Normal Wood Research Articles

The effect of ageing on bonding performance of plasma treated beech wood with urea-formaldehyde adhesive

In the process of wood bonding, the usage of aged and inactivated wooden elements can cause a reduction in mechanical properties of products containing wood-adhesive joints. Treating wood with an atmospheric air plasma represents a sophisticated technique for surface activation. With this regard, to enhance the bondability of normal beech wood (Fagus sylvatica L.) with urea-formaldehyde (UF) adhesive, a dielectric barrier discharge plasma in floating electrode configuration was implemented. In this study, fresh and aged wood specimen both, untreated and plasma treated, were investigated. X-ray photoelectron spectroscopy revealed promotion of carbon-rich species with ageing, but generation of a new functional oxygen-containing functional groups after plasma treatment. Microscopic observations with scanning electron microscope showed no obvious changes in the wood structure after plasma treatment. Surface oxidation consequently improved the wettability of the wood surface with water and UF adhesive. However, this enhanced wettability slightly diminished over time. As shown with dynamic mechanical analysis, the rheological properties of the UF adhesive in wood-adhesive joints were not affected by aging nor by plasma treatment. The positive influence of plasma treatment and negative impact of substrate ageing to the shear strengths of wood lap-joints were determined using an automated bonding evaluation system. Similarly, the negative effect of wood ageing and the positive effect of plasma pre-treatment were reflected in the bending strengths of the produced laminated veneer lumbers. Results showed that plasma treatment of beech wood improves the bonding performance of both fresh and aged wood.Graphic abstract

Comparative studies on lignin structures in normal and tension wood of Populus × euramericana cv. “74/76”

Tension wood is a type of defect of wood, however, it has some especial character and structure. In this study, cellulase lignin structures in normal and tension wood of Poplar 107 (Populus × euramericana cv. ‘74/76’) were compared using ultraviolet (UV), Fourier transform infrared (FT-IR), Raman and magnetic resonance (NMR) spectroscopy, gel permeation chromatography (GPC) and elemental analysis. The results showed that the lignins in both normal and tension wood were dominated by syringyl units, followed by guaiacyl and p-hydroxyphenyl units. The FT-IR result presented that the relative intensity of syringyl units in normal and tension wood were 0.87 and 0.90. The contents of aliphatic hydroxyl, methoxyl, condensed phenolic hydroxyl and carboxyl of lignin in tension wood were higher than those of phenolic hydroxyl groups and β-5. The contents of β-O-4, β-β and β-1 in tension wood were similar with those in normal wood. The average per-C9-unit formulae of the lignin in normal and tension wood of Poplar 107 were C9H7.21O1.79 (OH)1.17_x0001_(OCH3)1.55 and C9H7.23O1.76(OH)1.25_x0001_(OCH3)1.62, respectively.

Aceptación y confianza de Bitcoin en México: una investigación empírica

El Bitcoin forma parte de las llamadas criptomonedas y puede definirse como un sistema de pagos electrónico público y descentralizado universal, basado en la tecnología de Blockchain. El problema que enfrenta es la confianza en su uso; por lo tanto, el objetivo de la presente investigación es analizar los factores que influyen la adopción y uso de Bitcoin en México. Para ello, se utiliza el modelo UTAUT2 integrado con la variable de confianza. El modelo fue probado empíricamente mediante la aplicación de una encuesta de 106 cuestionarios, bajo el método de mínimos cuadrados parciales, con modelos de ecuaciones estructurales (PLS-SEM). Los principales resultados indican que la expectativa de rendimiento, la motivación hedonista, el hábito y su descentralización, son los principales factores que influyen en la confianza para la adopción y uso de Bitcoin. Los resultados ilustran a las empresas y cualquier interesado sobre las ventajas del uso de Bitcoin.

