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The paper investigates the bending moments under diagonal tensile and diagonal compression loads of L-type corner joints made of three wooden parts corresponding to the leg and the two stretchers used in chair construction. The wooden parts were jointed together with a 3D printed connector made of polylactic acid (PLA) filaments using Filament Fused Fabrication (FFF) as additive manufacturing technology. Larch (Larix decidua Mill.) wood was used to manufacture the wooden elements. In order to assess how the model orientation on the build platform influences the mechanical performance of the printed connector, two print positions were taken into account during the additive manufacturing (AM) process, namely horizontal and vertical. Mechanical testing under diagonal tensile and compression loads of the L-type corner joints, followed by the microscopic investigation of the fractured connectors with magnifications 50X, 80X, 100X were employed in this study. The results were compared with those of the reference L-type corner joint consisting of common mortise-tenon jointed wooden elements. The results show that the vertical orientation of the model on the build platform of the 3D printer is preferred for a better mechanical performance. The microscopy of the fractured connectors revealed the interlayer delamination of the filaments, especially in the case of the horizontal orientation of the model, which caused the wooden parts to slide out of the connector and record low values of the maximum failure loads. [ABSTRACT FROM AUTHOR]

Arabinogalactan is a biologically active water-soluble polysaccharide contained in great amounts in larch wood. A sulfate group introduced into the arabinogalactan molecule increases its biological activity and imparts new anticoagulant and hypolipedemic properties. A new method for the catalytic sulfation of arabinogalactan with ammonium sulfamate is proposed. The catalytic activity in the reaction of arabinogalactan sulfation with ammonium sulfamate has been investigated for both the base activators (urea and thiourea) and oxidants (KMnO4 and K2Cr2O7). It has been shown that, in this process, the most effective activator is KMnO4, which ensures the highest (11.3 wt %) sulfur content in sulfated arabinogalactan. The effect of temperature and time of the arabinogalactan sulfation with ammonium sulfamate and the nature of solvents used on the sulfur content in sulfated arabinogalactan has been examined. It has been found that the highest (11.3%) sulfur content in the product is obtained by sulfation of arabinogalactan in 1,4-dioxane at a temperature of 90 °C for 4 h with the KMnO4 activator. The introduction of a sulfate group into the arabinogalactan molecule has been confirmed by the FTIR and NMR spectroscopy data. The FTIR spectrum of sulfated arabinogalactan, in contrast to that of the initial arabinogalactan, includes an absorption band at 1249 cm−1. According to the 13C NMR spectroscopy data, the sulfate groups are located at carbon atoms C2 and C4 of the main galactan chain and at carbon atom C6 of the end galactose units of the main and side arabinogalactan chains. It has been established by gel permeation chromatography that, during the sulfation, the molecular mass of arabinogalactan molecules increases proportionally to the introduced sulfate groups. The absence of low molecular weight fractions is indicative of the absence of depolymerization under the conditions of sulfation and evolution of sulfated arabinogalactan. [ABSTRACT FROM AUTHOR]

Siberian larch wood (Larix sibirica Lebed.) contains such valuable biologically active substances as dihydroquercetin (DHQ) and arabinogalactan (AG), promising for the use in the pharmaceutical and food industries. An urgent task is to improve the methods of extraction isolation of these compounds from wood. In this work, we studied the possibility of simultaneous isolation of dihydroquercetin and arabinogalactan by extraction of larch wood with 5–25% aqueous ethanol solutions. It has been shown that by extracting wood with aqueous solutions with a low concentration of ethanol, it is possible to exclude the stage of separation of resinous substances from the target products of DHQ and AG. By experimentally optimizing of water-ethanol extraction process, it was shown that the highest yields of DHQ (1.8% mas.) and AG (18.0% mas.) were achieved by extraction of larch wood, crushed to particles of 1–3 mm in size, with a 15% ethanol solution for 2 h. It is shown that the preliminary mechanical activation of larch wood allows to reduce the duration of water-alcohol extraction to 30 minutes and to obtain DHQ and AG with high yield. The structure of DHQ and AG is confirmed by IR and NMR spectroscopy. The identification and purity of the DHQ isolated from larch wood was confirmed by photometric method using the cyanidine chloride formation reaction when heating the DQV in ethanol in the presence of hydrochloric acid. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of wood members in a fire are reduced as a result of strength loss of the outermost charring layer and strength reduction of the secondary outer layer in high temperature zones. The charring layer has strong oxygen isolation effects. The main mechanical characteristics of larch wood, including modulus of elasticity (MOE), parallel-to-grain compressive (fc), tensile (ft), bending strengths (fb), and ductility coefficient, were determined under oxygen-free conditions at higher temperatures. Fourier transform-infrared (FT-IR) and scanning electron microscopies (SEM) were used to analyze chemical composition and microscopic changes of wood. The results suggested that hemicellulose softening resulted in decreases in mechanical properties of wood between 20 and 70 °C. From 70 to 190 °C, FT-IR spectroscopy provided evidence that increases in MOE and fc, with relatively minor changes in fb and ft, were associated with cellulose crystallinity and lignin cross-linking/condensation. The use of SEM further indicated degradation of wood composition.

