Articles

WOOD RESEARCH Volume 64, Number 4, 2019
Radosław Mirski, Dorota Dziurka, and Aleksandra Banaszak

Effects of manufacture conditions on physical and mechanical properties of rape-polymer boards

The paper presents a method of manufacturing boards composed of lignin-cellulose chips and thermoplastic polymers (waste-based particle polymer composites, WPPC) by means of flat pressing. Rape chips, similar in size to wood chips in traditional particleboards, served as filling material, and polyethylene and polypropylene made up the outer layers. The polymers enriched only the external layers, as this allowed for considerable shortening of pressing time. The resulting boards featured satisfactory properties as compared with control, not polymer covered boards. Our study identified a temperature of 220°C and low moisture content of the polymer-containing layers as favorable for production of this type of boards. We also found out that using a sublayer with higher moisture content not only shortened the pressing time, but also improved the board properties evaluated by a bend test.

WOOD RESEARCH Volume 64, Number 4, 2019
Shuang Yan Zhang, Chuan Gui Wang, Xue Qin Fang, and Yuan Yuan Li

Characterization of lignins from the black liguor of Australian eucalyptus kraft of the nail

Lignin samples were separated from the black liquor of Australian eucalyptus kraft pulping by ethanol-acid precipitation or acid precipitation. Elemental analysis, FT-IR, and 1H NMR were conducted to compare their structural characteristics. The thermal behaviors were studied by TGA and heating value was examined with oxygen bomb calorimeter. The obtained C9 expanded formulas for acid-extraction lignin and ethanol-acid-extraction lignin were C9H9.52O2.96 and C9H9.58O3.18, respectively. According to FT-IR and 1H NMR analyses, the two lignins were similar to hardwood lignin of type GS. However, the acid-extraction lignin showed a high proportion of syringyl (S) unit. TG results showed that degradation process of the two lignins was similar, but their degradation temperatures were different. The weight loss rate reached its maximum value of 8.49 wt% / °C and 4.39 wt% / °C for ethanol-acid-extraction lignin and acidextraction lignin, whose temperature of maximum weight loss was 371°C and 356°C respectively. Results of oxygen bomb calorimeter tested showed the incendiary heat of ethanol-acid-extraction lignin was higher than that of acid-extraction lignin.

WOOD RESEARCH Volume 64, Number 4, 2019
ŽIKICA TEKIĆ, LJILJANA KOZARIĆ, MARTINA VOJNIĆ PURČAR, and Snježan Lukić

Load-bearing capacity of metal connector plates depending on location and geometry of the nail

This paper presents results of the experimental determination of the load-bearing capacity of structural timber connections realized by nail metal connector plates as a function of nail location, length and diameter. Three different diameters of the nails have been used, specifically 2.0, 2.5, and 3.1 mm. The length of the metal nails in connectors has been determined after the detailed analysis, and kept at 20 mm during the experimental research. Nails distribution over the connector plate is such that it forms the series of equilateral triangles, so that a side of the triangle equals five times the diameter of the nails used. Preceding the testing, and while using the above listed parameters certain analysis has been done. In order to experimentally determine the load-bearing capacity of the nail metal connectors, the penetration depth, i.e. the length of the nails has been kept constant, while using three different nail diameters. The testing has been done on multiple samples in the accordance with Eurocode 5.

WOOD RESEARCH Volume 64, Number 4, 2019
WAYAN DARMAWAN, Muhammad Azhari, Istie S. Rahayu, Dodi Nandika, Rumanintya L. Putri, and Satoru Nishio Malela

The chips generated during up milling and down milling of pine wood by helical router-bits

Development of new helical edge router bits (helix angle 15°, 30°, 45°, and 60°) with a cutting circle diameter of 8 mm was studied. The purpose of the research work was to investigate chips formation and surface roughness characteristics in milling the pine wood by the straight and helical edge bits. The generated chips were classified in four types by sieving into spiral chip (5 mesh), flow chip (10 mesh), thin chip (30 mesh), and granule chip (< 30 mesh). The experimental results showed that the spiral chip was generated most often (on a weight percentage basis) by the bits during down milling process. More flow and thin chips were produced by the bits during up milling process. Better surface roughness was produced by bits during down milling compared to up milling. When the helix angle of the bits increased the amount of spiral and flow chips were increased and granule chip was reduced. The machined surface was better in roughness (lower Ra values) as the helix angle of the bits increased both in up milling and down milling processes.

