Articles

Volume 55, Number 3, 2010

CONTENTS

1. V�CLAV SEBERA, M�RIA KOTL�NOV�, JAN TIPPNER, MICHAL KLOIBER: Numerical Simulation of Elastic Wave Propagation in Wood with Defined Tree Rings . . . 1

2. EDWARD ROSZYK, WALDEMAR MOLI?SKI, MONIKA JASI?SKA: The effect of microfibril angle on hygromechanic creep of wood under tensile stress along the grains . . . 13

3. STERGIOS ADAMOPOULOS, MARINA CHAVENETIDOU, COSTAS PASSIALIS, ELIAS VOULGARIDIS: Effect of cambium age and ring width on density and fibre length of black locust and chestnut wood . . . 25

4. LAURA OLTEAN, ALFRED TEISCHINGER, CHRISTIAN HANSMANN: Visual classification of the wood surface discolouration due to artificial exposure to uv light irradiation of several european wood species � a pilot study . . . 37

5. DANIEL KEUNECKE , DAVID MANNES, PETER NIEMZ, EBERHARD LEHMANN, ROBERT EVANS: Silviscan vs. Neutron imagin to generatte radial softwood density profiles . . . . . . . . . . . . . . . . . . . . . . . . . 49

6. WEI GAO, JINZHEN CAO, JIANZHANG LI: Some physical, mechanical properties and termite resistance of ammonium pentaborate-treated strand board . . . 61

7. ANTJE PFEFFER, HOLGER MILITZ: Laboratory tests of the performance of dmdheu, siloxane and water glass modified wood against blue stain fungi . . . 73

8. BEATA DOCZEKALSKA, MAGDALENA ZBOROWSKA: Wood chemical composition of selected fast growing species treated with naoh part 2: Non-structural substances . . . 83

9. SIBEL YILDIZ, �MIT YILDIZ, EYLEM DIZMAN, ALI TEM?Z , ENGIN GEZER: The effects of pre-acid treatment on preservative retention and compression strength of refractory spruce wood impregnated with cca and acq . . . 93

10. JING LIU, XUEFEI ZHOU: Dqp bleaching of eucalyptus urophylla �eucalyptus grandis lh 107 oxygen delignified kraft pulp . . . . 105

11. KRUTUL DONATA, RADOMSKI ANDRZEJ, ZAWADZKI JANUSZ, ZIELENKIEWICZ TOMASZ, ANTCZAK ANDRZEJ: Comparison of the chemical composition of the fossil and recent oak wood . . . 113

12. SANDRA BISCHOF VUKUSIC, DRAGO KATOVIC, SANDRA FLINCEC GRGAC, JELENA TRAJKOVIC, BOGOSLAV SEFC, BOJANA VONCINA: Study of the wood modification process with polycarboxylic acids and microwave tratment . . . 121

13. MUSTAFA ALTINOK, MURAT OZALP, S�LEYMAN KORKUT: The effects of heat treatment on some mechanical properties of laminated beech (fagus orientalis l.) Wood . . . 131

The objective of the study was to perform a finite element (FE) simulation of elastic wave (EW) propagation in wood (Picea abies spp.). Based on measuring of tree rings width a FE model of wood with defined tree rings, substituted as an ideal annulus, was created. FE model was loaded to force impulse at different positions via the specimen length. Subsequently a propagation and travel time of the EW through a material was observed. FE simulations were compared to the experimental ones acquired by different non-destructive acoustical tools (ADD, Geotron, FAKOPP and TICO). Results say that the FE model preserves trend of velocities of EW obtained from experiments, although comparing to them it embodies lower EW velocities in general. Relative difference of FE model towards experimental average is 20 %. Presented simulation of EW propagation can be supposed as a relatively accurate, but to achieve higher agreement with experiments, it needs to be optimized in terms of its material properties.

The relation between the microfibril angle in S2 layer of secondary cell wall and the character of deformation of pine wood subjected simultaneously to tensile stress along the grains and moistening in the hydroscopic range as well as after the tensile stress relieve, is analysed. The moistening of wood subjected simultaneously to tensile stress is found to considerably intensify the process of its creep, which becomes more intense than that in the wood of constant high moisture content. The creep compliance of wood upon constant tensile stress and changes in its moisture content in the hygroscopic range is proved to be practically independent of the microfibril angle (MFA) varied from 12 to 18 degrees. For higher MFA values the relative creep compliance increases with increasing MFA values. The contribution of instantaneous elastic recovery strain of wood earlier subjected to tensile stress and moistening in the total strain is proved to be the smaller the higher the mean MFA value. The contribution of delayed recovery strain in the total strain of wood is practically independent of MFA value, whereas that of permanent strain in the total strain increases with increasing MFA.

