WOOD RESEARCH Volume 64, Number 1, 2019
Bailing Sun, Zhe Wang, and Junliang Liu

Study on color and surface chemical properties of Eucalyptus pellita wood subjected to thermo-vacuum treatment

The objective of this study was to investigate the color and surface chemical properties of Eucalyptus pellita wood subjected to thermo-vacuum treatment. Specimens were thermally modified in a vacuum at various temperatures for 4 h. The color parameters of untreated and heattreated samples were measured using the CIE Lab method. Surface chemical properties were evaluated by UV-Vis spectroscopy, 13C NMR spectroscopy and X-ray photoelectron spectroscopy. The results showed that eucalypt wood became darker uniformly throughout with the increase of treatment temperature, and the total color variation ΔE* obviously increased at higher temperature. The spectral changes indicated that degradation and oxidation of hemicellulose, lignin and extractives contributed to the formation of color substances during thermo-vacuum treatment. Crystalline content of carbohydrates increased. The decrease in O/C ratio signified the increase of the relative content of lignin and extractives on the wood surfaces in the heating process.

WOOD RESEARCH Volume 64, Number 1, 2019
Pažitný Andrej, ALBERT RUSS, Boháček Štefan, Monika Stankovská, and Štefan Šutý

Various lignocellulosic raw materials pretreatment processes utilizable for increasing holocellulose accessibility for hydrolytic enzymes Part I: Evaluation of wheat straw pretreatment processes

New requirements for the biofuels industry force individual enterprises to develop various procedures for newly selected substrates pretreatments that could be applicable in processing of large quantities of raw materials. Even greater pressures are on second-generation biofuels producers justified by selection of waste lignocellulosic substrates and methods of substrate processing. Among the most suitable lignocellulosic raw materials in Slovak Republic (SR) for 2G bioethanol production is wheat straw. This raw material (Senec region, SR) for enzymatic hydrolysis was pretreated by dry milling (Brabender), cyclic freezing and thawing, wet milling (Sprout Waldron), two-step process of steam explosion at 180°C and extrusion at 145°C and one-step process of steam explosion at different temperatures. Wheat straw holocellulose accessibility was tested by adsorption of three commercially available dyes (Pylam Products Company, Inc., USA). Absorptivity coefficient of each dye at its maximum wavelength was determined from individual calibration curves of dyes and their values resulted ranging from 13.78 to 19.52 dm3.g-1.cm-1. The absorption of solution was measured and concentration of residual dye was calculated at given wavelength. The accessibility of holocellulose contained in wheat straw pretreated by steam explosion was controlled by SEM (scanning electron microscope) in correlation with the ratio of adsorbed dyes according to the modified Simons’ method.

WOOD RESEARCH Volume 64, Number 1, 2019
Xiangyu Zhao, Dengyun Tu, Chuanfu Chen, and Qiangfang Zhou

Prediction of the mechanical properties of thermally-modified rubber wood on the basic of its surface characteristic

The goal of this research was to investigate the effect of thermal treatment on mechanical properties and surface characteristic of rubberwood (Hevea brasiliensis) and find the mathematical model to predict the mechanical properties used by its surface characteristic. Rubberwood specimens were treated by steaming at five different temperature levels of 170, 185, 200, 215, and 230°C for two different durations of 1.5 and 3 h. Based on the results, the values of bending strength, modulus of elasticity, compression strength and impact bending decreased, and the glossiness and chromatic aberration (∆E) increased with increasing temperature and enlarging duration further. This study revealed that chromaticity parameters b*, ∆E and the gloss of perpendicular to grain (GZT) could evaluate the mechanical properties of thermally-modified wood to achieve the mechanical properties detection without destruction.

