WOOD RESEARCH Volume 68, Number 2, 2023
Sidong Wang, Fenghao Zhang, Dongsheng Chen, and Jinghui Jiang

Evolution and distribution of shakes in larch logs during air drying

This paper analyzed the length, width, and location of shakes in the air-drying process of larch log (Larix principis-rupprechtii Mayr) 1 m long and 66% initial moisture content. The development law and distribution characteristics of shakes during log drying of larch were studied and shake generation and development law were analyzed from two aspects of microstructure and growth defects. The variation of dry shrinkage deformation along the radial direction and knot influence on it was analyzed using the split-shaped stress test strips. At the cellular level, the cell wall shrinkage behavior of heartwood and sapwood and the microstructure of knots were observed. The results showed a significant relationship between eccentricity and shake distribution; the IIa region is the most prone to dry shake. The evolution of shakes is closely related to the drying rate. In the high-speed drying stage (MC ≥ 40%), shakes almost do not occur; in the decelerating drying stage (40% ≥ MC ≥ 20%), the amount, length, and width of shakes increase rapidly. In the low-speed drying stage (20% ≥ MC), the area of shakes tends to stabilize or even decline. The main reasons for dry shaking are the dry shrinkage difference between tangential and radial cell walls, early and late wood, heartwood and sapwood, and moisture content gradient during the drying process.

WOOD RESEARCH Volume 68, Number 2, 2023
Huachun Qi, Xiangrui Li, Mingli Liu, and Chunfeng Li

Discoloration of oak veneer induced by metal ions

The 3 mm thick oak veneers were discolored by single ions of Fe2+, Cu2+, and Mn2+ and mixed ions of Fe2+-Cu2+, Fe2+-Mn2+, and Cu2+-Mn2+. The brightness (L*), red-green index (a*), and yellow-blue index (b*) of the veneers changed by varying degrees with the changes in ion mass fraction, temperature, heating time, ion species, and ion mass fraction ratio. The maximum values of total color difference (△E*) of the veneers were 38.94, 11.79, and 9.42 for Fe2+, Cu2+, and Mn2+. Moreover, the total color difference (△E*) values of 24.07, 13.71, and 4.45 were observed for Fe2+-Cu2+, Fe2+-Mn2+, and Cu2+-Mn2+ mixed ions. The veneers showed different degrees of vibrational peaks after discoloration. According to the ultraviolet spectrum, Fe2+ had a red shift in the ultraviolet absorption band of the unsaturated carbonyl compound and benzene ring compound. Moreover, the dark effect of Fe2+, Fe2+-Cu2+, Fe2+-Mn2+, Mn2+, Cu2+-Mn2+, and Cu2+ gradually decreased. The surface of the veneer was flat, without any rupture or deformation, and the pores were clear after treatment.

WOOD RESEARCH Volume 68, Number 2, 2023
Rafidah Md Salim, Jahimin Asik, Mohd Sani Sarjadi, and Liew Kang Chiang

Chemical composition and potential uses of Leucaena leucocephala stem bark

Leucaena leucocephala stem bark that was eleven years old was studied for its chemical composition and usage. The samples were subjected to chemical analyses based on ASTM standard procedures after being air-dried for several days. The results found that the bark of L. leucocephala has a pH value of 6.04 and that the solubility of the bark in 1% NaOH alkali is the highest compared to the solubility in hot water (14.45%) and cold water (14.36%), while the chemical composition of the bark of L. leucocephala was ash (15.76%); extractives (8.39%); holocellulose (132.85%); hemicellulose (103.66%); cellulose (29.19%) and lignin (38.24%). Based on the findings, L. leucocephala bark was less acidic. When used as a source of carbohydrates, bark has a high solubility, and its chemical composition may have an impact on how quickly it burns when it is pyrolysed.