Comparison of tension wood and normal wood for oxidative nanofibrillation and network characteristics

Cellulose nanofibrils (CNFs) are top-down nanomaterials obtainable from abundant lignocelluloses. Despite recent advances in processing technologies, the effects of variations in the lignocellulose structure and composition on CNF isolation and properties are poorly understood. In this study, we compared the isolation of CNFs from tension wood (TW) and normal wood (NW) from Populus tremula (aspen). The TW has a higher cellulose content, native cellulose fibrils with a larger crystalline diameter, and less lignin than the NW, making it an interesting material for CNF isolation. The wood powders were oxidized directly by 2,2,6,6-tetramethylpiperidin-1-oxyl, and the morphology and mechanical behaviors of the nanofibril suspensions and networks were characterized. The TW was more difficult to fibrillate by both chemical and mechanical means. Larger nanofibrils (5–10 nm) composed of 1.2 nm structures were present in the TW CNFs, whereas the NW samples contained more of thin (1.6 nm) structures, which also comprised 77% of the solid yield compared to the 33% for TW. This difference was reflected in the TW CNF networks as decreased transmittance (15% vs. 50%), higher degree of crystallinity (85.9% vs. 78.0%), doubled toughness (11 MJ/m3) and higher elongation at break (12%) compared to NW. The difference was ascribed to greater preservation of the hierarchical, more crystalline microfibril structure, combined with a more cellulose-rich network (84% vs. 70%). This knowledge of the processing, structure, and properties of CNFs can facilitate the breeding and design of wood feedstocks to meet the increasing demand for nanoscale renewable materials.Graphic abstract

Occurrence of tension wood in two mangrove species and its effect on selected wood anatomical properties

The aim of the study is to characterise the cellular structures in tension wood and compare its effect on the selected anatomical parameters in two mangrove wood species viz. Excoecaria agallocha Linn. and Sonneratia caseolaris (L.) Engl. Wood blocks of 1 cm3 were prepared and thin sections of cross sections were cut using microtome and stained with Azure II to differentiate the structure of normal wood from tension wood fibres. The anatomical parameters analysed in this present study were vessel frequency, tangential vessel diameter and fibre wall thickness in tension wood as well as in normal wood. Vessel diameter and vessel frequency were significantly lower in tension wood compared to the normal wood in both the species. The reduction of tangential diameter in tension wood region is a way of protecting these elements from cavitation and providing mechanical support for the plant than liquid transport. A significant variation in fibre wall thickness was observed between tension wood and normal wood in both species.

Creep properties of compression wood fibers

To achieve efficient utilization of compression wood (CW), a deeper insight into the creep behavior of CW is necessary. In particular, the involvement of lignin for the creep behavior of CW needs to be better understood. In the present paper, wood fibers and slices from CW and normal wood were studied at both high constant humidity and cyclic 30–80% RH conditions. The micromechanical deformation explored by FTIR confirmed that in CW, lignin participated in the stress transfer during creep measurements. For all types of materials, the creep strain rate at constant and cyclic humidity conditions was linearly related to the applied load level. For single CW fibers, the creep rates were higher at a given load for native CW fibers compared to holocellulose CW fibers, due to the lower relative cellulose content. The CW fibers, with a microfibril angle of around 45°, were found to exhibit a greater creep rate during moisture cycling as compared to the higher but constant humidity level, i.e., a mechano-sorptive behavior. However, the mechano-sorptive effect, i.e., the ratio between the creep rates at constant and cyclic humidity, was only slightly higher for the CW holocellulose fibers as compared to the native CW fibers, indicating that the lignin most probably does not contribute to the mechano-sorptive effect.

Effect of thermo-hydro-mechanical densification on the wood properties of three short-rotation forest species in Costa Rica

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

Genome-wide analysis of lncRNA and mRNA expression and endogenous hormone regulation during tension wood formation in Catalpa bungei

