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.

WOOD RESEARCH Volume 65, Number 4, 2020
Włodzimierz Szewczyk and Maria Bieńkowska

Effect of corrugated board structure on mechanical properties

The article shows the method for prediction of corrugated board properties based on automatic generation of a database containing material compositions of all the boards possible to be produced by a given manufacturer. With their large number it is not possible to carry out on the basis of measurements made on earlier manufactured products. As a result of the tests carried out with the use of data provided by the corrugated board manufacturer, it was found that using his paper materials and machinery it was possible to more than double increase the bending stiffness and edge crush resistance indexes of produced board. In some cases, the options for improving the indexes are slightly smaller, e.g. bending stiffness in the cross direction of three-layer board with flute C, the mentioned manufacturer can increase by approx. 40% of the maximum value obtained so far.

WOOD RESEARCH Volume 65, Number 4, 2020
Quan Li, Huimin Zhang, Hongguang Yan, Wenyu Qi, Jinguo Lin, and Jiqing Li

Emission of volatile camphor compounds from Cinnamomum camphora wood

Essential oil volatilization of Cinnamomum camphora (L.) Presl can positively affect indoor air quality through insect dispersal, antibacterial effects, and inhibiting decay, and thus is an important economic species in China. Camphor is the most abundant aromatic compound in C. camphora, although how time and temperature affect the release of the camphor is unknown. To address this question Cinnamomum camphora (C. camphora) wood was investigated using headspace gas chromatography (HS-GC). Camphor decreased with increasing detection times over temperatures of different temperature. During the detection, the release rate of camphor decreased rapidly with increased heating time in the first 2.5 h, and leveled-off after 2.5 h. The release of camphor at different temperatures was linear between 0 ~ 1.4 h.
By fitting this linear model with reaction temperature camphor release could be expressed as Y = -75.369 + 2.3786.T + (41.125 – 1.1972.T). Evaluating the release of camphor from C. camphora wood and creating a model may be useful for promoting its application in the medical and chemical industries.

WOOD RESEARCH Volume 65, Number 4, 2020
Onur Ulker and Mercan Haddad Derafshi

Evaluation of corner joint strength of composite panels bonded with modified starch

The objective of this research was to evaluate the strength of corner joints of box shaped furniture made from eastern red cedar (Juniperus virginiana L.) and corn starch binder southern sample. Various types of corner joint techniques were evaluated (glued, glued and screwed, and glued with dowel corners). Eastern redcedar particle samples with corn starch and glutaraldehyde were used. Overlaid and non-overlaid particleboards along with sandwich panels were used at “L” type corner joints. Tension and compression strength moment values were measured. Particleboard panel joint mounted with dowel resulted in the highest tension strength moment values followed by the specimens having a sandwich-type configuration combined with a dowel. Particleboard and overlaid sandwich-type panels glued with polyvinyl acetate (PVAc) had the lowest strength values. It appears that composite panels manufactured with modified starch have the potential to be used for corner joints.

WOOD RESEARCH Volume 65, Number 4, 2020
Andreas Treu and Erik Larnøy

Short note: The impact of glue-lines on the protective effect of a low- pulsed electric field in wood

A wood protection method using electric fields to inhibit wood decay by brown rot fungi has been investigated in laboratory trials. Glued and non-glued wood samples were exposed to fungal attack for 6 weeks in Petri dishes and showed significantly reduced mass loss when connected to a low pulsed electric field (LPEF). The mass loss of LPEF-protected samples was in average lower than 10%, with a wood moisture content above 40%. The mass loss of untreated wood samples was above 30% in average. The glue line did not represent a barrier for the electric field in the test setup (a), where the glue line was applied on the transverse section of two glue-jointed wood sample halves. A test setup with two glue lines at the tangential side of three jointed wood samples, showed only slightly higher mass loss compared with wood samples consisting of two jointed halves. It is concluded that glue lines using the MUF glue mix used in this study do not impede the protective effect of LPEF.