WOOD RESEARCH Volume 68, Number 2, 2023
VLADIMÍR IHNÁT and HENRICH LÜBKE

Water retention of beech shavings heat-treated at lower temperatures

Water retention after 2 hours and 24 hours of soaking in water was determined for beech shavings subjected to heat treatment at temperatures of 120°C, 140°C and 160°C for 2 hours, 4 hours, 6 hours and 8 hours in order to reduce the equilibrium moisture content (EMC) of the wood shavings for use in wood based composites. EMC was determined after 14 days of air conditioning at 23°C and 55% relative humidity. The measured values were compared with the sample dried at 103°C. Water retention was determined after 15 min of centrifugation at 1400 rev.min-1 for a more objective assessment of the wood’s ability to retain water in the cell lumens. The results showed that heat treatment reduces the EMC of beech shavings heat-treated at 160°C for 8 hours in the given conditions from 8.7% to 6.19%. The reduction of EMC at lower temperature was not sufficient enough, especially in the shorter treatment duration of up to 6 hours. In parallel, the reduction of water retention from 65.53% to 47.79% was caused by heat treatment for 8 hours at 160°C.

WOOD RESEARCH Volume 68, Number 2, 2023
Özlem Özgenç Keleş and Sefa Durmaz

A synergic effect of water-based acrylic resin with boric acid on leachability

In this study, the Scots pine wood samples were impregnated (single treatment) with boric acid combined with two types of water-based acrylic resin (pure acrylic and semi-translucent acrylic emulsion) to limit the boron leaching and improve the decay resistance. The results showed dimensional stability in anti-swelling efficiency and water absorption improved in wood specimens treated with boric acid and acrylic types. While the leachability was over 90% for only 3% boric acid-impregnated wood (control), it was calculated at 36% for acrylic emulsions-impregnated wood. Although there were no weight losses for the unleached woods, it was up to 9% for leached woods impregnated with acrylic resin and emulsion. The 25% acrylic emulsion had no weight losses after the leaching test for Coniophora puteana and Trametes versicolor. The boric acid combined with acrylic resin can improve the leaching resistance with the synergic effect, enhancing resistance against biological threats.

WOOD RESEARCH Volume 68, Number 2, 2023
Karol Tomczak, Przemysław Mania, and Arkadiusz Tomczak

Quality of beech, birch and oak wood from stands growing on post-agricultural lands

This study assessed the quality of birch, beech, and oak for timber production on former agricultural land. All sample plots for the selected species had the same forest habitat type. All measured trees had already reached the age of felling. Thus, beech was over 120 years old, birch was over 70 years old, and oak was over 140 years old. On each plot, the same morphological features were measured for all trees: diameter at breast height, tree height, height of the first dead branch, height of the first live branch, and crown base. Based on collected data the length and percentage of the trunk suitable for industrial purposes were calculated. In general birch and beech trees from former agricultural land were higher, but had thinner trunks, when in oak reverse observation were noticed. Tree trunks from former agricultural lands have app. 7% shorter knots-free trunk section. The bigger different between forest and former agricultural land was noticed in case of the oak – 14%, then beech – 5% and birch – 1%. Considering the morphological characteristics of the trees and quality indicators, we showed that all species could be used for the afforestation of former agricultural lands to produce high-quality wood for future industrial purposes. However, it should be noticed, that in general calculated standing volume was lower on former agricultural land.

WOOD RESEARCH Volume 68, Number 2, 2023
Yiqing Qi, Yue Sun, Ziwen Zhou, Yi Huang, Jiaxi Li, and Guangyu Liu

Response surface optimization based on freeze-thaw cycle pretreatment of poplar wood dyeing effect

To improve the permeability of dye solution in wood, poplar was pretreated by freeze-thaw cycle. The effects of three parameters, such as freezing time, thawing time and circulation times on the dyeing effect of pretreated poplar were investigated by single factor method. On this basis, pretreatment conditions were optimized by response surface methodology. The optimum conditions of this treatment were freezing time of 11.9 h, thawing time of 7.2 h and two cycles. Under these conditions, the dye uptake and chromatic aberration of the treated wood were 25.77% and 21.14%, respectively, which were close to the theoretical predicted values. The results showed that freeze-thaw cycle pretreatment could effectively improve the permeability of poplar and enhance the dyeing effect of wood.

