WOOD RESEARCH Volume 63, Number 6, 2018
Jozef Kúdela, Ivan Kubovský, and Michal Andrejko

Impact of different radiation forms on beech wood discolouration

This study analyses beech wood surface discolouration induced through UV radiation during an accelerated ageing process and with radiation emitted from a CO2 laser beam operating under specific settings. The results show that the extent of beech wood surface discolouration was dependent on the amount and the type of the energy delivered and on the absorption performance of the main wood components. It was observed that increasing irradiation dose caused decreasing wood surface lightness in both UV radiation and CO2 laser-produced radiation scenarios. In most cases, the values of colour coordinates a* and b* increased, and the wood surface was gradually turning dark brown. At high irradiation doses from the CO2 laser, there were recorded decreasing trends in a* and b*, and the beech surface darkened substantially (up to black). To attain purpose-oriented wood surface discolouration under specific modification modes, there is necessary to carry out thorough chemical analyses of the treated wood surface and to express quantitatively the dependence between the energy supplied, colour, adsorption capacity of the main wood components and the ongoing chemical changes.

WOOD RESEARCH Volume 63, Number 6, 2018
Antal Kánnár, Laszlo Tolvaj, and Endre Magoss

Colour change of photodegraded spruce wood by water leaching

Spruce samples (Picea abies Karst.) were irradiated by strong ultraviolet (UV) light emitter mercury lamp and another series of specimens were treated with the combination of UV radiation and water leaching. The total duration of UV radiation for both series of specimens was 50 days. The colour parameters (CIE L*, a*, b*) were measured and evaluated after both UV radiation and water leaching. The increase of redness value was two times greater than the yellowness increase based on the initial value at the end of 50 days treatment. The leaching partly removed the yellow and red chromophore molecules generated by the UV radiation. The samples become slightly lighter after water leaching. The leached samples increased slightly more in yellowness and redness during the first 4-6 days of UV radiation than those of the dry series. The change of surface roughness of the specimens was monitored by diffuse reflectance infrared spectroscopy, because the change of roughness alters the light scattering properties of the surface. The roughness of the samples increased during the UV irradiation, and the tendency of roughness change mirrored that of yellowness change. The leaching reduced the roughness value in all examined cases. Good correlation was found between the hue angle and the lightness in both dry UV treatment and combined UV treatment and water leaching.

WOOD RESEARCH Volume 63, Number 6, 2018
Wu Shiqian, Song Xiaozhou, Lei Yafang, and Zhu Mingqiang

Characterizations and properties of torrefied Quercus variabilis cork

The energy properties and physicochemical structure of torrefied Quercus variabilis cork were investigated with torrefaction between 150°C and 300°C in a tubular furnace. The mass yield, energy yield, and physicochemical properties of torrefied cork were characterized via proximate analysis, elemental analysis, colour analysis, and scanning electron microscope. The results showed that volatiles, moisture content, and the ratios of oxygen to carbon and hydrogen to carbon decreased with increasing torrefaction temperature. Ash content and fixed carbon content increased with increasing temperature, and the enhanced fixed carbon content resulted in the increase of high heating value (HHV) of cork. The HHV compared to untreated cork increased by around 16% after torrefaction at 300°C for 1h. With increasing torrefaction temperature, the cell cavity increased in size, the corrugation was less deformed, and less sediment appeared on cell walls. In conclusion, torrefaction improved both the energy and physicochemical properties of cork. In addition, FTIR and CP/MAS 13C NMR spectra analysis showed that polysaccharide degraded at 200°C, and lignin degraded between 250 and 300°C. Although suberin had better thermal resistance, its NMR signal intensity decreased after torrefaction at 300°C.

WOOD RESEARCH Volume 63, Number 6, 2018
Diaz-Maroto I.J. and Tahir S.

Testing of wood physical properties in oak species (Quercus robur L., Q. petraea (matts) liebl. and Q. pyrenaica willd.) for cooperage. Part II: Wood grain

Our research about wood physical properties of Quercus robur L., Q. petraea (Matts) Liebl., and Q. pyrenaica Willd., for cooperage was founded on the calculate of wood grain to estimate the change of this property in the Galician oaks. Overall, 45 trees were selected in 15 oak forests of the provinces of Lugo and Ourense (Galicia, NW Spain), of which we obtained 45 thin slices of wood at 60 cm tall on the trunk, and 194 wood samples parallelepipeds of 2 × 2 × 4 cm ± 1mm. The grain of Quercus pyrenaica and Q. robur are similar to oaks Limousin region, France. Quercus petraea is comparable to the Vosges oaks. Now, both regions are among the most important sources in quality oaks for manufacturing barrels. Our global objective was to realize a detailed description on the physical properties of wood of these species for its possible use in industry cooperage. For this, the aim of this second work was to continue with the study of wood grain.

