Untreated Wood Research Articles

Synergistic improvement to dimensional stability of Populus cathay ana via hemicellulose removal/alkali lignin impregnation

Abstract Poor dimensional stability restricts the commercial utilization of fast-growing wood. In this study, fast-growing poplar (Populus cathayana) was treated by removing hemicellulose with hydrothermal treatment and impregnating alkali lignin via full-cell process, synergistically, for enhanced dimensional stability. After modification, hydroxyl groups were reduced in hemicellulose removed wood (DHC), alkali lignin was observed to fill in the cell lumens of vessels and wood fibers in the impregnated wood (AL) and in the wood modified by hemicellulose removal with alkali lignin impregnation (DHCAL). Compared with untreated wood, the volumetric swelling ratio of DHC and AL decreased by 11 % and 21 % under relative humidity (RH) of 89 %, respectively. The volumetric swelling ratio of DHCAL decreased by over 50 %, indicating a positive synergistic effect. The combination of hemicellulose removal and alkali lignin impregnation treatment improved the dimensional stability of wood significantly by reconstructing wood chemical components with various levels of hygroscopicity. This work could meaningfully contribute to the efficient utilization of fast-growing wood and promote the added value of industrial alkali lignin.

Susceptibility of surface-modified superhydrophobic wood and acetylated wood to mold and blue stain fungi

The susceptibility of surface-modified wood, surface-modified acetylated wood and acetylated wood to mold and blue stain fungi was investigated. The surface modifications were based on fluorinated and non-fluorinated silicone nanofilaments for increased hydrophobicity. Results showed an increased mold resistance of the surface-modified superhydrophobic wood with mold appearing later or with less intensity on the modified surfaces than on the untreated wood in accelerated mold chamber tests due to the increased water resistance of the samples. All acetylated wood samples exhibited good mold resistance as the available water in acetylated wood was reduced. The surface modifications on acetylated wood had a slightly negative effect on mold resistance due to side effects from the modification. The surface-modified wood showed high blue stain fungi coverage, whereas almost no blue stain fungi were observed on the acetylated wood and surface-modified acetylated wood. The surface-modified superhydrophobic wood showed high mold coverage after conditioning in a high-humidity environment or after exposure to UV irradiation. Meanwhile, the acetylated wood and surface-modified superhydrophobic acetylated wood showed a small amount of mold coverage in these conditions.

Moisture performance of various wooden shingles designs tested on the Golobar cable yarding

ABSTRACT Wood is a traditional roofing material in Europe and other parts of the world. In the seventeenth century, wooden roofing was generally used on more important buildings, but today it is mainly used on huts and houses in the Alpine regions. As wooden roofing is expensive, we investigated the possibility of extending the service life of the roofing through material selection and details. The roof of the Golobar cable yarding was covered with shingles made of spruce (Picea abies) and larch (Larix decidua). Part of the spruce roofing was thermally modified and/or treated with a water-wax emulsion. On the underside, we cut grooves in selected roof shingles to increase the specific surface of the wood and to accelerate drying after rainfall. In addition, wood moisture monitoring sensors were installed on the roof shingles. Based on three years of the wood moisture content measurements, it can be concluded that among shingles made of untreated spruce wood, the highest moisture content was recorded for shingles with a rectangular cross-section without additional grooves. The additional grooves positively affected the moisture performance of wood. Treating the wood with Silvacera wax had an even more pronounced effect on the moisture content of the shingles than the grooves.

Evaluation of Untreated and Surface-Treated Wooden Facades of Buildings in Sweden

In this research, untreated and surface-treated wooden facades of buildings are investigated and compared with regard to durability, environmental impact, and cost using the document and literature studies supplemented with quantitative data. The investigation is based on the influence on the wood by external factors, either in its natural form or with a protective layer of a surface treatment. It is resulted from the study that from a durability viewpoint, it is not always advantageous to paint a wooden facade. Yakisugi, a thermal modification for wooden facades that involves burning the wood to create a protective surface layer, has shown better properties, which, in combination with a lower need for maintenance, can be considered the leading treatment for facades. From an environmental perspective, Yakisugi, like untreated wood, has demonstrated advantages compared with conventional paints. Paints often come with maintenance requirements that should be carried out correctly to avoid extensive costs. Cost is an important factor that can be decisive when users choose a surface treatment. What determines the cost is the relationship between durability and maintenance intervals. The need for the maintenance of paints leads to large financial costs during the working life of a wooden facade, which differs from Yakisugi or an untreated wooden facade that can be considered maintenance-free. In order to meet the growing environmental demands from a national level to a global scale, unconventional surface treatments for wooden facades should be promoted in the future.

