WOOD RESEARCH Volume 62, Number 6, 2017
Richard Hrčka

Model of free water in wood

The derived model describes equilibrium in wood as it is placed it water. The model expresses the equality of density of water and coupled term of basic density and moisture content on the other side. The other part of the model is its extension to water in wood. The maximum moisture content is derived from the view point of density definition. Then Archimedes’ principle enables to measure bound water maximum moisture content. The model is applicable to wood of arbitrary wood species and also for different kind of materials as it is documented in the embedded table.

WOOD RESEARCH Volume 62, Number 6, 2017
Enhua Xi and Guangjie Zhao

Visual simulation on accumulation of the differentiating secondary wall layers

This study describes the accumulation of secondary wall layers of the fast-growing Populus×euramericana cv. ‘74 /76’ during the active phase by the methods of polarized light microscopy analysis and computer simulation technology. The results showed that the secondary wall layers of Populus×euramericana cv.‘74/76’ appeared light and shade stratification during the differentiating phase, and the wall layers corresponded to S1, S2 and S3 layer from outside to inside respectively. The S1 and S2 layer of wood fibers were differentiated in May, and the S3 layer was appeared until the July. In addition, the thickness of the three layers all showed a gradual increasing trend. The accumulation process of the secondary wall layers was visually displayed by the computational simulation technology during the active period.

WOOD RESEARCH Volume 62, Number 6, 2017
Luis Fernando Pintor-Ibarra, Artemio Carrillo-Parra, Rafael Herrera-Bucio, Pablo López-Albarrán, and José G. Rutiaga-Quiñones

Physical and chemical properties of timber by-products from Pinus leiophylla, P. montezumae and P. pseudostrobus for a bioenergetics use

This paper describes the chemical and physical properties of Pinus leiophylla, P. montezumae and P. Pseudostrobus timber by-products (wood chips, bark and wood-bark). The physical features determined were the initial moisture content, bulk density and calorific value whereas the determined chemical characteristics were pH, inorganic compounds, inorganic compounds microanalysis, extractives, lignin, and holocellulose. Such by-products were collected in the industrial complex at the Indigenous Community of Nuevo San Juan Parangaricutiro, located in Michoacán, México. The initial moisture content of the samples varied from 33.6 to 56%, while their bulk density ranged from 0.19 to 0.31 g.cm-3. The calorific value for the wood residues of the three different species of pines varied from 17.95 to 18.93 MJ.kg-1. Regarding their chemical characteristics, barks were more acid than woods, and in general, the inorganic content was lower in woods than in barks. According to the X-ray microanalysis, the major inorganic compounds found in ash were calcium, magnesium, and potassium. No heavy metals were detected at all. For the three pine species, extractives levels in barks were higher than in woods. Also, barks contained a higher concentration of lignin than woods. The highest holocellulose content was found in wood residues rather than in barks. It is concluded then that the three pine species timber by-products present physic and chemical properties that make them suitable for the production of solid biofuel.

WOOD RESEARCH Volume 62, Number 6, 2017
Muhammad Syazwan, Bin Azmi, Lee Choon Wai, Mohd Firdaus Bin Yhaya, Norli Ismail, Husnul Azan Bin Tajarudin, Hamidi Abdulaziz, and Kok Kwang Ng

Preservation of rubber wood against biological decay by salts derived from leachate

Wood preservatives are typically chemicals that granted antimicrobial properties to timber, while leachate is the liquid that percolated through accumulation of waste materials. Clostridium butyricum NCIMB 7423 was used to ferment leachate with 1.15 L working volume under anaerobic condition at 37°C and pH 6.5.This research focuses on preserving rubber wood by acids and salts derived from the fermented leachate. First and second set of treatment were performed to study fungal resistance of wood treated by acids and salts respectively. Biological decay test was conducted using Phanerochaete chrysosporium to determine the percentage of mass loss for different preservatives. The salt concentration of 0.5 M sodium acetate and sodium butyrate shows satisfactory result to preserve rubber wood. Thus, the salts derivative could be converted into rubber wood preservative. This research will reflect to material from waste to wealth and support sustainable technology.