WOOD RESEARCH Volume 63, Number 6, 2018
Ajuziogu G.C., Onyeke C.C., Ayogu V.O., Asuzu C.U., Urama D.C., and Odoh N.V.

Treatability indices of some plant species of fabaceae in Nigeria

The hydraulic conductance as estimated by Hagen Poiseuille equation was tested on five Nigerian timber species: Brachystegia nigerica, Afzelia africana, Periscopsis elata, Erythrophleum suaveolens, and Daniella oliveri using spent-engine oil (SAE 40), diesel, kerosene and solignum. The wood of Brachystegia nigerica and Afzelia africana gave more conductance (penetrability) to kerosene, diesel, solignum and spent-engine oil than the other three. The wood of Brachystegia nigerica and Afzelia africana gave the highest vessel lumen radius of 0.18±0.06 mm and 0.12±0.01 mm respectively, while Daniella oliveri, Erythrophleum suaveolens and Pericopsis elata gave the lowest vessel lumen radius 0.09 ± 0.01 mm, 0.07±0.01 mm and 0.05±0.002 mm respectively. The less viscous oils: kerosene, solignum and diesel with viscosities 0.015, 0.019, and 0.043 centipoises respectively at 28°C showed more penetrability than the more viscous spent-engine oil of 2.92 centipoises. There is a positive correlation between the vessel lumen radius and hydraulic conductivities of the four treatment fluids (P ≥ 0.05).

WOOD RESEARCH Volume 63, Number 6, 2018
Yingyang Liu, Haibei Xiong, and Jiahua Kang

Seismic evaluation of wood frame construction based on nail connection deflection status

This paper presents a concept for a seismic evaluation method for wood frame construction based on analyzing the nail connection performance status. An empirical nail model adjusted using an energy equivalence principle is proposed and experimentally validated. Then, a pushover analysis is conducted on a finite element model of a wood frame construction with a practical configuration, and the structural performances under different seismic hazard levels are evaluated based on the indicators given by FEMA 273. With the methodology proposed in this paper, engineers are able to directly perform an effective seismic evaluation by analyzing the nail connection performance status, from which the main nonlinearity of the wood frame construction originates.

WOOD RESEARCH Volume 63, Number 6, 2018
Eva Jeřábková, Daniela Tesařová, and Hana Polášková

Resistance of various materials and coatings used in wood constructions to growth of microorganisms

This contribution deals with the resistance of various materials and coatings used in wood constructions to mould growth and in the case of wood and varnishes also to bacterial growth. For testing the resistance to mould growth, the standard EN 14119, method A2 (without agar medium) and method B1 (with agar medium) were used. Tests were performed with Aspergillus niger, Chaetomium globosum, Penicillium funiculosum, Gliocladium virens and Paecilomyces variotii. Resistance to bacterial growth was tested according to the standard JIS Z 2801 with bacteria Staphylococcus aureus and Escherichia coli. Most of materials tested without agar medium were resistant to mould growth. However, the addition of the agar medium (simulation of real conditions; high dampness and presence of nourishment) predictably caused worse results. Cement bonded particleboard, extruded polystyrene and water-borne varnish were very resistant to moulds. Moreover, the water-borne varnish showed a heavy resistance to microbial growth, while a two solvent-borne polyurethane varnish showed no resistance to microorganisms.

WOOD RESEARCH Volume 63, Number 6, 2018
Oswaldo Moreno-Anguiano, José G. Rutiaga-Quiñones, Francisco Márquez-Montesino, José Luis Rico-Cerda, and Artemio Carrillo-Parra

Performance of activated carbon obtained from pine wood and determination of its adsorption capacities of ammonia and gasoline vapors

Two types of pine wood were used to produce activated carbon (AC) by chemical activation with phosphoric acid. The yield of the activated carbon (CAs) obtained by considering the following factors in the process: species, activation temperature and impregnation ratio (R = wood mass/dissolution mass), the variables of such factors being the species Pinus pseudostrobus (Pp) and Pinus leiophylla (Pl), temperature values 400 and 500°C, and values of R (1:1, 1:2, 1:3), respectively, thus having 12 combinations. The results indicate that the best performance was in the treatment with Pp 400°C and with R = 1:1. A surface area of 790 and 801 m2.g-1 and a total pore volume of 0.312 and 0.316 cm3.g-1 were obtained for the Pp 500-2 and Pl 500-2 carbons, respectively. Likewise, the adsorption capacity of ammonia and gasoline vapors of the carbon obtained was determined.

