WOOD RESEARCH Volume 61, Number 6, 2016
Xuexia Zhang, Yan Yu, Zehui Jiang, and Hankun Wang

Influence of thickness and moisture content on the mechanical properties of microfibrillated cellulose (MFC) films

Microfibrillated cellulose (MFC) films with a layered structure and controlled thickness were successfully prepared, from bamboo processing resides as the source material, using ultrasonication followed by simple vacuum filtration. The effects of thickness and moisture content on the mechanical properties of the films were then investigated. It was shown that tensile stress and elongation at break were notably affected by the thickness of the MFC film, where the tensile stress and elongation at break of the film increased from 124 to 179 MPa and 0.9 to 5.5 %, respectively, as film thickness increased from 7.4 to 205.4 μm. However, no notable effect of thickness was observed on the Young’s modulus (~10.8 GPa). It was also found that moisture content has a significant impact on the tensile properties of MFC films, in lowering the Young’s modulus from 12 to 2 GPa and tensile stress from 180 to 90 MPa, and increasing the elongation at break from 4.2 to 17.5 %, as moisture content increased from 3 to 60 %. This is due to the effect of water in softening MFC films, resulting in a reduction in strength and increase in flexibility.

WOOD RESEARCH Volume 61, Number 6, 2016
Lenka Melzerová, Lucie Kucíková, Tomáš Janda, and Michal Šejnoha

Estimation of orthotropic mechanical properties of wood based on non-destructive testing

This paper presents a simple approach for the derivation of effective properties of wood while accounting for its inherent anisotropy. These properties are found by combining the results of structural indentation using the Pilodyn 6J testing device and analytical homogenization in the framework of an inverse approach. This approach provides first a rough estimate of a microfibril angle and subsequently yields the predictions of the effective properties of wood. While applicable to any kind of wood we adopted the proposed methodology to spruce as a typical representative of soft wood. This allows us to exploit the presented results directly in the analysis of glued laminated timber beams made of spruce wood which is a principal goal of the present research.

WOOD RESEARCH Volume 61, Number 6, 2016
Olena Pinchevska, Andriy Spirochkin, Ján Sedliačik, and Rostislav Oliynyk

Quality assessment of lumber after low temperature drying from the view of stochastic process characteristics

The quality of lumber drying is traditionally evaluated after the process. This paper proposes the algorithm of quality assessment of low-temperature convection lumber drying in accordance with the target values of the average final moisture content and its dispersion in the stack. The stochastic model of the process with random initial and boundary conditions, which allows calculating the dispersion of the final moisture content (MC) was proposed. To describe the kinetics of the wood drying process in the low-temperature chamber in view of the thermodynamic characteristics, 34 processes of drying of oak and pine lumber with the thickness of 30, 40 and 50 mm were made at the wood-processing enterprises in Ukraine. The theoretical equations of lumber low-temperature drying and the values of the coefficients that characterize the influence of material thickness, temperature and moisture fields’ distribution in the material during the drying process were obtained. The check of the proposed models on the uniformity of the average values and dispersion of the current moisture content showed a slight difference between the experimental and calculated values. These models allow predicting the quality of the low-temperature drying on the spread of target moisture content, which enables selection of rational drying schedules.

WOOD RESEARCH Volume 61, Number 6, 2016
Alperen Kaymakci, Nadir Ayrilmis, and Huseyin Akkilic

Utilization of tinder fungus as filler in production of HDPe/wood composite

Selected physical and mechanical properties of high density polyethylene (HDPE) composites filled with various mixtures of wood flour and tinder fungus (Fomes fomentarius) were investigated. For this aim, different mixtures of tinder fungus flour and wood flour (0/40, 10/30, 20/20, and 30/10, and 40/0) (by weight) were compounded with HDPE with a coupling agent (maleic anhydride grafted polyethylene (MAPE) in a twin screw co-rotating extruder. The test specimens were produced by injection moulding machine. The thickness swelling and water absorption of the HDPE/wood composites significantly decreased with increasing content of the tinder fungus flour. The mechanical properties of the composites were negatively affected by increasing amount of tinder fungus flour but there were no significant differences up to 30 wt % tinder fungus content, except for the tensile strength. The optimum physical and mechanical properties for the filled HDPE composites were found to be a 10/30/60/3 formulation of wood flour, tinder fungus, HDPE, and MAPE, respectively.

