WOOD RESEARCH Volume 62, Number 3, 2017
Partson Tinarwo, Temesgen Zewotir, and Delia Nort

Modelling the effect of eucalyptus genotypes in the pulping process with generalised additive models and fractional polynomial approaches

The advent of lean (waste reduction), six sigma (process variation minimisation) and proper raw material selection are the essential challenges to achieve the required quality on the overall industrial processes. Accordingly a laboratory experiment for the dissolving wood pulping process was conducted on nine Eucalyptus genotypes to measure the change in lignin, viscosity and α-cellulose at each of the six pulp processing stages. The changes to these properties were modelled using the Generalised Additive Models (GAM) and Fractional Polynomial (FP) models. These models proved to be equally important in their unique ways and produced complementary results. The results revealed that Emearnsii genotype produced the best results for both α-cellulose and viscosity, while Enitens genotype was selected for the optimal lignin reduction. Egrandis genotype is the only genotype that proved to have adverse effects on the viscosity property.

WOOD RESEARCH Volume 62, Number 3, 2017
Martin Zachar, Andrea Majlingová, Iveta Mitterová, and IVETA ČABALOVÁ

Influence of an age and damage of the oak wood on its fire risk

The aim of this work is to study the effects of different ages and damage of the oak wood (Quercus petraea Mattusch) in relation to its flash point temperature and ignition temperature, as well as on determination of the ratio of changes in extractives, cellulose and lignin, in the heat loaded samples of 5 – years old oak wood, 160 – years old oak wood, and also 160 – years old oak wood degraded by wood-destroying insects and fungi. The results of the analyses showed that the flash point temperatures were in the range of 357.52°C – 360.63°C.The ignition temperatures were at interval of 398.93°C – 414.92°C. The time to reach the ignition point was at the interval between 344 and 365 seconds. Under the thermal loading of oak wood, there comes to the significant changes, especially in the surface layers. These are, in addition to colour changes, demonstrated the chemical changes of the main components of wood and extractives. Increasing the temperature, there increases also the content of the substances extractable with ethanol and toluene. Increase in their amount is mainly due to the lignin, but partially also due to the polysaccharides decomposition products.

WOOD RESEARCH Volume 62, Number 1, 2017
Tomasz Jelonek, Witold Pazdrowski, and Magdalena Arasimowicz-Jelonek

Correlation between the stem hydraulic conductivity rates in scots pine (Pinus sylvestris L.) and the lignin content in tracheid walls

This paper is an attempt to evaluate the lignin formation in tracheid walls within the stem circumferential area in mature Scots pine (Pinus sylvestris L.), and establish the correlation between lignin content, and diameter at breast height and hydraulic conductivity in mature pine. The independent variables included lignin content (Lc) in tracheid walls within the stem circumferential area, and pine diameter at breast height (DBH), and the dependent variable was the relative conducting surface of stems (Sa/Nmass, Eas/Nmass). Research material came from the 89-91 year old pine stand in the north of Poland. Chemical analysis included mature wood area, i.e. last ten annual rings at 1.30 m (DBH). The results show clear interdependence between the relative conductive surface (stem hydraulic conductivity), and tree diameter at breast height and lignin content in tracheid walls within the stem circumferential area. Biometric features of pines grown in fresh coniferous forest (FC) and in fresh mixed coniferous forest (FMC) conditions were functionally linked. The link between these values was clear, although it varied, and could be approximated using the linear function.

WOOD RESEARCH Volume 63, Number 5, 2018
Vladimir Ilyich Fedyukov, Mikhail Vladimirovich Boyarsky, Ekaterina Yuryevna Saldaeva, Maria Sergeyevna Chernova, and Vasiliy Yuryevich Chernov

