juvenility/maturity in the analysed in vitro propagated silver birch samples. Expression patterns of these miRNA precursors and target genes were also investigated in samples cultured under different in vitro conditions. This study provides an initial survey of molecular markers for assessment of phase change in birch in vitro micropropagation.

Decay Resistance of Surface Carbonized Wood

Surface carbonization, or charring, of wood is a one-sided modification method primarily intended for protection of exterior cladding boards. The heavily degraded surface acts as a barrier layer shielding the interior from environmental stresses, and as such acts as an organic coating. To test the durability of surfaces created in this manner, unmodified, contact charred, and flame charred spruce and birch samples were exposed to the brown rot fungus Coniophora puteana and white rot fungus Trametes versicolor for a period of nine weeks. All sides of the samples except the modified surfaces were sealed to investigate the protective effect of the surface. Mass losses were greatest for unmodified references (up to 60% and 56% for birch and spruce, respectively) and smallest for contact charred samples (up to 23% and 32%). The wood below the modified surfaces showed chemical changes typical of brown rot and simultaneous white rot. The measured glucosamine content revealed fungal biomass in both the modified surface as well as the layers beneath. According to the recorded values, the fungal biomass increased below the surface and was higher for flame charred samples in comparison to contact charred ones. This is likely due to the more intact, plasticized surface and the thicker thermally modified transition zone that restricts fungal growth more effectively in contact charred samples in comparison to the porous, cracked flame charred samples. Scanning electron microscope images verified the results by revealing fungal hyphae in all inspected wood types and species.

ACCUMULATION OF PARTICULATE MATTER BY URBAN FORESTS FROM POLLUTED AIR

Purpose is to investigate the ability of natural urban forests to purify atmospheric air polluted with particulate matter (PMx), based on the correlation between the level of PMx in the air and the concentration of pollutants accumulated by trees.
 Materials and methods. The studies were carried out in 8 large forest areas on the Irkutsk city territory. In each area, a test site was selected, where the concentrations of particulate matter of the size range: PM0.3, PM0.5, PM1, PM2.5, PM5, PM10 were measured and the AQI index, used in world practice to assess air pollution, was calculated. To determine the level of pollutants accumulation by trees, needles/leaves samples of Scotch pine, Siberian larch, and Silver birch were taken for their analysis on the content of heavy metals (HMs) and polyaromatic hydrocarbons (PAHs). The instrumental park of the Baikal Analytical Center, the Siberian Branch of the Russian Academy of Sciences, and the equipment of the Republican Analytical Center (Ulan-Ude) were used in the work.
 Results. At test sites in urban forests, the level of air pollution was assessed using the AQI index and the IZA index adopted in the Russian Federation. A significant similarity of estimates for both indices was established. The large role of urban forests in air purification from various sizes of particulate matter is shown. It is evidenced by the active accumulation of pollutants present in PMx (heavy metals and PAHs) by needles and leaves. A direct correlation was established between the AQI index and the content of pollutants (sum 8 HMs and sum 14 PAHs) in needles/leaves of trees. It was revealed that all surveyed forests of Irkutsk are polluted to one degree or another, and most of them, with the exception of two forest areas, cannot cope with air purification to a permissible level.
 Application of results. It is recommended to increase the area of urban forests by creating plantations that are structurally close to natural forest ecosystems.
 Conclusion. It is shown that urban forests are a powerful factor in the purification of the air environment from particulate matter within the city. At the same time, significant pollution of the forests themselves requires optimization of their condition.

Natural weathering of soft- and hardwoods modified by contact and flame charring methods

Exterior cladding boards benefit from a known service life that makes planning of maintenance and replacement procedures easier. Among the different wood modification methods, surface charring of wood is expected to increase the lifespan of wooden elements in building façades. This paper reports the properties of surface charred Norway spruce, Scots pine and Silver birch in Southern Finnish climate over a natural weathering period of one year. Several modifications were examined, namely variants of contact and flame charring. These also included oiled and brushed surfaces. The flame charred samples of spruce and birch withstood the weathering well, with some minor flaking and cracking. The thick pine samples cracked extensively regardless of modification, raising questions on suitable density and thickness of wood destined for a charring modification. Contact charring did not seem suitable for outside uses at least in direct sunlight, as the colors faded, and surfaces cracked within all examined groups. The spectroscopical methods employed also revealed degradation of contact charred wood lignin, whereas the flame charred surface consisted mostly of recalcitrant carbon structures rather inert towards weathering. This highlights the importance of sufficient structural degradation of wood components in creating a weathering resistant surface, and also shows that a thicker thermally modified layer does not necessarily improve the weatherability in contact charred wood.

