Research Articles

Eichhornia crassipes biomass collected in Lake Cuitzeo, Mexico was analyzed to determine the chemical components (pH, ash, ash microanalysis, extractives, lignin, holocellulose, and alpha cellulose) in the whole plant, as well as segmented analysis in roots, stems, and leaves. The plant contained an ash content of 14.3 to 20.7% and extractives content from 21.8 to 35.6%. The inorganic elements detected were potassium (K), chlorine (Cl), calcium (Ca), sodium (Na), magnesium (Mg), silicon (Si), aluminum (Al), phosphorous (P), sulfur (S), manganese (Mn), iron (Fe), and titanium (Ti). In addition, low amounts of lignin (12.5 to 25.7%) and holocellulose (26.7 to 37.1%) were obtained. Thus, E. crassipes biomass could complement cellulosic fibers in pulping processes of low yield, such as the fibers used to produce handmade paper.

The engineered bamboo/wood composites (EBWCs) studied in this work included solid wood, wood-based composites, and bamboo-based composites. The basic characteristic of these products is that they have similar stress-strain relationships in the parallel to the grain direction because of their similar microscopic structures. The asymmetric stress-strain relationship in tension and compression presents a great challenge for the inelastic analysis of intermediately slender EBWC columns. In this study, a novel model was developed for the inelastic analysis of biaxially loaded intermediately slender EBWC columns with rectangular cross sections. The model provides a step by step method to evaluate the nonlinear responses and load-carrying capacities of these columns. Experiments on parallel strand bamboo columns loaded with biaxial eccentric loads were conducted to validate the model. Good agreement between the experimental and predicted results was achieved. The innovative elements of the model were the asymmetric properties of EBWCs in tension and compression, and its simplicity, which lends itself to implementation in engineering design calculations. The present work is an extension of a previous study by Huang et al. (2015a), and its objective was to develop an innovative inelastic analysis model evaluating biaxially loaded intermediately slender EBWC columns with rectangular cross sections.

Acoustic tomography is based on the velocity variation inside the inspected element. However, wood is heterogeneous and anisotropic, which causes natural velocity variations. In wood, the great challenge to apply this technology is to interpret and differentiate the natural variations of the material from those caused by deterioration. This study aimed to evaluate the interference caused by knots, the wave propagation direction, and the effect of juvenile and reaction wood on the velocities determined via ultrasonic tomography. The tests were performed using 40 disks of Pinus elliottii. From the results it was concluded that intrinsic orthotropy of the wood was reflected in the wave propagation on the disks with radial velocities greater than the tangential ones, higher velocities in the knot zones, and different velocities in the zones of compression and opposition wood. In the measurements using the diffraction mesh, the edge velocities (tangential direction with the maximum angle from the radial direction) were always lower than all of the other velocities in the disk. More significant variations in the velocity were obtained in the juvenile wood. These results contribute to quantifying some interferences associated with tomography images, such that the misinterpretation can be minimized.

The co-pyrolysis of Salix psammophila and coal was conducted in a pyrolysis reactor. The interaction between coal and S. psammophila at different ratios was investigated. It was found that the promotion and inhibition effects were more obvious at 20 wt.% and 40 wt.% Salix psammophila, respectively, indicating a certain synergistic effect. The results of the N₂ adsorption-desorption experiment showed that the addition of S. psammophila increased the surface area and decreased the pore size of the co-pyrolysis char. The Fourier transform infrared (FT-IR) spectra indicated that the pyrolysis tar contained mainly aromatic rings and fatty compounds. The addition of S. psammophila was beneficial to the decomposition of phenolic hydroxyls, ether bonds, and oxygen-containing heterocyclic rings in the coal tar. However, the addition of 50 wt.% S. psammophila blocked the pores of the coal and thus obstructed its pyrolysis, while the porosity of the co-pyrolysis char became more abundant. Richer porosity of the char implies great potential to be widely used in the sewage treatment industry.

The reactivity of rayon-grade dissolving pulp is an important parameter in the subsequent production of viscose fiber. It can determine the processability and the quality of the viscose fiber. This study focused on improving the reactivity of kraft-based rayon-grade dissolving pulp through a mechanical treatment with mechanical refining, which could induce more fiber ends and channels or reactive sites via fiber cutting and fibrillation. Results showed that the Fock reactivity of a softwood kraft-based dissolving pulp increased from 54.4% to 68.4%, and the viscose filterability improved from 3743 s to 11 s when the beating degree of dissolving pulp was increased from 9 ºSR to 16 ºSR. Such a treatment also led to increases in the fines content, pore diameter, water retention value, and specific surface area while decreasing the fiber length. Meanwhile, it was beneficial that the intrinsic viscosity of dissolving pulp fiber was almost unaffected by the beating treatment.