WOOD RESEARCH Volume 68, Number 2, 2023
Katarína Vizárova, Soňa Malečková, Michal Jablonský, Štefan Varga, František Kačík, and Svetozár Katuščák

Prediction of efficacy of deacidification process

The aim of this work is to propose the first model hypothesis and function for predicting the efficacy of deacidification. We have used the dDEA as the first basic factor influencing the efficacy. The resulting relationship is based on the best achieved reliable η data and related dDEA data, from mass deacidification technologies used for the lifetime and usability increase of millions of books, historical documents worldwide. The resulting η predicting function is as follows η = 0.732984+0.125612*dDEA^(-0.214237). This first 1D function can serve as an impulse for continuing improvement of the prediction, and 2D, 3D and multidimensional models. It can be used for comparisons and connecting η with η-characteristic mechanical, physical, cellulose solution properties; the prediction can serve for continuing improvement of efficacy of the conservation technology in increasing the paper carriers of information, documents longevity and usability.

WOOD RESEARCH Volume 68, Number 2, 2023
Linhan Mi, Wei Tan, Ting Wu, Xiaolan Cai, Chenqian Pan, and Yanxiong Fang

Fixation of dye-type red and blue ink handwriting on aged paper

In this article, red and blue ink handwriting on aged paper was fixed by fixative to prevent handwriting from fading or diffusion during aqueous deacidification. Firstly, four fixatives were selected: polydimethyl ammonium chloride (PDDA), the quaternary ammonium salt of chitosan (HACC), cationic guar gum (CGG), and benzyl triethyl ammonium chloride (TEBAC) alcohol solution, according to their fixation effects on filter paper dyes, and derive the optimal composition ratio of the above four fixatives. Experimentally derived that PDDA has an excellent fixation effect on red ink handwriting, and HACC has an excellent fixation effect on blue ink handwriting. In addition, HACC also has a positive impact on the conservation of handwriting in real archives. The mechanical properties of aged paper were improved, and the paper fibers had no obvious change after the fixation and deacidification processes.

WOOD RESEARCH Volume 68, Number 2, 2023
Marija Todorović, Mathieu Koetsier, Nađa Simović, Ivan Glišović, and Marko Pavlović

Determination of mode I fracture properties of European spruce

In this paper an efficient procedure for obtaining a cohesive law for Mode I timber fracture (crack opening), based on the Double Cantilever Beam (DCB) tests is given. DCB tests were performed on ten European spruce specimens in order to determine the energy release rate vs crack length (R curves). Two crucial parameters – crack length during the experiment and the crack tip opening displacement were obtained using 2D Digital Image Correlation (DIC) technique. In order to determine accurate fracture resistance (R curve), procedure which includes calculating cumulative released energy was employed. The cohesive law for Mode I fracture of wood was obtained by differentiation of the strain energy release rate as a function of the crack tip opening displacement. This cohesive law is further implemented in the successful numerical modelling of failure modes in large-scale end-notched glulam beams which were experimentally tested in four-point bending configuration.

WOOD RESEARCH Volume 68, Number 2, 2023
Xinyou Liu, Changjun Zhang, Shufan Yang, and Anca Maria Varodi

Effects of Pyrolysis process on products yield of plywood from abandoned furniture

In this paper, the plywood obtained from dismantling discarded furniture was selected as pyrolysis experimental materials. Pyrolysis was performed at a heating rate of 100°C/h, 150°C/h and 200°C/h and pyrolysis temperatures of 400°C, 500°C, and 600°C to evaluate the effects of pyrolysis process on products yield and the products features. The results show that the yield of solid products gradually decreases with the increase of pyrolysis temperature and heating rate while liquid products and non-condensing gases’ yield gradually increases. The carbon content in solid products reached 80.76 – 94.35%. Carbon content gradually decreases with pyrolysis temperature, but the proportion of C/H and C/N gradually increases. The pyrolysis solution is weakly acidic due to the adhesives in pyrolysis material.

