Articles

WOOD RESEARCH Volume 67, Number 2, 2022
Dorota Dukarska, Jakub Kawalerczyk, and JUSTYNA WŁODARCZYK

Properties of the water-resistant plywood glued with pf resin with the addition of tannin filler and nanoclay

The conducted study was aimed at finding the phenol-formaldehyde adhesive formulation containing both the nanoclay and the tannin filler which allows to manufacture water-resistant plywood characterized by the improved properties. The research assumed the application of six experimental variants having a different proportions of the mentioned components which were compared with the mixture prepared according to the industrial recipe. Properties of liquid mixtures such as their gelation time and viscosity were investigated. Moreover, the differential scanning calorimetry (DSC) was performed. The manufactured plywood panels were tested in terms of bonding quality, bending strength and modulus of elasticity. Studies have shown that after the adjustment in components proportions it is possible to achieve the proper viscosity level of adhesive mixtures. The results also indicated that the suitable amount of nanoclay can contribute to the acceleration of resin gel time, however, the DSC analysis showed no effect on its reactivity. The nanoclay concentrations ranging from 2 to 4 pbw (parts by weight) per 100 g of adhesive positively influenced the bonding quality of plywood. Furthermore, there was no clear tendency in case of the effect of applied formulation on the modulus of elasticity and bending strength of plywood. The mixture containing 3 pbw of nanoclay and 5.3 pbw of tannin filler was distinguished as the most beneficial taking into account the improvement in the properties of manufactured plywood.

WOOD RESEARCH Volume 67, Number 2, 2022
LINDA MAKOVICKÁ OSVALDOVÁ, PAULINA MAGDOLENOVA, Frank Markert, SAMUEL L. ZELINKA, LOUISE FREDERIKKE ENOKSEN, and MALTHE KLINT

Modelling a clt specimen protected with gypsum exposed to parametric fire curve heat flux

This paper models bench-scale experiments using computational fluid dynamics (CFD). The experiments measured the temperature profiles of fire-protected cross laminated timber (CLT) specimens exposed to parametric fire curve. The bench-scale experiment specimen is 250 x 250 mm and consists of a CLT panel 100 mm with three layers of gypsum plasterboard 15.5 mm as thermal and fire insulation The specimens were exposed to a heat flux generated by a heat-transfer rate inducing system (H-TRIS) device. Two numerical models were created in order to copy the experiment conditions, one by using basic modelling techniques and one using advanced method. Comparing the layer temperature values of the experiment and basic model, a great difference was found. The difference between experimental and model temperatures increases the closer the analysed layer is to the heat source. The results show a good agreement between the model and the experiments, especially for the advanced numerical model.

WOOD RESEARCH Volume 67, Number 2, 2022
Kang Zhou, LI LUO, and Bin Na

Study on flame retardant leach resistant of modified poplar wood

After flame retardant and enhancing treatment, fast-grown poplar face the problem of leaching of pharmacy, which affected the effective permanence of the retard and further use is limited. In this paper, we study the fixed effect of low molecule phenol-formaldehyde (PF) resin on nitrogen and phosphorus (N-P) inorganic flame retardant composite under the condition of high relative humidity. The change of lateral sizes and quality of the specimens were emphasized in the experiment. Results reveal that the greater the concentration of flame retardant was, the greater weight gain percentage of the samples was, and the more serious leach was in the test, after the specimen was modified with the flame retardant. When weight gain percentage of the specimens is same, the greater the concentration of PF resin test solution was, better effect of the leach resistant will be obtained with the concentration of PF test solution increased. The PF resin with 25% concentration had the best effect to reduce the leach of N-P inorganic composite retards. From the comparative analysis above, it was advisable to indicate the PF resin with 25% concentration had the best effect to reduce the leach of N-P inorganic composite retards.

