Articles

WOOD RESEARCH Volume 68, Number 4, 2023
Xiaoyan Zhang, Lanxing Du, and Sijin Li

Stepwise Extraction of Hemicelluloses with Water and Alkali from Larch Wood and their Sugar Compositions

The aim of the present study was to isolate hemicelluloses by stepwise extraction with water and alkali from larch (Larix principis-rupprechtii Mayr) sapwood and heartwood. One water-soluble arabinogalactan (AG) and three alkali-soluble hemicelluloses- arabinoglucuronoxylan (AGX), galactoglucomannan (GGM) and glucomannan (GM) were obtained. The yield of AG extracted with hot-water from larch heartwood was 7.57%, it was 17.96% in total of three alkali-extracted hemicelluloses. There was no significant difference in the yield of hemicelluloses from sapwood and heartwood. Monosaccharide compositions of the hemicelluloses were determined by high performance liquid chromatography after acid hydrolysis. The results showed that galactose and mannose were the main glycosyl units of hemicellulose, followed by xylose. Galactose mainly derived from AG, whereas mannose and xylose originated from alkali-extracted hemicelluloses.

WOOD RESEARCH Volume 68, Number 4, 2023
Ceyhun Kiliç, Sibel Yildiz, Ayşenur Gürgen, and Derya Ustaömer

Effects of Different Climate Types on Color Change of Wood Material used Outdoor

Field tests are important for evaluating how wood performs in real-world conditions and making informed choices for material selection. These tests help assess wood’s durability, strength, decay processes, and resistance against harmful organisms. Furthermore, it helps users make more informed decisions about the color of wood and understand the importance of color changes depending on the place and time of use. Because weather conditions are a significant factor that influences the color of wood. Wood that is exposed to prolonged sunlight, moisture, and rain may experience fading, darkening, or staining in its color. In this study, heartwood, sapwood, and CCB impregnated sapwood samples of Scotch pine, spruce, beech and alder were exposed to the soil contact (hazard class 4) according to EN 252 for 3 years in Trabzon, Muğla, Çanakkale, and Elazığ provinces of Turkey with completely different climatic conditions from each other. Color parameters and color change values were evaluated using L*, a*, b* and ΔE* of the samples collected from test sites. The most significant color change was observed at Scotch pine in Çanakkale province. Greater color changes were observed in the heartwood of coniferous species. Impregnated samples showed the least color change.

WOOD RESEARCH Volume 68, Number 4, 2023
Pedro Gutemberg de Alcântara Segundinho and Antonio Alves Dias

Analysis of Finger-Joints in Glass Fiber-Reinforced Polymer (GFRP) Composite Glued Laminated Timber Beams

The objective of this paper was to evaluate the effect of finger-joint reinforcement on the bending strength and stiffness of glulam beams made from high-density Eucalyptus spp. glued with resorcinol-formaldehyde adhesive. Six glulam beams were tested: three reinforced with glass fiber-reinforced polymer (GFRP) and three unreinforced for comparison. The GFRP was placed between the last two laminates and at the bottom edge of the glulam only in the finger-joint position. The stiffness and strength of glulam beams were evaluated using static bending tests, which showed that the use of GFRP reinforcement resulted in a gain of more than 100% in average ultimate bending moment and about 10% in average bending stiffness. To calculate the theoretical bending stiffness and normal stresses, a theoretical analysis of beam bending was performed using the transformed section method, which showed agreement with the experimental results.