WOOD RESEARCH Volume 61, Number 6, 2016
ROMAN RÉH and Martin Guoth

Thermoplastic plywood and it’s drawback when moderately heated

GradaTM is new plywood which contains the thermoplastic adhesive. There are so far two material versions 1000 and 2000 which have wide potential in production of wooden products with new perspective of manufacturing. This paper investigates possibilities of including GradaTM material and its versions in skateboard production. Bending strengths at the moderate heat up of this material are presented, specifically at 30, 40°C for both material versions. All increased temperatures are compared to the room temperature (20°C). Mechanical properties that were obtained from the test are modulus of elasticity, modulus of rapture, and stroke strain. The results show the undesirable level of changes present in both versions however version 1000 acts significantly better than 2000.

WOOD RESEARCH Volume 61, Number 6, 2016
Suleyman Ustun, Ergun Baysal, Turkay Turkoglu, Hilmi Toker, Cevdet Sacli, and Huseyin Peker

Surface characteristics of scots pine treated with chemicals containing some copper compounds after weathering

In this study, it was aimed to investigate surface hardness, gloss, and color changes of Scots pine treated with chemicals containing some copper compounds after six months weathering. Adolit KD-5 (AD KD-5), celcure AC-500 (CAC-500), and wolmanit CX-8 (WCX-8) were used as impregnation chemicals containing copper compounds. Scots pine wood specimens were treated with 2 % aqueous solution of chemicals according to ASTM D1413-07e1 (2007) standard. Results showed that while surface hardness and gloss values of untreated Scots pine wood specimens were decreased after weathering, they increased treated Scots pine wood specimens after weathering. The decrease in L* of untreated and treated wood indicates that the specimens became darker after weathering. While weathering caused less green and less yellow for untreated control specimen, it caused less red and less yellow for treated wood. Treated Scots pine wood specimens showed better color stability compared to untreated Scots pine after weathering. In terms of surface hardness, gloss, and color stability values CAC-500 treated Scots pine gave the best results after weathering.

WOOD RESEARCH Volume 61, Number 6, 2016
Juraj Gigac, Monika Stankovská, and Pažitný Andrej

Influence of the coating formulations and base papers on inkjet printability

At the coating were used two substrates, commercial base paper and base paper produced in pilot experimental paper machine. The printing quality varied at both base papers. The coating colours contain commercial silica and precipitated calcium carbonate pigments. As a binder was used polyvinyl alcohol and cationic starch combined with high-cationic polymer SMAI 1000. Colour gamut significantly improved when the inkjet ink contact angle decreased below 14° independently of the base paper. The order of coating colours effect on the base papers was similar. Application of silica pigment in the coating colour provided papers with the largest inkjet ink wetting, the best colour gamut area, print sharpness and smoothness. By using of polyvinyl alcohol, a high colour gamut area was reached but it resulted in a markedly low print sharpness in comparison with cationic starch. Coating of base paper produced in pilot experimental paper machine introduces papers with higher colour gamut and also print sharpness.

WOOD RESEARCH Volume 61, Number 6, 2016
Birol Üner, Kenan Kömbeci, and Mehmet Akgül

The utilization of tomato stalk in fiber production: NAOH and CAO pulping process

This study was conducted to explore the utilization of tomato stalk in the paper industry. Fiber morphology of the material was determined according to standard test methods and average fiber length was found to be 980 μm and the width of the fiber was 15 μm. As a result, slenderness ratio was resolved to be around 60. This was considered to be comparable fiber with the most of the hardwood species. Tomato stalks were cooked with soda and lime in a separate process. Screened pulp yield was determined to be 35-45 %. Soda pulp of tomato stalks showed good mechanical properties when temperature raised to 135ºC and low alkali concentration (10 %) and lime pulps showed properties as well as that soda pulp at 135ºC and high alkalinity ratio (30 %).

WOOD RESEARCH Volume 61, Number 6, 2016
Adam Wójciak

Deacidification of paper with Mg(OH)2 nanoparticles: The impact of dosage on process effectiveness

The aim of the work was to analyse the influence of Mg(OH)2 nanoparticle dosage on the deacidification process, especially in relation to paper permanence. Samples of model papers were characterised by SEM-EDX and XPS methods which proved effective neutralisation. The influence of the suspension concentration was evaluated on cellulose DP and on the optical properties after the paper thermal ageing process. Generally, the protective effect of deacidification increased along with an increased dosage of the magnesium hydroxide nanoparticles in artificially acidified paper samples and in papers covered with iron gall ink.