WOOD RESEARCH Volume 67, Number 2, 2022
ARIF CAGLAR KONUKCU

Determination of mode I fracture behavior of southern yellow pine (Pinus taeda L.) wood using single-edge-notched bending test

The fracture behavior of southern yellow pine (Pinus taeda L.) was experimentally analyzed in the radial-longitudinal and the radial-tangential crack propagation systems using a single-edge-notched bending test method in mode I loading condition. Three fracture parameters, the initial slope, the fracture toughness, and the specific fracture energy, were determined from the obtained load-deformation curves of each test sample. The results were statistically analyzed and compared with each other using the independent samples t-test. The radial-longitudinal crack propagation system had a significantly greater fracture toughness than in the radial-tangential crack propagation system. The stiffness in the radial-longitudinal system was also significantly higher than in the radial-tangential system. It was observed that the crack growing in the tangential direction needed more energy per unit area to separate a wood sample into two halves. However, there was no significant difference between the specific fracture energy values of crack propagation systems.

WOOD RESEARCH Volume 67, Number 2, 2022
Mingbin Liu, NAN SU, and XIURONG ZHU

Design and performance of nail connection in wood framing shear walls

As the preferable lateral resistance system of a wood shear wall is attributed to the good lateral performance of nail connection, this paper aims at investigating the pull-out and shear performances of framing members’ nail connection in wood shear walls under monotonic loading. It was found that the main failure mode of the pull-out behavior of nail connection was the withdrawal of threaded nails from framing members. In addition, the shear behavior of nail connection was characterized by plastic hinge of threaded nails, local tear of spruce-pine-fir (SPF) on the top of nails, and nail caps that were obliquely embedded into the surface of SPF. The average ultimate load and displacement of shear mode were 1.48 times and 5.12 times higher than those of pull-out mode, respectively. According to the research results, the corresponding exponential numerical model was established, which provided basic data for the lateral performance research and finite element simulation analysis of wood shear walls nail connection.

WOOD RESEARCH Volume 67, Number 2, 2022
Sefa Durmaz

Effect of wood flour content on the properties of flat pressed wood plastic composites

This study focused on the effect of wood flour content on some mechanical and physical properties of flat pressed wood plastic composites (WPC). The results revealed changes in the wood flour content affected the density of flat pressed WPC. Moreover, as exposure time increased, water absorption values were increased. The changes in the wood flour content considerably affected the mechanical properties of WPC. The decrease in the flexural strength reached up to 58%, while it was 61% for tensile strength. However, modulus of elasticity increased with increasing wood flour content. Meanwhile, the decrease was inevitable for screw withdrawal strength, where the increase in wood flour content resulted in a reduction of up to 50%. It was clearly determined that wood flour content above 60% evidently affects the physical and mechanical properties of flat pressed WPC, which should be considered in the utilization areas where high mechanical properties are critical.

WOOD RESEARCH Volume 67, Number 2, 2022
QIANWEN HU, XIAOHE LI, HAI FANG, and Qian Wan

The tactile perception evaluation of wood surface with different roughness and shapes: A study using galvanic skin response

By adopting the methods of PAD subjective emotion measurement and galvanic skin response physiological measurement, this study explores the differences in people’s tactile perception evaluation of the surfaces of beech materials with different roughness and shapes. The results show that females prefer beech samples with arc shapes, while males prefer the samples with rectangle shapes; participants’ emotional stability under a higher emotional arousal level can to a certain extent be maintained due to the beech materials with arc shapes. The tactile perception of males for beech materials has a greater range of emotional arousal than that of females, but the arousal speed of males’ emotions is lower than that of females’ emotions. Moreover, a better tactile perception experience can be created for participants when the roughness of beech materials is limited within a certain range of conditions, and a certain sense of “anxiousness” will be brought to participants if the surface of beech materials is too rough.

WOOD RESEARCH Volume 67, Number 2, 2022
BAI JUE and GUAN HUIYUAN

Study on thermal comfort of wood tabletop materials

The purpose of this study is to investigate the contact temperature and thermal comfort when the upper extremity touches a wooden table top, and to seek an efficient accurate simulation device instead of human testing. Therefore, three parts of this paper were conducted. First, 20 subjects were selected for the temperature test experiment. Secondly, the perceptual thermal comfort evaluation was quantified by recording the thermal comfort evaluation at a specific moment. Finally, a device was developed to replace the human forearm for upper limb thermal comfort study. The results show that the ambient temperature, type and thickness of material all have significant effects on the local contact temperature. In terms of thermal comfort evaluation, the correlation between temperature and thermal comfort was significant. The simulation device in the study is not only simple to operate, but also can continuously and stably replace the heat transfer process of the upper limb.