Surface Treatment of Mongolian Scots Pine Using Phosphate Precipitation for Better Performance of Compressive Strength and Fire Resistance

Wood, as a naturally green and environmentally friendly material, has been widely used in the construction and decoration industries. However, the flammability of wood poses serious safety problems. To improve the fire resistance of wood, In this study, it is proposed to use calcium chloride (CaCl2) and disodium hydrogen phosphate (Na2HPO4, DSP) to impregnate wood for multiple cycles. The experimental results show that phosphate mineral precipitation can be deposited on the surface of the wood. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are used to analyze the micromorphology of mineral precipitation and use the MIP test to analyze the treated wood pore structure. The results show that with the increase in the number of cycles, the phosphate deposited on the surface of the wood increases, and the cumulative pore volume and water absorption rate of the wood after 10 cycles are 54.3% and 13.75% lower than that of untreated wood respectively. In addition, the cone calorimeter (CONE) confirmed that the total heat release (THR) and total smoke production (TSP) of wood treated in 10 cycles have decreased by 48.7% and 54.2% respectively compared with the untreated wood. Hence, this treatment method not only improves the mechanical properties of wood. It also improves fire resistance.

Oxidative Conversion of Chars Generated from the Fixed-Bed Pyrolysis of Wood Torrefied at Different Temperatures and Holding Times

Fixed-bed pyrolysis of torrefied spruce wood, for a heating temperature of 800 K, results in char yields between about 27–57 wt% (versus 23 wt% for untreated wood), depending on both pre-treatment temperatures (533–583 K) and holding times (8–25 min). In this study char oxidation behavior and kinetics are investigated by means of thermogravimetric analysis. The differential thermogravimetric curves always showed a low-temperature zone of slow rates (oxidative devolatilization), followed by a high-rate zone with a well-defined peak (oxidation). As the torrefaction severity increases, the temperature range of the oxidative devolatilization enlarges. Moreover, the oxidation rates become slower (both burning and burnout temperatures tend to increase). As already found for untreated wood chars, the two stages are well described by a linear and a power-law rate reaction, respectively. Volatiles released from the devolatilizations are approximately around 20 wt%, but torrefaction causes lower activation energies (66–92 kJ/mol versus 117 kJ/mol). The oxidation activation energies also decreas (170–168 kJ/mol versus 193 kJ/mol), accompanied by small variations in the reaction order.

Impregnation of Norway spruce with low melting-point binary fatty acid as a phase-change material

Norway spruce was impregnated with a eutectic mixture of capric acid and stearic acid. The binary fatty acid was used as a bio-based phase-change material (PCM) for further applications with wood as a latent heat-storage material in building components. For this purpose, different concentrations of impregnation were evaluated. The weight-percentage gain of 124% was the highest for the pure fatty acid mixture, and the PCM-impregnated wood increased density from 470 kg/m³ (untreated wood) to 1045 kg/m³. Compressive strength and hardness were significantly elevated with higher content of fatty acids in the wood. Microscopy analysis confirmed the presence of the PCM within the wood cells. The treated wood also exhibited a larger time delay during heating and cooling due to the temperature shift in the phase transition. Depending on the concentration of the fatty acid in the wood, the latent heat during melting ranged from 50 to 125 J/g in the temperature from about 24°C to 30°C. These results suggest that the use of the capric acid and stearic acid mixture has a great potential to increase the heat-storage capacity of wood and reduce energy consumption for heating and cooling indoor spaces.