WOOD RESEARCH Volume 62, Number 6, 2017
Song Xiaozhou, Zhu Lingyan, Wu Shiqian, and Lei Yafang

Structural and mechanical properties of cork cell walls from quercus variabilis blume (Fagaceae)

The properties of cork are strongly dependent on its cell wall properties. Thus, it is very important to characterize the cork cell walls in order to understand structure-property relationships. The reproduction cork tissue from Quercus variabilis Blume was examined with field-emission scanning electron microscopy to detect the structural characteristics of the cell walls. Several noteworthy anatomical features were present in the cells of Quercus variabilis cork. In most instances, the inner wall of cork cells was not smooth and showed an irregular surface. Solid deposits of various shapes were observed in the inner surfaces of the cell walls. Cell walls of cork tissue had severe corrugations in transverse and radial sections. Trabeculae were found for the first time in the cork tissue of Quercus variabilis Blume. They extended across a few cells, with a rod-like form. Nanoindentation techniques provide a new view of the mechanical properties of the cork cell walls. The hardness of cell walls of untreated and boiled reproduction cork from Quercus variabilis was 0.54 GPa and 0.51 GPa. The elastic modulus was 11.47 GPa and 11.81 GPa, respectively. Boiling treatment of cork could improve mechanical properties of cell walls.

WOOD RESEARCH Volume 62, Number 6, 2017
Christian Brischke, Antje Gellerich, Holger Militz, and Michael Starck

Performance of coated and uncoated horizontal lap-joint members during 20 years of outdoor exposure

Horizontal lap-joint trials were set up using eleven different wood species representing a wide range of natural durability. Coated and uncoated lap-joint specimens as well as non-jointed reference specimens were exposed for up to 20 years and evaluated with respect to decay, formation of cracks and performance of the coating. The tropical wood species Tatajuba, Cedrorana, and Dark Red Meranti performed still very well and also some Europe-grown softwoods with coloured heardwood were still in good shape. The lap-joint set up turned out to be a method that can be used also for determining the durability and performance of untreated naturally durable wood, but suffered from several drawbacks such as time-consuming and costly specimen preparation, difficult to detect onset of decay, and generally long exposure times needed for a reliable durability assessment. Cracks were often the starting point for internal decay, but did not exclusively occur in the lap area.

WOOD RESEARCH Volume 62, Number 6, 2017
Zsolt Molnár, GÁBOR NÉMETH, Sándor Héjja, Endre Magoss, and Sándor Tatai

The effect of the position of 2D roughness measurement on the roughness parameters by natural wood material

There are notable differences between the 2-D standardized surface roughness parameters depending on the position of the profil of the surface roughness eavluation of natural wood.Therefore it is fundamental to determine which parameters are the least dependent on the position of the measured profil. The dependence of the standardized roughness parameters on the different measuring positions varies. We observed the smallest average dependence at the arithmetic average roughness (Pa) parameter of the P-premary profile, and at the Mr1 (threshold as the minimal Asperities’ height distribution AHD )and Mr2 (threshold as the maximal AHD) parameters and “reduced” height peak amplitude (Ppk) was more dependent. The greatest deviation occurs in the mean roughness depth (Pz), maximum height of the profile (Pt), and the maximum roughness depth (Pmax) values. These three parameters whoed the highest differences in function of the measuring positiions.

WOOD RESEARCH Volume 62, Number 6, 2017
Mustafa Kucuktuvek, Ergun Baysal, Turkay Turkoglu, Huseyin Peker, Ahmet Gunduz, and Hilmi Toker

Surface characteristics of scots pine wood heated at high temperatures after weathering

This study was conducted to investigate some surface properties of wood specimens of heat treated Scots pine (Pinus sylvestris L.) after weathering such as surface hardness, surface roughness, gloss, and color changes. Heat treatment of Scots pine wood was carried out by hot air in an oven for 1, 2, and 3 hours at 210, 220, and 230°C. The results showed that generally surface hardness losses of heat treated Scots pine wood were lower than that of un-heated Scots pine wood after weathering. Heat treated Scots pine wood gave smooth surface after weathering. Except for heat treatment at 230°C for 1 and 2 hours, heat treatment resulted in better glossiness compared to un-heated Scots pine wood after weathering. According to the test results, while heat treated Scots pine wood become lighter after weathering, un-heated wood become darken after weathering. In general, heat treated wood surface to become reddish and yellowish after weathering.