WOOD RESEARCH Volume 67, Number 2, 2022
Halaj Michal, Boháček Štefan, Pažitný Andrej, MONIKA STANKOVSKÁ, and ALBERT RUSS

Methods of preparation of nanofibrillated cellulose for special filter papers with effective air filtration. Short notes

Nanofibrillated cellulose was prepared from distillery refuse based on maize starch using the extraction with NaOH and HCl involving centrifugation. SEM images of bleached kraft pulp with/without the addition of nanofibrillated cellulose were compared. The results showed that the application of nanofibrillated cellulose caused a visible reduction in the surface porosity. Conversely, mixing of the pulp with the nanofibrillated cellulose resulted in large pores among the fibres. The effect of the cationic retention aid on porosity was not significant, observed in the fines retention. A minimal difference in porosity was found among of fine and coarse fibres. When lyophilisation as drying method was used it yielded nanofibrillated cellulose with a size in the range of approximately 100 to 150 nm.

WOOD RESEARCH Volume 67, Number 1, 2022
Jingjing Li, Xi Ma, and Haiyan Duan

Preparation, chemical constituents and antimicrobial activity of pyroligneous acids from salix psammophila branches

In order to improve the additional values of Salix psammophila bio-waste, pyroligneous acids (PAs) from Salix psammophila branches were extracted by the pyrolysis process at two temperature ranges: 90-380°C and 380-550°C. The chemical constituents and antimicrobial activities of PAs were investigated in detail. The GC-MS results showed that 34 compounds were identified from the two kinds of PAs. The main components were organic acids and ketones for PA at 90-380°C, while they were organic acids and phenols for PA at 380-550°C. The total content of acids and phenols was as high as 67.96% for PA at 380-550°C, which contributed to the strong antimicrobial activity. Two PAs both showed good antimicrobial activities for five pathogenic fungi and two pathogenic bacteria, especially against Verticillium dahlia. Compared with the antimicrobial activity of PA at 90-380°C, PA at 380-550°C showed greater antifungal activity but against Fusarium oxysporum.

WOOD RESEARCH Volume 67, Number 1, 2022
Fengxia Han, Qing Liu, Xin Guo, Meng Zhang, and Xia Han

Analytical study on axial and eccentric compressive behavior of poplar column strengthened by BFRP

In this work, the compression behaviour of the Xinjiang poplar column was reinforced by basalt fibre reinforced polymer (BFRP) strips with different reinforced configurations, and the numerical simulations were performed on the axial and eccentric compressions of poplar columns unreinforced and reinforced with BFRP to assess the effect of the bearing capacity and deformation of the columns. The results show that the use of BFRP to reinforce the Xinjiang poplar column effectively improves its axial compressive bearing capacity (axial compression) and bending bearing capacity (eccentric compression), and at the same time, the bearing capacity and stiffness of the columns strengthened by BFRP increased with the bonding area of BFRP.

WOOD RESEARCH Volume 67, Number 1, 2022
Juraj Gigac and Mária Fišerová

Effect of smoothing in calender and hot stamping machine on the properties of coated paperboards for printed electronics

The methods of coated paperboards smoothing with a hot stamping machine using a smooth metal die and a conventional calender were compared. The printing roughness required for printing electrical and electronic components was achieved by both smoothing methods. The printing roughness of the coated paperboards decreased after hot stamping by 18 to 42% and after calendering by 22 to 41% depending on the grade of coated paperboard. The stiffness of coated paperboards decreased after hot stamping by only 4 to 21%, while by up to 38 to 51% after calendering. The ratio of specific stiffness and printing roughness of coated paperboards after hot stamping ranged from 2.5 to 8.1 mN. μm-2 and after calendering from 2.0 to 6.7 mN. μm-2. The stiffness of the coated paperboards decreased less after hot stamping, and that only in the printed electronics area, while after calendering the stiffness decreased significantly more in the whole profile. It can be assumed that packaging made from coated paperboards smoothed by hot stamping will have a lower weight and thus lower costs than packaging from calendered coated paperboards.