Determining patterns in the formation of a polymer shell by powder paint on wood surface

An issue related to using wood and wood products for building structures is to ensure their stability and durability during operation within wide limits. Therefore, the object of this study was a change in the properties of the polymer shell of powder paint on wood during thermal modification. It is proved that in the process of thermal modification of wood, its structure changes, and accordingly, during the polymerization of powder paint, degassing occurs, which affects the polymer shell. Namely, during the thermal polymerization of powder paint at a temperature of 180 °C for untreated wood, shallow bubbles and craters are characteristic of the formed polymer shell. Instead, a smooth surface is marked for a sample of thermally modified wood. Thermogravimetric analysis data show thermogravimetric curves characterized by the loss of mass of the sample of the original wood with increasing temperature due to the processes of dehydration, destruction of hemicellulose and lignin. This is dehydration, accompanied by the destruction of the pyranose cycle, and carbonization to form a carbon residue and a complex mixture of volatile products. Due to this, bubbles and craters are formed in the polymer shell of the coating. Based on the obtained results of adhesion of the polymer shell on wood, which is treated with a mixture of epoxy polyester system with functional additives and a polymerization temperature of 180 °C, the adhesion level is 2.1 MPa. Reducing the polymerization temperature of a mixture of the epoxy polyester system with functional additives to 130 °C increases adhesion by 1.75 times, and the nature of the destruction passes through the polymer shell. For thermally modified wood, the level of adhesion is within 2.1 MPa, and the destruction takes place through the wood. This is due to the increased fragility of the surface after thermal modification of wood

Delignified porous wood as biofilm support for 1,4-dioxane-degrading bacterial consortium

ABSTRACT Delignified porous wood samples were used as carriers for biofilm formation of a bacterial consortium with the ability to degrade 1,4-dioxane (DX). The delignification treatment of the natural wood resulted in higher porosity, formation of macropores, increase in surface roughness and hydrophilicity of the treated wood pieces. These superior properties of two types of treated carriers (respectively, A and B) compared to the untreated wood resulted in 2.19 ± 0.52- and 2.66 ± 0.23-fold higher growth of biofilm. Moreover, analysis of the fatty acid profiles indicated an increase in proportion of the saturated fatty acids during the biofilm formation, characterising an enhancement in rigidity and hydrophobicity of the biofilms. DX initial concentration of 100 mg/L was completely degraded (detection limit 0.01 mg/L) in 24 and 32 h using the treated A and B woods, while only 25.84 ± 5.95% was removed after 32 h using the untreated wood. However, fitting the DX biodegradation data to the Monod model showed a lower maximum specific growth rate for biofilm (0.0276 ± 0.0018 1/h) versus planktonic (0.0382 ± 0.0024 1/h), because of gradual accumulation of inactive cells in the biofilm. Findings of this study can contribute to the knowledge of biofilm formation regarding the physical/chemical properties of biofilm carriers and be helpful to the ongoing research on bioremediation of DX.

Evaluation of the potentials of Jatropha curcas seed oil and in combination with leaf extracts of Cymbopogon citratus, Ocimum basilicum, and Eucalyptus globulus as wood preservatives against Macrotermes bellicosus termites

The preservation of non-durable woods such as Ayous through the use of environment friendly products is nowadays a major concern to many tropical wood researchers. The objective of this work was to assess the potentials of Jatropha curcas oil (JCO) alone and in combination with Cymbopogon citratus (JCO + CC), Ocimim basilicum (JCO + OB), and Eucalyptus globulus (JCO + EG) leaves extracts at different concentrations (1, 2, 4, 8, and 16 mg) as wood preservatives of Ayous (Triplochiton scleroxylon) against Macrotermes bellicosus termites. The extracts were tested for their toxicity and repellency on termites. Subsequently, treated and untreated wood was exposed to termites for four weeks. Termite response to treatùents varied with plant species, concentration, and exposure time. Ocimum basilicum extracts combined with J. curcas oil appeared to be the most effective against termites at 16 mg/l for in-vitro tests. It was also shown that the tested treatments were repellent to termites and therefore their mortality could not result from inhalation. J. curcas oil significantly improved the persistence of the treatments. Finally, a combined treatment of J. curcas oil and methanolic extracts of O. basilicum yielded the best protection of Ayous to termite attack, as shown by an average mass loss of 2%. Further research is needed to improve the longevity of the treatments on wood over time.