WOOD RESEARCH Volume 63, Number 6, 2018
Kuňa Vladimír, Balberčák Jozef, Pažitný Andrej, Albert Russ, Boháček Štefan, and VLADIMÍR IHNÁT

Tackiness reducing of the stickies surfaces by inorganic agents and organic polymers

This paper present the results of application of inorganic minerals and organic polymers for elimination of sticky impurities “macrostickies” in the processing of recovered paper. The impact of individual agents has been monitored on different species of suspensions. On the dark suspension of recycled fibres VL5 with a brightness 53% ISO and an ash content of 17.6%, and the suspension VL1 with a brightness 64% ISO and an ash content of 29.4%. From inorganic minerals, the highest efficiency was achieved in the elimination of macrostickies using bentonite Hydrocol OT. At a dose of 5 kg bentonite.t-1 b.d. recycled fibres efficiency of 65.1% for suspension VL5 and 58.7% for VL1 was achieved. The highest performance of the Acefloc 2550 was achieved from the polymers. When applied to the VL5 suspension, the macrostickies were reduced by 57.1%, and when applied to the VL1 suspension, the macrostickies content dropped by 56.5%.

WOOD RESEARCH Volume 63, Number 6, 2018
Jiajun Wang, Junliang Liu, Lin Ni, and Jianzhang Li

Thermopressed binderless fiberboards from wheat straw by adding black liquor

For the shortage of timber resources and the sake of the formaldehyde emissions, people desire to use non-adhesive bonding technology. This paper studies the chemical composites of black liquor, at different contents ranging from 20 to 40 wt%, into fiberboards made from wheat straw pulp. Adding a little black liquor has positive effect on qualities of boards, contributing to presence of proteins and lignin in black liquor, but adding too much liquor would decrease properties of them for the ash content. The FT-IR measurements indicated that there are more low-molecular substance and hydrogen bonds producing after fining and thermopressing processes. The thermo analysis were conducted to better understand these results. The physical and mechanical properties of the resulting fiberboard were evaluated. The results showed that binderless fiberboards by adding 30 wt% have good mechanical and water resistance properties which can partly satisfy the requirements of the relevant standards specifications.

WOOD RESEARCH Volume 63, Number 6, 2018
Selim Sen, M. Said Fidan, Elif Alkan, and S. Sadiye Yasar

Determination of some properties of Scotch pine (Pinus sylvestris L.) wood which is impregnated with boron compounds and quechua

As the industrialisation and technological developments increase; the search for functional material which is environment-friendly, non-toxic, flame resistant, with a broad applicability and with high-temperature endurance also increases. Even though the wood material corresponds most of these features, its possession of an organic structure causes it to be affected negatively by damages occurring under proper conditions in the outdoor environment. Due to this reason, this study is conducted to prevent damages (biotic, abiotic pests, fire, etc.) caused by the environment to the wooden material, and to determine some physical and mechanical properties of wooden material impregnated with quechua, borax and boric acid, which are used to extend the usage life. Those features are needed in an outdoor environment. The Scotch pine (Pinus sylvestris L.) test specimens are prepared with borax, boric acid, borax+boric acid, from borax compounds, which have a great potential in Turkey, and with quechua, one of the natural impregnation substances. Then these samples are impregnated with three different (1%, 3%, 5%) solution concentrations according to ASTM 1413-76 standards and some physical-mechanical property changes are investigated. After impregnation, samples are tested and compared with control samples. According to the test results; the lowest oven dried density change is obtained in borax as 0.46 g.cm-3 in terms of boron compounds and the retention amount is determined to be highest with 3.83 kg.m-3 in the samples impregnated with boric acid. The bending strength and elastic modulus are found to be highest with 83.53 MPa and 10281 MPa in the samples impregnated with boric acid. When examined at the concentration level, it is determined to be highest with 81.89 MPa in samples with 3% concentration. There are statistical discrepancies with 55.77 MPa in the comprehensive strength parallel to grain in boric acid in terms of boron compounds.