WOOD RESEARCH Volume 64, Number 4, 2019
B. Li and Z. Zhang

Laser shock process as new tensioning method for circular saw blade

Laser shock process for circular saw blade was proposed and analyzed in this paper. The high pressure plasma shock wave generated by strong laser beam was applied to many local areas of circular saw blade to generate local plastic deformation. Resistance strain rosette and static strain acquisition instrument were used for measuring the stress field of laser shocked circular saw blade. The natural frequency of circular saw blade after laser shock process was tested by hammer vibration test method. Based on reasonable simplification and hypothesis, laser shock process for circular saw blade was built by finite element method. The stress field obtained by experiment and theoretical calculation shows that investigated process is feasible. The natural frequencies of laser shocked circular saw blade for nodal diameters Nd = 2 and Nd = 3 are increased which means that the dynamic stability of circular saw blade is enhanced after modification.

WOOD RESEARCH Volume 64, Number 4, 2019
Paweł Czarniak, Karol Szymanowski, Jacek Wilkowski, Jarosław Górski, and Fabrice Dagrain

Machinability characterization of solid wood with scratching and drilling techniques

This paper describes the characterization of four wood species (alder, oak, jatoba and obeche) with regards to their machinability, i.e. susceptibility to mechanical processing expressed by different machinability indicators. Three types of tests were performed. Drilling tests were conducted on a computer numerical control (CNC) working center as well as on a conventional vertical drilling machine. Both machines were fully instrumented with transducers to continuously measure the torque and the thrust force while drilling. Scratching tests were performed on an instrumented shaper, allowing continuous measurement of the normal and tangential components of the total force applied on a cutter while cutting. This resulted in correlations between particular machinability indicators that were estimated with usage of different measurement benches. Moreover, machinability indicators obtained in this way were compared to the mechanical properties of the wood species. Especially strong correlations were obtained with density or strength in static bending. Those alternative techniques were to some extent coincidental. Particularly, similar results occurred with assessments on CNC machine indicators (torque and thrust force) and friction coefficients (MIε-drilling) during drilling on a conventional drilling machine or indicator C2. The necessity of some improvements in fitting the geometry of an elementary cutter regards to specific properties of solid wood proved in described below experiments should result in higher reliability and usefulness of testing method.

WOOD RESEARCH Volume 64, Number 4, 2019
Li W. G. and Zhang Z. K.

The effect of micro-pits texture on the coefficient of friction between wood and cemented carbide under different wood moisture content

Friction is an important factor during cutting of wood. Micro-texture has been proven to be an effective measure for the improvement of material friction performance. This paper investigates the effect of the cemented carbide surface micro-pits texture on the performance of wood cutting tools with the purpose to reduce the coefficient of friction on knife/workpiece contact zone. Birch (Betula spp.) and pine (Pinus sylvestris) were selected as the research object, the impacts of wood moisture content and the load used on the friction coefficient of different micropits structures were assessed and compared. We found that at a diameter of the micro-texture of 60 μm, the coefficient of friction can be effectively reduced at different wood moisture contents. The average friction coefficient between cemented carbide and wood surface increased with increasing moisture content below fiber saturation point (FSP). But the increase in free water quantity can lead to a more considerable decrease in the friction coefficient. At a higher working load, the value of the average coefficient of friction between the surfaces increases.

WOOD RESEARCH Volume 64, Number 4, 2019
Meihong Liu, Limin Peng, Zhengqiang Fan, and Dong Wang

Sound insulation and mechanical properties of wood damping composites

The sound insulation performance and mechanical properties of medium density fiberboard (MDF) and rubber multilayer panels were studied. The MDF and rubber materials were compounded under certain conditions of hot pressing, temperature and amount of glue. The weighted sound reduction was 28.0 dB for 6 mm MDF, while it was 37.4 dB for 6 mm wood composite damping material, increased by 25.1%. Compared to the monolayer MDF, the composite panels showed increased sound insulation at the resonant frequency, and the critical frequency moved to a higher frequency. The coincidence valley became shallow, effectively suppressing the anastomosis effect. As the rubber thickness increased, the multilayer composite material exhibited enhanced sound insulation efficiency and mechanical properties, and the damping properties of the composite increased, making the composite resistant to bending deformations caused by incident sound waves.