WOOD RESEARCH Volume 68, Number 4, 2023
Zhitao Lei, Jie Liu, Zhiyuan Zhang, Xuesong Zhao, and Qi Li

Study on preparation and properties of Anti-Ultraviolet Aging Wood-Plastic Composites

The degradable wood-plastic composites (WPC) were prepared by compression molding in this study. Polylactic acid (PLA), poly (butylene adipate-co-terephthalate) (PBAT) and salix powder were used as the main raw materials and nano-titanium dioxide (nano-TiO2) was used as anti-ultraviolet filler. The results show that when the addition amount of nano-TIO2 was 2%, the static bending strength and elastic modulus of WPC reach 41.88 MPa and 3730 MPa, respectively, which can meet the commercial application of WPC in building formwork. At this time, the composite material has a better effect of absorbing and reflecting ultraviolet light. The static bending strength, elastic modulus, tensile strength and impact strength of WPC were reduced by 68.3%, 61.5%, 51.9% and 57.4%, respectively. The mass loss rate and water absorption were 6.1% and 22.6%, respectively, that shows its good degradation performance. This study provides a low-cost and simple method for the design of anti-UV aging, high-performance and degradable WPC, which has broad application prospects in packaging, construction and other fields.

WOOD RESEARCH Volume 68, Number 4, 2023
Tania Méndez-Pérez, Ma. del Carmen Chávez-Parga, Jared Maya-Alavez, Crisanto Velázquez-Becerra, Jaime Espino-Valencia, José Apolinar-Cortés, and Mauro M. Martínez-Pacheco

Stain Fungi Control in Pinus sp. Wood with Silica mesoporous Particles Loaded with Essential Oils

The use of essential oils (EO) carried onto mesoporous silica particles (MSPs) was tested to control pinewood stains. Three types of MSPs were synthesized and physicochemically characterized with N2 physisorption (type IV), X-ray diffraction [Miller indices (100), (110), (200)], scanning electron microscopy, zeta potential (negative values), dynamic light scattering (< 200 nm) and thermogravimetric analysis (5% to 10% weight loss). A response surface design was used to find the EO loading conditions to control stain, the latter was measured as colour change with the CIEDE2000 formula. The essential oil loading onto MSPC was physicochemically confirmed by a weight loss of 47% in the thermogravimetric analysis. The Citrus, Syzygium sp. and Tagetes sp. oils carried onto mesoporous particles MSPC (30:1 w/w) controlled the pinewood stain caused by Alternaria sp. and Geosmithia sp. This was demonstrated by the absence of pigmentation and scarce fungal growth.

WOOD RESEARCH Volume 68, Number 4, 2023
HENRICH LÜBKE and VLADIMÍR IHNÁT

Technology of Particleboard’s Preparation by Cold Pressing after Hot Mat Compression

The article describes a method of preparing particleboards (PB) from fresh and recycled chips by a new technology of cold pressing after hot compression of the mat according to PCT/SK2023/000007 (ÚPV SR, 13.06.2023) using polyvinyl acetate (PVAc) glue. For comparison, the experiment was also carried out using urea formaldehyde (UF) glue and their mutual combination. The new method shortens hot pressing, or causes reduction of pressing temperatures, while the prepared PB released from pressure no longer spring and cure over time. The curing kinetics of both PVAc and UF adhesives were described by monitoring the flexural strength and modulus of elasticity of PB as a function of time after release of pressure.
Modeling of the PB pressing process based on PVAc glue, which consists of overheating the pressed cross-section of the board to 90°C and its subsequent cooling to a temperature when the board is already stable, i.e. below a temperature of 70°C, was carried out using of a hot and cold press, while the pressing cycle lasted 140 s. Shortening the pressing cycle to 100 s was achieved by applying the glue to the chips already preheated to 92°C. Laboratory tests have confirmed that the mechanical properties of PB are in accordance with the requirements of EN 312/3 for chipboards for interior conditions, including furniture, for use in dry environments.

