Articles

WOOD RESEARCH Volume 66, Number 1, 2021
Juraj Gigac, Mária Fišerová, and Svetozár Hegyi

Comparison of thermal transfer and inkjet printing of UHF RFID tag antennas on paper substrates

UHF RFID printed antennas on conventional and experimentally coated papers by thermal transfer and inkjet technique were not conductive due to high surface roughness. Reducing the surface roughness of paper and hence the electrical resistance of the antennas printed by thermal transfer and inkjet printing was achieved by coating and subsequent calendering process. Papers for thermal transfer and inkjet printed of aluminum and silver antennas were prepared by coating with top functional coating, whose main component was pigment – precipitated calcium carbonate with addition of polyvinyl alcohol, cationic polymer PDADMAC and glyoxal. The desired quality of inkjet-printed silver antennas was achieved by using coated paper with a polyvinyl alcohol barrier layer and a top functional hydrophilic layer. Silver nanoparticles of inkjet ink require a sintering process to obtain a conductive printed trace. The microstructure and thickness of antennas printed by thermal transfer and inkjet technique were compared. Thermal transfer printing created a more homogeneous antenna with greater sharpness of drawing compared to inkjet printing.

WOOD RESEARCH Volume 66, Number 1, 2021
Samson Masulubanye Mohomane, SETUMO VICTOR MOTLOUNG, LEHLOHONOLO FORTUNE KOAO, and TSHWAFO ELIAS MOTAUNG

Effect of silica on alkaline bagasse cellulose and softwood cellulose

This study investigates the effect of silica on sugarcane bagasse (SCB) and softwood (SW) cellulose. Cellulose was extracted from raw SCB and SW chips using a three-step process, namely thermal pre-treatment, alkaline treatment and bleaching treatment. Alkali treated cellulose was then subjected to silica surface modification using the solvent exchange method. The effect of silica modification on SCB and SW cellulos was investigated using X-ray diffractions analysis (XRD), Fourier transform infrared (FTIR) spectroscopy and optical microscope (OPM) techniques. Both the FTIR and XRD results confirm successful extraction of cellulose from both raw fibers and addition of silane functional groups in the cellulose surface. XRD patterns of all samples revealed typical spectra for natural fibers corresponding to crystalline peaks of cellulose and undissolved amorphous hemicellulose respectively. SCB and SW showed similar increasing patterns of crystallinity with nanosilica surface modification. The surface morphology results showed that both SCB and SW cellulose modified with silica were swollen and displayed small particles agglomerating on the surface of the fibers. The solvent exchange method proved to be a successful method for modifying SCB and SW cellulose with nanosilica. It also proved to be cost-efficient and time-efficient.

WOOD RESEARCH Volume 66, Number 1, 2021
Xin You Liu, Xin Wei Tu, and Mihaela Liu

Effects of light thermal treatments on the color, hygroscopity and dimensional stability of wood

Ailanthus wood (Ailanthus desf.) was thermally treated at three different low temperatures (140, 160, 180°C) for 2 and 4 h in order to investigate the effects on wood color, hygroscopity and dimensional stability. Results indicate that mass loss increased following the treatments, while equilibrium moisture content decreased from 11.86% to 9.88% for the 180°C and 4 h treatment. Moreover, improvements in the dimension stability were observed for post-treatment samples. The thermal treatment induced color changes in the Ailanthus wood, with a significant reduction in the lightness, yet the redness and yellowness exhibited minimal changes. FITR spectra of the thermally treated wood suggest that the heat treatment resulted in the deacetylation of hemicellulose. These results help to conclude that thermal treating temperature under 160°C can improve wood dimensional stability and maintain original color.