Dependence of spruce wood resonance properties on its chemical composition

Nowadays there are no reasoned scientific data on inter relation of resonant properties of spruce-tree wood and its chemical composition. Thus the purpose of the study was to reveal the features of sonorous spruce in view of the content of basic organic substances in their timber. 20 model trees at the age of 180-190 years were selected as material for studies in taiga woods in the north of Kirov region of Russia. Special 0.5 m long blocks were made from each model tree at height of 1.3 m. Standard 20×20×300 mm samples were made from those blocks. Test samples were kept at room dry conditions for 2 years. After that dendro acoustic studies were carried out on them to define acoustic constant in different directions with respect to timber fibers. Further the percentage of cellulose, lignin, extractives and ashes in them was defined applying standard techniques. As a whole the chemical composition of spruce tree resonant wood lies approximately within the same limits as in common wood of the breed given. However significant influence of cellulose on a longitudinal acoustic constant and lignin on a radial constant is revealed. Joint influence of lignin and cellulose on a tangential constant is found out, the influence of lignin in the latter case being dominant. Continuation of fundamental research in this field has great cognitive value for revealing the nature of unique acoustic properties formation in sonorous spruce wood. Such studies acquire special topicality when dealing with outstanding violins as well as the wood kept for many decades in old buildings subject to demolition.

WOOD RESEARCH Volume 63, Number 4, 2018
Chenah May and Amrani Moussa

Chemical and structural analysis of lignocellulosic biomass of Ampelodesmos mauritanicus (diss) and Stipa tenacissima

Chemical composition, anatomical characteristics and cell wall structure of Ampelodesmos mauritanicus (Diss) and Stipa tenacissima (Esparto grass) fibers were analyzed. The results reveal the % (W/W) holocellulose content of Diss and Esparto grass was found to be 54.39 % and 51.8 %, respectively. Esparto grass had the greatest % (W/W) lignin content of 32.2 % while Diss had the last lignin content of 24.95 %. Estimation of %( W/W) extractives contents in Diss and Esparto-grass were observed to be 12.03 % and 13.5 % in that order. According to XRD data, Diss showed, as expected, a lower crystallinity index (CI) 52.5 % when compared to Esparto grass samples 55.2 %. The results of the thermal decomposition of natural fibers are shifted to higher temperatures with increasing the cellulose crystallinity. Based on the results of the chemical composition of Diss and Esparto grass, it was confirmed that straw is rich in cellulosic fibers and, therefore, a valuable raw material for the paper and manufacture industry.

WOOD RESEARCH Volume 66, Number 4, 2021
Sahin Akyurek, Murat Akman, and Murat Ozalp

Effects of heat treatment on some chemical compound and mechanical properties of black pine wood

In this study, effects of heat treatment on bending strength, compression strength, chemical compound and solubility of Black pine wood (Pinus nigra J.F. var. seneriana) was examined. For this purpose, Black pine wood samples were kept in temperature of 250°C for 2 hours. Test results of heat-treated Black pine wood and control samples indicated that mechanical characteristics including compression strength and bending strength were affected negatively with heat treatment. Bending strength of heat treated and non-treated test samples were 129 and 76 N.mm-2, respectively. Compression strength of heat treated and non-treated test samples were 53 and 43 N.mm-2, resp. In addition, level of extractives, cellulose and hemicellulose decreased while lignin content increased with percentage of 40%. Significant decreases occurred in all chemical solubility values.

WOOD RESEARCH Volume 64, Number 5, 2019
Han Que, Yuguo Dong, Haoquan Guo, Xinyu Lu, Xiaojun Zhu, Yimeng Zhang, and Xiaoli Gu

Pyrolytic kinetics of steam exploded lignin by TG/DTG analysis

Steam exploded lignin (SEL) thermal decomposition was investigated by thermogravimetric technique (TG/DTG) within the temperature range from room temperature to 920°C under different heating rates (10, 20, 30, 40, and 50°C. min-1). Little differences in the mass losses with heating rates were observed from TG analysis. It was established that SEL pyrolysis consisted of three main stages: water evaporation (< 200°C); devolatilization of organic volatiles (200-600°C); and char formation (> 600°C). The kinetic processing of non-isothermal TG/DTG data was performed by model-free methods proposed by Flynn-Wall-Ozawa (FWO) and Kissing-Akahira-Sunose (KAS). The average activation energies calculated from FWO and KAS methods are 74.2 kJ. mol-1 and 173.2 kJ. mol-1, respectively. Experimental results showed that values of kinetic parameters from both methods were analogous and could be successfully applied to understand the complex degradation mechanism of SEL. It is also helpful to achieve a better understanding of the devolatilization process of different type of biomass.