WOOD RESEARCH Volume 61, Number 6, 2016
Bo-Han Xu, Yan-Hua Zhao, Jing-Hua Guo, and Ya-Xun Wang

Fracture toughnesses of interlaminar fracture of glued-laminated timber

Critical strain energy release rate GC and stress intensity factor KC are both defined as fracture toughness, and they can be converted to one another through an equivalent elastic modulus for wood fracture. Whereas the equivalent elastic modulus for interlaminar fracture toughness of glued-laminated timber (glulam) is kept unknown. This paper briefly presented Modes I and II interlaminar fracture toughnesses of glulam, which were obtained from double cantilever beam (DCB) and three-point bending end-notched flexure (3ENF) tests using finite element method (FEM). On the basis of Hankinson-type formula and equivalent elastic modulus of wood fracture, this study developed two empirical expressions to calculate the equivalent elastic moduli for Modes I and II interlaminar fracture of glulam.

WOOD RESEARCH Volume 61, Number 6, 2016
Onur Ülker and Erol Burdurlu

Some mechanical properties of densified and laminated Lombardy poplar (Populus nigra L.)

In this study, it was studied the effects of densification and then lamination processes on some mechanical properties of Lombardy poplar (Populus nigra L.), which is one of the low density tree species. Densification temperatures were 80, 100, 120 and 140ºC and ratios of densification were 15, 30 and 50 %. Furthermore, lamellas with a thickness of 4 mm cut from densified materials were laminated by bonding one on top of the other with urea formaldehyde (UF) and polyvinyl acetate (PVAc) adhesives. Bending, modulus of elasticity, compression and tensile tests were applied by preparing specimens from the pieces. According to test results, the most suitable temperature level was 120°C. As the ratio of densification was increased at this temperature level, increase were observed in the mechanical properties. Also, lamination provided significant increases in the mechanical values compared to laminated but undensified Lombardy poplar. Increases were observed in the mechanical properties reaching 444 % with application of densification and lamination processes.

WOOD RESEARCH Volume 61, Number 6, 2016
Xu Jiahe, Zhou Yucheng, Qi Yuhan, Hou Xiaopeng, Ge Zhedong, and Chen Yongping

A weighted filtered back projection algorithm for log CT two-dimensional and three-dimensional image reconstruction

Log computer tomography (CT) image reconstruction is the kernel of wood CT nondestructive testing (NDT) technology. In this paper, based on the logs physical properties and the X-rays propagation characteristics in solid, the X-ray wave equation inside logs is deduced. A weighted filtered back projection (FBP) algorithm for log CT image reconstruction is proposed. Four group of logs are chosen for simulations on the weighted FBP algorithm. In the twodimensional image reconstruction process, the capabilities between conventional FBP algorithm and weighted FBP algorithm are compared to verify the effectiveness of the algorithms for logs of different species. From both the image quality and data results, it can be clearly seen that the weighted FBP algorithm has good performance and advantages for image reconstruction process of log CT scan. The three-dimensional log image reconstruction is well completed, but has a big room for improvement.

WOOD RESEARCH Volume 61, Number 6, 2016
Iveta Marková, Eva Mračková, Alena Očkajová, and Juraj Ladomerský

Granulometry of selected wood dust species of dust from orbital sanders

Formation and presence of dust in the timber premises is part of the technology. Dust is generated as a byproduct based on the method of machining. The paper deals with granulometric analysis of selected samples of wood dust sessile oak (Quercus petraea Liebl.) and from deciduous multiple-pore wood there was chosen European beech (Fagus sylvatica L.) and alder (Alnus glutinosa L.) and the mixture taken directly from timber production of grinders SCM SANDYA 300RCS) for the purpose of selecting the percentages of the various fractions (0.032; 0.063; 00:08; 0.125; 0.250; 0.5; 1; 2 mm) of samples of wood dust. Wood dust samples were made using a hand orbital sander BOSCH PSS 200AC and sizing on the automatic mesh vibratory sieve machine Retsch AS 200 control. The most frequent percentages of dust particles (between 50-79 %) in all samples of wood dust there were fractions of 32 and less than 32 μm (bottom). The most abundant percentage creates conditions of the risk of inhaling and respirable components contained in the fraction over 32 μm and the potential of formation of a dust-air explosive mixture. Comparison of results granulomertic fractions contribution of wood sanding dust typically processed wood in the furniture industry (beech, oak, spruce, fir, and alder) was significantly confirmed of the particle size.