WOOD RESEARCH Volume 66, Number 1, 2021
Ladislav Dzurenda and Michal Dudiak

Cross-correlation of color and acidity of wet beech wood in the process of thermal treatment with saturated steam

The paper presents changes in the color and acidity of Fagus sylvatica L. in the process of heat treatment of wood with saturated water steam in the temperature range t = 105 – 135°C during τ = 3 to 12 hours. The light white-gray color of beech wood with a yellow tint changes on the pale pink, red-brown to a brown-red color in the heat treatment process. The color changes of beech wood expressed in the form of the total color difference are in the range of values ΔE* = 1.97 – 26.85. Due to the hydrolysis of hemicelluloses, the acidity changes in the process of thermal treatment of wet beech wood. Decrease in acidity of beech wood in the range of temperatures t = 105 – 135 °C and time τ = 3 – 12 hours is in the range of pH values = 4.9 to 3.4. The dependence of the total color difference ΔE* on the change in acidity of beech wood is described by the polynomial of function II. degree. The above knowledge is a suitable tool for evaluating the degree of change in beech wood color in the technological process based on the change in pH of wood.

WOOD RESEARCH Volume 66, Number 1, 2021
Beatriz Segura-Elizondo and Róger Moya

Wood properties comparation of Cedrela odorata from trees in agroforestry and in pure plantation

The aim of this work was to compare the general, physical, mechanical, chemical and energy properties of the wood from Cedrela odorata trees growing in two agroforestry condition (tree-agroforestry) with Theobroma cacao (9 and 10 years old), with a ten-year-old C. odorata tree growing in pure plantation (tree-plantation). The results showed that there growing in agroforestry presented higher heartwood diameter (6.7 to 7.6 cm) and heartwood (approx. 17%) and lower bark (12-13%) and sapwood (69-70%) percentages than trees in pure plantation. In addition, this tendency was observed through different heights of the tree. Moreover, wood from 9-tree-agroforestry presented highest specific gravity and volume shrinkage. Then wood from this growing condition presented highest strength in axial hardness and flexure relative, and extractives in cold water and ethanol-toluene. No differences were observed between the energy properties. In general, wood from trees in agroforestry present better properties than the trees growing in pure plantation. According with these results, the potential of agroforestry systems relative to pure plantations, as regards to differences in tree growth produced by crop fertilization, pruning and other management measures to which the agricultural crop is subjected, which can give the wood qualities different from those found at earlier ages.

WOOD RESEARCH Volume 66, Number 1, 2021
Zhipeng Zhu, Dengyun Tu, Ziwei Chen, Chuanfu Chen, and Qiangfang Zhou

Effect of hot pressing modification on surface properties of rubberwood (Hevea brasiliensis)

This research aims to investigate the effect of thermal modification by hot pressing on surface characteristics of rubberwood. For this purpose, rubberwood specimens were thermally modified by hot pressing in an open system at three different temperatures (170, 185, and 200°C) for two different durations (1.5 or 3 h). Based on the results, the values of chromatic aberration (ΔE), contact angle and glossiness increased, and roughness decreased with increasing temperature and enlarging duration further. Although the contact angle had increased, it was still less than 90°. This aesthetic surface of rubberwood could be retained by using transparent organic coatings. The thermally modified rubberwood with excellent performance could be used as a material for solid wood flooring, wallboard, and furniture applications.

WOOD RESEARCH Volume 66, Number 1, 2021
Minghua Wang, MING LI, TINGTING DENG, SAIYIN FANG, Xiaosong Li, and Fei Lai

Study on lamb wave propagation characteristics along the grain of thin wood sheet

Through the time-frequency analysis of the propagation waveform of the acoustic emission (AE) signal propagating in the thin sheet of Pinus sylvestris var. mongolica, the propagation characteristics of the stress wave when propagating as a lamb wave was studied. An AE source was generated on the surface of the specimen, the discrete wavelet transform method was used to achieve AE signal de-noising and reconstruct the waveform of the AE signal. On this basis, the time difference positioning method was used to calculate the propagation velocity of lamb waves, and compared with the propagation characteristics of lamb waves in the metal specimen. The results show that the high-frequency mode of lamb waves attenuated sharply as they propagate in the thin wood sheet, indicating that the microstructure of wood has a significant low-pass characteristic for lamb waves. The average attenuation rates of lamb waves in metal and thin wood sheet were 87.1% and 75.7%, and the velocity was 4447.0 m.s-1 and 1186.3 m.s-1, respectively. This shows that AE signals can travel longer distances in the thin wood sheet, but the propagation velocity is significantly reduced.