Analysis of the phase-dependent fluorescence decay time of treated wood using FD-FLIM

Abstract For sustainable handling of wood and high material utilization, post-consumer wood has to be sorted by post-consumer wood categories in Germany. The non-destructive FD-FLIM method could improve the wood recycling process by automatic classification of waste wood into post-consumer wood classes. Thus, the phase-dependent fluorescence decay time of treated wood is analysed in this study to obtain the impact of the treatment on the fluorescence decay time. It is shown that treated and untreated wood can be differentiated using the fluorescence decay time, although the state-of-the-art theoretical fluorescence decay time differs from the experimentally determined fluorescence decay time.

Improved dimensional stability and mechanical properties of rubberwood via modification with maleated lignin and densification

Abstract Rubberwood was modified using a two-step process involving impregnation with maleated lignin (ML) followed by densification. The effects of ML modification and densification on the physical and mechanical properties of modified wood were studied. The successful preparation of ML was confirmed using Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. In addition, scanning electron microscopy was used to characterize the densified rubberwood structure, which featured fully compressed cell walls and cell lumina filled with ML. The rubberwood modification resulted in a more uniform structure and increased density compared to untreated wood. Further, water immersion and moisture absorption experiments revealed thickness swelling of only 27.7% and 20.9%, a reduction of nearly 76% and 55%, respectively, compared to the densified wood that was only impregnated with water. The ML modification can alleviate the embrittlement of wood caused by densification. The modulus of rupture and modulus of elasticity of ML-treated and densified wood improved by nearly 54% and 200%, respectively, compared to untreated wood. Therefore, the synergistic treatment strategy can contribute to the high-value utilization of low-quality rubberwood.

Effects of NaOH/H2O2/Na2SiO3 Bleaching Pretreatment Method on Wood Dyeing Properties

Bleaching is a common modification method widely used in the industrialization of wood dyeing. Bleaching can regulate the color of the wood, and it also has great effects on the subsequent wood dyeing properties. In this work, three woods, Ayous, Linden, and Poplar, were processed by using the NaOH/H2O2/Na2SiO3 bleach pretreatment method. Then, the pretreated wood and untreated wood were stained separately by means of water bath dyeing with three dyestuffs: blue anthraquinone and red and yellow double-azo dyestuffs. The study mainly focused on the effect of the bleach pretreatment on the color control and dyeing properties of the wood by analyzing the color difference, staining rate, and final dyeing rate of the dyed wood. The results were as follows: For the color difference, the L* and h* values showed increasing tends, while the a*, b*, and c* values showed decreasing trends. For the staining rate, Ayous reached an equilibrium staining rate at 3~4 h, but for the others, this was not obvious. For the dyeing rate, red and blue Linden veneers and blue Ayous veneers were similar to the unbleached ones, while the final dyeing rate of the other veneers was less than that of the original wood, and the staining rate of the Ayous red and yellow veneer, Linden yellow veneer, and Poplar veneer was less than that of the original wood. The final dyeing rate of the Ayous red and yellow veneers, Linden yellow veneer, and Poplar red, yellow and blue veneers decreased by 4.54%, 2.91%, 5.45%, 10.75%, 2.66%, and 9.55%, respectively. In general, the bleach pretreatment made the staining color of the material surface uniform. The dyeing rate increased due to the increase of the veneers’ permeability. Thus, the veneers quickly reached the equilibrium staining rate, but the equilibrium staining rate of some test pieces decreased. This work provides scientific support for the dyeing process.

Effect of Wood Dust Fibre Treatments Reinforcement on the Properties of Recycled Polypropylene Composite (r-WoPPC) Filament for Fused Deposition Modelling (FDM).