WOOD RESEARCH Volume 62, Number 6, 2017
Juraj Gigac, Mária Fišerová, Monika Stankovská, and Pažitný Andrej

Enzymatic hydrolysis of extruded wheat straw with addition of sodium hydroxide and calcium hydroxide

Extrusion pretreatment of wheat straw in a single screw extruder was investigated in terms of effectiveness of enzymatic hydrolysis and the formation of fermentation inhibitors. The effect of sodium hydroxide in extrusion pretreatment was compared with calcium hydroxide. The accessibility of wheat straw structure to hydrolytic enzymes increased with NaOH and Ca(OH)2 loadings, whereby more with the addition of NaOH. With 6% w/w of NaOH loading, the conversion of polysaccharides was 76.1% and with the same Ca(OH)2 loading it was 47.3%. The conversion of polysaccharides with 12% w/w of Ca(OH)2 loading was 66.6%. Without alkali in extrusion pretreatment, the conversion of polysaccharides was only 36.7%. The polysaccharides conversion of original extruded wheat straw was about 1.5 to 3.3% higher in comparison to washed extruded wheat straw. Fermentation inhibitors such as lignin, acetic and formic acid are primarily formed in the presence of alkali during extrusion pretreatment, most of which was lignin. Alkaline extrusion is a suitable method for pretreatment of lignocellulosic biomass.

WOOD RESEARCH Volume 62, Number 6, 2017
Samson M. Mohomane, Linda Z. Linganiso, Thuli Buthelezi, and Tshwafo E. Motaung

Effect of extraction period on properties of sugarcane bagasse and softwood chips cellulose

This work evaluates the extraction of sugarcane bagasse (SCB) and soft wood (SW) celluloses with alkali treatment followed by bleaching process using sodium chlorite at different time. The influence of extraction time (2 hrs and 4 hrs) on the thermal, crystallinity and morphological properties was investigated. The extracted celluloses were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The aromatic skeletal vibrations of lignin and hemicellulose confirmed the extraction of cellulose which varied extraction time. TGA analysis shows that the untreated SCB degrade earlier than their respective celluloses and the prolonged treatment affects the onset of main degradation. XRD results showed that extracted celluloses had greater crystallinity index, and was affected at prolonged time due to long range destruction of cellulose crystals. The SW revealed a complex behaviour due to the dominated lignin content as revealed from chemical composition analyses.

WOOD RESEARCH Volume 62, Number 6, 2017
Tibertius Agus Prayitno, Ragil Widyorini, and GANIS LUKMANDARU

Bonding ability of sengon wood treated with natural extracts

Wood preservation technology has been using a lot of synthetic preservatives for a long time. However, some disadvantages have been recorded such as environment quality degradation and killing more untargeted wood destroying organism than targeted one. Recently environment quality maintenance has been required causing a significant change in general wood processing technology and wood preservation paradigm. In terms of wood preservatives has changed from synthetic to natural wood preservatives application. Sengon is the fast growing wood species chosen in Indonesia to fulfill national and international wood demand. Unfortunately this wood species is class V of wood durability and has to be treated with preservatives. Glued wood products such as plywood, lamination, particleboard and fiberboard use low durability wood such as sengon. The objective of this research is to know the adhesion strength of sengon wood after treatment with the natural preservatives. This research was conducted by wood adhesion block method. The fast growing sengon plantation wood was chosen since this type of sengon wood was classified as low grade of wood quality (Class V). This type of wood had high portion of sapwood which was susceptible to wood destroying organism and absence of natural preservatives. The sources of natural wood preservative chosen were gadung tubers, pulai bark and kumis kucing leaves, while the extraction methods were hot water and alcohol toluene. The wood adhesive used was bio-industrial PVAc. Extraction procedure of natural wood preservatives followed ASTM D1110-1984 and D-1107-1996-2013. The procured naturally extracts was processed to obtain extract concentration 1 gram per liter. Wood preservative application used padding method on the wood surface by 0; 1; 2 and 3 application times. Each padding method was processed was applied after the former one was air dried. Wood adhesion test followed block type with with 196.gm-2 glue spread and cold press system. Compression shear test of block samples followed British Standard (1957). The research results showed that adhesion strength was highly significantly affected by single factor of padding application. Padding application exerted a negative correlation to adhesion strength. Increased natural preservatives treatment (padding application) on the wood surface resulted lower adhesion strength. The average sengon wood adhesion strength of control, 1; 2 and 3 padding application were 5.10; 3.00; 2.22 and 1.05 MPa respectively. The average wood failure were 69.20; 66.71; 62.12 and 45.83% respectively.