WOOD RESEARCH Volume 67, Number 1, 2022
Darius Albrektas, Simona Gauronskaitė, Vaida Dobilaitė, and Milda Jucienė

Effect of open-holes on mechanical properties of wood composite materials

A few variations of open-holes in wood-based pieces, particle board and plywood were modeled in this article. The modulus of elasticity and the coefficient of damping for these pieces were determined using static and dynamic methods and the effect of holes of different quantity and size on mechanical properties were evaluated. As regards to wood particle boards, it was found that the modulus of elasticity decreased to10% after drilling holes, and the coefficient of damping increased to 13%. With regard to plywood pieces these changes were up to 14.5% and up to 21.5%, respectively.

WOOD RESEARCH Volume 67, Number 1, 2022
YINLUAN QIN and LONGHAI CHEN

Effects of modification with melamine–urea–formaldehyde resin on the properties of urea pretreated eucalyptus

Eucalyptus urophylla was treated with melamine-urea-formaldehyde resin (MUF) after pretreatment with urea solution. The properties of the wood were then determined. The weight percent gain (WPG) and, antiswelling efficiencies (ASE) of the wood treated with urea+MUF were 14% and, 45% higher than those of untreated wood, respectively. The water absorption (WA) of the wood treated with urea+MUF was decreased approximately 50% lower than that of the untreated wood. However, the mechanical properties of the wood treated with urea+MUF were weakened due to the destruction of the structure of wood. An X-ray photoelectron spectroscopy (XPS) analysis revealed that the atomic concentration ratio of O/C was increased. The ratio of C1 was decreased as the lignin and extractives contents were decreased, while the ratios of C2 and C3 were increased. The urea solution pretreatment was conducive to the impregnation of wood functional modifiers.

WOOD RESEARCH Volume 67, Number 1, 2022
Xue Feng, Boxin Wang, Yongmei Qian, and Wei Tian

Influence of size effect on the bearing capacity of the axially compressed components of corn straw integrated material and its calculation method

Our paper proposed a new type of environmentally friendly biomass material, corn straw integrated material (CSIM). In this paper, the ultimate bearing capacity of the axially compressed components under parallel, vertical and combined texture-integrated methods are compared and analyzed through the experimental research. The influence of size effect on the bearing capacity of the axially compressed components of the CSIM is determined, and the calculation method of the bearing capacity of the axially compressed components under vertical texture-integrated method is proposed. Results showed that the slenderness ratio of 35 was the dividing point between the strength and instability failures of the CSIM axially compressed component, and the calculated value of the revised bearing capacity calculation method agreed with the test value. The result is very close to the American National design specification for wood construction (ANSI/AF&PA NDS, 2005).

WOOD RESEARCH Volume 67, Number 1, 2022
Murzabyek Sarkhad, FUTOSHI ISHIGURI, IKUMI NEZU, Bayasaa Tumenjargal, Bayartsetseg Baasan, Ganbaatar Chultem, JYUNICHI OHSHIMA, Naoto Habu, and SHINSO YOKOTA

Wood chemical components and decay resistance of four common mongolian softwoods

To utilize wood resources in Mongolia, amounts of wood chemical components (hot-water extracts, 1% NaOH extracts, ethanol-toluene extracts, holocellulose, -, -, and -cellulose, Klason lignin, and ash) were determined in four common Mongolian softwoods, Pinus sylvestris, Pinus sibirica, Picea obovata, and Larix sibirica. In addition, decay resistance of heartwood was evaluated against a white-rot fungus Trametes versicolor, and a brown-rot fungus Formitopsis palustris. Among the four species, heartwood of Larix sibirica was chemically characterized by higher amounts of hot-water and 1% NaOH extracts, and lower amounts of holocellulose and Klason lignin. These characteristics may be related to the presence of arabinogalactan which is easily extracted with cold water. Mean mass loss in each softwood ranged from 6.9% to 28.1% in white-rot fungus, and from 24.8% to 48.3% in brown-rot fungus. Among four species, Pinus sibirica showed the highest decay resistance against both fungi. By the linear mixed-effects model analysis, negative relationships were found between mass loss and amounts of extracts in heartwood, suggesting that heartwood having larger amounts of extracts showed higher natural decay durability.