WOOD RESEARCH Volume 64, Number 1, 2019
Saban Kart, Ergun Baysal, Mustafa Kucuktuvek, Turkay Turkoglu, Hilmi Toker, Caglar Altay, Cihan Cibo, and Huseyin Peker

Some surface characteristics of varnished thermowood after weathering

This study was designed to investigate some surface characteristics such as glossiness and surface roughness changes of varnished thermowood after six months of weathering. Thermal modification of Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) wood were carried out by hot air in an oven for 1, 2, and 3 hours at 205, 215, and 225°C. After the modification process, wood specimens were varnished using a polyurethane varnish (PV) and cellulosic varnish (CV). The natural weathering process caused an increase in the surface roughness of the test specimens according to the test results. The Scots pine and Oriental beech test specimens which were heat treated and varnished gave more favorable results compared to only varnish test specimens after natural weathering in terms of surface characteristics such as surface roughness and glossiness. Generally, as the heat treatment time and temperature increase, it is observed that the surface characteristics of the Scots pine and Oriental beech wood specimens improve positively. According to the results of the tests, the samples varnished with polyurethane varnish gave better results in terms of surface roughness at the end of the natural weathering process, whereas the samples varnished with cellulosic varnish gave better results in terms of glossiness values.

WOOD RESEARCH Volume 64, Number 1, 2019
Krzysztof Joachimiak, Renata Wojech, and Adam Wójciak

Comparison of Miscanthus giganteus and birch wood nssc pulping Part I: The effects of technological conditions on certain pulp properties

Chemical composition and susceptibility to delignification by neutral sulfate liquor of Miscanthus giganteus stems and of birch wood were compared. The yield of pulping as well as degree and selectivity of delignification were tested in various technological conditions (cooking time, hydro module, alkali charge). Having a similar chemical composition, Miscanthus giganteus stems are subjected to quicker and deeper delignification with neutral sulfite liquor than birch wood. This phenomenon is probably associated with differences in the qualitative composition of lignin, distribution of lignin in the cell walls and in the morphological features of both raw materials.

WOOD RESEARCH Volume 64, Number 1, 2019
S. Sadiye Yasar

Effects of wood preservatives on the combustion process and combustion quality of wood

This study examines the combustion properties of Scots pine (Pinus sylvestris L.) and Oriental beech (Fagus orientalis L.) in 3 stages (CWF, SC and EC) according to ASTM E 160-50 (1975). Wood samples were impregnated with Tanalith-E (T) and Wolmanit-CB (WC) and then were varnished with Synthetic (St) and water based (wb) varnishes. When the combustion was completed, the weight loss, combustion temperatures, illuminance values, total time of combustion, and demolition time were measured. As the result, illuminance value of Oriental beech wood decreased, while the smoke density increased. Scots pine was later destroyed in the combustion process. Areas with a risk of fire are advised to use pine wood instead of beech. Wolmanit-CB and synthetic varnish reduced the temperature and illuminance values. Oriental beech, Tanalith-E, and synthetic varnish resulted in the highest temperatures for all combustion stages. This triple interaction increased total combustion time values by more than 90% when compared with the control samples.

WOOD RESEARCH Volume 64, Number 1, 2019
Faustino Ruiz-Aquino, Sandra Ruiz-Ángel, Javier R. Sotomayor-Castellanos, and Artemio Carrillo-Parra

Energy characteristics of wood and charcoal of selected tree species in Mexico

This study determines the main energy characteristics of wood and charcoal within five tree species of the forest of Ixtlán de Juárez, Oaxaca, México: Alnus acuminata, Arbutus xalapensis, Myrsine juergensenii, Persea longipes and Prunus serotina. Basic density, moisture content, charcoal yield, volatile material, ash content, high heating value, fixed carbon and fuel value index were determined for each one. The average results of the species are in the range of 0.372 to 0.498 g. cm-3 for wood density; 26.19 to 34.12% for charcoal yield; 77.29 to 83.66% for wood volatile matter and 28.40 to 34.25% for charcoal volatile matter; 0.56 to 1.50% for wood ash and 1.13 to 4.83% for charcoal; 19.50 to 24.99 MJ. kg-1 for high heating value of wood and 29.38 to 32.11 MJ. kg-1 for charcoal. It was determined that these species provide a good alternative for burning wood and charcoal. Additionally, these remain untapped resources in the Sierra Juárez region, meaning that awareness and inclusion in management plans could be of relative importance to the development of the forestry sector.

