Dynamic relationship between mechanical properties and chemical composition distribution of wood cell walls

Wood is a natural composite material with a complex structure. Its mechanical properties are mainly due to the cell walls. In order to investigate the relationship between mechanical properties and chemical composition of wood cell wall. Nanoindentation and Raman imaging were used to characterize the longitudinal mechanical properties and chemical composition distribution of wood fibers of three years old fast-growing poplar (Populus×euramericana cv. ‘74 /76’) during the growing season at different times. The results were showed that the content and distribution of cellulose and lignin are closely related to the mechanical properties of wood fiber cell walls, especially the cellulose for the longitudinal elastic modulus and the lignin for the hardness of cell walls. It was also demonstrated that the longitudinal elastic modulus and hardness of the secondary wall 2 layer (S2) were strongly correlated to the micro fibril angle (MFA) and crystallinity of cellulose during the active phase.

Chemical characteristics of Eucalyptus pellita with heart rot

Eucalyptus pellita has been posited as a primary raw material in Indonesia due to its fast growth. In some areas, however, trees with heart rot were found. Thus, the wood with heart rot was analysed chemically both in sound (sapwood, outer heartwood, inner heartwood) and degraded parts (heart rot-affected wood/HRAW). The results revealed that there was a different trend in the wood chemical composition between bottom and centre parts. In bottom parts, wood with bigger diameter of heart rot, the slight changes in polysaccharides and lignin amounts was observed in HRAW compared to sound wood parts. On the contrary, comparatively high lignin and low polysaccharide levels in HRAW were measured in centre parts. HRAW was also characterized with high content of inorganic materials and high pH values but low in extractive content, mostly ethanol soluble extractives or its polar fraction. Increasing of phenolic contents was more pronounced in HRAW of lower part than that of upper of the stem. The difference trend of chemical composition between bottom and centre parts suggesting the cause of heart rot could be several wood degraders.

Indoor fungal destroyers of wooden materials – their identification in present review

The wood-destroying fungi traditionally were separated from one another primarily on a basis of their sporocarp and/or strain morphology. Their diversity and simple macro- and micromorphology of fungal structures have been major obstacles for more rapid progress in this regard. However, over the past two decades, there has been substantial progress in our understanding of genetic variability within traditionally recognized morphospecies. In this study we have overviewed genetic variation and phylogeography of macrofungi, which are important destroyers of wooden materials indoor of buildings. Several morphologically defined species of these fungal destroyers (Coniophora puteana, C. olivacea, C. arida, Serpula himantioides) have been shown to actually encompass several genetically isolated lineages (cryptic species). The protective efficacy against cryptic species within traditionally recognized morphospecies through laboratory tests (EN 113) and field trials (EN 252) might be sufficient to better prognosis of decay development in wooden materials for hazard assessment and for proper conservation and management plans.

Dynamic and damping properties of novel bio-composites using the hammer excitation vibration technique

The dynamic and damping properties of nine different wood-based bio-composites at varying volume fraction of Corn starch (CS), methylene diphenyl diisocyanate (MDI), microcrystalline cellulose (MCC), processing time and pressure have been studied. The samples used for the study consisted of southern yellow pine particles with 2% Corn starch (CS), 4% methylene diphenyl diisocyanate (MDI); 4% CS 4%MDI; – 4% MDI; – 2% CS 2% MDI; – 4% CS 4% MDI; – 2% microcrystalline cellulose (MCC) 4% MDI; – 4%CS2% MDI; – and 1% MCC 4% MDI; – (all on a solids basis). The panels were manufactured using a Dieffenbacher hot press at a temperature of 185oC. The dynamic and damping properties were determined using hammer excitation vibration technique. The responses were obtained from frequency and time domain for the fundamental natural frequency (fn), and the results obtained were consistent. The panel manufactured with 4% MDI and formed at relatively high pressure (10.5 MPa) had the highest average storage modulus (E’), and this shows that increasing manufacturing pressure and density of material contributed to the high elasticity of the material. The panel produced with 2% CS and 2% MDI had the highest damping ratio (ξ) and Loss factor (η) when compared with other wood samples, and this demonstrates that the CS contributed to the high damping of the material.

Effect of macro characteristics on rolling shear properties of fast-growing poplar wood laminations

Rolling shear modulus (GR) and strength (fR) of the cross layers are decisive mechanical properties in cross-laminated timber (CLT) plates. The influences of macro characteristics, such as annual ring orientation, distance to pith, and presence of pith on the rolling shear properties of fast-growing poplar boards were evaluated throughout this study. It were found the presence of pith had significant influence on the rolling shear properties of poplar board. Distance to pith and annual ring orientation both had effects on the rolling shear properties jointly. The rolling shear properties increase with the increase of distance to pith. The mean rolling shear modulus and characteristic rolling shear strength values of the poplar wood were determined to be 177 MPa and 2.24 MPa, respectively, which indicates a great potential of using poplar wood as the cross-layers in CLT.