WOOD RESEARCH Volume 68, Number 4, 2023
Dritan Ajdinaj, Holta Çota, Fakije Zejnullahu, Rrahim Sejdiu, Agron Bajraktari, and Keli Mustafaraj

Noise Emission and Quality of Surface of Thermally Modified Silver Fir Wood Planed by Horizontal Milling Machine

This study was conducted to provide information regarding to noise emission and the surface quality of silver fir wood (Abies alba Mill.) planed at different feed rates after thermal modification. Four groups of sixteen samples were prepared. One group was used as control and the others were heated at 160°C, 190°C and 220°C, at atmospheric pressure for 3 h. After, all samples were processed along the grain by a planer machine, 3 m/min and 10 m/min feed rates were applied. Noise was measured using a sound level meter, while surface roughness measurements were performed by a stylus profilometer. Higher feed rates produced noticeably higher noise emission as for natural wood as for thermally modified one. The temperature was found to have a modest positive effect on the noise reduction. The increase of temperature and feed rate affected the increase in the surface roughness of the wood. Feed rate resulted as a more significant factor on the noise emission and on the surface roughness than temperature.

WOOD RESEARCH Volume 68, Number 4, 2023
Igor Wachter, Tomáš Štefko, Jozef Martinka, Peter Ďuriš, Peter Rantuch, and Zuzana Mária Buchtová

Optical Properties of Transparent Wood prepared from Balsa

In this study, transparent wood was prepared by deactivating chromophore groups in raw balsa wood, followed by solvent free dehydration and a subsequent vacuum-assisted polymer infiltration. Thermal degradation of transparent wood takes place in two main steps. Optical properties (colorimetry, transmittance) of transparent wood made from balsa wood and acrylic polymers were studied. Highest values of transmittance in the visible part of spectra were achieved by 0.7 mm thick samples at approx. 77%. The dependence of thickness on transmittance showed a linear decrease with increasing thickness of transparent wood. The created material also exhibits absorbing properties in visible and UV spectra.

WOOD RESEARCH Volume 68, Number 4, 2023
Feilong Mao, Saiyin Fang, Ming Li, Gezhou Qin, Yue Zhao, and Ning Xu

Study on Acoustic Black Hole Effect of Acoustic Emission Signals in Pinus sylvestris var. mongolica litv

The difference in density and wave velocity causes distinct wave impedance between air and wood, resulting in complex acoustic emission (AE) signals due to reflection on the wood’s surface. This study explores the suppression of AE signal reflection by modifying the structure of thin wood panels, utilizing the theory of acoustic black holes (ABH). Initially, a one-dimensional ABH structure was created by forming a wedge structure on one side of the specimen. Pencil-lead break (PLB) tests simulated sudden AE sources on the specimen’s surface. AE signals were collected using three equidistant sensors on the upper surface, with a sampling frequency of 2 MHz. The AE signal was then segmented into frequency bands using the differential method and analyzed in both time and frequency domains. Comparisons were made to understand the impact of the one-dimensional ABH on AE signal propagation. Results demonstrated that the one-dimensional ABH effectively suppressed AE signal reflection on the wood’s surface, reducing the high-frequency components by 18.31%, 20.83%, and 12.09% for each sensor, respectively. Furthermore, the experimental cut-off frequency of 0.98 kHz surpassed the theoretically calculated value of 0.39 kHz due to the disparity between the ABH structure’s thickness and the theoretical prediction.

WOOD RESEARCH Volume 68, Number 4, 2023
Helena Hybská, Martina Mordáčová, Dagmar Samešová, and IVETA ČABALOVÁ

Ecotoxicological Tests of the Particleboards Containing Rubber Waste

The article is focused on the production and environmental evaluation of wood composites using waste rubber in the construction industry. Used aqueous extracts were prepared from the experimental wooden composites with various additions of the waste rubber from tires and waste seals. The pH value and organic pollution (by COD) were determined in the aqueous extracts. The effect on the environmental components (aquatic and terrestrial) was ecotoxicologically tested using the test organisms Sinapis alba, Lemna minor and Daphnia magna. Preliminary acute ecotoxicity tests were performed.