WOOD RESEARCH Volume 64, Number 1, 2019
Xujie Lu, Yong-Gui Li, Xue-Fei Zhou, Fu-Hou Lei, Zu-Guang Liu, and Ting Wang

Degradation of wood fire retardant by UV assisted biomimetic oxidation over Cu([H4]salen) using BDE209 as a model

This work aimed to study mineralization and detoxification of BDE209 by biomimetic oxidation. The removal rate (RR) of BDE209 of process was comparatively investigated in the presence of UV radiation using immobilized Cu([H4]salen) complexes (Cu([H4]salen)/IM and Cu([H4]salen)/SB) as biomimetic catalysts. Their neat and [H2]salen complexes were compared towards BDE209 degradation. UV effects were evaluated according to RR. Ecotoxicities were measured for treated BDE209 solutions and explained in terms of total organic carbon (TOC). The results showed that UV-Cu([H4]salen)/SB process evidently gave high RR and low ecotoxicity in BDE209 degradation, indicating a significant superiority of biomimetic catalysis, complex reduction and immobilization and UV radiation.

WOOD RESEARCH Volume 64, Number 1, 2019
Chuangui Wang, Rongrong Li, Chengqian Liu, and Xiaodong (Alice) Wang

Effects of medium-low temperature hydrothermal treatment on microstructure and dimensional stability of chinese sweetgum wood

To investigate the changes of microstructure and dimensional stability during hydrothermal treatment, the Chinese sweetgum (Liquidambar formosana Hance) wood samples were treated in a numerical show constant temperature water bath with temperature of 60, 80 and 100°C for 4 h. The dry shrinkage rate and water absorption of untreated and treated samples were measured. Scanning electron microscopy (SEM) was selected to observe and investigate the changes of wood microstructure, which caused by hydrothermal treatment. The results showed that dry shrinkage rate increased from 4.92% to 7.00% and 9.62% to 10.12% in tangential direction and radial direction, respectively. However, the shrinkage rate difference (SRD) as an index to evaluate possibility of wood deformation, decreased from 1.96 to 1.45, which meant the shape stability of treated samples improved. The water absorption increased from 93.15% to 112.11%. From the results of SEM, the most sediment on aspirated pits were removed and pit membrane was ruptured after treatment. It had positive effect on moisture migration and wood permeability. It is maybe the reason of the variation of water absorption and dry shrinkage rate.

WOOD RESEARCH Volume 64, Number 1, 2019
Bruno Miguel De Morais Lemos Esteves, Luisa Paula Valente Cruz-Lopes, Ana Paula Fernandes, Jorge Manuel Martins, Idalina De Jesus Domingos, José Vicente Ferreira, Silvia Helena Fuentes Da Silva, and Jalel Labidi

Adhesives from liquefied eucalypt bark and branches

Adhesives made from lignin are one of the most promising alternatives to common ureaformaldehyde adhesives. One of the possible sources is from wood or bark liquefaction at low temperatures and pressure. The possibility of using forest wastes for the production of adhesives was the objective of this work. Eucalypt bark and branches are wastes produced in the company Pedrosa & Irmãos, which is a forest management company based in Portugal (Leiria). The wastes were liquefied with polyalcohols catalyzed by sulfuric acid. The water insoluble fraction of the liquefied material was used for the production of the bio-adhesive. Both fractions were characterized and the bonding performance of the bio-adhesive was tested by ABES. The bio-adhesives obtained from bark or branches were similar, exhibiting a bonding strength approximately half of the conventional UF resin.