The bending modulus of elasticity of subfossil elm wood

The paper presents the results of the research of the bending modulus of elasticity of some 700 year old subfossil elm wood (Ulmus minor) retrieved from the Sava riverbed (Bosnia and Herzegovina). The subfossil elm wood is very rare to find and is highly appreciated in this form for its beautiful appearance and specific mechanical properties. Adult elm trees are nowadays also very scarce in natural forest stands of SE Europe, due to the invasion of the Dutch elm disease (Ophiostoma novo-ulmi Brasier) some fifty years ago. The bending MOE was determined in the longitudinal direction and the angles between the direction of load and the annual growth ring orientation were 0°, 45°, and 90°. The obtained values of the bending modulus of elasticity are within the range of those obtained for a recent elm, which shows that numerous centuries spent in anoxic aquatic conditions have not affected the investigated property of subfossil elm. The study showed that the annual growth ring orientation significantly affects the MOE of subfossil elm wood in the longitudinal direction. The highest values were obtained at the angle of 45° (L45°), and the values for L0° and L90° are very similar. The variability and heterogeneity of the MOE was described with the two-parameter Weibull distribution and the results follow the Weibull distribution.

Study on thermal insulation and heat transfer properties of wood frame walls

Steady-state heat transfer performance of wood frame wall is an important index to assess its energy efficiency. In order to study the factors that affect the heat transfer coefficient of wood frame wall, the method of improving the thermal insulation property of the wall was studied. In this paper, 12 wall specimens with different structures were manufactured, and the effective heat transfer coefficient was measured by the hot box-heat flow meter test method. The reliability of the theoretical calculation value of thermal resistance was verified by the experimental value. The results showed that the moisture content of Spruce-pine-fir (SPF), insulation materials, spacing and thickness of studs had influence on the heat transfer coefficient of walls. The effective heat transfer coefficient values of three walls ranged from 0.325 to 0.398 W•m-2•K-1, which met the thermal level It of the severe cold area. The linear correlation between the theoretical calculation value and the test value was up to 0.9587, effective thermal resistance value of wood frame wall can be estimated by calculating without extra experiment.

Change in the wood moisture dependency on time and drying conditions for heating by wood combustion

The aim of this study was to determine the drying time of firewood under the climatic conditions of the Czech Republic to decrease the moisture content to an acceptable level for combustion (under 20%). The effects of log size, outdoor/indoor trying and wood species were evaluated.

Probabilistic approach of the failure of Lovoa trichilioides and Triplochiton scleroxylon

The aim of this work is the probabilistic modeling of the failure of Lovoa trichilioides and Triplochiton scleroxylonspecies. A general presentation of the wood while focusing on the Weibull distributions was carry out. Parameters of the Weibull distribution for each of the materials were determined. We remark that when the Weibull shape parameter is small, the failure stresses dispersion is greater and the Weibull scale parameter increase or decrease depending on the stress. It is also shown that Lovoa trichilioides exhibits a high dispersion of breaking stress in contrast to Triplochiton scleroxylon. A comparison of the experimental data with the statistical laws allowed us to show that the three-parameter Weibull distribution better models the failure than the normal and the two-parameter Weibull distributions. The studies of variance prove that the failure stresses of Triplochiton scleroxylon vary less in comparison with that of Lovoa trichilioides.

Characteristics of nontoxic bamboo bioboard by melamine and cellulose adhesive

In this research, the influence of various factors on the performance of the melamine bamboo cellulose gum is investigated by orthogonal test method, with the pressing temperature, pressing time, the added amount of cellulose gum, melamine dosage as factors. And analyze the samples by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), DTG, etc. The amount of melamine is the main factor affecting the quality of bamboo composite material and its physical and mechanical properties, it has a significant impact on MOR board, internal bond strength, elastic modulus and other properties; cellulose gum is a secondary factor affecting performance. The results showed that cellulose gum ratio of 5 %, ratio of melamine of 2.5 % and the hot press time of 9 min provided the optimum conditions for hot press.