WOOD RESEARCH Volume 64, Number 4, 2019
Chenqian Pan, Wei Tan, Bifeng Kuang, Yanxiong Fang, Yintao Lin, and Xiaolan Cai

A novel glue remover for pressure sensitive tapes on aged paper

Pressure-sensitive adhesives consisting of polymer (t-butyl acrylate, PtBA) was widely used to repair aging paper. Over time, whiteness, mechanical properties and durability of paper degrade with the aging of adhesive. In this study, novel paper-friendly glue-remover (GR), consisting of organic solvents, was designed for removal of PtBA from aging paper. Dichloromethane and hexane were screened to prepare GR according the swelling degree of aged adhesive. For detail, the component of GR was adjusted to optimize removal effect and minimize the damage of GR on aged paper. Treated with GR consisting of 40% (v/v) dichloromethane/ normal hexane, the removal rate of PtBA was high to 56%. Results of mechanical and chromatism test indicates the GR will not damage the mechanical strength or handwriting on the paper. Moreover, the pH of paper increased from 3.55 to 5.75 after removal of glue, which suggested that GR help remove acid from aging paper.

WOOD RESEARCH Volume 65, Number 4, 2020
Huimin Zhang, Kai Tu, Qiandong Hou, Hui Lin, and Quan Li

The physiological and biochemical mechanisms of Cinnamomum camphora xylem extracts inhibit wood-decay fungi

The present study investigated the physiological and biochemical mechanism of extracts derived from Cinnamomum camphora (L.) Presl. The methanol and chloroform extracts of C. camphora xylem exhibited inhibitory activity against oxygen consumption in Coriolus versicolor and Gloeophyllum trabeum. The inhibitory effect of cellulose secreted by G. trabeum was concentration-dependent. The application of the ethyl acetate extracts of C. camphora xylem on the G. trabeum hyphae resulted in an improvement in electric conductivity, which followed a concentration-dependent fashion. Protein permeability increased with higher concentrations of the ethyl acetate extracts of C. camphora xylem. This research provided theoretical basis for understanding of the physiological and biochemical mechanisms of C. camphora extracts inhibit wood-decay fungi and the development of natural extracts as wood preservatives.

WOOD RESEARCH Volume 65, Number 4, 2020
Laércio Serenini Jr., Rafael Rodolfo De Melo, Diego Martins Stangerlin, and Alexandre Santos Pimenta

Wood quality of six eucalyptus clones planted in northern Mato Grosso State, Brazil

The present work had the goal of assessing the wood quality through physical-mechanical properties of six 5-year old eucalyptus clones currently planted in northern Mato Grosso State, Brazil. The following clones were assessed, five of them Eucalyptus grandis x Eucalyptus urophylla hybrids and one a clone of Eucalyptus camaldulensis. The physical-mechanical properties were basic density as a function of tree height; pith-to-bark direction; linear, tangential and radial shrinkage; and anisotropic coefficient, longitudinal and parallel compression and static bending strengths; and hardness. Eucalyptus grandis x Eucalyptus urophylla hybrids showed the best wood quality. Concerning to mechanical results, the clones reached intermediate values of strength and rigidity, qualifying them for use in structural applications with less stringent requirements. Considering that all the clones had juvenile wood, the mechanical properties were satisfactory, making the clones suitable for industrial uses.

WOOD RESEARCH Volume 65, Number 4, 2020
Endre Magoss, Sándor Tatai, Zsolt Molnár, and Ingrid Fuchs

A calibration method of the laser triangular measuring system to evaluate wood surface roughness

Due to the fact that wood roughness measurement results measured with stylus and optical methods are not always comparable a new calibration method was proposed. In order to compare the surface roughness parameters of the stylus tactile 2D roughness parameters and the optical 3D roughness parameters a systematic experiment has been carried out on fourteen wood species. The essence of this calibration method is the use of metal calibration etalons for Rz = 20 μm and Rz = 30 μm and the filter option of the optical measuring apparatus. After the calibration process, the roughness profiles taken with the optical and stylus units were much closer each to other decreasing the difference in the measurement results of the two systems. Our study prove that the laser triangular method is less usable for the planed wood surfaces.