The relationship between wood density (WD) and fibre length (FL) with cambium age (CA) and ring width (RW) was studied in two ring-porous species, black locust and coppice-grown chestnut, collected in the Sithonia Peninsula, Chalkidiki, Greece. Using regression analysis methods, models of WD and FL in relation to CA and RW were obtained. It was found that the effect of CA and RW on WD and FL was similar for both species examined. WD of black locust and chestnut was predicted better through a model using CA and RW. A model for FL variations was also obtained with CA and RW and was more accurate than the simple models based on the two factors, CA and RW, separately. The multiple regression models suggested that the use of cambial age of growth rings together with their width might explain better their effects on WD and FL of black locust and chestnut.

This paper displays the results of a survey as the second part of a research work concerning the wood surface discolouration of the most traded wood species in Europe due to UV light irradiation. The aim of this study is to visually classify the wood surface discolouration according to the L*, a*, b* and ?E* values after 120 hours of artificial indoor sunlight exposure. A questionnaire was prepared in order to evaluate the attitude of researchers in the field of wood science, towards the surface discolouration due to UV light irradiation of sixteen wood species. From this survey it emerged that there was a low uniformity of answers, and the observers appreciate colour and colour changes subjectively. A visual classification of the wood surface discolouration of specific wood species and a correspondence to the measured values is given. Recommendations for future research works are also presented.

Knowing the mean and the intra-ring density of wood enables to estimate mechanical and physical wood properties, and it provides important climatological information. Many methodological approaches to determine wood density are in use, and they undergo a permanent development and improvement. Goal of this study was to compare two up-to-date non-destructive radiographic techniques - SilviScan (based on X-rays) and Neutron Imaging - in terms of their methodology, the specimen handling, and the generated density data. At the present time, the systems clearly differ regarding their user-friendliness (and thus their suitability) especially for measurements on wooden samples. However, the measurement results of both techniques, i.e. the qualitative and quantitative characteristics of the density profiles, show good to high congruence.

In order to improve termite resistance and reduce formaldehyde emission level of strand board, ammonium pentaborate (APB) was introduced into strand board with phenol formaldehyde (PF) resin as its adhesive. The physical and mechanical properties, termite resistance and formaldehyde emission of panels were evaluated. The results showed that APB was very effective on improving the termite resistance even at low APB loadings. Its significant effect on reducing formaldehyde emission of strand boards was also obtained as expected, which can be explained by the reaction of ammonium and acetic acid with formaldehyde caused by APB during hot pressing. As same as the other borates such as disodium octaborate tetrahydrate (DOT) and zinc borate (ZB), APB also showed a negative effect on physical and mechanical properties of strand board. The adverse effect could be compensated by a 3-layer structure which contained APB only in the surface layers of the strand board. Compared with DOT and ZB, APB showed the least influence in 3-layer strand board at same BAE level of 1.8%.

Specimens of Scots pine sapwood (Pinus sylvestris) and Beech wood (Fagus sylvatica) were treated with an amino-alkyl-functional oligomeric siloxane, a sodium water glass solution and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). Untreated and biocide treated specimens were used as references. Four different test versions with the test fungus A. pullulans were carried out to investigate the suitability of predicting blue stain in service from modified wood in laboratory screening tests. The results showed that the infestation of blue stain was depending on the test version. The water glass treatment could prevent blue stain in every test version for specimens of Scots pine sapwood. The DMDHEU and siloxane treatment could reduce the surface discoloration, but not fully prevent fungal infestation. Based on the results of the different test versions it can be concluded that the most appropriate test method for uncoated modified wood was the use of vermiculite and the inoculation with spore suspension.

In this study was to determine the impact of sodium hydroxide concentrations and duration of treatment on the non-structural constituents of two fast growing wood species: willow (Salix viminalis) and poplar. Alkalisation of willow and poplar wood with sodium hydroxide solutions of 10 to 20 % concentrations resulted in the removal of significant quantities of wood non-structural substances. The content of substances soluble in the ethanol-benzene mixture from willow wood treated with NaOH decreased by about 80%, in cold water � by about 90 %, in hot water � by about 45 % and in 1 % NaOH solution � by about 50%. Smaller changes in the content of these constituents were determined in poplar wood: substances soluble in organic solvents declined by approximately 40 % and substances soluble in 1% NaOH � by about 30 %. The highest mass losses for both of the examined wood species were recorded in the lignocellulosic material after treatment with 10 % NaOH. The duration of treatment with solutions of sodium hydroxide failed to exert a significant influence on quantitative changes in the examined constituents.