WOOD RESEARCH Volume 62, Number 6, 2017
Turkay Turkoglu, Yahya Kabasakal, Ergun Baysal, Ahmet Gunduz, Mustafa Kucuktuvek, Dursun Kemal Bayraktar, Hilmi Toker, and Huseyin Peker

Surface characteristics of heated and varnished Oriental beech after accelerated weathering

This study was performed to investigate some surface characteristics such as surface hardness, surface roughness, and color changes of heated and varnished Oriental beech (Fagus orientalis Lipsky) after accelerated weathering. Heat treatment of Oriental beech wood was carried out by hot air in an oven for 0.5, 1, and 1.5 h at 210, 220, and 230°C. After heat treatment, Oriental beech wood specimens were varnished using a polyurethane varnish. The results showed that accelerated weathering generally caused increase of surface hardness of Oriental beech. Surface roughness and total color changes of heated and varnished Oriental beech were lower than only varnished (control) Oriental beech after accelerated weathering. Heated and varnished Oriental beech wood gave better surface characteristics than only varnished oriental beech after accelerated weathering.

WOOD RESEARCH Volume 62, Number 6, 2017
Peter Rantuch, Ivan Hrušovský, Jozef Martinka, Karol Balog, and Siegfried Hirle

Determination of the critical heat flux for floating flooring

The paper deals with the possibility of floating flooring ignition due to radiant heat. Samples of floating flooring with dimensions of 100 ± 1 mm x 100 ± 1 mm and thickness of 6 mm were thermally loaded by different densities of external heat flux. The flaming combustion was initiated either solely by means of radiant heat, or in combination with electric spark igniter. Cone calorimeter was used for the determination of the critical heat flux. Time to ignition for each sample was recorded and the obtained data were used for the calculation of the critical heat flux density.

WOOD RESEARCH Volume 62, Number 6, 2017
Bin Luo, Siyu Jin, Feng Cheng, Junhua Ying, Xue Bao, Hongguang Liu, and Li Li

Study on sanding force, power consumption and quality of calibrating sanding recombinant bamboo

Recombinant bamboo is a new kind of bamboo-based panel material that has been widely used as a structural material. However, there are many problems in the sanding process of this material. This study analyzes the impacts of sanding parameters on sanding force, sanding active power and sanding efficiency in sanding recombinant bamboo, which is meaningful for improving the sanding quality, reducing power consumption and collocating the sanding parameters more reasonably. Granularity, feed speed, sanding speed and setting sanding thickness have different influences on sanding force, sanding active power and sanding efficiency, and the grey relevancy results show that feed speed has the most significant effect on sanding force, sanding active power and sanding efficiency. The actual sanding thickness is smaller than setting sanding thickness, and the difference between actual and setting values (ΔTs) is influenced by sanding parameters. Taking a comprehensive consideration of ΔTs and standard deviation of actual sanding thickness, determine the optimum schemes according to the method of fuzzy comprehensive evaluation.

WOOD RESEARCH Volume 62, Number 6, 2017
Fu Yang and Fang Hai

Investigation of performance of recombinant bamboo chair through finite element technology

Recombinant Bamboo is a newly bamboo material which breaks through the traditional processing mode, and its excellent physical properties can fully replace the wood widely used in furniture manufacturing. In this paper, take the classic back chair for example, in order to research the application of recombinant bamboo material in the furniture, using ANSYS finite element analysis software to compare the stress and deformation of recombinant bamboo, rosewood and elm under stress states. Meanwhile, in order to find out which leg shape is most suitable for the back chair of recombinant bamboo, the impact of the current mainstream three legs on the mechanical properties of the back chair is analyzed. Moreover, the parametric design method can work out the optimum size of legs and seat which are the most important design elements of back chair. This provides an evidence-based and effective method for furniture design.