One likely reason why cross-laminated timber (CLT) panels are not applied in furniture designing is their unaesthetic appearance, with a crosswise arrangement of layers visible on narrow surfaces of furniture panels. The objective of this investigation was to manufacture and determine physic-mechanical properties of solid and cell Longitudinally-Laminated Timber (LLT) panels. The cognitive goal of the performed experiments was to determine orthotropy, linear elasticity moduli, and bending strength of LLTs. It was also decided to ascertain swelling coefficients of composites caused by changes in air humidity. Advantageous MOE and MOR values of LLTs were determined in relation to similar solid panels. In addition, it was demonstrated that, for furniture panel designing, it was rational to employ facings from beech wood as well as cores from beech wood free from anatomical defects.

Alkali lignin (AL) was prepared by the acidification of black liquor obtained from a pulp and paper factory. The average molecular weight of the AL (2,530 g/mol) was determined using gel permeation chromatography (GPC). Alkali lignin modified by ethylene glycol and lignin nanoparticles (LN) were prepared via acid precipitation technology. Reactions in a pH range of 4 to 6 were evaluated while preparing the nanoparticles. Lignin nanoparticles were stable at pH 4 to 10. The sizes of the nanoparticles were assessed with dynamic light scattering (DLS); the average diameter of the nanoparticles at pH 4 was 52.7 nm, which was confirmed by SEM. LN has polar centers that can produce an interacting interface with the polymer matrix in which it will be dispersed. The morphologies and structures of combinations of AL and LN were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis-derivative thermogravimetric (TGA-DTG). The FTIR spectra clearly showed that the positions of the peaks in lignin nanoparticles shifted to slightly lower values due to the interaction between lignin molecules and ethylene glycol.

Torrefaction is a thermal process that improves the energy properties of plant biomass pellets, providing greater biofuel efficiency for gasification technologies, as well as replacing coal in thermoelectric plants. In Brazil, many agroforestry residues can be improved in value through this technological process, transforming them into modern solid biofuels. There are few studies comparing torrefied wood and elephant grass pellets, especially in relation to their energetic characteristics. This study analyzed the high heat value, energy density, ash content, fixed carbon, volatile materials, lignin, holocellulose, extractives, bulk density, and mechanical durability of these pellets. Due to the absence of Brazilian normative standards for these pellets, the international standard ISO 17225 (2014) was used for comparisons. The results revealed substantial differences among the samples, mainly regarding their moisture content, higher heating value, and energy density in torrefied pellets. It was concluded that these torrefied pellets are biofuels having lower water adsorption, higher heating value, and higher energy density than the pine and elephant grass pellets.

The dynamic Young’s modulus (E_d) and moisture content (MC) were determined for two tropical wood species, Gymnacranthera eugenifolia and Sindora sp. using the free-free vibration method. The wood species were tested at the sap, median, and internal regions. The dynamic Young’s modulus was found to be linearly correlated to the radial distance, with E_d gradually increasing with respect to the reduction in radial distance to the centre of the wood. Linear correlation was observed between the radial distance and E_d, with E_d gradually decreasing with respect to the radial distance from the centre. For Sindora sp. and Gymnacranthera eugenifolia, E_d ranged from 0.8 to 2.4 GPa and 0.9 to 1.6 GPa, respectively. Moisture content in Sindora sp. displayed a broad range, from 10 to 20 wt.%, while Gymnacranthera eugenifolia displayed a narrower range from 8 to 15 wt.%. Free-free flexural vibration testing is a fast, inexpensive, and reliable method for determining E_d. However, further studies are needed to investigate the acoustic qualities of these woods, such as the speed of sound and damping within the wood.

Agarwood can be divided into resinous heartwood from the Hoi-An zone and Sin-Chew zone. Traditionally, an experienced human grader classifies agarwood by odor. However, sensory errors can follow from subjectivity, poor reproducibility, and time consumption during manual work. In this study, agarwood samples were heat-treated to release volatile organic compounds (VOCs), which were analyzed using the thermal desorption – gas chromatograph mass spectrograph (TD-GCMS) method and chemometrics analysis. The classification of agarwood was then identified. Sesquiterpenes and other aromatic compounds were the main compounds of heat-treated VOCs. Twenty-six characteristic compounds were screened via stepwise regression. Fisher discriminant analysis and Bayes discriminant analysis were conducted, based on the 26 compounds, to classify the agarwood samples. Discriminant functions of the two analysis methods were obtained.The results showed that it is feasible to use the TD-GCMS method combined with chemometrics analysis to analyze VOCs from heat-treated agarwood instead of experienced graders to classify the agarwood samples as being from either the Hoi-An zone and Sin-Chew zone. This study also provides a way to classify unknown samples by odor through 26 characteristic compound’srelative peak area and the discriminant equations, offering the possibility of testing an unknown sample’s cultivation region.