WOOD RESEARCH Volume 68, Number 3, 2023
Yoshikazu Mori, Mio Nakajima, Akihiro Ishida, Noboru Ito, Yohei Kurata, Kazumasa Shimizu, Yoshihiro Katayama, Makoto Kiguchi, Kana Yamashita, Takeshi Fujiwara, and Mario Tonosaki

Changes in Hemicellulose Structure Associated with the Transition from Earlywood to Latewood at Juvenile Wood in Cryptomeria Japonica

The chemical composition and variations in chemical structure of hemicellulose in earlywood (EW) and latewood (LW) of two individual Japanese cedar trees (C-Boka and T-Boka) were investigated. The trees were cultivated under different growth conditions: C-Boka grew slowly in a forest, while T-Boka grew rapidly in a location rich in nutrients and sunshine. For the chemical structure of hemicellulose, arabinoglucuronoxylan (AGX) showed varied side-chain substitution rates with glucuronic acid and different molecular weights in the transition between EW and LW. In contrast, the fundamental composition of glucomannan/galactoglucomannan (GM/GGM) was relatively unchanged between EW and LW. The modification of AGX and GM/GGM from EW to LW differed between C-Boka and T-Boka and might be influenced by the growth rate of the trees.

WOOD RESEARCH Volume 68, Number 3, 2023
Sarah Augustina, Wahyu Dwianto, Muhammad Adly Rahandi Lubis, Ratih Damayanti, Danang Sudarwoko Adi, Jamaludin Malik, Imam Wahyudi, Wayan Darmawan, Philippe Gerardin, Sari Delviana Marbun, and Hiroshi Isoda

Effect of Anatomical Structure on Dimensional Stability of Low Molecular Weight Phenol-Formaldehyde Impregnated Wood

This research deals with low molecular weight-phenol formaldehyde (LMW–PF) impregnation on sepetir (Sindora spp), nyatoh (Palaquium spp.), and pisang putih (Mezzettia spp.) woods to determine the effect of different anatomical structure on weight percent gain and dimensional stability improvement. The wood samples were impregnated using LMW–PF solutions with 7, 8, 9, 10, and 11% of concentrations (w/w), vacuum-pressured (–98 kPa, 15 min, 350 kPa, 4 h), and re-immersed in 80°C for 3 h. According to the findings, LMW–PF impregnation reduced coefficient of swelling by 9.64–29.95%, and increased anti-swelling efficiency by 12.24–29.91%. Additionally, the water absorption and thickness swelling reduced by 2.43–38.75% and 15.94–34.21%, respectively, indicating the improvement of dimensional stability. Microscopy and NIR analysis revealed the presence and reaction of LMW–PF within porous wood matrix. The effect of diverse anatomical structures caused complexity on LMW–PF impregnation. Sepetir-treated wood with fewer anatomical barriers resulted in better dimensional stability improvement than others.

WOOD RESEARCH Volume 68, Number 3, 2023
Mehmet Gunes and Mustafa Altunok

Investigation of Bending Strength of Tannin Impregnated Wooden Beams after Heat Treatment

In this study, the changes in bending strength were investigated by applying heat-treatment to laminated beams modified with acorn tannin to improve the mechanical properties of wooden load-bearing structural members. For this purpose, acorn tannin was impregnated on samples prepared from Scotch pine (Pinus sylvestris L.), oak (Quercus petraea L.), and chestnut (Castanea sativa Mill.) woods. Heat treatment was applied to the samples impregnated with acorn tannin at 150ºC for 3 hours. Untreated, heat-treated, and tannin-modified samples were conditioned until they reached constant weight at 20ºC at 65% relative humidity (RH), 40ºC at 35% RH, and 10ºC at 50% RH. Bending resistance tests were applied to the elements that are conditioned in outdoor conditions according to ISO 13061-3. The results of bilateral interaction between tree species and treatment type were compared, the highest bending strength increase was found in Scotch pine samples by 5% compared to control samples.