WOOD RESEARCH Volume 66, Number 1, 2021
Pavol Harvánek, Ján Kováč, and Ján Melicherčík

Analysis of cutting force in the process of chipless felling wood

This study compared the magnitude of the value of the cutting force using different tools with different thickness for different wood species with the same size. Measurements were made on wooden samples of spruce, aspen, and beech wood with dimensions 30 × 30 × 200 mm (w × d × h). The tearing machine pushed knives with dimension 150 × 100 mm and thicknesses of 4, 6, 8, and 10 mm with a 30° angle of cutting edge into the wood samples in a direction perpendicular to the fiber growth. Research shows that this angle of cutting edge is most effective for chipless cutting. The results were analysed by the Statistica 12 software. From the measurement results, for chipless wood felling is most preferred the 10 mm cutting knife thickness.

WOOD RESEARCH Volume 66, Number 1, 2021
Günay Özbay, Erkan Sami Kokten, and Ayhan Ozcifci

Synthesis and characterization of resol type phenol-formaldehyde resin improved by SiO2-Np

In this work, resol type phenol–formaldehyde (RPF) resin was modified with silicon dioxide nanoparticles (SiO2-Np). SiO2-Np was added at varying ratios from 1 to 4 wt.% to improve the bonding performance of the RPF resins. The physical characteristics of the nano-modified RPF (nano-RPF) resins were examined. The effects of modification were studied by Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). The results of FT-IR revealed that the nano-RPF resins were successfully produced by phenol, formaldehyde, and SiO2-Np. The nano-RPF resins demonstrated high thermal stability at temperatures above 500°C. The adhesive performance of the nano-RPF resins was investigated under dry and wet conditions. The nano-RPF resins indicated better adhesive performance than unmodified RPF resin. The RPF resin could be improved by SiO2-Np.

WOOD RESEARCH Volume 66, Number 2, 2021
Faustino Ruiz-Aquino, Rossy Feria-Reyes, José Guadalupe Rutiaga-Quiñones, Wenceslao Santiago-García, Maario Ernesto Suárez-Mota, and Héctor Hugo Esquivel-Reyes

Development and validation of an analytical method for condensed tannin extracts obtained from the bark of four tree species using HPLC

Herein, we evaluated the content of condensed tannins present in the bark of four tree species that are Quercus laurina Humb. & Bonpl., Quercus crassifolia Humb. & Bonpl., Arbutus xalapensis Kunth, and Prunus serotina Ehrn. An analytical method using high-performance liquid chromatography (HPLC) for condensed tannin extracts was developed and validated. Also, the aqueous extracts were analyzed by Fourier transform infrared spectroscopy (FTIR). Based on the Stiasny number, A. xalapensis, and Q. laurina represent an important source of condensed tannins, which may be subject to exploitation. Using infrared spectroscopy, it was observed that tannins do not show an important signal of carbonyl groups (aromatic esters) with respect to high purity catechin. Furthermore, the band of the hydroxyl group is less pronounced in tannins, because various hydroxyl are interacting with each other. However, it can be seen that the method of extraction of wood tannins developed in this work, presents satisfactory results.

WOOD RESEARCH Volume 66, Number 2, 2021
Qiang Ma, Zhao Liu, Henglin Xiao, and Zhi Chen

Tensile properties of surface modified bamboo slices coated with epoxy resin considering the corrosion of acid and alkali environment

This paper presents an anticorrosive method to protect bamboo from the corrosion induced by coating a layer of epoxy resin on the surface of bamboo slices. Four surface modifications including heat treatment, alkali treatment, coupling treatment and acetylation treatment are applied to bamboo slices. The results indicate that the ultimate tension of bamboo slices decreases when corroded in solutions with different pH for different time, while epoxy resin protects the bamboo slices from corrosion to maintain the tensile properties by coated on its surface. The surface morphology indicates that four modifications have different degrees of influence on the surface and material of bamboo slices, which can reduce the ultimate tension of bamboo slices, but improve the interfacial combination between the surface of bamboo slices and epoxy resin. Acetylation treatment was the most effective modification analysed by Fourier-transform infrared spectroscopy (FT-IR) among them.