WOOD RESEARCH Volume 64, Number 4, 2019
Shuang Yan Zhang, Chuan Gui Wang, Xue Qin Fang, and Yuan Yuan Li

Characterization of lignins from the black liguor of Australian eucalyptus kraft of the nail

Lignin samples were separated from the black liquor of Australian eucalyptus kraft pulping by ethanol-acid precipitation or acid precipitation. Elemental analysis, FT-IR, and 1H NMR were conducted to compare their structural characteristics. The thermal behaviors were studied by TGA and heating value was examined with oxygen bomb calorimeter. The obtained C9 expanded formulas for acid-extraction lignin and ethanol-acid-extraction lignin were C9H9.52O2.96 and C9H9.58O3.18, respectively. According to FT-IR and 1H NMR analyses, the two lignins were similar to hardwood lignin of type GS. However, the acid-extraction lignin showed a high proportion of syringyl (S) unit. TG results showed that degradation process of the two lignins was similar, but their degradation temperatures were different. The weight loss rate reached its maximum value of 8.49 wt% / °C and 4.39 wt% / °C for ethanol-acid-extraction lignin and acidextraction lignin, whose temperature of maximum weight loss was 371°C and 356°C respectively. Results of oxygen bomb calorimeter tested showed the incendiary heat of ethanol-acid-extraction lignin was higher than that of acid-extraction lignin.

WOOD RESEARCH Volume 64, Number 2, 2019
Seung-Won Oh, In Yang, Dae Hak Park, Soo Min Lee, and Byoung Jun Ahn

Lignin and sugars contents of Liriodendron tulipifera L. sawdust immersed in acidic/alkaline solutions and the fuel characteristics of wood pellets fabricated with the sawdust

This study was conducted to determine the lignin and sugars contents of yellow poplar (YP) sawdust immersed in tap water (TW), sulfuric acid (AC) and sodium hydroxide (AK) solutions. Klason lignin content of TW- and AC-immersed YP sawdust was higher than that of AK-immersed YP sawdust. Glucose showed the highest content among sugars extracted from YP sawdust. Durability of non-immersed YP pellets was the highest, followed by TW-, AC- and AK-immersed YP pellets. YP pellets became more durable by increasing the Klason lignin and xylose contents as well as decreasing the glucose content. Through microscopic observations and quantitative analysis of lignin distribution, lignin content on the surface of non-immersed YP pellets was higher than that of TW-, AC- and AK-immersed YP pellets. In conclusion, there are significant correlations between lignin or sugars contents of YP sawdust and fuel characteristics of wood pellets fabricated with the YP sawdust.

WOOD RESEARCH Volume 66, Number 2, 2021
Matshidiso Makhalema, Percy Hlangothi, Setumo Victor Motloung, Lehlohonolo Fortune Koao, and Tshwafo Elias Motaung

Influence of kraft lignin on the properties of rubber composites

The influence of lignin content on reclaimed rubber (RR)/natural rubber (NR) blend composite properties has successfully been studied. Scanning electron microscopy (SEM) were used to understand morphology. Fourier-transform infrared spectroscopy (FTIR) for the possible chemical interaction, whereas thermogravimetric analysis (TGA) and tensile tester were used to predict strength and elongation for possible practical applications. The results indicated that the presence of lignin forms cavities which seemed to arise from complex interactions of the blend with the lignin. Those cavities dominated tensile fractured surface and the increase in lignin indicated inconsistencies of interfacial interactions. Lignin RR/NR blend composites revealed a drop in tensile strength and shift in glass transition temperature, except for the highest lignin containing blend composite. More active interactive constituent of the blend appeared to be NR. The interaction has not favored the thermal stability and crosslinking density.