The composition and physicochemical characteristics of polysaccharides extracted from spent liquors of catalytic and noncatalytic delignification of larch wood in the acetic acid-hydrogen peroxide medium were studied. The following were used as catalysts: (NH4)6Mo7O24, MnSO4, TiO2, and ZnSO4. The structure of polysaccharides was identified by FTIR and NMR spectroscopy. Their composition was established using gas chromatography, and the physicochemical characteristics were studied using gel permeation chromatography, scanning electron microscopy, thermogravimetric analysis, gas adsorption, and elemental analysis. It was shown that in the process of oxidative delignification, a significant amount of hemicelluloses and arabinogalactan passes into the spent liquor. The yield of polysaccharides was up to 16.9 wt%. Polysaccharides had a weight-average molecular weight of up to 22.9 kDa and a narrow molecular weight distribution. [ABSTRACT FROM AUTHOR]

As a green and low-carbon natural polymer material, wood has always been popular in engineering applications owing to its excellent physical and mechanical properties. In this study, compression tests in conjunction with in situ test methods (DIC method) were used to investigate the compression mechanism of wood samples in the longitudinal, radial, and tangential directions. The macroscopic failure modes, energy dissipation results, and variations in the strain field were analyzed. The results showed that the load–displacement curve in each grain orientation included three stages: an elasticity stage, yield stage, and strengthening stage. Both the compressive strength and elastic modulus in the longitudinal direction were significantly higher than those in the radial and tangential directions, but there was no significant difference between the radial and tangential directions. Specimens in the longitudinal direction mainly presented fiber buckling, fiber shear slippage, and fiber fracture failure; in radial directions mainly presented compression compaction of the fiber cells; and in the tangential directions presented buckling and shear failure of the laminar layers. The energy absorption in the longitudinal direction was better than in the other directions. The strain changed significantly in the loading direction in the elastic stage while the shear strain changed remarkably in the yield stage in each grain orientation. In this paper, the compression mechanical properties of larch wood in different grain orientations were studied to provide a reference for its safe application in engineering. [ABSTRACT FROM AUTHOR]

Arctic driftwood can be used as an alternative source of wood as construction timber and furniture material, especially in Iceland and Greenland. The use of Arctic driftwood can help in the fight against climate change, by developing land reforestation processes and reducing the volume harvested wood from forests and sustainability of harvesting processes. In this paper the results of an analysis of the effect of long-term residence of pine (Pinus sylvestris L.) and larch wood (Larix sibirica L.) stay in Arctic ice and seawater on the granulation of wood sawdust and the distribution of fine wood dust particles during the frame sawing process are presented. The distribution of wood chips and dust was analysed using sieve and laser diffraction methods. The results confirmed that Arctic driftwood, compared to normal wood for both analysed species, generate slightly more fine wood dust particles during the frame sawing process, which can be harmful to human health. However, these differences are not significant, indicating that the same dust extraction systems can be used for both sawing processes. • The particle size of larch driftwood dust is similar that of normal larch wood. • Increasing the feed per tooth increases the proportion of smaller particles. • The distribution of fine dust particles (<20 μm) is stronger in pine driftwood. • In the process of sawing driftwood, more the finest sawdust fractions were obtained. [ABSTRACT FROM AUTHOR]