WOOD RESEARCH Volume 66, Number 2, 2021
ANTAL KÁNNÁR and Csilla Csiha

Comparative analysis of static and dynamic MoE of pannónia poplar timber from different plantations

The aim of this study has been to investigate the suitability of Pannónia poplar (Populus × euramericana cv. Pannónia) timber for structural purposes. Static and dynamic modulus of elasticity (MOE) has been determined on samples of 4 different Hungarian plantation origins. The results of the dynamic test showed the same range as the static test, showing a good correlation of the two measurements. As result it can be stated that the domestic Hungarian Pannónia poplar species have in average 11000 N.mm-2 modulus of elasticity. This exceeds considerably the threshold limit value (7000 N.mm-2) necessary for structural applications according to Eurocode 5. Therefore Pannonia poplar is suitable for structural applications, and are a good alternative of the widely used coniferous species in construction sector.

WOOD RESEARCH Volume 66, Number 2, 2021
DONATA KRUTUL, ANDRZEJ RADOMSKI, ANDRZEJ ANTCZAK, MICHAŁ DROŻDŻEK, Teresa Kłosińska, Dominika Szadkowska, and JANUSZ ZAWADZKI

Influence of the environmental pollution on the distribution and polymerization degree of cellulose in bark and wood from scots pine (Pinus Sylvestris L.) stem

The pine stems were cut from three different polluted environments – Ist trees degradation degree (weak pollution), IInd trees degradation degree (strong pollution) and IIIrd trees degradation degree (connected with very strong pollution). On the basis of obtained results it was stated that environmental pollution caused changes in late wood participation, as well as distribution of cellulose on the stem cross- and longitudinal section. It also changed cellulose content in bark from the butt-end section, which was about 26% regardless the degradation degree. The environmental pollution caused also an increase of viscometric average polymerization degree of cellulose in heartwood in relation to heartwood adjacent sapwood and sapwood from butt-end section. Regardless the degradation degree, cellulose polymerization degree in heartwood adjacent sapwood from the middle part of the stem was higher in comparison to sapwood and heartwood. Moreover, the environmental pollution caused the increase of viscometric average polymerization degree of cellulose in bark. The polymerization degree of cellulose in bark from the butt-end section of IIIrd degradation degree stems was 22% and 23% higher in comparison to the Ist and IInd degradation degree.

WOOD RESEARCH Volume 66, Number 2, 2021
Zeyu Zhang, Bingru Shao, Fapeng Wang, Jiuyin Pang, and Ling Su

Preparation The Rose-like hydrophobic surface of wood based materials by soft lithography

To prepare hydrophobic wood with rose-like hydrophobic surface and avoid moisture damage to wood. In this paper, With polyvinyl alcohol (PVA) as the elastic mold, the microstructure of the rose petals was replicated on the wood surfaces by soft lithography. The soft lithography technique was used to modify the wood sur-face, transferring over it a rose-like topography, based on a micro/nano hierarchical structure using fresh rose as the template. The surface of poplar coated with polystyrene was reconstructed twice using 1, 3, 5, 8 and 10% PVA as templates, respectively. The results show that the average contact angle of poplar surface coated with polystyrene is more than 130°, that of fresh rose surface is about 140°, and that of untreated wood is about 60°. Therefore, the wood surface with polystyrene has obtained a similar structure to that of rose surface and has a certain hydrophobicity. In addition, the microstructures observed by means of SEM, showing rough surface structures with micro-nanopapillate hills on wood surfaces. Water droplets could easily roll down on such wood surfaces, exhibiting super-hydrophobic and low adhesion properties. The successful fabrication of rose-like wood provided a new direction for researches on the super-hydrophobic of wood, which could effectively prevent the damage of moisture to wood.