WOOD RESEARCH Volume 64, Number 1, 2019
Patrícia Kadlicová, Linda Makovická Osvaldová, Juraj Jancík, and Milan Gaff

Effect of thermal and retarding treatment on flammability rate of tropical tree species

Wood is integral to the construction industry despite the fact that it is a highly flammable material. Due to thermal stress, it is subject to the process of pyrolysis. However, not every type of wood burns the same. This dissimilarity is caused by the changes in its internal structure. Flammability rate of tree species can be modified by means of thermal modification, i.e. change in its internal structure or by using coating compositions which form a fire-protecting layer on its surface. The paper comprises a testing and an evaluation of iroko wood which is predominantly used as floor covering and cladding material for building structures. The authors focus on determining the connection between the structure of this exotic tree type and the eventual thermal degradation (burning course, significant changes, amount of material burnt, etc.) of the samples. Small size samples were used during laboratory measurements. Their width and thickness were approximately the same as for commonly used cladding boards. The data obtained in the laboratory have been processed, transformed into evaluation criteria and connected with theoretical knowledge, creating an overview of its eventual flammability. Laboratory test results prove low flammability rate of test samples. Mass loss was an important criterion. Thermal treatment, which changes the internal structure and thus improves its properties (T group; test samples), had no significant effect on the eventual flammability. On the other hand, the flammability rate of samples was better when using a fire retardant (R and TR group; test samples), because the retardant lowers the flammability by more than half.

WOOD RESEARCH Volume 64, Number 1, 2019
Burak Turkan and Akin Burak Etemoglu

Numerical investigation of wood drying

In this study, forced convective drying process of wood material with rectangular shape was investigated. Firstly, governing equations for the flow field were solved by using ANSYS Fluent. Then average heat transfer coefficient on the surface was calculated by using Standard k-ɛ Turbulence Model. It was found that mass transfer coefficient making use of the relationship between heat and mass transfer. Simultaneous heat and mass transfer equations were solved transiently with Comsol Multiphysics using surface boundary conditions for selected air velocity, air temperature and material thickness. In drying process the moisture and temperature distributions inside the solid were obtained transiently. The mathematical model for equations was formed using Fourier heat and Fick diffusion models. Results acquired from the present model were compared with a study results which are available in literature and it was shown a very good agreement.

WOOD RESEARCH Volume 64, Number 1, 2019
Yushu Chen and Jing Zhu

Study on bending chracteristics of fast growing eucalyptus bookcase shelves by using burgers model

This paper used fast-growing eucalyptus wood to prepare three shelf structures as solid wood puzzle, frame panels, and flat puzzle plus metal wear belt, respectively, and then, a creep tests was examined. After fitting the examined results by Burgers creep model, the long-term creep tendency was predicted from the short-term creep behavior of the three structures. Based on the Burgers creep model analysis, an optimized structure that can alleviate the bending problem on bookcase shelf was obtained. The results also provide practical reference for fast-growing eucalyptus wood for furniture design. During comparative analysis of the bending creep and strain, the results show that the flexural creep properties of frame panel and flat puzzle plus metal wear belt were superior to those of solid wood puzzle. After considering the aesthetics, frame panel was the best structure. Furthermore, the fitting results show that using the Burgers model to analyze the creep process of furniture is a very effective method and has strong theoretical and practical significance.

WOOD RESEARCH Volume 64, Number 1, 2019
Liu Ming-Li, Li Chun-Feng, and Liu Yan-Long

Physical and mechanical properties of modified poplar wood by heat treatment and impregnation of sodium silicate solution

The objective of this study was to improve physical and mechanical properties of fast-growing Chinese white poplar wood (Populus tomentosa Carrière). To this purpose, the heat treatment and impregnation by sodium silicate solution were investigated. In experiments, four processes under four different conditions were applied on poplar wood samples: temperature treatment (T), solution treatment (J), first solution and then temperature treatment (J-T) and first temperature and then solution treatment (T-J). The results showed that all measured mechanical properties were improved under conditions of J process. The hardness, impact toughness, bending strength and modulus of elasticity were improved by 8.4%, 29.2%, 12.0% and 16.1%, respectively. Additionally, tested wood samples exhibited significant increasing of values some mechanical properties such as hardness (70.1%) and modulus of elasticity (80.4%) in comparison with values for untreated samples if treatment was conducted under J-T process conditions. Treated wood by this technology could be utilized as solid wood composite or material for flooring substrate.