Fretwork, as a decorating technique, can today be performed with modern means by laser or CNC routing, but the tool influence on the surface quality must be well understood for further optimization of the cutting parameters. The paper presents an experimental work for the determination of the influence of the cutting angle with respect to the grain on the surface quality of larch wood (Larix decidua Mill.) cut through by laser and CNC routing at different feed speeds. The research considered geometric fretwork patterns derived from triangle, where the cutting angles with respect to the wood grain were 0°, 15°, 30°, 45°, 60°, 75° and 90°. The feed speeds of the CNC routing were set for 2, 2.5, 3, 3.5 and 4 m/min. The surface quality was analyzed by a range of roughness, waviness and primary profile parameters combined with stereomicroscopic images. Although the principle of cutting and interaction with wood of the two processing tools, laser and CNC, is very different, the analysis with roughness parameters has revealed that the cutting angle with respect to the grain has an essential influence, whatever the cutting tool. The surface quality decreases with an increase in the feed speed of the CNC router and processing at 15° and 60° appears to be the worst option from all angle variants for both types of processing. Cutting by laser is melting wood in latewood areas resulting in a smoothing effect. [ABSTRACT FROM AUTHOR]

Lignin is a large-scale waste product of hydrolysis and the pulp-and-paper industries. The problem of lignin utilization is addressed by developing techniques for the comprehensive processing of wood biomass that are based on preliminary catalytic fractionation into its key components, which are subsequently used for obtaining target products. Hemicelluloses of larch wood are known to undergo effective depolymerization (~95 wt %) in ethanol at 250°C. Using hydrogen in combination with a catalyst enables us to increase the lignin conversion to 61 wt %, with 47 wt % of the cellulose left in the solid residue. The highest lignin conversion (67 wt %) is achieved using formic acid, but there is undesirable cellulose depolymerization (conversion, 66 wt %) under these conditions. The main monomer products of the catalytic conversion of lignin are 4-propenylguaiacol and 4-propylguaiacol. The content of 4-propenylguaiacol among the liquid products obtained using ethanol and formic acid as reducing agents can be as high as 36 and 33 rel %, respectively. The content of 4-propylguaiacol among the liquid products obtained using hydrogen grows to 33 rel % when a catalyst is used. This work describes the first study of the catalytic fractionation of larch wood in supercritical ethanol in the presence of the bifunctional 3%Ru/C catalyst containing acidic groups. The aim is to identify the effect of the catalyst and the nature of the hydrogen donor (ethanol, H2, or formic acid) on the yield and composition of the product. [ABSTRACT FROM AUTHOR]

Experiments and calculations are used to determine the optimum parameters of the peroxide delignification of larch wood in the presence of MnSO4 catalyst that provides high yields of cellulose (44.3 wt %) with low residual lignin contents at a temperature of 100°C, an H2O2 content of 6 wt %, a CH3COOH content of 25 wt %, a LWR of 15, and a duration of 3 h The cellulose obtained under optimum conditions has a chemical composition of cellulose, 92.7 wt %; lignin, 0.6 wt %; and hemicellulose, 5.7 wt %. IRS and X-ray diffraction are used to determine that cellulose obtained from larch wood has a structure similar to that of industrial microcrystalline cellulose. The proposed catalytic approach allows cellulose to be obtained from larch wood with a minimal lignin content under mild conditions in one step and with a high yield, a degree of crystallinity of 0.8, and a crystallite size of 3.0 nm. [ABSTRACT FROM AUTHOR]

Fretwork, as a decorating technique, can today be performed with modern means by laser or CNC routing, but the tool influence on the surface quality must be well understood for further optimization of the cutting parameters. The paper presents an experimental work for the determination of the influence of the cutting angle with respect to the grain on the surface quality of larch wood (Larix decidua Mill.) cut through by laser and CNC routing at different feed speeds. The research considered geometric fretwork patterns derived from triangle, where the cutting angles with respect to the wood grain were 0°, 15°, 30°, 45°, 60°, 75° and 90°. The feed speeds of the CNC routing were set for 2, 2.5, 3, 3.5 and 4 m/min. The surface quality was analyzed by a range of roughness, waviness and primary profile parameters combined with stereomicroscopic images. Although the principle of cutting and interaction with wood of the two processing tools, laser and CNC, is very different, the analysis with roughness parameters has revealed that the cutting angle with respect to the grain has an essential influence, whatever the cutting tool. The surface quality decreases with an increase in the feed speed of the CNC router and processing at 15° and 60° appears to be the worst option from all angle variants for both types of processing. Cutting by laser is melting wood in latewood areas resulting in a smoothing effect.