WOOD RESEARCH Volume 68, Number 3, 2023
Chun-Won Kang, Kazuharu Hashitsume, EUN-SUK JANG, and Haradhan Kolya

Relationship between Wood Anatomical Features and Surface Roughness Characteristics

This study aimed to investigate the relationship between surface roughness and anatomical features of wood in 15 different species of boards. Surface roughness was measured parallel and perpendicular to the wood grain using a surface profilometer, and anatomical features such as pore size and distribution were analyzed using microscopic techniques. The results showed that surface roughness perpendicular to the grain direction was consistently higher than that parallel to the grain direction for all wood samples. This difference in roughness was correlated with pore size and density. It shows that the larger pores and lower density lead to higher roughness perpendicular to the grain. The study also found that traditional hand planning methods (push and pull) produced a smooth surface finish, with no statistical differences in roughness.

WOOD RESEARCH Volume 68, Number 3, 2023
Qiaofang Zhou, Dongdong Liang, Aokai Cheng, Xianju Wang, and Dengyun Tu

Effects of Pressing Temperature and Compression Ratio on Density Distribution and Hardness of Surface Densified Poplar Wood

Process parameters play an important role in wood surface densification. In this study, the poplar (Populus tomentosa Carr.) wood was heated on one side at 100℃, 150℃ and 180℃, and compressed in the radial direction with the speed of 10 mm/min. The initial thickness of the wood samples were 30 mm, 26 mm and 23 mm, and they were all compressed to 20 mm and resulting in three different compression ratios: 33.3%, 23.1% and 13.0%. When the surface densification completed, the density distribution and hardness of the densified and un-treated samples were measured and analyzed. Results show that the compressing temperature mainly decided the formation of the density distribution curve and the peak density increased with the increasing temperature; as the compression ratio increased, the peak density increased and the thickness of the densified zone broadened; the surface hardness was highly correlated with the density distribution which was affected by temperature and compression ratio, and as the peak density increased and the thickness of the densified broadened the hardness increased accordingly. Therefore, by optimizing the process parameters such as the compressing temperature and compression ratio could generate a targeted density distribution which has the desired hardness.

WOOD RESEARCH Volume 68, Number 3, 2023
Dimitrina S. Kiryakova, Antoniya S. Ilieva, and Neli А. Simeonova

Effect of Water Absorption on the Mechanical Properties of Silane-Treated Wood Flour Polypropylene Composites

The behavior of the wood flour-polypropylene composites prepared with various contents of untreated and silane-treated wood flour by immersion in water was studied, as well as the effect of the water absorbed by the samples on their mechanical properties. The highest degree of water absorption was observed for the composites containing 30 – 50 mass% alkali pre-treated wood flour. For the materials with 50 mass% untreated, silane-treated and alkali pre-treated wood flour, the water absorption measured was 8.76%, 7.84% and 13.91%, respectively, after 15 days immersion in water. The value of the thickness swelling calculated for the samples prepared with 50 mass% silane-treated wood flour – polypropylene was the lowest – 1.29%. It was proved that the absorption of water molecules results in change of the tensile profile of the thermoplastic polypropylene composites filled with hygroscopic filler.

WOOD RESEARCH Volume 68, Number 3, 2023
Chunmei Yang, Zanbin Zhu, Tongbin Liu, Bo Xue, Wen Qu, and Tingting Wang

Determination of Urea-Formaldehyde Resin Content in Poplar Fiber Based on Hyperspectral Techniques

In this experiment, poplar fibers containing 0%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 25% and 30% of urea-formaldehyde resin were prepared. A model for the detection of urea-formaldehyde resin content in poplar fibers was established by the hyperspectral near-infrared imaging system combined with relevant algorithms. The spectral images of poplar fibers containing different contents of urea-formaldehyde (UF) resin were measured separately using hyperspectral imager. The results of four preprocessing methods, namely mean centering (MC), multiple scattering correction (MSC), standard normal variables (SNV) and first-order derivative (1-Der) were analyzed, and the optimal preprocessing method was selected as SNV. The band combinations with the highest correlation with the urea-formaldehyde resin content were compared and analyzed with the full-band model to establish the partial least squares regression (PLSR) model. The experimental results show that the hyperspectral imaging system combined with the corresponding algorithm can achieve rapid detection of UF resin content in poplar fibers, and the results of this study provide technical support and theoretical reference for determination of resin content in ultra-thin fiberboard production. The method is an innovative model for the determination of UF resin in wood fibers.