This study investigates the effects of pre-acid (sulphuric acid and phosphoric acid) treatment on preservative retention and compression strength of refractory spruce wood (Picea orientalis L.) impregnated with chromated copper arsenate (CCA) and ammoniacal copper quat (ACQ). Before the CCA and ACQ treatments, the samples were treated by sulphuric acid or phosphoric acid solutions of 0.5 % by using pressure and non- pressure methods. After the pre-acid treatments, the samples re-impregnated with the solutions of 2 % CCA-Type C and 2 % ACQ-1900 preservatives according to the non-pressure method. The results of this study indicated that pre-acid treatment with pressure was more effective than non-pressure method for increasing of retention of both CCA and ACQ. The compression strength of oriental spruce wood samples was reduced 12-31 % after pre-acid treatment for both pressure and non-pressure methods.

On the basis of optimum variables of parameters was determined that there was operating conditions was achived as follows for DQP bleaching of E. urophylla �E. grandis LH 107 oxygen delignified kraft pulp: GIF pretreatment stage: 80 �C, 5.0 h, 1.2 % NaOH (o.d.p.), 1.4 % H2O2 (o.d.p.), 0.06 % CuSO4 (o.d.p.), 2.8 % pyridine (o.d.p.), 0.2 MPa O2, 5 % pulp consistency; Co-salen pretreatment stage: 70 �C, 5.0 h, 3 % NaOH (o.d.p.), 1.5 % H2O2 (o.d.p.), 0.03 % Co-salen(o.d.p.), 1:1 pyridine/Co-salen (molar ratio), 0.2 MPaO2, 5 % pulp consistency; D stage: 60 �C, 0.5 h, 0.2 % ClO2 (o.d.p.), 1:3 NaOH/ClO2 (dosage ratio), 10 % pulp consistency; Q stage: 50 �C, 1.0 h, 0.5 % DTPA (o.d.p.), 10 % pulp consistency; P stage: 90 �C, 1.5 h, 0.7 % H2O2 (o.d.p.), 0.7 % NaOH (o.d.p.), 0.6 % Na2SiO3 (o.d.p.), 10 % pulp consistency. The maximum increase of brightness (2.8 % ISO for GIF pretreatment; 2.2 % ISO for Cosalen pretreatment), tensile index (except for GIF biomimetic pretreatment ) and burst index was observed adding GIF and Co-salen biomimetic pretreatment to DQP.

This study was perform to compare the chemical composition of fossil oak wood and recent oak wood. About 2500 years old fossil oak wood and 100 years old recent oak wood were examined. Samples were gained from the outer wood, middle wood and heartwood on the cross section of three stems (both fossil and recent). Contents of extractives, cellulose, 1 % NaOH soluble substances, lignin and ash were analysed. Additionally, concentrations of elements such as Ca, K, Mg, Fe, Mn, Na, Zn and Cu were examined. The results show that there is lower content of cellulose and higher content of lignin in fossil oak wood in relation to recent wood. There is also much higher amount of calcium and iron, and lower amount of potassium in fossil wood.

Wood specimens of fir (Abies alba Mill) and beech (Fagus sylvatica L.) are chemically modified by polycarboxylic acids (PCA) and analysed by Fourier transform infrared (FT-IR) spectroscopy that is used to evaluate the differences between convection and microwave curing. A new non-formaldehyde crosslinking system is composed of two most prominent PCAs, e.g. 1,2,3,4-butanetetracarboxylic acid (BTCA) and citric acid (CA). These reagents require a phosphono-based catalyst, thus a sodium hypophosphite (SHP) catalyst is used in the study. The effects of the PCAs treatment are compared with the previously introduced 1,3-dimethylol 4,5-dihydroxy-ethylene urea (DMDHEU) treatment. Further intensification of the processes of wood modification and an increase in the quality of wood-based materials is achieved by microwave treatment. Dimensional stability of the modified wood is determined by anti-swelling efficiency (ASE), using the water soak/oven dry method. The results revealed the improvement of ASE of the wood modified by PCAs, as compared by the DMDHEU treatment.

Heat treatment is often applied to wood species to improve their dimensional stability. This study examined the effects of heat treatment on certain mechanical properties of laminated beech wood (Fagus orientalis L), which has industrially high usage potential and large plantations in Turkey. Wood specimens obtained from Simav- Kutahya, Turkey. For this purpose; first beech wood samples used in this study were kept in temperatures of 100 ?C and 150 ?C for 4 hours, and after that they were laminated with polyurethane and polyvinyl acetate adhesives. The test results of heat-treated laminated beech wood and control samples showed that mechanical properties including compression strength, bending strength and bonding strength effected positively with heat treatment, and increase in temperature and duration further increased strength values of the laminated wood specimens.