WOOD RESEARCH Volume 68, Number 2, 2023
Young-Kyu Lee, Ohkyung Kwon, Wonsil Choi, Myoungcheol Moon, Jae Min So, Vilasit Thithai, Joon Weon Choi, Daye Kim, and In Yang

Volatile organic compounds and metals adsorption capacity of wood bark-based activated carbons

This study was conducted to investigate the applicability of wood bark-based activated carbon (AC) for the adsorption of metal ions and volatile organic compounds (VOC) from the atmosphere. Contents of Fe and Al in the AC made with coconut shell, and the bark of larch and cork oak (CSA, LBA and COA, respectively) were higher than those of the unexposed AC and increased with the exposure to various indoor/outdoor spaces when compared to the unexposed AC. However, Fe and Al contents of the exposed AC, which is a coal-based one used as a control (SAA), were lower and scarcely higher than the unexposed SAA. From the results, it is evident that the wood bark-based AC examined in this study is more effective to adsorb metals than SAA. The SEM-EDS analysis exhibited prominent metal-adsorptivity of COA, although its total surface area and pore volume were lower than those of SAA. Total VOC-adsorptivity was the highest in COA followed by CSA, CBA (cypress bark activated carbon), LBA and SAA. In conclusion, wood bark-based AC can be utilized as an effective adsorbent for the removal of metals and VOC from the atmosphere. The optimum AC is COA, an industrial by-product, in view of the techno-economic aspect.

WOOD RESEARCH Volume 68, Number 2, 2023
Huimin Zhang, Yu Yang, Yu Liu, Yahua Jiang, and Renyuan Liu

Optimization of the manufacturing of Metasequoia-based three-layer structure parquet flooring by a response surface methodology

On the basis of a single-factor experiment, a mathematical model was established by the response surface analysis method based on the Box-Behnken experimental design principle. The effects of three factors, including hot-pressing temperature, hot-pressing time, and hot-pressing pressure, and their interactions on the modulus of rupture (MOR) of Metasequoia-based three-layered structure parquet flooring were studied. The results show that the quadratic polynomial model in the regression equation is significant, and the correlation between the value predicted by the model and the experimental value is 91.17%. The optimized best hot-pressing process parameters are determined to be as follows: hot-pressing temperature of 96.03°C, hot-pressing time of 6.70 min, and hot-pressing pressure of 8 kg·cm-2. Under these conditions, the best MOR are obtained, reaching a value of 102.05 MPa. The theoretically predicted value is in good agreement with the experimental results.

WOOD RESEARCH Volume 68, Number 2, 2023
Chunmei Yang, Zanbin Zhu, Jiuqing Liu, Bo Xue, and Yucheng Li

Model construction and microwave preheating experiments using fiberboard

Microwave heating is a new type of pre-heating for fiberboard mats. Compared to conventional heating, microwave heating is faster and the surface and interior are evenly heated, thus avoiding the phenomenon of premature hardening of the surface layer of the fibreboard mats. In this paper, the heat transfer law of microwave preheated fiberboard mats was analyzed, and a thermodynamic model of fiberboard microwave heating was established. Furthermore, a microwave preheating simulation was established through COMSOL software; the temperature distribution of the fiberboard after microwave heating was analyzed and the reliability of the simulation model was verified through experiments. The temperature changes of fibers in the two preheating methods were compared by direct contact preheating experiment and microwave preheating experiment. Microwave preheating is more efficient than direct contact preheating, and more uniform temperature distribution in fiberboard mats. The core layer temperature is higher than the surface layer temperature, which can shorten the preheating time. By comparing the COMSOL model with the test, the model can basically reflect the temperature change law of microwave preheating, and the temperature of each layer of the slab is more uniform in the model simulation process. The heating law of the fiberboard was obtained, which provided a theoretical reference for the industrialized microwave preheating of fiberboard.

WOOD RESEARCH Volume 68, Number 2, 2023
Oussama Chauiyakh, Elmostafa El Fahime, Oumaima Ninich, Samar Aarabi, Mustapha Bouziani, Abdelaziz Chaouch, and Aziz Et Tahir

Short notes: First report of the lignivorous fungus Paecilomyces maximus in Cedrus atlantica M. In Morocco

This study is interested in isolating fungi from the wood parts of cedar trunks withered and identifying these lignivorous fungi. A sample was isolated from the cedar grove of Tazekka National Park located south of the city of Taza in Morocco. The culture and purification of the isolated fungus were done on a water agar medium and then on a PDA medium. After the purification of the fungus, a morphological study by scanning electron microscope allowed us to identify the pathogen Paecilomyces. A molecular characterization identified Paecilomyces maximus with a coverage percentage of 99% and an identity of 98.77%. To our knowledge, this is the first report of P. maximus in decayed cedar wood.