BackgroundPhytohormones are the key factors regulating vascular development in plants, and they are also involved in tension wood (TW) formation. Although the theory of hormone distribution in TW formation is widely supported, the effects of endogenous hormones on TW formation have not yet been assessed. In this study, TW formation was induced in Catalpa bungei by artificial bending. The phytohormone content of TW, opposite wood (OW) and normal wood (NW) was determined using liquid chromatography-mass spectrometry (LC-MS), and transcriptome sequencing was performed. The hormone content and related gene expression data were comprehensively analyzed.ResultsThe results of analyses of the plant hormone contents indicated significantly higher levels of cis-zeatin (cZ), indoleacetic acid (IAA) and abscisic acid (ABA) in TW than in OW. Genes involved in the IAA and ABA synthesis pathways, such as ALDH (evm.model.group5.1511) and UGT (evm.model.scaffold36.20), were significantly upregulated in TW. and the expression levels of ARF (evm.model.group5.1332), A-ARR (evm.model.group0.1600), and TCH4 (evm.model.group2.745), which participate in IAA, cZ and Brassinolide (BR) signal transduction, were significantly increased in TW. In particular, ARF expression may be regulated by long noncoding RNAs (lncRNAs) and the HD-ZIP transcription factor ATHB-15.ConclusionsWe constructed a multiple hormone-mediated network of C. bungei TW formation based on hormone levels and transcriptional expression profiles were identified during TW formation.

Structural differences between reaction wood and opposite wood with different drying temperatures

Reaction wood is characterized by having different anatomical and chemical features than normal wood. The different composition of cell walls, the higher quantitative proportion of thick-wall fiber cells, diameter, and the abundance of vessels have remarkable effects on reaction wood’s physical and mechanical properties. Reaction wood has fewer vascular cells. In addition, it has a smaller lumen diameter, which results in reduced permeability. Therefore, reaction wood is more difficult to dry at a certain moisture content. The differences in the drying times of the reaction wood and the normal wood were largest at a temperature of 60 °C and durations greater than 30 h, and the reaction wood dried more slowly. At a temperature of 120 °C, the differences in drying time were minimalized, and drying end times were almost identical. The expected negative effect of higher temperature on the morphology of reaction wood and opposition wood was not confirmed.

Deformation mechanisms of wood cell walls under tensile loading: a comparative study of compression wood (CW) and normal wood (NW)

Macromolecule deformations of the wood cell wall are of great significance for wood deformation and failure. In this paper, the deformation mechanisms of wood cell walls with different microfibril angles (MFAs) under longitudinal tensile load were investigated by the deformation responses of compression wood (CW) and normal wood (NW). The results indicated that the shift rates of the glucosidic bond and intramolecular hydrogen bond of the cellulose were lower for the CW sample than the NW sample, and no shift was observed in the position of the characteristic peak of the lignin in the spectrum of the CW and NW samples. Under dynamic deformation, the lignin in the wood participated in the stress transfer, and this effect was more pronounced in the CW sample with the larger MFA than the NW sample. In addition, the larger slippage deformation between the cellulose and matrix in the CW resulted in greater deformation of the CW sample than the NW sample. The differences of molecular deformations between CW and NW also could indirectly prove deformation mechanisms of different layers of cell wall, and then wall layer failure under longitudinal tensile stress.

Transcriptomics and Proteomics Reveal the Cellulose and Pectin Metabolic Processes in the Tension Wood (Non-G-Layer) of Catalpa bungei.

Catalpa bungei is an economically important tree with high-quality wood and highly valuable to the study of wood formation. In this work, the xylem microstructure of C. bungei tension wood (TW) was observed, and we performed transcriptomics, proteomics and Raman spectroscopy of TW, opposite wood (OW) and normal wood (NW). The results showed that there was no obvious gelatinous layer (G-layer) in the TW of C. bungei and that the secondary wall deposition in the TW was reduced compared with that in the OW and NW. We found that most of the differentially expressed mRNAs and proteins were involved in carbohydrate polysaccharide synthesis. Raman spectroscopy results indicated that the cellulose and pectin content and pectin methylation in the TW were lower than those in the OW and NW, and many genes and proteins involved in the metabolic pathways of cellulose and pectin, such as galacturonosyltransferase (GAUT), polygalacturonase (PG), endoglucanase (CLE) and β-glucosidase (BGLU) genes, were significantly upregulated in TW. In addition, we found that the MYB2 transcription factor may regulate the pectin degradation genes PG1 and PG3, and ARF, ERF, SBP and MYB1 may be the key transcription factors regulating the synthesis and decomposition of cellulose. In contrast to previous studies on TW with a G-layer, our results revealed a change in metabolism in TW without a G-layer, and we inferred that the change in the pectin type, esterification and cellulose characteristics in the TW of C. bungei may contribute to high tensile stress. These results will enrich the understanding of the mechanism of TW formation.