WOOD RESEARCH Volume 65, Number 4, 2020
Jianhua Lyu, Weihui Huang, Ming Chen, Xianwei Li, Shilin Zhong, Siyuan Chen, and Jiulong Xie

Analysis of tracheid morphological characteristics, annual rings width and latewood rate of Cupressus funebris in relation to climate factors

Based on the principle of tree chronology, this paper measures tracheid morphological characteristics, ring width, and latewood rate of harvested wood from Cupressus funebris plantation in Deyang, Sichuan Province. Using meteorological data of average temperature, precipitation, relative humidity, sunshine percentage, and average ground temperature from 1983 to 2015, correlation analyses were conducted. The results of the analysis showed that the correlation between tracheid morphological characteristics, ring width, and latewood rate was not consistent with a single climatic factor. Moreover, the correlation between tracheid morphological characteristics and climatic factors, and the correlation between ring width, latewood rate, and climatic factors were significantly different. Temperature was the main limiting factor for ring width and latewood rate. In addition, relative humidity was positively correlated with ring width and negatively correlated with most indicators of tracheid morphological characteristics. Fewer indicators were affected by sunshine percentage. Meanwhile, precipitation was not significantly correlated with ring width and latewood rate. In conclusion, the correlation between various indicators and climate factors was from high to low in order of temperature, relative humidity, sunshine percentage, and precipitation.

WOOD RESEARCH Volume 65, Number 4, 2020
Pažitný Andrej, ALBERT RUSS, Boháček Štefan, MONIKA STANKOVSKÁ, VLADIMÍR IHNÁT, and Štefan Šutý

Effect of steam explosion on enzymatic hydrolysis of various parts of poplar tree

The effect of steam explosion on enzymatic hydrolysis of various parts of poplar tree (heartwood, sapwood and 1-year coppice) was investigated. These parts were milled, the obtained sawdust was chemically analysed and then steam explosion of 0.7 mm poplar particles at temperature of 205°C was performed. Concentration of monomers obtained after enzymatic hydrolysis was considered as the main indicator for cellulose accessibility. Analysis of high performance liquid chromatography showed that non-treated poplar sawdust does not enable sufficient cellulose accessibility, while excessively high temperature and rapid pressure release resulted in substantial breakdown of polysaccharides and lignin and formation of inhibitors. The concentration of monomers increased gradually in the order of coppice, sapwood and heartwood. Steam exploded heartwood gave the maximum monosaccharides concentration of 90.0 g.L-1 after 72 hours of enzymatic hydrolysis. However, glucose concentration culminated after 48 hours of this hydrolysis. This corresponds to the best holocellulose accessibility for enzymes. The maximum concentration of inhibitors (9.3 g.L-1) was determined for poplar coppice after 24 hours of enzymatic hydrolysis.

WOOD RESEARCH Volume 65, Number 4, 2020
Zhu Liu, Liang Wen, Xuan Wang, Yaoli Zhang, and Liping Cai

Leachability of ACQ-D after three different preservative treatments

In this study, the ACQ-D preservative treatments of poplar wood were carried out using the method of living tree injection treatment and the leachability was examined by comparing with the traditional treatment methods, namely, immersion and pressure treatment. In addition, the effects of injection experiment on the soil environment and preservative stability in wood were examined. The results showed that the effect of injection experiment on soil environment around the treated trees was insignificant and the preservative stability of the injection treatment was the best among three methods. ACQ-D preservatives leached easily as the increase of concentration. The retention of preservative after pressure treatment was greater than that of the injection and immersion treatment, but after the leaching tests, three methods had the same preservation grade.

WOOD RESEARCH Volume 65, Number 4, 2020
Katarína Dúbravská, Ľudmila Tereňová, and Jaroslava Štefková

CLT construction performance under thermal loading

The paper deals with testing fire resistance of a vertical wooden building construction made of CLT panels subjected to the medium-scale test of the fire resistance. A model test of fire resistance with the ceramic radiation panel as the radiation heat source, with achievable temperature of radiation surface of 935°C at maximum was used. The aim of the experiment was to assess the experiment sample whether it meets the request of the thermal insulation and integrity under thermal loading of the model fire for 30 min. The test resulted in the increase of temperatures on observed thermocouples and assessment of the integrity on the unexposed side of the CLT panel. The construction clearly resisted the effects of the radiation heat during 30 min and maintained the observed criteria of fire resistance. Charred layer of the CLT panel created on the surface of the exposed side in the thickness of 20 mm inhibited the heat transfer into the further layers of construction.

