WOOD RESEARCH Volume 65, Number 3, 2020
Darius Albrektas, Milda Jucienė, Vaida Dobilaitė, and Raimondas Bliūdžius

The influence of thermal modification on the resistance to water impact properties and strength of wood used in outdoor conditions

In this study the influence of thermal modification on the resistance of wood to the impact of water and mechanical properties and to compare the durability of thermally modified and coated wood products operating in wet conditions was investigated. It was found that the weight of thermally unmodified non-coated oak wood after 48 h of soaking increased on average up to ~ 15%, and the weight of coated oak wood increased up to ~ 8%. If wood was thermally modified, the weight of non-coated oak wood increased up to ~ 9%, and the weight of coated oak wood increased up to ~ 5%. After 168 h of soaking these change is about 2 times larger. In the case of pine wood compared to oak wood these change of weight after 48 h is about 2.0 – 2.4 times and after 168 h about 1.4 – 2.0 larger. It can be stated that wooden constructions intended to be used in very wet conditions should be made of thermally modified wood without coating. Thermally modified wood will have greater dimensional and shape stability. Thermal modification reduces the swell up to 1.6 times in the case of oak, more than 2 times in the case of pine.

WOOD RESEARCH Volume 65, Number 3, 2020
Sheikh Ali Ahmed, Stergios Adamopoulos, Francesco Poggi, and Thomas Walther

Resonance and time-of-flight methods for evaluating the modulus of elasticity of particleboards at different humid conditions

Non-destructive testing of wood panels by either resonance or time-of-flight (TOF) methods provides possibilities for predicting their static bending properties. In the present study, three non-destructive devices (BING – Beam Identification by Non-destructive Grading by CIRAD, Montpellier, France, Fakopp Ultrasonic Timer and Sylvatest TRIO) were used for measuring the dynamic stiffness of different particleboard types. Fakopp Ultrasonic Timer and Sylvatest TRIO produce ultrasonic pulses to measure the sound velocity while BING uses resonance frequencies. Commercially produced particleboards with different thickness and densities were used to measure the dynamic modulus of elasticity (MOEdyn) in two directions (parallel and perpendicular to the production line) and at three different humidity levels (dry – 35%, standard – 65% and wet – 85% RH in constant temperature of 20°C ). MOEdyn of particleboards were correlated with the static moduli of elasticity (MOEstat) and rupture (MORstat). It was found that the non-destructive methods gave higher MOEdyn values in both production directions than that of MOEstat values. MOEdyn was found to decrease from dry to wet conditions. A very strong and statistically significant correlation existed between MOEdyn and static bending properties. MOEdyn correlated stronger to MOEstat than MORstat. At different humidity level, all three methods- Fakopp Ultrasonic Timer, BING and Sylvatest TRIO analyses showed good predicting capabilities to estimate MOEstat and MORstat of different particleboard types with high level of accuracy.

WOOD RESEARCH Volume 65, Number 3, 2020
Ruyuan Yang, Xiaofeng Zhang, Youfu Sun, Tingting Zhou, and Quan Yuan

Effect of the metallization treatment on the surface properties of Populus euphratica

To improve the surface-finishing performance and enhance the protection of surface coatings, this study employed metallization treatment of fast-growing poplar through an orthogonal experiment. The poplar specimens were impregnated using a low-melting point alloy at different temperatures (75°C, 85°C, 95°C), pressures (0.5MPa, 1 MPa, 1.5 MPa), and times (0.5h, 1h, 2h) to obtain the optimum process parameters and determine the paint film adhesion of metalized poplar. The test results showed that the impregnation effect was obvious with an increase in the pressure and time. The optimum process parameters were 0.5 MPa, 85°C, and 1 h. Contact angle of the treated wood increased, the surface free energy dropped to some extent, wetting property of tread wood decreased. Whether the treated wood or the untreated wood, film adhesion of treated wood got a higher level. After anti-aging treatment, the treated poplar still had a higher level of film adhesion.