ATR-FTIR Microspectroscopy Brings a Novel Insight Into the Study of Cell Wall Chemistry at the Cellular Level.

Wood is a complex tissue that fulfills three major functions in trees: water conduction, mechanical support and nutrient storage. In Angiosperm trees, vessels, fibers and parenchyma rays are respectively assigned to these functions. Cell wall composition and structure strongly varies according to cell type, developmental stages and environmental conditions. This complexity can therefore hinder the study of the molecular mechanisms of wood formation, underlying the construction of its properties. However, this can be circumvented thanks to the development of cell-specific approaches and microphenotyping. Here, we present a non-destructive microphenotyping method based on attenuated total reflectance–Fourier transformed infrared (ATR-FTIR) microspectroscopy. We applied this technique to three types of poplar wood: normal wood of staked trees (NW), tension and opposite wood of artificially tilted trees (TW, OW). TW is produced by angiosperm trees in response to mechanical strains and is characterized by the presence of G fibers, exhibiting a thick gelatinous extra-layer, named G-layer, located in place of the usual S2 and/or S3 layers. By contrast, OW located on the opposite side of the trunk is totally deprived of fibers with G-layers. We developed a workflow for hyperspectral image analysis with both automatic pixel clustering according to cell wall types and identification of differentially absorbed wavenumbers (DAWNs). As pixel clustering failed to assign pixels to ray S-layers with sufficient efficiency, the IR profiling and identification of DAWNs were restricted to fiber and vessel cell walls. As reported elsewhere, this workflow identified cellulose as the main component of the G-layers, while the amount in acetylated xylans and lignins were shown to be reduced. These results validate ATR-FTIR technique for in situ characterization of G layers. In addition, this study brought new information about IR profiling of S-layers in TW, OW and NW. While OW and NW exhibited similar profiles, TW fibers S-layers combined characteristics of TW G-layers and of regular fiber S-layers. Unexpectedly, vessel S-layers of the three kinds of wood showed significant differences in IR profiling. In conclusion, ATR-FTIR microspectroscopy offers new possibilities for studying cell wall composition at the cell level.

Mechanical properties of “flexure wood”: compressive stresses in living trees improve the mechanical resilience of wood and its resistance to damage

& Key message Mechanical acclimation of young poplars (Populus tremula × Populus alba, INRA 717-1B4) submitted to periodic stem bending is mainly driven by strains. Flexure and exhibit higher mechanical resilience and lower mechanical damage. & Context It is well known that thigmomorphogenesis modulates tree growth and the anatomical structure of However, nothing is known about the mechanical behaviour of the tissues of fresh formed under mechanical stimulation. & Aims We investigated the elastic and plastic properties of the fresh of young poplar trees (Populus tremula × Populus alba, INRA 717-1B4) submitted to periodic controlled stem bending that mimics the mechanical effect of wind. & Methods For a set of trees, we applied symmetrical bending treatments, which led to the formation of flexure wood. For another set of trees, asymmetrical bending treatments, including compression (or tension) only, were applied and generated specific formation: compressive wood and tensile wood. We investigated the elastic and plastic properties of these woods at the stem and at the local tissue levels. & Results The results revealed that fresh formed under treatments is more resistant to damage (damage reduced by 44%) and a higher mechanical resilience (+ 33%), suggesting that this tissue is able to withstand higher mechanical strains than normal wood. This improvement could explain the higher mechanical strength of the stem to bending (+ 42%). & Conclusion When trees experience repetitive mechanical stimulations, they adjust the plastic plastic behaviour of their in a way that improves the mechanical safety. This demonstrates the adaptive benefit of the mechanical acclimation of trees.