Investigation of Acoustic Efficiency of Wood Charcoal in Impedance Tube for Usage in Sound-Reflective Devices

Charcoal is an environmentally friendly, biodegradable, and economical material. This material is usually produced by slow pyrolysis—the heating of wood or other substances in the absence of oxygen. The aim of this study was to investigate the acoustic efficiency of charcoal and design an acoustic diffuser that utilizes charcoal. Samples of different types of tree charcoal—birch (Betula pendula), pine (Pinus sylvestris), and oak (Quercus robur)—with different thicknesses were used for the acoustic efficiency measurements. The sound absorption and sound reflection properties of charcoal were investigated. The bulk density of charcoal was measured. In this study, an impedance tube with two microphones was employed as the measurement method. The results of the impedance tube measurements showed that the charcoal samples had high sound reflection coefficients, the highest value of which was 1. The 50 mm samples of birch had a high bulk density of 473 kg/m3. The sample of 50 mm thick oak had the best reflection coefficient at 0.99. Reflection depended on the surface’s acoustic properties, and the sound reflection coefficient increased with the increase in the density. Charcoal measurements, due to the high reflection coefficient of the material, were used for the design of a sound diffuser, which included wooden perforated plates filled with cylindrical elements of wood charcoal.

Indentation Hardness and Elastic Recovery of Some Hardwood Species

The purpose of the study was to measure the Brinell hardness (HB) of six wood species and evaluate the ability to recover the depth of the imprint (self-re-deformation). Straight-grain clear samples of ash, beech, alder, birch, iroko, and linden wood were prepared. Measurements were made in the three main reference timber cross-sections: radial (R), tangential (T), and axial/longitudinal (L) and with two measuring loads of 30 kG and 100 kG (294.2 N and 980.7 N). The tested wood species could be classified into hard (ash, beech), medium-hard (alder, birch, iroko), and soft (linden) wood species. The HBs of each tested wood species differed in the cross-sections, i.e., side hardness (R, T) and end hardness (L). Higher HB values were obtained at 100 kG load in all species and all three cross-sections. The lowest influence of the measurement force value on the HB value was revealed for the soft wood species (linden: 107–118%). This influence was visible for the other five medium-hard and hard wood species, ranging from 125% to 176%. The percentage of temporary imprint in total imprint depth (x/H) varied from 12 to 33% (linden 12–18%—the lowest self-re-deformation ability; beech 25–33%—the highest self-re-deformation ability). The results of this study underline that the higher the density of the wood, the higher the Brinell hardness, and, simultaneously, the greater the measurement force used, the higher the Brinell hardness measured. The ability of self-re-deformation in wood’s R and T cross-sections depends on the wood density and the measuring force used. In contrast, this ability only depends on the wood density in the L cross-section. Those observations imply that the compaction of the cell structure during side compression is mainly non-destructive, while the longitudinal deformation of the cell structure (the buckling of cell walls and fracture of ends of the cells) is to a great degree destructive and irreversible. These results can be used in the construction and furniture sectors, especially when designing products and planning the woodworking of highly loaded wood floors and furniture elements.

Geochemical Partitioning of Heavy Metals and Metalloids in the Ecosystems of Abandoned Mine Sites: A Case Study within the Moscow Brown Coal Basin