WOOD RESEARCH Volume 65, Number 3, 2020
Candan Kus Sahin, Mehmet Topay, and Ahmet Ali Var

A study on suitability of some wood species for landscape applications: Surface color, hardness and roughness changes at outdoor conditions

In this study, each of the commonly used two types of woods (softwood and hardwood) from five species was studied. All wood species show a systematic trend to change to higher values of surface roughness with natural weathering progress. The Black pine, Calabrian pine and beech wood samples show a more or less smooth trend, whereas basswood gives the highest surface roughness changes under all conditions. However, the hardwood species, except basswood, have higher hardness properties both initially and at the end of weathering process when compared to softwoods. The surface discoloration that occurs is clearly visible as a natural texturing. However, the degree of, and the pattern of texturing, may vary with different kinds of woods; the color changes also vary to some extent. It was revealed that the discoloration is strongly dependent on the botanical origin of wood species. The lower lightness changes (ΔL %) were found for all three pine species (16.2 to 37.2%) when compared to fir (54.9%) and spruce samples (91.8%). The Scotch pine wood showed highest values for the contribution of red color initially and low redness change on the surface after the weathering process, among the other softwood species.

WOOD RESEARCH Volume 65, Number 3, 2020
Adam Krajewski, Paweł Kozakiewicz, and Piotr Witomski

Comparison of selected properties of natural aged wood and contemporary timber of Pinus sylvestris L. investigated using standard methods and measuring of transition speed of ultrasounds along the fibre

Scots pine wood (Pinus sylvestris L.) is the most common wood material used in historical buildings in many parts of Central and Eastern Europe. Experiments were conducted natural aged wood (263 – 459 years old), extracted from construction elements of four historical buildings (from seven construction elements), and contemporary wood extracted from 5 construction elements. A strong relationship was observed between density and static bending strength (MOR) of natural aged wood (R2 = 0.5599), and also of contemporary timber (R2 = 0.7863). Antique wood compared to contemporary wood with the same average moisture content and density is characterized by significantly lower modules (static and dynamic), the speed of ultrasonic waves transitions, and bending strength. Differences in these properties increase with increasing wood density.

WOOD RESEARCH Volume 65, Number 3, 2020
Mengpei Liu, Qingxin Du, Panfeng Liu, Jun Qing, Hongyan Du, and Lu Wang

Characterization of new mutant Eucommia ulmoides constituents in the discoloration during growing

A new mutant E. ulmoides with red xylem is found, and this red color will gradually metabolize over time. Comparisons of chemical properties and metabolites of xylem between the mutant and wild type were analyzed in this study in order to discover the cause of the red mutation. The results showed that the acid-insoluble lignin content of mutant type was about 13.83% higher than that of wild type, but the crude protein of wild type was almost 2 times of mutant type. Meanwhile, 6 most important amino acids and amino acid derivatives were detected, which had significant correlation with crude protein. Additionally, the contents of organic acids, polyphenols and alkaloids in the mutant type were 243%, 316% and 281% of those in the wild type, respectively, while the contents of flavonoids and phenolamines contents were 78.8% and 27.3% of those in the wild type, respectively. These results will provide an important reference for understanding the wood color variation during growing.

WOOD RESEARCH Volume 65, Number 3, 2020
Matej Holc, Igor Karlovits, David Ravnjak, Aleš Palatinus, and Ita Junkar

Influence of gaseous plasma treatment on functional properties of coated papers

Three different types of paper with different coatings have been used in order to study the influence of gaseous plasma treatment on surface properties of paper. Radio frequency (RF) oxygen plasma was used for treatment of papers that contain different parts of organic and inorganic components in their coatings. Surface properties like surface morphology, roughness, surface energy, wettability, and chemistry were studied. The influence of plasma modification was also studied in terms of printability and paper gloss, which are one of the key parameters that dictate the use of such paper in desired applications. The results indicate that plasma modification of different types of coatings indeed influences paper printability as well as gloss function, which was shown to be highly connected with surface morphology, as micro- and nanopores were opened or formed due to selective plasma etching of organic part of the coating. Moreover, significant increase in surface energy was observed on all plasma treated papers, however this seemed not to influence much on the printing and gloss properties.

WOOD RESEARCH Volume 65, Number 3, 2020
Ivana Plazonić, Željka Barbarić-Mikočević, and Nikola Španić

Effect of agricultural residue fibers on newsprint strength properties

As newsprints, mostly made from recycled wood pulp, are not high quality papers according to its optical, mechanical and chemical characteristics, in this research the usage of straw pulp as an alternative raw material was analyzed. For that purpose, straw pulp was mixed with recycled wood pulp and strength properties of laboratory made papers were determined according to TAPPI standards. Selection of agricultural waste for preparing straw pulp was based on annual yield of crop species (Triticum spp., Hordeum vulgare L. and Triticale sp.). Results indicated that straw pulp can be efficiently used in portions up to 20% as a substitute for wood fibers or as an additive in order to obtain particular newsprint properties.