The bridge deck slab and the rectangular beam of the glued-wood beam bridge are connected by bolts and studs; thus, the joint surface is prone to slippage, and the beams and plates experience difficulty in bearing loadings together. This difficulty results in problems, such as stress concentration and screw corrosion and loosening, and weakens structural bearing capacity, stiffness, and integrity. In this study, an experimental model of glued timber T-section beams formed by gluing between bridge decks and rectangular beams and a calculation method for T-beam shear stress were proposed to improve the bearing capacity, stiffness, and integrity of the structure for ensuring that the bridge deck and the rectangular beam jointly bear stress. Three sets of beams, namely orthogonal T-beams, parallel T-beams, and rectangular beams were made using Larix gmelinii larch boards and structural glue to perform static bending bearing capacity test for examining the strain, deflection, and ultimate bearing capacity of the members and observe the destruction pattern. During the test, the bending shear strength was calculated following the principle of equivalent stiffness and the shear strength formula proposed by Rammer. Furthermore, a finite element model of glulam beams based on elastoplastic theory was established using structural analysis software. The displacement, strain, and failure mechanism of the members under the test loads were simulated and analysed using the model to verify the test results. Results demonstrate that, when the three types of beams are bent, they are sheared along the grain near the central axis of the section. The bonding surface between the wing plate and rib of the T-beam is undamaged, and the bonding is reliable with strong structural integrity. Compared with those of rectangular beams, the bearing capacity (limit load), bending stiffness, and ductility coefficient of the parallel T-beams are increased by 71%, 189%, and 23%, respectively. Compared with those of rectangular beams, the bearing capacity, bending stiffness, and ductility coefficient of the orthogonal T-beams are increased by 33%, 28%, and 25%, respectively. Compared with those of rectangular beams, the bearing capacity, bending stiffness, and ductility coefficient of the glulam T-beams are greatly improved. By considering the principle of equivalent stiffness and using the Rammer formula, the shear strength test values of orthogonal T-beams and rectangular beams of glulam deviate from the calculated values by 8.0% and -5.6%, respectively, which indicates good agreement. However, the shear strength test value of the parallel T-beams deviates from the calculated value by 19.2%, which indicates slightly lower calculation accuracy. The finite element analysis is consistent with the results of the experiment. This study provides certain references for the engineering design of glulam T-beams. [ABSTRACT FROM AUTHOR]

The effects of vacuum heat treatment were studied relative to the chemical composition of larch wood. The samples were heat-treated in vacuum at 160 °C, 200 °C, and 240 °C for 4 h, and the chemical changes were investigated by wet chemical analysis, elemental analysis, calorific value determination, and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The relative percentage contents of lignin and extractives increased after heat treatment. Additionally, the relative percentage contents of holocellulose, cellulose, and hemicelluloses decreased as a result of the thermo-vacuum treatment. Elemental analysis showed a slight reduction in the contents of hydrogen and oxygen. Vacuum heat treatment also increased the calorific value compared with untreated samples.

The objective of this study was to investigate the color and chemical changes of thermo-vacuum treated larch wood. Specimens were heat treated in a vacuum at various temperatures for 4 h. The color parameters of untreated and heat-treated samples were measured using the CIELab color system. Changes in the chemistry of larch wood were investigated using X-ray photoelectron spectroscopy (XPS), electron spin resonance (ESR) spectroscopy, and UV-Vis spectroscopy. The results showed that the color of larch wood became darker at higher treatment temperatures. The O/C ratio decreased with an increase in treatment temperature. The C1 peaks showed that there was an elevated content of lignin and extractives on the wood surface after heat treatment. There were more free radicals for thermally treated wood samples, as demonstrated by the increase in the intensities of the ESR signals. Some groups of lignin that contribute to the darkness of the wood increased after thermo-vacuum treatment. Changes in surface chemistry may be the cause of discolorations that occurred during thermo-vacuum treatment.