Hygrothermal recovery of compression wood in relation to DMSO swelling and drying shrinkage

Abstract To understand the irreversible dimensional changes caused by hygrothermal treatment of green wood, i.e. hygrothermal recovery (HTR), green hinoki compression wood (CW) and normal wood (NW) were hygrothermally (HT) treated in water at 100°C for 120 min and their HTR strains were determined. The specimens were then swollen using dimethyl sulfoxide (DMSO) and then completely dried after solvent exchange with water at room temperature. Their HTR strains were then compared with their DMSO swelling and drying shrinkage strains. The volumetric HTR strains in the CW were about twice as large as those in the NW. Moreover, the microfibril angle (MFA) was found to be an important factor for controlling the HTR intensity. A clear commonality between the HTR behavior and both DMSO swelling and drying shrinkage behavior was identified, which indicates that HTR is caused by volumetric changes in the matrix substances. HTR has been defined as a phenomenon due to the release of locked-in growth stress when a wood specimen is HT treated. To determine whether DMSO treatment has a similar effect as hygrothermal treatment, both HT-untreated and HT-treated specimens were swollen using DMSO, and their dimensional changes during and after DMSO treatment were compared. The results showed that DMSO treatment is a possible alternative for releasing the locked-in growth stress.

Effect of drilling parameters on Neem wood veneer epoxy composites using grey relational analysis

In recent trend the composites based wood are replacing the normal wood and other materials in various fields. The wood composites have cosmic properties like cheaper in cost, denser, free from defect, they can be machined in any way to make desired output product. This paper is all about investigation of wood properties and its behavior for drilling process. Drilling is one of the universal machining process that being carried out in the world .The purpose of drilling is to remove the excess of material from the work piece (specimen) to produce a hole and drilling is the primary process that need to be carried on the specimen to perform other machining operation (boring, reaming and tapping) as drilling got various level of importance in different applications, studying about drilling process and its parameter on different materials is important. This paper is all about the analysis of different drilling parameters such as feed rate (mm/min), spindle speed (rpm), Drill diameter on the quality of drilled hole. To study these factors Grey relation technique and Taguchi analysis is implemented. The result shows that feed rate is the major influencing parameter when compared to other cutting parameter and by selecting the optimal value ,the quality of the drilled hole can be improved

Diversity of anatomical structure of tension wood among 242 tropical tree species

ABSTRACT Angiosperm trees produce tension wood to actively control their vertical position. Tension wood has often been characterised by the presence of an unlignified inner fibre wall layer called the G-layer. Using this definition, previous reports indicate that only one-third of all tree species have tension wood with G-layers. Here we aim to (i) describe the large diversity of tension wood anatomy in tropical tree species, taking advantage of the recent understanding of tension wood anatomy and (ii) explore any link between this diversity and other ecological traits of the species. We sampled tension wood and normal wood in 432 trees from 242 species in French Guiana. The samples were observed using safranin and astra blue staining combined with optical microscopy. Species were assigned to four anatomical groups depending on the presence/absence of G-layers, and their degree of lignification. The groups were analysed for functional traits including wood density and light preferences. Eighty-six% of the species had G-layers in their tension wood which was lignified in most species, with various patterns of lignification. Only a few species did not have G-layers. We found significantly more species with lignified G-layers among shade-tolerant and shade-demanding species as well as species with a high wood density. Our results bring up-to-date the incidence of species with/without G-layers in the tropical lowland forest where lignified G-layers are the most common anatomy of tension wood. Species without G-layers may share a common mechanism with the bark motor taking over the wood motor. We discuss the functional role of lignin in the G-layer.

Distribution of lignin, pectins and hemicelluloses in tension wood fibers of European ash (Fraxinus excelsior)