WOOD RESEARCH Volume 65, Number 3, 2020
Monika Stankovská, Mária Fišerová, Juraj Gigac, and Elena Opálená

Blending impact of hardwood pulps with softwood pulp on tissue paper properties

The influence of proportions of bleached birch, eucalyptus, beech kraft pulps as well as the bleached aspen chemi-thermomechanical pulp (BCTMP) in the mixture with bleached pine kraft pulp on tissue paper properties was compared. Increase of bleached beech kraft pulp and aspen BCTMP proportion in a mixture with bleached pine kraft pulp leads to significant rise of porosity ε as well as bulk. The water absorption after immersion increased significantly with increase of aspen BCTMP content in the mixture while other hardwood pulps in the mixture had only moderate impact. Increasing of bleached beech and eucalyptus kraft pulps content in the mixture continually increased initial water absorption. As a result of blending of bleached birch kraft pulp with bleached pine kraft pulp, bulk softness improved and the tensile index increased slightly. The increased content of bleached birch and beech kraft pulp in the mixture increased the brightness while the addition of aspen BCTMP and bleached eucalyptus kraft pulp increased of coordinate b* value. Mixed pulps with properties suitable for different types of hygienic products were selected.

WOOD RESEARCH Volume 65, Number 3, 2020
Yulai Yanbaev, Rida Sultanova, Liubov Blonskaya, Svetlana Bakhtina, Albina Tagirova, Vadim Tagirov, and Aleksey Kulagin

Gene pool of Scots pine (Pinus sylvestris L.) under reforestation in extreme environmen

The article is devoted to the study of the gene pool formation mechanisms of arboreal plant populations at the sites of mining and processing of mineral resources and may be useful in managing the processes of natural forest remediation of disturbed lands. The aim of the research is to study the genetic diversity and spatial differentiation of the Scots pine (Pinus sylvestris L.) undergrowth thriving on the industrial waste discharge of the Uchaly Mining and Processing Plant (the Southern Urals).
Isoenzymes of 7 enzymes were used as markers (encoded by 10 polymorphic loci Aat-1, Aat-2 and Aat-3, Gdh-1, Fdh-1, Lap-1, Lap-1, Skdh-1, 6-Pgdh-1 and Dia-1), separated by polyacrylamide disc electrophoresis. Genetic variability of the undergrowth under the forest canopy (7 samples, average number of avenues per locus A = 2.3-2.8, the observed heterozygosity was HO = 0.207 – 0.260, the expected heterozygosity HE = 0.201 – 0.273) and in industrial waste discharges (4 samples, A = 1.9 – 3.1, HO = 0.225 – 0.277; HE = 0.240 -0.298) varies over a wide range. In the parent stand, the observed heterozygosity (HO = 0.203) was lower than in any of the undergrowth samples. A comparatively high genetic differentiation of the undergrowth was found (the between-sample subdivision FST index was 3.8%, the average Nei genetic distance DNei = 0.015 with changes in individual pairs from 0.003 to 0.032), comparable with genetic differences in geographically separated populations.

WOOD RESEARCH Volume 65, Number 3, 2020
Peixing Wei, Wanyong Tuo, Sheng He, and Guohua Liu

Heat-induced inkless eco-printing inspired by paper discoloration: A review

In this paper, the art-of-the-state of heat-induced inkless eco-printing (HIEP) technology in recent years was summarized and prospected, mainly from the printing effect, degree of carbonization, environmental impact and feasibility. The main results were as following: (1) The paper used in HIEP is predominantly yellow in color, which enables a practical printing effect. (2) After HIEP, the paper exhibits no significant carbonized microstructure and keeps its high strength. (3) HIEP is an ecologically and environmentally preferable technology. Only a small amount of toxic products is generated, and no carcinogens are emitted. (4) No significant damage to the paper is evident following HIEP, as the degree of heat experienced during HIEP is far below that experienced during a thermogravimetric (TG) experiment. Additionally, the evaporated water has a buffering effect. Based on the previous research results, this paper finally pointed out the possible research direction in terms of discoloration mechanism and printing effect, environmental impact improvement, paper damage mechanism and strength during HIEP, high-temperature printing head installation and relevant techniques, optimization of printing process parameters.