WOOD RESEARCH Volume 65, Number 4, 2020
Hong Yun, Chuangshuang Hu, Jin Gu, Yilin Han, and Xiaojing Hu

Study on the permeation and fixation of ACQ-C in poplar

In this paper, the effects of atmospheric pressure, vacuum and vacuum pressure impregnation on the permeability of alkaline copper quat in poplar were studied, and the permeability and fixation of preservatives were improved by pretreatment of poplar. The results show that the volume loading of wood can be increased by about 60 – 150% after 30 min of vacuum treatment, so the vacuum method is a simple and efficient preservation treatment method. In addition, ethanol treatment, heat treatment and microwave treatment can increase the fixation rate of copper ions by 5 – 10%, but the fixation rate of copper ions dropped by 17.83% after NaOH treatment for the dissolution of partial hemicellulose.

WOOD RESEARCH Volume 65, Number 4, 2020
Ehsan Yousefi, Mohammadreza Dehghani Firoozabadi, Omid Ghaffarzadeh, and Kuňa Vladimír

Investigation of urea usage in soda pulping of Populus deltoides

In this study, the use of the urea was investigated as an additive in soda pulping of Populus deltoides in comparison with the conventional soda and Kraft processes. Urea was used at the ratios of 1.5%, 3%, 4.5%, and, 6% based on the dry weight of wood in the soda process. The constant factors were determined for each distinct cooking of soda, soda-urea, and Kraft treatments. The dry weight of the chips was 150 g, the ratio of the liquor to wood (L/W) 4: 1, the maximum temperature 170°C and active alkaline content 18% (based on Na2O). Cooking time, the only changing factor, was varied from 30 to 330 min depending on the type of cooking. Besides, the sulfidity ratio was 25% for all Kraft treatments. After ending pulping time, the pulp samples were fully washed. Then, the screen accepts and the screen rejects were evaluated using a 20 and a 200-mesh screen. The observation shows that the more urea usage is in a pulping liquor, the more total yield, however, the screen reject value unexpectedly increased. Hence, the optimum values were determined by 1.5% and 3%. The investigation of handsheet samples indicated an increment trend of mechanical strengths with an addition of urea; so that the tear, tensile, and burst indexes of soda-urea samples were significantly higher than for each symmetric soda sample. It has been supposed that cellulose carbamate is essential in the enhancement.

WOOD RESEARCH Volume 65, Number 4, 2020
HUICHUAN JIANG, QUANJI LU, GUANJUN LI, MIN LI, and JIANING LI

Effect of heat treatment on the surface color of rubber wood (Hevea brasiliensis)

In this study the effect heat treatment process parameters (temperature, duration and heating rate) on the surface color of rubber wood was evaluated. The color of the rubber wood was determined using CIE L*a*b* system before and after the heat treatment. The colorimetric properties, including total color difference (ΔE*), lightness index (L*), red-green index (a*), and yellow-blue index (b*), were investigated at different treatment conditions. The results of analysis of variance (ANOVA) indicate that the heat treatment temperature has a significant effect on the colorimetric properties of the heat-treated rubber wood, duration and heating rate has no effect. Within the experimental range, as the heat treatment temperature and duration increasing, the color of the rubber wood gradually deepens. In order to achieve a surface color like the teak wood, the optimum process conditions are heat treatment temperature 190°C, duration 4 h, heating rate 10°C.h-1.

WOOD RESEARCH Volume 65, Number 4, 2020
Roman Fojtík, Viktor Dubovský, Kateřina Kozlová, and Lenka Kubíncová

Prestress losses in spruce timber

Prestressing force and its change is one of the key factors that affect wooden constructions, especially those using methods of transverse prestressing. To achieve a description of a prestress force (P) in transversally prestressed wooden constructions a simulated experiment was done. Prestressing force, external temperature, and moisture were measured during 669 days. The main goal of this article was to model the primary losses of the prestress force at the spruce element of the 138 x 138 mm cross-section with the sensor installed. For this purpose, all measurements were statistically analyzed and the period of primary loss was found. During this period the prestress force was decreasing with time mainly and the influence of temperature and moisture could be omitted. Based on this analysis a mathematical model of losses of the prestress force was found as P = 8.538-0.014.day.