High-intensity microwave radiation was applied to treat and modify larch wood. Using scanning electron microscopy, changes in the microstructure of larch wood due to microwave irradiation were analyzed. After the microwave treatment, the microstructure of the larch wood was varied in its weakest section. The changes of the microstructure, in the pits of the tracheid wall, the plane of the tracheid wall, and the wood ray tissue of the radial section, were notable. The cracks were located among the latewood tracheid, and some of them were throughout the wood ray section, so wood rays were broken along the vertical cell arrangement. The results showed that high-intensity microwave treatment effectively penetrates the narrow channels of larch wood. [ABSTRACT FROM AUTHOR]

Understanding and mastering the color change of wood during heat treatment is essential in the wood working industry because it saves time and reduces energy costs. An artificial neural network (ANN) was employed in this study to establish the relationship between the process parameters of heat treatment and the color change of wood. Three important parameters: temperature (180 °C, 190 °C, 200 °C, 210 °C, and 220 °C), treatment time (2 h, 4 h, 6 h, and 8 h), and wood species (larch and poplar) were considered as inputs to the neural network. There were four neurons in the hidden layer that were used, and an output layer as wood color. According to the results, the mean absolute percentage errors were determined as 0.53%, 0.65%, and 0.31% in the prediction of color change color (ΔE) values for training, validation, and testing data sets, respectively. Determination coefficients (R2) greater than 0.99 were obtained for all data sets with the proposed ANN models. These results showed that ANN models can be used successfully for predicting the color changes in wood during heat treatment. [ABSTRACT FROM AUTHOR]

This paper studies the influence of ammonia gas on wood color changes in response to an increasing demand for dark colored wood specimens. The darker wood color in ammonia fuming is accomplished through chemical reactions between ammonia gas and wood compounds. We exposed oak, maple, spruce, and larch wood samples to ammonia gas for 16 days. During fuming, the color changes were studied using CIE L*a*b* parameters. After fuming, the changes in extractives content, tannin, and nitrogen content were analyzed. The chemical changes of wood and residues of wood extractives after fuming were analyzed by FTIR spectroscopy. Oak wood reacted intensively with ammonia gas in a very short time, and the darkening was prominent for all the investigated wood species. It was established that tannin had no major influence on color changes of maple and larch wood in the ammonia-fuming process. The FTIR spectra of fumed wood indicated involvement of carbonyl groups, and the FTIR spectra of wood extractives indicated involvement of carbonyl, aromatic, and alcohol groups in reaction with ammonia gas.

• The influence of age of larch wood on its strength was determined. • The influence of worm damage on the fatigue life of the wood was estimated. • A model for wood density equivalent fatigue life was developed. • The dynamic properties of larch wood are more affected by the aging process than the static properties. In many cultural heritage buildings, structural members are made of wood. Over the years, wood is exposed to various biotic and abiotic degradation factors, including moisture oscillations, mechanical stress, and insect and fungal decay. In the present respective study, an experimental study on the fatigue life of 350 years old larch wood was carried out. The fatigue life of the old wood was compared to the fatigue life of the recent larch wood. A statistical model for the fatigue-life curves and their scatter was built for both kinds of wood. The model can consider different factors to the fatigue life, e.g. wood density, specimen orientation during loading, and extent of insect damage. An equivalent number of load cycles to failure was also defined, enabling a direct comparison of the fatigue life data for specimens with different wood densities or orientations during loading. From the results, it can be concluded that the proposed statistical model adequately describes the fatigue behaviour of both the old, insect-damaged wood and the recent larch wood. [ABSTRACT FROM AUTHOR]

Larch wood is known to be a challenging substrate for waterborne coatings on windows or claddings in exterior applications. In earlier studies the surface properties of larch heartwood were characterised with low pH-values and high content of arabinogalactan. A systematic variation of formulations with different combinations of binders and thickening additives was investigated regarding the sensitivity of the coating materials to high acidity and arabinogalactan. Panels of spruce wood were treated with low-pH buffer solutions and arabinogalactan solutions and after drying the coating materials were applied by spraying. Acetic acid and arabinogalactan solutions were added stepwise to wet samples of coating materials while pH-values and viscosity were measured. Different buffer capacities, changes in viscosity and qualities of film formation were observed depending on coating formulation. The selection of binder and thickening additives enables the formulation of coating materials with lower sensitivity to specific surface properties of larch wood and thus higher quality. [ABSTRACT FROM AUTHOR]

Samples of arabinogalactan (AG) were isolated by aqueous extraction from wood of different larch species ( Larix sibirica Ledeb., Larix gmelinii (Rupr.) Rupr., Larix cajanderi Mayr., and Larix olgensis var. Koreana) and studied by HPLC, IR spectroscopy, and quantitative C NMR spectroscopy. The wood of the studied larch species was shown to contain significant amount of arabinogalactan (10-17% of the a.d.w. mass) and could be a source of its industrial production. The studied AG samples had similar structural and molecular-mass characteristics. This fact could facilitate the product standardization during its industrial production both from the wood of a single larch species and from mixed raw materials. [ABSTRACT FROM AUTHOR]