WOOD RESEARCH Volume 65, Number 3, 2020
Nurdan Cetin Yerlikaya and Abdurrahman Karaman

Effect of the fabric reinforcement of structural holes in wood based panels

The objective of this study was to determine the effects of the glass fiber fabric reinforced holes in MDF, PB, OSB, and PL. The fabrics of 19 mm or 50 mm wide were used to reinforce the edge or flat surface of test specimens. The experimental sample groups were formed in 34 different ways. Three different holes configurations were prepared. The samples were subjected to the 3 points bend testing in the flatwise and edgewise directions. As a result of tests, bending strength and modulus of elasticity were determined. The data obtained separately in flatwise and edgewise bending tests were subjected to multiple variance analysis. According to experiment results, the lowest values were obtained in the “fabricless” in both tests. The lowest value was obtained as 12.35 N.m-2 (in PB material) in the group 12, which has samples with the fabric on the edge and 2 holes on the surface in the flatwise test, while the highest value was obtained as 49988 N.m-2 (in PL material) in the group 19, which has samples with the fabric on the bottom edge and holeless in the edgewise test. According to the materials, the lowest values were as 18.32 N.m-2 in PB material, while the highest values were 49988 N.m-2 in PL material. It was determined that the BS and MOE values decreased between 0.3 and 49% in terms of the effect of the hole with fabric on the edge. In the holeless groups, the lowest values 18.32 N.m-2 in flatwised were obtained in fabricless group in PB, while the highest values 49988 N.m-2 in edgewised were obtained in the group of fabric on top surface in PL. The results showed that the fabric reinforcement has a positive impact on the strength.

WOOD RESEARCH Volume 65, Number 3, 2020
Wen-Gang Hu, Na Liu, Lu Xu, and Huiyuan Guan

Study on cold/warm sensation of materials used in desktop of furniture

The aim of this study was to investigate the cold/warm sensations of materials used in desktop when forearms touching desktop. Both experimental tests and subjective evaluations were conducted in this study. A device was developed used to simulate forearm in order to replace subjects. Five men and five women were selected and introduced to six types of materials and two types of environmental temperatures in the tests. The results showed that the effects of environmental temperature on contact temperature of all tested materials were statistically significant, and the differences among wood and wood based materials, plastic materials, and artificial stone were also statistically significant. The device developed in this study was qualified to measure the contacting temperature between forearm and desktop sustainably and steadily, which can reduce the error introduced by subjects. Although qualitative relation was found between contact temperature and subjective evaluations, no quantitative correlation was proved.

WOOD RESEARCH Volume 65, Number 3, 2020
Nikola Velimirović, Ivan Stanimirović, Dragoslav Stojić, Nemanja Marković, and Milivoje Milanović

Economical design of timber-concrete composite beams

The aim of the presented study is to find the best solution for the cross-sectional dimensions of timber-concrete composite (TCC) beam by focusing on serviceability limit state verification and cost of the beam, simultaneously. The population of 10.000 samples of the observed variables according to the predetermined ranges using Monte Carlo sampling method was generated. In order to find a number of Pareto-optimal solutions on the Pareto front, the weighted sum method was employed using original algorithm. The results have shown that minimum relative cost of the TCC beam can be increased even by 26.6% if the rheological effects that are neglected by the Effective modulus method are counted in the calculation of the final deflection. The presented trade-off strategy in design of the TCC beams has shown that with the slight increase of relative cost compared to the minimum, it is possible to get Pareto optimal design solution of the TCC beam that has drastically decreased final deflection and therefore is a more reliable design solution.

WOOD RESEARCH Volume 65, Number 3, 2020
Esra Celik, Ismail Cengiz Yilmaz, and Deniz Yilmaz

An experimental study on sustainability of historical wooden buildings exposed to open sea streams

This research deals with the impact of the microclimate on historical wooden buildings exposed to open sea streams. The Florya Ataturk Marine Mansion in Istanbul, erected on the sea, totally defenceless to weather and sea effects, has been selected as representative case study for many other buildings located in Bosphorus line. In order to address the effect of the environment on the building exposed to open sea streams microclimatic data were collected for one year. The synergistic effect of the sea-salt aerosol and microclimatic conditions were discussed for the assessment of the impact of the marine environment on the durability of the Mansion, identifying the more vulnerable parts of the building as well as the more critical periods. The results indicate that while moisture content changes from 20.9% to 36.7% and temperature changes from 14.1°C to 28.7°C, thermal conductivity coefficient changes from 0.18 W.m-1K-1 to 0.26 W.m-1K-1, according to the facade of the building and the season as similar to previous studies.