Significant environmental impacts of mining activities connected with high-sulfur materials result from the production of acid mine drainage and potentially toxic elements, which easily migrate to adjacent ecosystems due to the typical absence of vegetation on spoil heaps and toeslope talus mantle. In this paper, we present the results of the first comprehensive study of the ecosystems affected by acidic and metal-enriched (Al, Ca, Co, Cu, Fe, Mg, Mn, Ni, and Zn) mine drainage conducted at spoil heaps and adjacent talus mantle under semihumid climate conditions within the Moscow Brown Coal Basin (Central Russian Upland, Tula Region, Russia). A total of 162 samples were collected, including 98 soil samples, 42 surface water samples, and 22 plant samples (aerial tissues of birch). Coal talus mantle materials of Regosols were characterized by the increased concentration of water-soluble Ca, K, Mg, and S, and all mobile fractions of Al, Co, S, and Zn. The chemical composition of birch samples within the zones affected by acid mine drainage differed insignificantly from those in the unpolluted ecosystems with black soils, due to the high tolerance of birch to such conditions. Differences between the affected and undisturbed sites in terms of the chemical composition decreased in the following order: waters > soils > plants. The geochemical characterization of plants and soils in coal mining areas is essential for the mitigation of negative consequences of mining activities.

Ways to improve the properties of natural wood when using waste vegetable oils

The article is devoted to the development and study of new compositions based on spent sunflower oil for the protective treatment of natural wood. Samples of birch and aspen wood were selected as the subjects of the study. The processing of wood samples was carried out by the method of “hot-cold impregnation”. Refined sunflower oil was used as the oil base of the propearized compounds developed. Plant oil fillers were chosen wood flour, stearic acid, canifol and sikkativ based on metal salts. The use of developed compounds can improve the hydrophobic properties of wood, increase its water and water resistance, as well as reduce swelling in tangential and radial directions. The optimal compositions on the basis of spent vegetable oil for protective processing of birch wood have been selected. The difference in the modifying capacity of the developed compositions for different types of wood is shown on the example of birch and aspen. Propiary compounds based on spent vegetable oil have environmental safety and their use allows the disposal of food waste.

Structural analysis of biomass pyrolysis and oxidation using in-situ X-ray computed tomography

Detailed measurements are performed to examine the heterogeneous processes that occur within the solid fuel during the combustion of biomass. Specifically, the pyrolysis, char oxidation, and volume shrinkage are examined using X-ray computed tomography (XCT). Simultaneous 3D in-situ measurements of solid density and gas-phase temperature are acquired at a spatial resolution of 300 μm for 1.6-cm size samples of birch, douglas fir, oak and walnut. To simultaneously measure the heterogeneous combustion processes and the gas-phase temperature, the flow is doped with Kr, a high X-ray contrast agent. By varying the molar oxygen concentration from 0% to 21%, regimes of pyrolysis, smoldering, and flaming are identified for different types of biomass and grain orientations. Results from these multidimensional XCT measurements provide new insights about the fuel volume reduction, from which shrinkage parameters are experimentally determined. The simultaneous acquisition of gas-phase temperature measurements also highlights the direct dependence of flame anchoring upon grain orientation. In addition, the char oxidation is found to be limited to a narrow region with 2 mm thickness at the smoldering surface, while the propagation of the pyrolysis front is measured up to 1 cm within the sample. For some biomass materials, significant density fluctuations are measured at the millimeter scale, indicating non-homogeneous reaction rates.

Chemical Analysis and Anthelmintic Activity Against Teladorsagia Circumcincta of Nordic Bark Extracts In vitro.

Helminth parasitic infections are common in small ruminants in Norway; infection is usually treated with anthelmintic drugs, but anthelmintic resistance is an increasing problem. It is necessary to identify strategies to reduce the use of anthelmintic drugs and mitigate the impact of anthelmintic resistance. Condensed tannin (CT)-rich forages have been shown to reduce the helminth burden in small ruminants, but these forages have limited cultivation potential in Scandinavia. A good source for CT in cold climatic regions may be the bark of several commercially utilized tree species. In the present study, we determined the content and characterized the type of CT in bark extracts of pine (Pinus sylvestris L.), spruce (Picea abies L.), and birch (Betula pubescens). Extracts of selected bark samples were tested for their anthelmintic efficacy against the ovine infectious nematode Teladorsagia circumcincta. Total CT content was higher in the bark from younger (10–40 years old) pine and spruce trees; it decreased with tree age in pine, whereas it remained relatively stable in the bark of spruce and birch. Pine trees consisted of 100% procyanidins, whereas prodelphinins were present in most spruce (4–17%) and all birch samples (5–34%). Our studies clearly showed that there is variation in the anthelmintic activity of water and acetone extracts of bark samples collected from various sites around Norway, as this was measured with two independent in vitro assays, the egg hatch and larvae motility assays. The anthelmintic activity of some extracts was consistent between the two assays; for example, extracts from the three samples with the highest CT content showed very high activity in both assays, whereas the extract from the sample with the lowest CT content showed the lowest activity in both assays. For other extracts, activity was not consistent across the assays, which could be attributed to the susceptibility of the different stages of the parasitic life cycle. We demonstrated that bark extracts from commercially used trees in Scandinavia have the potential to be used as alternatives to anthelmintics. Further work should focus on refining the associations between bark extracts and anthelmintic activity to identify the best strategies to reduce the input of anthelmintic drugs in livestock production systems.