WOOD RESEARCH Volume 68, Number 3, 2023
Sumanta Das, Miroslav Gašparík, Anil Kumar Sethy, Peter Niemz, Rastislav Lagaňa, Tomáš Kytka, Martin Sviták, and Gourav Kamboj

Suitability of Aspen (Populus Tremula L.) for Cross-Laminated Timber (CLT)

Cross-laminated timber (CLT) CLT is an excellent material for building and high load-bearing structural applications, but its fabrication and use are limited to softwood only. The suitability of aspen (Populus tremula L) wood for manufacturing CLT was assessed by using two adhesives, one-component polyurethane (1C-PUR) and melamine adhesive (ME). Physical properties like water absorption (WA), thickness swelling (TS), delamination, and mechanical properties like bond shear strength, bending modulus of elasticity, bending strength, and rolling shear strength were evaluated to examine its suitability. Compared to ME-bonded CLT, 1C-PUR bonded CLT panels displayed superior physical characteristics, with 70% passing the delamination test. CLT panels bonded with 1C-PUR adhesive also have better mechanical properties than ME-bonded CLT. CLT panels experienced three types of bending failure: rolling shear, delamination, and tension. Aspen CLT has similar or higher mechanical properties than traditional softwoods, making it suitable for CLT manufacturing.

WOOD RESEARCH Volume 68, Number 3, 2023
HARUNA SEIDU, RÓBERT NÉMETH, Francis Wilson Owusu, James Korang, Appiah-Kubi Emmanuel, James Kudjo Govina, Fath Alrhman A.A Younis, and Safia Ibrahim

Mechanical Properties of PF and MUF Bonded Juvenile Hybrid Eucalyptus Plywoods Produced in Ghana

To obtain the mechanical properties of plywood produced from six yearold hybrid Eucalyptus in Ghana was the objective of this research. The samples for the experiment were prepared and tested according to GS EN 326-1, GS EN 310, GS EN 314-1, and GS EN 314 -2. The data obtained were analysed using the factorial ANOVA analysis. The mean results obtained for the various treatments were MOE (6520 – 7638 N/mm2), MOR (53.29 – 60.56 N/mm2, shear strength (2.47 – 5.51 N/mm2), failure (72 -90%) and density (725 – 748 kg/m3). The orientation of the surface veneer caused variations among treatments whiles the adhesives PF and MUF largely did not cause any variations among treatments. This study has proven that it is possible to produce sufficiently strong and resistant plywood from the juvenile wood of eucalyptus.

WOOD RESEARCH Volume 68, Number 3, 2023
Dénes Horváth, Sándor Fehér, and Mátyás Báder

The Potential of Producing High Added Value Structural Timber from Lamellae Waste. Classification and Visual Grading

This study is the continuation of the first part (Horváth et al. 2023), in which density, bending strength and modulus of elasticity of 100 oak lamellae generated as small-sized production waste were investigated. In this part of the study series, the classification of our sample set is carried out according to the EN 338. A visual pre-grading is presented, to remove the worst specimens and achieve a better final result and a standardized visual grading is also shown. Our results are compared with literature values of clear specimens as well. Amount of 80% of the specimens were found to be suitable for further structural use. The total sample set is classified in strength class D35 (average density 712.6±72.5 kg/m3; average MoRadj 65.4±16.2 MPa; average MoEadj 13.4±3.1 GPa), while the visually pre-graded part with better average test results is classified in strength class D45. Industrial wood residues contain a sufficiently high proportion of elements for further processing, so that after sorting it can be used as raw material for glued-laminated load-bearing timber.