The efficacy of wood dust fibre treatment on the property of wood dust reinforced recycled polypropylene composite (r-WoPPC) filament was investigated. The wood dust fibre was treated using alkali, silane, and NaOH-silane. The treated wood fibre was incorporated with r-PP using a twin-screw extruder to produce filament. The silane treatment on wood dust fibre enhances interfacial bonding between wood fibre and recycled PP; hence, a filament has the highest wire pull strength, which is 35.2% higher compared to untreated and alkaline-treated wood dust filament. It is because silanol in silane forms a siloxane bond that acts as a coupling agent that improves interfacial bonding between wood dust fibre and recycled PP. The SEM micrograph of the fracture structure reveals that treated silane has strong interfacial bonding between wood dust fibre and recycled PP, having minimal void, gap, and good fibre adhesion. The water absorption test results indicate that filament with treated wood dust absorbs less water than filament with untreated wood because the treatment minimizes the gap between wood fibres and recycled PP. The FTIR analysis identified the presence of silane on the wood dust surface for silane-treated wood dust. The DSC studies suggest that the temperature range 167-170 °C be used in the extrusion machine to produce r-WoPPC filament. As a result, r-WoPPc filaments containing silane-treated wood dust have better mechanical properties and have a greater potential for usage in FDM applications.

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

«Птицы и ЛЭП» в России: наследие СССР, современные достижения и вопросы

Evaluation of Water Transfer Capacity of Poplar with Pectinase Treated under the Solar Interface Evaporation

Poplar wood, which was used as the absorption material for the solar-driven interfacial evaporation, was treated for 3 days, 6 days and 9 days with the pectinase, and then was simulated for photothermal evaporation test at one standard solar radiation intensity (1 kW⋅m−2). The effects of pectinase treatment on cell passage and water migration capacity of poplars were analyzed by the mercury intrusion porosimetry, the scanning electron microscope and fractal theory. It was found that the pit membrane and the ray parenchyma cells of poplar wood were degraded and destroyed after pectinase treatment. Compared with the untreated poplar wood, the evaporation rate of three sections of the specimen was changed. Especially the evaporation rate of radial and tangential direction was significantly increased. At the same time, based on the experimental data and fractal dimension deduction, fractal characteristics could be found in that the structure of poplars treated with pectinase. The porosity decreased with the increase of the fractal dimension in a certain range. It was shown that it is feasible to evaluate solar-driven water migration capacity by using fractal theory.

Durability and wettability of varnishes on the modified and aged surfaces of short rotation teak wood

PurposeThe surface characteristics of thermally and chemically modified wood, such as surface roughness, surface free energy (SFE) and wettability, are important properties that influence further manufacturing processes such as gluing and coating. The aim of this paper was to determine the influence of the surface roughness of thermally and chemically modified teak wood on their SFE, wettability and bonding quality for water-based acrylic and solvent-based alkyd varnishes. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated to give a valuable information for their further application.Design/methodology/approachThe woods tested in this study were fast-growing teak woods that were prepared in untreated and treated with furfuryl alcohol (FA), glycerol maleic anhydride (GMA) and thermal. SFE values were calculated using the Rabel method. The wettability values were measured based on the contact angle between varnish liquids and wood surfaces using the sessile drop method, and the Shi and Gardner model model was used to evaluate the wettability of the varnishes on the wood surface. The bonding quality of the varnishes was measured using a cross-cut test based on ASTM 3359-17 standard. In addition, durability against subterranean termites in the field of these modified teak woods was also investigated according to ASTM D 1758-06.FindingsThe results showed that furfurylated and GMA-thermal 220°C improved the durability of teak wood against termites. The furfurylated teak wood had the roughest surface with an arithmetic average roughness (Ra) value of 15.65 µm before aging and 27.11 µm after aging. The GMA-thermal 220°C treated teak wood was the smoothest surface with Ra value of 6.44 µm before aging and 13.75 µm after aging. Untreated teak wood had the highest SFE value of 46.90 and 57.37 mJ/m2 before and after aging, respectively. The K values of untreated and treated teak wood increased owing to the aging treatment. The K values for the water-based acrylic varnish were lower than that of the solvent-based alkyd varnish. The untreated teak wood with the highest SFE produced the highest bonding quality (grades 4–5) for both acrylic and alkyd varnishes. The solvent-based alkyd varnish was more wettable and generated better bonding quality than the water-based acrylic varnish.Originality/valueThe originality of this research work is that it provides evaluation values of the durability and SFE. The SFE value can be used to quantitatively determine the wettability of paint liquids on the surface of wood and its varnish bonding quality.