WOOD RESEARCH Volume 66, Number 2, 2021
Kuňa Vladimír, Balberčák Jozef, Boháček Štefan, and VLADIMÍR IHNÁT

Elimination of adhesive impurities of the recovered paper in flotation process

The article presents results of the elimination of sticky impurities from recovered paper in laboratory flotation of three pulp suspensions with different whiteness, obtained directly from the production line before entering flotation. A combination of commercial agents releasing undesirable substances from recovered paper and means for regulation and stabilization of froth and modified micronized bentonit was used. In the flotation purification of pulp suspension with a whiteness of 53%, the combination of Prodeink Extra, Prodeink AS10 and Hydrocol OT reduced the macrostickies content by 58%, the ash content decreased from 18.5% to 4.5%, the whiteness increased from 53% to 56.4% and the residual color content was reduced from 385 ppm to 294 ppm. The pulp suspension with a whiteness of 64% showed a reduction in the content of macrostickies by 66%, a reduction in the ash content by 23.2%, an increase in whiteness by 1.4% and a reduction in the residual color content from 245 ppm to 194 ppm. The pulp suspension with a whiteness of 68.3% showed a decrease in the content of macrostickies by 58.1%, the ash content decreased from 35.7% to 6.3%, the whiteness increased by 1.1% and the content of residual color decreased from 157 ppm to 117 ppm.

WOOD RESEARCH Volume 66, Number 2, 2021
Sławomir Krzosek, Marek Grześkiewicz, Izabela Burawska-Kupniewska, Piotr Mańkowski, and Marek Wieruszewski

Mechanical properties of polish-grown Pinus Sylvestris L. structural sawn timber from the butt, middle and top logs

The research consisted in testing Polish sawn timber dedicated for construction applications made of pines (Pinus sylvestris L.) that grew in the Silesian Forestry Region, taking into account three parts of the log: butt, middle and top. The boards had the same cross section, a nominal thickness of 40 mm and width of 138 mm, typical for Polish structural timber. The mean nominal length of the boards under research amounted to 3500 mm. Each set was composed of 70 boards. Before the tests, boards were dried in an industrial drier until reaching the moisture content of 12%, and they were planed on 4 sides. First of all, the sawn timber was graded into strength classes, and their dynamic modulus of elasticity (MOE_dyn) was tested with a non-destructive method, with the use of a portable MTG device. The next step consisted in a bending test with four points of support, according to the EN 408 standard, and with the use of the TiraTest 2300 machine, in order to determine the global modulus of elasticity (MOE_EN-408) and the static bending strength, also referred to as modulus of rupture (MOR). Finally, the average growth ring width was determined for each board (PN-D-94021), as well as wood density according to EN-408. The hereby paper presents the test results for all the tested sawn timber boards, taking into account the part of log that each board came from: butt, middle or top. The hereby paper presents the influence of density on the mechanical properties of wood, taking into account the location on the round timber. The analysis does not include the influence of the width of annual growth rings and the proportion of latewood on the wood properties under research.

WOOD RESEARCH Volume 66, Number 2, 2021
Emília Orémusová and Eva Výbohová

Changes in gross calorific value of thermally treated scots pine (Pinus Sylvestris L.) and sessile oak (Quercus Petraea L.) wood and their explanation using ftir spectroscopy

Scots pine (Pinus sylvestris L.) and Sessile oak (Quercus petraea L.) wood were thermally treated in an oven at the temperatures of 160°C, and 200°C under atmospheric pressure in the presence of air for 3 and 9 hrs. The mass loss and gross calorific value were determined. Non-treated wood samples achieved a gross calorific value of 22 193 J.g-1 for pine wood and 19 277 J.g-1 for oak wood. Whereas the calorific value of pine wood with increasing severity of treatment decreased, in the case of oak it increased. The mass loss increased with increasing treatment severity by both wood species. Mentioned differences in pine and oak wood behaviour using ATR-FTIR spectroscopy were explained. In the case of pine wood with increasing temperature and time of exposure a decrease of resin acids was observed. This may be contributed to decrease in GCV. In the case of oak wood, mainly at temperature of 200°C the degradation of hemicelluloses was observed that results in relative increasing in the lignin content with followed increase in the GCV.