ABSTRACT Although there is considerable information on the chemistry of gelatinous (G) layers in tension wood (TW) fibers consisting of S1 + S2 + G cell wall structure (poplar), little is known on the chemistry of G-layers in TW fibers organized with S1+ G structure. This study investigated the distribution of lignin and non-cellulosic polysaccharides in ash TW fibers (S1+ G) using histochemistry and immunolocalization methods. TW fibers studied were fully developed (mature fibers) and obtained from two (TW-1, TW-2) mature European ash trees (Fraxinus excelsior L.). Based on differences in microfibril angle (MFA) and TW trees used, TW fibers were mainly classified into three types; 1) Type-1 fibers with MFA almost parallel to the fiber axis that were found in TW-1, 2) Type-2 fibers with 12° MFA that were abundant at the end of growth rings of TW-1 and 3) Type-3 fibers with 10° MFA that were found in TW-2. The S3 layer was absent in all TW fibers. In this study, the secondary cell wall structure of Type-1 and Type-2/Type-3 fibers were defined as G and GL (gelatinous-like) layers, respectively. Lignin with syringyl (S) units was detected in G/GL-layers, in which intensity and patterns of lignin staining likely related to the difference in MFA between G- and GL-layers. With hemicelluloses, heteroxylan and heteromannan epitopes were detected in G/GL-layers but these were much less abundant than those in S2 layers of normal wood (NW) fibers. Like lignin, distribution patterns of heteromannan epitopes in G/GL-layers likely related to differences in MFA between fiber types. Sparse xyloglucan epitopes were also detected in G/GL-layers. Homogalacturonan epitopes were absent in G/GL-layers. All fiber types showed abundant a-1, 5-arabinan epitopes in G/GL-layers. Overall results indicate that the chemistry of ash TW fibers studied differs significantly from that of other species reported previously, specifically TW fibers composed of S1 + S2 + G structure.

Contribution of lignin to the stress transfer in compression wood viewed by tensile FTIR loading

Abstract To achieve efficient utilization of compression wood (CW), a deeper insight into the molecular interactions is necessary. In particular, the role of lignin in the wood needs to be better understood, especially concerning how lignin contributes to its mechanical properties. For this reason, the properties of CW and normal wood (NW) from Chinese fir (Cunninghamia lanceolata) have been studied on a molecular scale by means of polarized Fourier transform infrared (FTIR) spectroscopy, under both static and dynamic loading conditions. Under static tensile loading, only molecular deformations of cellulose were observed in both CW and NW. No participation of lignin could be detected. In relation to the macroscopic strain, the molecular deformation of the cellulose C-O-C bond was greater in NW than in CW as a reflection of the higher microfibril angle and the lower load taken up by CW. Under dynamic deformation, a larger contribution of the lignin to stress transfer was detected in CW; the molecular deformation of the lignin being highly related to the amplitude of the applied stress. Correlation analysis indicated that there was a direct coupling between lignin and cellulose in CW, but there was no evidence of such a direct coupling in NW.

A preliminary investigation of various signal phenomena generated by termite infestation

Subterranean termites are major urban pests in Indonesia and lead damage to wooden structures and buildings. Termite pest management involves two sections: prevention and control. The most crucial part of termite control is to detect termites; however, due to their cryptic behavior, the termite infestation evidence on wooden structures is difficult to detect visually. When termite infestation is active and wood damage is occurring, the distinction of various signal phenomena are released including moisture content, temperature and acoustic emission. The identification of these phenomena becomes the basic foundation for designing a future termite detection system. The aim of this study is to identify various signal phenomena generated by termite infestation. In this investigation, the pine wood, as the medium for termite infestation, was divided into two groups, i.e., the wood infested by 220 termites (‘infested’) and the normal wood as a control (‘uninfested’). Each signal phenomenon generated by termites was observed and analysed to produce six pieces of information, i.e., (a) moisture content; (b) temperature; (c) four information of acoustic emission such as energy, entropy, peak frequency and zero moment power. Based on statistical analysis of Duncan multiple range test (DMRT; two-way ANOVA, P ≤ 0.05), it was revealed that the information that can distinguish significantly between infested and uninfested wood are moisture content, temperature, energy, entropy and zero moment power. Finally, various phenomena (i.e., moisture content, temperature and acoustic emission) can be embedded and integrated in the sensing technology of termite detection.

Impact of high temperature drying process on beech wood containing tension wood

Abstract The technology of high temperature drying has a great influence on dimensional and selected physical changes in tension wood. Article is focused on the measurement properties such as moisture content, color changes and longitudinal warping. The quality of beech wood is determined based on structure and properties of wood, frequency of defects in wood material. The tension wood is considered as an important wood defect causing negative alterations in solid wood quality and limits industrial application of wood. The different values of longitudinal warping which were measured after drying were higher in tension wood than in normal wood. Impact of radial and tangential angle of growth rings is non-significant factor.