The effect of drought on the expression of stress resistance genes in perspective forms of birch

Drought stress greatly limits distribution of forest-forming species, in particular, birch. The actual task is to identify resistance mechanisms in order to select perspective genotypes for further reproduction. The purpose of this work was to identify drought-tolerant genotypes of silver birch (B. pendula Roth.), downy birch (B. pubescens Ehrh.) and their hybrids based on the analysis of drought tolerance. We studied the expression of genes encoding proteins of metabolic pathways that are activated in response to abiotic stress (phenylpropanoid way) associated with the pathogenesis of proteins (PR1 and PR10), transcription factors (DREB2), and proteins of late embryogenesis (LEA). As a result of the effects of drought, a significant increase in expression was detected for the PAL, PR-1, PR-10, and DREB2 genes in the analyzed samples; at the same time, expression changes were revealed for the LEA8 gene for two out of ten genotypes. Birch samples 29-58 and 233 was selected as most stable showing adaptive response for all genes analyzed. Analyzed genes can be recommended as markers for assessing drought resistance of other woody plant species.

Experimental Determination and Modeling of Drying Process of Woody Biomass

Birch is a kind of readily available woody biomass resource, which can be used to crush and manufacture fuel particles and animal bedding. One of the important aspects during the production system is the drying of biomass prior to storage or processing. Moisture migration in wood is a particularly important factor in determining the drying process. The objectives of this study are to investigate the drying characteristics of Birch and develop a model to simulate moisture diffusion in Birch during the drying process. Experiments were conducted in a controlled environment chamber. Different temperatures and relative humidity were set to simulate the different drying conditions. The mechanism of moisture movement in Birch samples during the drying process was represented by a diffusion model according to Fick’s second law. A computer program in Matlab software was developed to simulate the infinite element model. Moisture diffusivity of Birch was determined by minimising the sum of squares of the residuals between experimental results and numerically predicted data. Results showed that the moisture diffusion coefficients of Birch ranged from 1.2×10−7m2/hr to 9.6×10−7m2/hr with temperature varying from 20°C to 60°C. And the trend of diffusion coefficient versus temperature was in accordance with the Arrhenius equation.

Bonding Wood Veneer with Biobased Poly(Lactic Acid) Thermoplastic Polyesters: Potential Applications for Consolidated Wood Veneer and Overlay Products

This study reports on the use of poly(lactic acid) (PLA) as a renewable thermoplastic adhesive for laminated panels using birch, spruce, and pine veneers. Consolidated panels were prepared from veneer and PLA foils by hot-pressing from 140 to 180 °C to achieve minimum bondline temperatures. Evaluation of panel properties revealed that the PLA-bonded panels met minimum tensile strength and internal bond strength performance criteria. However, the adhesion interface which developed within individual bondlines varied with distinctions between hardwood and softwood species and PLA grades. Birch samples developed greater bondline strength with a higher pressing temperature using semi-crystalline PLA, whereas higher temperatures produced a poorer performance with the use of amorphous PLA. Panels formed with spruce or pine veneers had lower bondline performance and were also similarly distinguished by their pressing temperature and PLA grade. Furthermore, the potential for PLA-bonded laminated panels was demonstrated by cold water soak testing. Samples exhibiting relatively greater bondline adhesion had wet tensile strength values comparable to those tested in dry state. Our study outcomes suggest the potential for PLA bonding of veneers and panel overlays with the added benefits of being renewable and a no added formaldehyde system.