WOOD RESEARCH Volume 66, Number 2, 2021
CHUNYAN LI, XINJIE ZHOU, Changhao Yang, LILI YU, HUI LI, and Benhua Fei

Effects of different flame retardant treatments on the combustibility of bamboo filament

Bamboo filaments were treated with boric acid and borax (the mass ratio of 1:1, the concentration of 20%) with four different treatment methods including atmospheric immersion, cold and hot bath immersion, vacuum impregnation and vacuum-pressure impregnation. The different treatment methods on the boron loading were analyzed and the corresponding flame resistance of bamboo filaments were evaluated by the cone analysis. The results showed that suitable treatment method with optimized processing indexes, such as hot and cold bath immersion in the condition of 100°C/2 h and 20°C/2 h with 3 cycles, was more credible to accelerate the percentages of boron loading in the bamboo filaments, and the lowest result was found in the samples with vacuum impregnation. Compared to the untreated samples, the heat and smoke release would be decreased significantly, especially for the samples with the promising hot and cold treatment, and promising pressure treatment, attributed to the more stable boron fixed in the bamboo filaments.

WOOD RESEARCH Volume 66, Number 2, 2021
Vinicius Borges De Moura Aquino, Marcus Vinicius Pereira De Freitas, Claudia Queiroz De Vasconcelos, João Paulo Boff Almeida, Felipe Nascimento Arroyo, Edson Fernando Castanheira Rodrigues, André Luis Christoforo, Diego Henrique De Almeida, Sergio Augusto Mello Silva, Diogo Aparecido Lopes Silva, Roberto Vasconcelos Pinheiro, and Francisco Antonio Rocco Lahr

Physical and mechanical characterization of Planchonella Pachycarpa wood species for use in structural purpose

This research aimed to characterize the wood species Goiabão (Planchonella pachycarpa), following the precepts set forth in the Brazilian standard ABNT NBR 7190, as well as to evaluate the possibility of estimating physical and mechanical properties, using the analysis of variance (ANOVA) as a function of apparent density, and also to estimate the stiffness properties as a function of the respective strength property. The physical and mechanical properties were considered adequate for the use of this wood for structural purposes, being classified in class C40. According to the results of the regression models, it is possible to estimate the tensile strength parallel to the fibers as a function of the apparent density. It was also possible to estimate the longitudinal elastic modulus in the compression parallel to the fibers as a function of the compressive strength parallel to the fibers.

WOOD RESEARCH Volume 66, Number 2, 2021
Jialin Zhang, Hui Xiao, Yuzhu Chen, Jinqiu Qi, Jiulong Xie, Xingyan Huang, and Yongze Jiang

Porosity and pore size distribution of recent and ancient buried Phoebe Zhennan wood determined by mercury intrusion porosimetry

The porosity and pore size distribution of recent and ancient buried Phoebe zhennan are studied in this paper by means of mercury intrusion porosimetry. The results show that the micropore and mesopore diameters of recent and buried wood are mainly distributed in range of 40.3 nm and 183.1 nm respectively, while the macropore in 45276.6 nm and 3503.9 nm separately. For both samples, the pores with diameters below 349.9 nm account for about 60% of the total intrusion volume, and contribute more than 98% of the surface area. The cumulative pore area of recent wood is slightly greater and the pore diameter ranges from 50.3 nm to 349.9 nm. While the cumulative pore area of buried wood is significantly larger than and the pore diameter ranges until 50.3 nm. These results can provide information for further investigations on the sorption behaviour and the liquid permeability of ancient buried wood.