The optimum parameters for the process of extraction of the dihydroquercetin (DHQ) isomer with the greatest antioxidant activity were identified. Use of ethyl acetate as extractant in this process was found to have clear advantages over other industrial solvents. An optimum method of extracting DHQ from larch wood with a large enantiomer excess was proposed. The method was developed and the quantitative content of the (+)-2 R,3 R isomer of DHQ extracted from wood of Larix sibirica Ledeb. was assayed. [ABSTRACT FROM AUTHOR]

High-energy irradiation of a biogenic polymer is of interest from different perspectives, as this type of modification process may beneficially influence various functional and structural properties of wood. This study deals with the influence of electron beam irradiation (EBI) on the artificial weathering behavior of larch wood. The results of color measurement and infrared spectra show different effects of the EBI at dosages of 1 and 30 kGy during weathering tests. The results may provide a helpful basis for further fundamental research to improve weathering of wood by EBI. [ABSTRACT FROM AUTHOR]

Py-GC-MS was used to examine the components of vapor from rapid pyrolysis of larch wood and its model components, i.e. example cellulose, xylan, and lignin, and their mixture in accordance with the proportion of the components in larch wood. In this study, a total of 97 compounds in 12 categories were identified in the pyrolysis vapor and were compared. It was found that the most abundant chemical species in these five types of pyrolysis vapor were different. Saccharides and ketones were the major compounds in the pyrolysis vapor from microcrystalline cellulose and xylan, respectively, whereas the most abundant compounds in the pyrolysis vapor from alkaline lignin were sulfur compounds and phenols. Saccharides and ketones were major components of the pyrolysis vapor from MMC, whereas the main compounds in the pyrolysis vapor from larch wood were ketones, phenols, aldehydes, and saccharides. The different composition of the pyrolysis vapor from larch wood and its model mixture was explained on the basis of their different structural frameworks and the non-structural components of larch wood. It was also concluded that the presence of non-structural components, including extractives and ash, affect the pyrolysis reaction of larch wood. Nevertheless, the detailed patterns of this process must be further studied. [ABSTRACT FROM AUTHOR]

This paper studies the influence of ammonia gas on wood color changes in response to an increasing demand for dark colored wood specimens. The darker wood color in ammonia fuming is accomplished through chemical reactions between ammonia gas and wood compounds. We exposed oak, maple, spruce, and larch wood samples to ammonia gas for 16 days. During fuming, the color changes were studied using CIE L*a*b* parameters. After fuming, the changes in extractives content, tannin, and nitrogen content were analyzed. The chemical changes of wood and residues of wood extractives after fuming were analyzed by FTIR spectroscopy. Oak wood reacted intensively with ammonia gas in a very short time, and the darkening was prominent for all the investigated wood species. It was established that tannin had no major influence on color changes of maple and larch wood in the ammonia-fuming process. The FTIR spectra of fumed wood indicated involvement of carbonyl groups, and the FTIR spectra of wood extractives indicated involvement of carbonyl, aromatic, and alcohol groups in reaction with ammonia gas. [ABSTRACT FROM AUTHOR]

type II arabinogalactan-degrading enzyme, termed Exo-1,3-Gal, was purified to homogeneity from the culture filtrate of Sphingomonas sp. 24T. It has an apparent molecular mass of 48 kDa by SDS-PAGE. Exo-1,3-Gal was stable from pH 3 to 10 and at temperatures up to 40 °C. The optimum pH and temperature for enzyme activity were pH 6 to 7 and 50 °C, respectively. Galactose was released from β-1,3- d-galactan and β-1,3- d-galactooligosaccharides by the action of Exo-1,3-Gal, indicating that the enzyme was an exo-β-1,3- d-galactanase. Analysis of the reaction products of β-1,3-galactotriose by high-performance anion-exchange chromatography revealed that the enzyme hydrolyzed the substrate in a non-processive mode. Exo-1,3-Gal bypassed the branching points of β-1,3-galactan backbones in larch wood arabinogalactan (LWAG) to produce mainly galactose, β-1,6-galactobiose, and unidentified oligosaccharides 1 and 2 with the molar ratios of 7:19:62:12. Oligosaccharides 1 and 2 were enzymatically determined to be β-1,6-galactotriose and β-1,6-galactotriose substituted with a single arabinofuranose residue, respectively. The ratio of side chains enzymatically released from LWAG was in good agreement with the postulated structure of the polysaccharide previously determined by chemical methods. [ABSTRACT FROM AUTHOR]