WOOD RESEARCH Volume 63, Number 6, 2018
Lucie Jezerska and Jiri Zegzulka

Pelletization of invasive Reynoutria japonica with spruce sawdust for energy recovery

The article focuses on processing of Reynoutria japonica an invasive alien species that is generally extirpated with major costs for its negative impact on biodiversity. It is the biodegradable waste that could be effectively used in energy industry. By examining first energy data (ash content, low melting temperature, nitrogen content etc.) it was found that Reynoutria japonica is not possible to be used separately for energy purposes. Therefore, the alternative of pelletizing six mixtures containing Reynoutria japonica and spruce sawdust in various content ratio was examined with the aim to produce alternative fuel pellets for automated boilers. The pelletization conditions were determined and the pellets quality was evaluated (durability, density etc.). Ash melting temperature was also evaluated. It was found none of the prepared mixtures needed an additional binder for a pelletizing process. It was assessed that the Reynoutria japonica input sample did not need to be dried after collection, since its moisture was sufficient for the pelletization. All samples met the parameters of the calorific value, which is greater than 10 MJ.

WOOD RESEARCH Volume 63, Number 6, 2018
Ergün Güntekin and Hulusi Kaya

Moisture dependent elastic constants of particleboard layers by ultrasound and compression tests

Elastic constants of particleboard layers were investigated using by means of ultrasonic waves and compression tests under different humidity regimes. Three Young’s modulus, three shear modulus and six Poisson ratios were determined. Three longitudinal and six shear wave velocities propagating along the principal axes of anisotropy, and additionally, three quasi-shear wave velocities at 45° angle with respect to the main axes of anisotropy were measured. Compression tests were also conducted in order to measure the accuracy of ultrasonic method. Comparing with calculated values, the predicted Young’s modulus values in the principle directions are acceptable. The shear values calculated using ultrasonic method are higher than those determined from compression tests, particularly in the perpendicular directions. Some of the Poisson’s ratios predicted by ultrasound seem to be extreme. The influence of moisture content on Poisson’s ratios is variable. It can be concluded that ultrasonic method can be used as alternative in determination of elastic modulus for particleboard layers at different moisture conditions. The accuracy of ultrasound for determining the Poisson’s ratios of particleboard layers is questionable.

WOOD RESEARCH Volume 63, Number 6, 2018
Yong Guo, Shiliu Zhu, Yuxia Chen, Shengquanliu, and Qiqiqin

Contrastive analysis of screw withdrawal resistance between bamboo oriented strand board and conventional particleboard

Effects of screw diameter, pilot hole diameter, and material’s anisotropy on the withdrawal resistance of bamboo oriented strand board (BOSB) has been evaluated and the results has been compared with conventional particleboard (CPB). Results indicate that the effects of screw diameter on the face withdrawal resistance in BOSB have significant differences, whereas the edge withdrawal resistance was not. In contrast, the effect of screw diameter on face and edge withdrawal resistance in CPB has been statistically significant difference. The effect of pilot hole diameter on the face and edge withdrawal resistance both in BOSB and CPB has significant difference, the withdrawal resistance decreased as related to increasing pilot hole diameter. Furthermore, the withdrawal resistance in BOSB is anisotropic, whereas the relative superiority is sorted by the face, edge and end in turn. In addition, the withdrawal resistance in BOSB was much higher than CPB in all directions.

WOOD RESEARCH Volume 63, Number 6, 2018
Qinqin Zhang, Xiaoshuai Han, and Junwen Pu

Impact of cationic polyacrylamide for a new kind of pulp ultrasonic wheat straw on alkyl ketene dimer sizing

As a new kind of pulp that can protect the environment by conserving wood resources, ultrasonic wheat straw pulp has received increasing attention. It is prepared by the mechanical effect of ultrasound, the effect of cavitation, and thermal effect, and it does not require a large amount of chemical additives. Different pulp methods yield differences in performance. The conventional method of sizing is difficult to achieve the ideal of wheat straw pulp ultrasonic sizing effect. This work examined the effects of additives and surface charge on sizing by studying ultrasonic wheat straw pulp with 0.25% alkyl ketene dimer (AKD) added in the form of
a commercial emulsion without separate retention aids. As a retention aid cationic polyacrylamide (CPAM) contents were prepared and added to fiber suspensions at the wet end of the papermaking process. The relationship between CPAM and the zeta potential of papermaking furnish and sizing degree, the strength properties of the paper sheet, and the factors that affected measuring the zeta potential were investigated. As the CPAM content increased, the surface morphology, the zeta potential and the strength properties of the paper sheet presents a curve.

WOOD RESEARCH Volume 63, Number 6, 2018
Ján Kanócz and Viktória Bajzecerová

Analysis of composite action of various mass timber structural panels with concrete layer

In the presented paper composite actions of various mass timber panels with concrete layer are compared. The composite action of timber and concrete by grooves in wood and by adhesive was realized. In the frame of experimental investigation bending test of real scale composite panels with cross-laminated and nailed/glued vertical planks mass timber was performed. In the analysis, vertical mid-span deflection of tested panels was compared and also some technological aspects of their production were taken into account.