АНАЛИЗ ЭКСПРЕССИИ ГЕНОВ СТРЕССОУСТОЙЧИВОСТИ В УСЛОВИЯХ ВОЗДЕЙСТВИЯ ЗАСУХИ НА РАСТЕНИЯ БЕРЕЗЫ В ЦЕНТРАЛЬНО-ЧЕРНОЗЕМНОМ РЕГИОНЕ

Birch is one of the main deciduous forest-forming species in the European part of Russia, but the impact of stress (in particular, drought) greatly limits its distribution. In this regard, it seems relevant to identify resistance mechanisms in order to select promising genotypes for their further reproduction. The aim of this work is to identify drought-tolerant genotypes of European birch (B. pendula Roth.), pubescent birch (B. pubescens Ehrh.) аnd their hybrids. For the study, we have taken samples of birch at the age of 26 years, which remained viable after the droughts of 2010 and 2013. Birch leaves have been selected in the third decade of June 2019 to analyze drought resistance. Leaves of birch, selected during the period with optimal conditions of air temperature and precipitation, have been used as control ones. A modified CTAB method has been proposed for RNA isolation. We studied the expression of genes encoding proteins involved in the activation of cell defense pathways under the influence of abiotic stress (pal, PR-1, PR-10, lea8, DREB2) during the drought period (June 2019). A study of the expression of genes encoding proteins of metabolic pathways that are activated in response to abiotic stress (phenylpropanoid pathway) associated with the pathogenesis of proteins (PR1 and PR10), transcription factors (DREB2), and late embryogenesis proteins (LEA) has been made. As a result of the effects of drought, a significant increase in the expression of pal, PR-1, PR-10 and DREB2 genes has been detected in the analyzed samples. At the same time, changes in lea8 gene expression were detected for two out of ten genotypes. The largest increase in expression for all five genes is shown for birch samples 29-58 and 233. It indicates the development of adaptive mechanisms in these genotypes and can characterize them as the most stable. The studied genes can be recommended as markers for the analysis of stress resistance in various species of woody plants

Influence of Site Conditions and Quality of Birch Wood on Its Properties and Utilization after Heat Treatment. Part II—Surface Properties and Marketing Evaluation of the Effect of the Treatment on Final Usage of Such Wood

This work is a follow-up contribution to the characteristics of Betula pendula (silver birch) wood from different habitats and the impact of the subsequent heat treatment. Specifically, it focuses on the surface properties of birch wood in the form of veneers, namely color, hardness, roughness and wetting, and in particular on the marketing evaluation of the attractiveness of colored birch wood and, thus, its possible use in practice in the Czech Republic. Three heat treatment steps at 170, 190 and 200 °C were used. The resulting values of the properties of the treated birch veneers were compared with the untreated reference veneers and also with beech veneers. These properties were the wood density, the colorimetric parameters, the roughness parameters, the wetting parameters, the hardness and density, and none of the parameters studied showed negative changes due to the temperature adjustment. Overall, both in terms of properties and in terms of marketing appraisal, there is the potential for birch to replace, for example, beech, especially in the furniture industry, by application in the form of heat-treated veneers after suitable heat treatment. The conclusions of the marketing analysis resulting from the questionnaire survey conducted on a sample of respondents show the significant preference for the heat-treated birch wood compared to reference birch samples without heat treatment.

Oxidative degradation of archaeological wood and the effect of alum, iron and calcium salts

Oxygen consumption measurement was used to study potential oxidative degradation reactions occurring in wooden artefacts from the Viking age Oseberg collection in Norway. Model samples of fresh birch were impregnated with iron, calcium and alum salts to mimic concentrations of such compounds found in Oseberg artefacts and to assess their effect on oxygen consumption rates. The results showed that heated impregnation with alum salt (KAl(SO4)2·12H2O) significantly increased the rate of oxygen consumption, confirming a previously observed link between alum-treatment and wood oxidation. The presence of iron salts in alum-treated wood specimens, even at low concentrations, also substantially increased the oxidation rate. However, the mechanism by which this occurred appeared to be influenced by the alum-treatment. Samples treated with both iron and calcium salts were also studied, in order to investigate a proposed inhibition of iron-induced oxidation by calcium ions. However, these did not appear to consume oxygen at significantly different rates. In Oseberg samples, a large variation in oxygen consumption rates from 0.48 to an apparent 8.2 μg O2 (g wood)−1 day−1 was observed, and these values were consistently higher than those for reference fresh wood. The results demonstrated that oxygen consumption measurement is a viable method of evaluating chemical stability in this case, but is best applied to model samples with limited compositional variability.