The larch wood was treated by microwave irradiation under different radiant intensity and treating duration. The microwave-treated wood specimens together with the un-treated for comparison were impregnated by water in pressure vessel and then tested for permeability, mechanical properties and microstructure change by SEM to study the modification performance of microwave treatment on larch wood. The results showed that under suitable conditions of microwave treatment the permeability of larch wood was improved without noticeable decreasing of the modulus of rupture (MOR) and the modulus of elasticity (MOE). The radical parenchyma and some pit membrane were ruptured, and tiny cracks were formed in the cell walls. The formation of tiny cracks in the cell walls serves as man-made channels of gas and liquid and this contribute to improve the permeability of the wood. [ABSTRACT FROM AUTHOR]

Arctic driftwood has reached the coast of Iceland for centuries. This material was used by the inhabitants of the island as a building material for houses, boats, churches and pasture fences. Nowadays, the driftwood is used in the furniture industry, for the finishing of internal and external walls of buildings and also by artists. The properties of driftwood differ to that of original resource due the long-term effects of exposure to Arctic Sea water and ice. This process can be considered as a natural modification, even if its effect on various wood properties and the potential use of driftwood are not yet fully understand. This research is focused on the comparison of cutting forces measured for Siberian larch (Larix sibirica L.) from Siberia provenance and driftwood found on the coast of Iceland. The cutting forces were determined directly from the cutting power signal that was recorded during the frame sawing process. A new procedure for compensation of the late/early wood ratio variation within annual rings is proposed to homogenize mechanical properties of wood. It allows a direct comparison of machinability for both types of larch wood investigated (driftwood and natural). Noticeable differences of normalized cutting force values were noticed for both wood types, which were statistically significant for two set values of feed per tooth. These results provide a new understanding of the effect of the drifting process in the Arctic Sea (natural modification) on mechanical and physical properties of wood. Such a natural modification may influence transformation processes of driftwood as well as performance of the coating systems applied on its surface. [ABSTRACT FROM AUTHOR]

Reducing discoloration of wood due to photodegradation caused by ultraviolet (UV) and visible (VIS) radiation enhances its aesthetical value and prolongs the overall service life of protective coatings. In this study, the efficiency of pretreatments with different active ingredients to reduce degradation and stabilize the color of Siberian (Larix sibirica Ledeb.) and European larch (Larix decidua Mill) wood was investigated. UV absorbers (UVA), hindered amine light stabilizers (HALS) and zinc oxide nanoparticles were used in twenty different pretreatments. The ability to protect wood surface against radiation was evaluated via color and gloss change measurements during artificial ageing. The efficiency of tested color-stabilizing pretreatments differed for Siberian and European larch and not all of them reduced discoloration. The most effective pretreatments were based on a combination of UVA and HALS in a synergistic effect. Overall, the best efficiency from tested variants for larch wood generally was observed for combination of Eversorb 80 on benzotriazole basis + Eversorb 93 on a piperidinyl basis. The pretreatments did not significantly affect the gloss values. The results revealed convenient variants of stabilizers for Siberian and European larch wood and confirmed different compatibility between specific wood species and color stabilizers. [ABSTRACT FROM AUTHOR]

This paper compares the resistance of 20 commercial transparent and semi-transparent coatings applied to European and Siberian larch during artificial weathering in Xenotest. The change in gloss, colour, contact angle of wetting, resistance to Aspergillus niger and Penicillium brevicompactum moulds was evaluated, and visual changes at the top surface of treated wood species were measured. Overall, the durability of coatings on European larch was higher than that on Siberian larch. The most durable of the tested coatings was a thin-film, i.e., semi-transparent oil-based film containing TiO2 pigment and propiconazole fungicide. Of the transparent coatings, the most stable was a thick acrylic coating. Conversely, penetrating transparent oil systems had low colour stability and overall lifespan. Artificial weathering of all of the coatings resulted in a marked decrease in their resistance to moulds. [ABSTRACT FROM AUTHOR]