WOOD RESEARCH Volume 64, Number 1, 2019
Dong Chen, WEI ZHANG, Yu-Sheng Wu, Zheng Jin, and Qian-Wei Zhang

Investigation on the mechanical properties of open-hole spruce and douglas fir

Spruce and Douglas fir are the main materials of today’s modern wooden structure buildings. In wooden structure buildings, holes often have to be created on the building components in order to reserve channels for pipelines. At present, there are no detailed studies regarding the mechanical properties of these two kinds of lumber under open-hole condition. In this paper, universal mechanical testing machine was utilized to perform three-point bending tests on small samples of spruce and Douglas fir with open-hole (opening diameters being Ø13, Ø16, Ø20 respectively) and without open-hole. The bending strength and modulus of elasticity of openhole and no open-hole samples were compared, the effects of hole sizes on samples mechanical properties were analyzed and discussed, and the samples’ failure patterns and failure mechanisms were also studied. The experiments were loaded at a constant speed 5 mm. min-1 until the sample was broken, with the loading time controlled within 2 – 3 minutes. The results showed that: open-hole had significant impact on the bending strength of both kinds of lumber. In terms of failure modes, most of the Douglas fir samples were deformed only at the compression point before failing, while the Spruce samples not only formed grooves at the compression point but also cracked at the bottom. This indicated that compared with Douglas fir, the impact of open-hole on Spruce lumber was greater, thus open-hole should be avoided on Spruce components during construction. The experimental results provided a basis for future studies on the failure modes of these two materials and also the strength design of relevant components.

WOOD RESEARCH Volume 64, Number 1, 2019
Jing Qian, Jinpeng Li, Zhenyu Wang, Lijie Qu, Yu Ding, Songlin Yi, and Zhengbin He

Effects of wax and dimethyl silicone oil mixed impregnation on dimensional stability of two hardwoods

In this experiment, cocobolo (Dalbergia retusa Hesml.) and African padauk (Pterocarpus soyauxii) specimen were selected before treating with wax, wax + 20% dimethyl silicone oil, wax + 40% dimethyl silicone oil at 120°C for 3 h and 6 h respectively. The weight gain percentage (WPG), radial swelling coefficients (RS), tangential swelling coefficients (TS), chemical composition and strength of hydroxyl groups were investigated. The results indicated that three factors affect dimensional stability, including the impregnation time, tree species and ratio of wax /dimethyl silicone oil. The degree of a melioration in the dimensional stability increase as the impregnation time increase from 3h to 6h. The effect of the impregnation on the dimensional stability of the African padauk was better than that of the cocobolo. Wax+ 40% dimethylsilicone oil was the optimal condition in this study. Wax and dimethylsilicone oil mixed impregnation can improve the dimensional stability to a certain extent, which provides a new idea for the wood modification.

WOOD RESEARCH Volume 64, Number 1, 2019
Tungalag Ayush, Ayursed Jigjjav, Bayartsetseg Baasan, Yus Andhini Bhekti Pertiwi, FUTOSHI ISHIGURI, and SHINSO YOKOTA

Drying performance of a direct-fired kiln developed in Mongolia

Smoke drying by means of a direct-fired kiln is considered to be one of the most cost-effective methods of drying lumber. In the present study, Siberian larch (Larix sibirica) lumber was dried using a direct-fired kiln developed in Mongolia. When approximately 500 kg of sawdust was used as fuel, the maximum and mean temperatures in the kiln were 78.2°C and 54.2°C for the lower side, respectively, while they were 70.4°C and 50.1°C for the upper side, respectively. The temperature inside the kiln was above 60°C for a duration of about 40 to 50 hours. The moisture content of the lumber decreased from 56.4% to 23.2%. No significant differences in terms of the mechanical properties were found between air- and smoke-dried wood. Based on these results it appears that the direct-fired kiln developed in Mongolia is useful for the low-cost drying of Siberian larch lumber, although improvements to the kiln and a prolonged drying schedule are needed in order to obtain more dried lumber.