The Effect of Surface Treatment on the Antibacterial Properties of Wood and the Possibility to Detect the Antibacteriality with Fluorescence Method

Wood is a widely used indoor material, and thus it is important to consider wood performance in microbial cross contamination via surfaces. In this study, both untreated and surface- treated wood materials were studied by simulating airborne bacterial contamination and evaluating the number of bacterial colonies on the material surfaces. The materials studied were untreated pine heartwood and sapwood, spruce, silver birch, and glass as a reference. The intensity of UV-excited fluorescence was measured to find the most antibacterial Scots pine heartwood. The coatings used were varnish and wax for Scots pine sapwood. The surface roughness of all material types was compared, and it was found to be uniform. All untreated wood surfaces had less viable bacterial colonies at all time points compared to the glass reference, and the surface treated samples did not differ from the glass reference indicating that the antibacterial properties of wood were blocked by both varnish and wax. The fluorescence method was practical to use, but wider testing will be needed to validate it more thoroughly. The results indicate also that silver birch has similar antibacterial properties as pine and spruce and hence should be studied further.

Alumina as an Antifungal Agent for Pinus elliottii Wood.

This work deals with the durability of a Pinus elliotti wood impregnated with alumina (Al2O3) particles. The samples were impregnated at three different Al2O3 weight fractions (c.a. 0.1%, 0.3% and 0.5%) and were then exposed to two wood-rot fungi, namely white-rot fungus (Trametes versicolor) and brown-rot fungus (Gloeophyllum trabeum). Thermal and chemical characteristics were evaluated by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric (TG) analyses. The wood which incorporated 0.3 wt% of Al2O3 presented a weight loss 91.5% smaller than the untreated wood after being exposed to the white-rot fungus. On the other hand, the highest effectiveness against the brown-rot fungus was reached by the wood treated with 5 wt% of Al2O3, which presented a mass loss 91.6% smaller than that of the untreated pine wood. The Al2O3-treated woods presented higher antifungal resistances than the untreated ones in a way that: the higher the Al2O3 content, the higher the thermal stability. In general, the impregnation of the Al2O3 particles seems to be a promising treatment for wood protection against both studied wood-rot fungi. Additionally, both FT-IR and TG results were valuable tools to ascertain chemical changes ascribed to fungal decay.

Degradation of Chemical Components of Thermally Modified Robinia pseudoacacia L. Wood and Its Effect on the Change in Mechanical Properties

Currently, emphasis is placed on using environmentally friendly materials both from a structural point of view and the application of protective means. For this reason, it is advisable to deal with the thermal modification of wood, which does not require the application of protective substances, to increase its service life. The main reason for the thermal modification of black locust is that although black locust grows abundantly in our country, it has no industrial use. It is mainly used outdoors, where thermal modification could increase its resistance. This article deals with the thermal modification of black locust wood (Robinia pseudoacacia L.) and the impact of this modification on the chemical components of the wood with an overlap in the change in mechanical properties compared to untreated wood. Static (LOP, MOR, and MOE) and dynamic (IBS) bending properties were evaluated as representative mechanical properties. At the same time, the impact of thermal modification on the representation of chemical components of wood (cellulose, lignin, hemicellulose) was also tested. As a result of the heat treatment, the mechanical properties gradually decreased as the temperature increased. The highest decrease in mechanical values found at 210 °C was 43.7% for LOP and 45.1% for MOR. Thermal modification caused a decrease in the content of wood polysaccharides (the decrease in hemicelluloses content was 33.2% and the drop in cellulose was about 29.9% in samples treated at 210 °C), but the relative amount of lignin in the wood subjected to increased temperature was higher due to autocondensation, and mainly because of polysaccharide loss. Based on the correlations between chemical and mechanical changes caused by thermal modification, it is possible to observe the effects of reducing the proportions of chemical components and changes in their characteristic properties (DP, TCI) on the reduction in mechanical properties. The results of this research serve to better understand the behavior of black locust wood during thermal modification, which can primarily be used to increase its application use.