Optimization of the clearance angle in industrial disc chipper

Wood chips used for chemical pulp must be of relatively uniform size. The penetration of the pulping chemicals and thus the cooking time, is considerably determined by chip length. The clearance angle (pull-in angle) is a significant parameter of the knife positioning in the disc chipper, that affects the length of the chips.” In many production plants, this angle is wrong set depending on the diameter of the chipped wood. This causes problems in obtaining the appropriate length of the chips. The disc chipper in one of the industrial plants in Poland was investigated because it produced chips with smaller lengths from the assumed. This also included the numerical calculations to optimize the clearance angle. In the disc chipper, the variability of the clearance angle (α) along the cutting edge of the knife (helical knives) gives the possibility of improving the quality of the wood chips. Simulations to determine the variability of the clearance angle on the radius of the disc of chipper assuming the continuity of cutting wood in the chipper was also performed.

The synergistic smoke suppression effect of ferric oxide on flame retardant wood-polyurethane composites

Wood flour-polyurethane composites (WPC) with ammonium polyphosphate (APP) and ferric oxide (Fe2O3) were prepared to research the cooperative influence of smoke suppression and fire resistance. By the methods of cone calorimeter test (CCT), smoke density test (SDT), thermogravimetric analysis (TG), limiting oxygen index (LOI), field emission scanning electron microscope (FE-SEM) and Fourier transform infrared spectroscopy (FTIR). Remarkably, Fe2O3 has significant improvement on heat release rate (HRR), total heat release (THR), smoke factor (SF), and total smoke release (TSR) of the APP/WPC.SDT implied that Fe2O3 played a positive role during burning and there is a synergistic effect of smoke suppressing for Fe2O3 on APP/WPC. The LOI results showed that compared with samples without flame retardant, adding Fe2O3 improved the LOI value of WPC. TG indicated that Fe2O3 and APP played an effective role in the course of thermal degradation of WPC. And the SEM and FTIR showed that Fe2O3 and APP played a role in ameliorating the residual carbon structure.

Determination of viscosity curve and PVT properties for wood-polymer composite

In the presented study the injection mold equipped with the test apparatus were used to determine the viscosity curve of wood – polymer – composite (WPC). During the test the polymer temperatures, flow rates and pressure data measured inside of mold cavity were recorded. In addition the pressure – volume – temperature (PVT) characteristic of this composite was determined using the capillary rheometer. The determined properties were used in numerical simulations of injection molding process of WPC. The results were verified on the basis of pressure profiles measured in the mold cavity during experiment. The simulation was performed using the Autodesk Moldflow Insight 2013 commercial code. The calculated and measured pressure profiles were compared.

Study on continuous cold-pressing technology of engineered wood flooring with EPI adhesive

The effects of process parameters (adhesive spread, press time, and applied pressure) on the gluing performance of engineered wood flooring bonded with emulsion-polymer-isocyanate (EPI) adhesive were studied. The results showed (shear strength and aging test) that the major factors were adhesive spread and press time. The optimized parameters for best gluing performance of engineered wood flooring were 160 g. m-2, 14 s, and 60 s for adhesive spread, heat time, and press time, respectively, within certain ranges.

Measuring the surface roughness values of european hop-horn beam (Ostrya carpinifolia Scop.) wood

In this study, the samples obtained from European hop-horn beam (Ostrya carpinifolia Scop.) wood has been subject to cutting with circular saw, planing with a thickness machine and sanding with a caliber sanding machine (with no: 80 sand). After the specimens were processed in the machines in radial and tangential surfaces, their surface roughness values (Ra, Ry, Rz) have been determined in accordance with the ISO 4288 standard. According to the statistical results, the lowest roughness values have been achieved with the thickness machine. Similarly, the roughness values of tangentially cut surfaces have been found to be lower than the radially cut surfaces.

Fabrication of superhydrophobic wood surface with a silica/silicone oil complex emulsion

The superhydrophobic wood surface was fabricated in this study by impregnating oven-dry poplar (Populus cathayana Rehd.) samples with a silica/silicone oil complex emulsion (SSOCE), mainly composed of two silicone oils(hydroxy silicone oil and hydrogen silicone oil) and two different sized silica particles (micron and nano scaled, respectively). Different concentrations of the complex emulsion (5%, 10%, 20%, 30% and 40%) were used and their effect on static contact angles (CAs) and surface free energy (SFE) of wood were investigated. The chemical and morphological changes of modified wood surface were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The superhydrophobic wood surfaces were manifested by the water CA of about 154.8° on the transverse section, 151.3 °on the tangential section and 150.2° on the radial section, respectively. It was confirmed that silicone oilsin the complex emulsion formed a silicon resin filmand uniformly attached on the wood surface, with silica particles in micron and nano scales helped to make the surface rougher.