WOOD RESEARCH Volume 67, Number 1, 2022
Mengxue Li, Lei Shi, Fuxian Xia, Jiang Deng, Huaijian Liao, Ting Du, and Bingyi Wang

Chemical constituents of the stem in dalbergia sissoo

The chemical constituents of ethyl acetate extracts from heartwood and sapwood of different ages of Dalbergia sissoo were studied by gas chromatography-mass spectrometry. The results showed that the chemical composition of wood heartwood and sapwood is significantly different. In the vertical direction, the type of the ethyl acetate extract from Dalbergia sissoo tends to decrease from the base to the upper portion; in the horizontal direction, the type of extract gradually decreases from the center to the periphery. And it showed an increasing trend with the age of the trees. The experiment also revealed that there were significant differences in chemical components between heartwood and sapwood. We speculated that the main chemical component trismethoxyresveratrol of heartwood extract may be related to the formation of heartwood, and the specific correlation needs to be further verified.

WOOD RESEARCH Volume 67, Number 1, 2022
Fais Rahman

Extractive contents of the juvenile stemwood and bark of teak

Teak wood is used at the juvenile stage due to short-rotation, therefore, this study aims to describe the extractive content of stem, bark, branch, and twig parts of the wood as value-added chemicals from secondary metabolites. Moreover, the main stems comprise of sapwood, heartwood, and bark while the branch and twig are made of sapwood together with bark. In this study, the sample trees were 6 and 8 years old with three replications from clonal superior teak wood and were extracted using n-hexane, methanol, and hot water as the solvents. The average of n-hexane, methanol, hot water, and total extractives ranged from 0.49 to 2.77%, 2.27 to 17.76%, 0.65 to 7.47%, and 5.96 to 25.40%, respectively. Furthermore, the total phenolic content from soluble n-hexane and methanol extracts ranged from 162.16 to 295.24 mg GAE/g, while the total soluble polysaccharides ranged from 166.28 to 423.97 mg GluE/g. The results showed that the 8-year-samples had higher values in methanol extractive content (MEC) and lower in hot-water extractive content (HWEC) than the 6-year-old trees. In addition, the bark together with sapwood in branch and twig parts had higher concentrations of MEC and total extractive content (TEC) compared to the main stems. For radial direction, MEC, HWEC, and TEC levels were greater in bark than in other parts. The branch and twig parts also had higher phenolic concentrations compared to the main stem at the base part. Meanwhile, the sapwood at the branch and twig parts have higher total soluble polysaccharide concentration compared to the main stem.

WOOD RESEARCH Volume 67, Number 1, 2022
Junfeng Hu, Xi Yu, Yafeng Zhao, Kai Wang, and Wenlin Lu

Research on bamboo defect segmentation and classification based on improved u-net network

In this paper, computer vision technology is used to quickly and accurately identify and classify the surface defects of processed bamboo, which overcomes the low efficiency of manual identification. The datasets consist of 6360 defective bamboo mat images of four categories taken by the author at the same position, which are split at a ratio of 8:2 for training and testing. In this experiment, we improved the U-net to segment the datasets and use VGG16, GoogLeNet and ResNet50 with attention mechanism for classification and comparison. The experimental results show that the accuracy of this method is 5.65% higher than the commonly used neural network method. The highest accuracy rate is 99.2%.

WOOD RESEARCH Volume 67, Number 1, 2022
Seref Kurt

Effects of liquid nitrogen in hardly impregnable fir wood

The main purpose of this study was to develop new methods to eliminate the problems encountered during the impregnation of wood material, and in this context, to improve the retention of wood material by using liquefied nitrogen. Uludağ Fir (Abies nordmanniana subsp. Bornmulleriana) was used as wood material impregnated with Tanalith-E, Immersol aqua and borax. The effects of liquid nitrogen and the amount of retention on the mechanical properties were investigated. Application of liquid nitrogen before impregnation has increased the retention in fir wood by an average of 150-200% in all impregnation methods, compared to the groups without liquid nitrogen application. Despite this increase in retention amounts, no significant changes were observed in mechanical properties due to the application of liquid nitrogen.