Impregnation of lumber due to the pressure of the impregnating liquid

Storage of the container is one of the most serious problems faced by the manufacturer. At temperatures above 5 °C, the fungus and blue stain affect the container board. Because of this, enterprises suffer losses, which most often occur due to the fact that customers reject wooden containers, since it is important to use wooden pallets without mold and mildew in food and packaging industries. The article describes the methodology and results of experimental studies on the impregnation of wood due to the hydrostatic pressure of the impregnating liquid. Graphic dependencies are made to determine the main technological parameters of the impregnation process - its duration. We studied wood samples of spruce, birch, alder and aspen, the main species from which container sets and pallets are made. A description is given of the use of a densitometer of a fundamentally new design, which makes it possible to determine the density of samples with positive buoyancy.

ВЛИЯНИЕ ВИДА НАПРЯЖЕННО-ДЕФОРМИРОВАННОГО СОСТОЯНИЯ НА ДИНАМИЧЕСКУЮ СЖИМАЕМОСТЬ БЕРЕЗЫ

The results of dynamic tests for compression across the fibers at room temperature of birch samples with air humidity are presented. Dynamic tests were carried out on a setup with a split Hopkinson bar according to the Kolsky method at a strain rate of ~2000 s–1. To assess the effect of the type of stress-strain state on the behavior of the material, in addition to specimens in the form of cylinders with its free expansion during loading (uniaxial stress state condition), specimens were tested in a rigid casing that prevents the radial expansion of the specimen (uniaxial deformation condition), as well as local compressive tests of rectangular board fragments. In the latter case, the material surrounding the loading zone plays the role of a compliant confining casing. In this case, a certain intermediate stress-strain state is realized in the sample. For these three types of stress-strain state, dynamic deformation diagrams were obtained with registration of additional loading cycles. Comparison of obtained deformation diagrams shows a significant effect of the type of stress-strain state on the behavior of the material under study. In the case of free expansion of the specimen in the radial direction, the absence of strain hardening is observed in the first loading cycle. In subsequent cycles, hardening is negligible. The deformation diagrams of specimens in the casing as well as board fragments are characterized by a noticeable increase in the modulus of the hardening branch with increasing deformation. In this case, it can be noted that the behavior of the material in the case of testing a piece of board is intermediate between the cases of uniaxial stress state and uniaxial strain state. Some mechanical characteristics of the material are determined using the diagrams obtained. The obtained experimental results can serve as the basis for the subsequent identification of the model of deformation and destruction of wood.

Термическая переработка древесных отходов

Describes the processes of thermal conversion of soft– and hardwood waste to obtain gaseous, liquid and solid products. During the initial stage of the work, the thermogravimetric study of initial samples of birch and pine sawdust was performed in the temperature range from 35 to 1000 °C. On the basis of the thermal analysis data obtained, a method of pyrolysis process of wood waste in the temperature range of 400–500 °C in an inert environment was developed. As a result of experiments on pyrolysis of wood waste, the dependence of the conversion of selected samples into final products, the properties of the resulting gaseous and solid carbon-containing products depending on the conditions of the process, the size of the fraction and the type of wood were obtained. It was found that the optimal temperature of the pyrolysis process in the studied range of system parameters is 450 °C, and the particle size of wood waste is 1–2 mm. Data on the molecular mass distribution of volatile pyrolysis products and kinetic parameters of the pyrolysis process were obtained. The activation energies of the pyrolysis process for pine and birch sawdust samples were 119.3 and 128.2, respectively. The specific surface area of the initial samples of birch and pine wood waste was 9.3 and 8.5 m2/g, respectively. The specific surface area of coal pyrolysis residues for hardwoods increased by 2.4 times and for conifers by 2.1 times, respectively, and assumed values of 22.3 and 17.9 m2/g. Therefore, the coal residues of pyrolysis of wood waste can potentially be used as raw materials for the production of activated carbons and carbon sorbents of various applications.