WOOD RESEARCH Volume 61, Number 6, 2016
Ergün Güntekin and Tuğba Yilmaz Aydin

Prediction of bending properties for some softwood species grown in Turkey using ultrasound

Ultrasound has been used in prediction of bending properties for some important wood species grown in Turkey including Calabrian pine, Anatolian black pine, Cedar and Oriental Spruce. Sound velocities of small clear wood specimens were determined using EPOCH 650 ultrasonic flaw detector with 2.25 MHz contact longitudinal transducers at constant moisture content. Following non-destructive measurements, specimens were subjected to three point bending tests. The measured average sound velocities for species tested in L directions were ranged from 4510 to 5254 m∙s-1. Although spruce had the lowest density (425 kg∙m-3), it had the highest sound velocity. The predicted average dynamic modulus of elasticity (Edyn) values for the species tested varied from 10137 to 12856 N∙mm-2. The correlation coefficients between Edyn values and MOE values were higher than those between Edyn and MOR. Edyn values are higher than calculated MOE values. The correlation coefficient between predicted Edyn and calculated MOE values ranged from 0.81 to 0.89. The correlation coefficient between Edyn and MOR varied from 0.78 to 0.88 for the species tested. Results indicated that there was no certain relationship between the density and wave velocity except Calabrian pine which showed negative weak correlation. MOE is better indicator of MOR than Edyn as expected.

WOOD RESEARCH Volume 61, Number 6, 2016
Martin Boldiš, Miroslav Gašparík, Milan Gaff, and Daniel Ruman

Compression set of PU foam mattresses with self-clamping joints and sandwich structure

This paper deals with research on the impact of composition on compression set of the PU foam mattresses. Three type of mattress composition, with sandwich structure and self-clamping joints, were used for research. The fourth type, which contained traditional glued joint, served as a reference. During static compression of mattresses, the properties of the individual layers have been recorded or calculated, such as Young’s modulus, shear modulus and coefficient of shear friction, which were necessary for the SolidWorks simulation of the permanent deformation. The results, as well as simulations of mattress compositions, have proven that the compression set is strictly dependent on the loading time. The highest permanent deformation was recorded for mattress type A and the lowest ones for mattress type B, which had permanent deformation almost identical to that of the composition with glued joints. The last two mattress types had permanent deformation 35 % greater. It is clear from the results that the properties of selfclamping joints in upholstery can equal those of conventional glued joints. Using self-clamping joints is more advantageous in that they exclude the negative effects of glues as well as the gluing process itself.

WOOD RESEARCH Volume 61, Number 6, 2016
Kaiting Zhang, Yuxia Chen, Yong Guo, Shengquan Liu, Tingliang Guan, Na Su, and Shiliu Zhu

Research of bamboo qualitative material tactile characteristics

In this study, the semantic differential method was employed for investigating the tactile properties of bamboo qualitative material, such as bamboo integrated timber (vertical splicing plate), bamboo integrated timber (transverse splice plates), bamboo parallel strand lumber, whole bamboo unfolding plate (outer of bamboo), whole bamboo unfolding plate (remove outer of bamboo), bamboo plastic composite plate, while Liquidambar formosana and Abies fabri (Mast) were selected as contrast. Respondents rated the samples by descriptive words, such as natural, exclusive, eco-friendly, rough, inexpensive, reliable, warm, modern, snug, and solid. Moreover, statistical analysis was employed for analyzing the data. The results showed that material and tactile characteristics exhibit significant correlation. Principal component analysis yielded four attributes based on tactile perceptions. Summing up the main points of the experiment, the tactile properties of different bamboo qualitative material were obtained.

WOOD RESEARCH Volume 61, Number 6, 2016
Jin Heon Kwon and Nadir Ayrilmis

Short note. effect of hot-pressing parameters on selected properties of flakeboard

Physical and mechanical properties of flakeboards produced from radiata pine flakes under different hot-pressing conditions were investigated in this study. The flakeboard mats were hot-pressed at 2.8 MPa with two different temperatures (170 and 190°C) and three different durations (7, 10, and 15 min). At the 170°C of hot-pressing temperature, the highest bending strength was found in the flakeboards pressed for 7 min while the highest modulus of elasticity was found in the flakeboards pressed for 15 min. The highest internal bond strength was found to be 0.13 MPa for the flakeboards pressed at 190°C for 15 min. The thickness swelling and water absorption of flakeboards pressed at 190°C were lower than those of the flakeboards pressed at 170°C. The control of hot press temperature and duration appears an effective method to enhance serviceability of flakeboard.