Research Articles

Wood-based paper fibers are inherently biodegradable. In contact with moist soil and in compost, papermaking fibers are readily broken down by soil microbes. Resistance to biodegradation is needed, as paper is used for special applications such as mulching in agriculture and forestry, the coating of construction materials, and for packing and wrapping under conditions where packaging materials may be exposed to contact with moist soil or other type microbial active contamination. A preceding study showed that paper chemical crosslinking with glyoxal, citric acid (CA), or methylated 1,3-dimethylol-4,5-dihydroxyethylene urea (mDMDHEU) results in substantially improved paper wet strength and lower paper water absorbency. The present study examined the efficiency of chemical crosslinking treatments with CA and with mDMDHEU to decrease the biodegradation rate of laboratory paper sheets and a sack paper, both made of kraft fibers. The biodegradation was examined using a 48-h enzymatic degradation test and a 2-month soil burial test. The results indicate that chemical crosslinking is an effective non-biocidal method for making sulphate kraft paper more resistant to biodegradation. In some end-uses, improved resistance to biodegradation, along with improved paper wet performance, can enhance paper performance comparable to plastic films.

Accelerated weathering experiments were used to examine the durability and changes in various attributes of WPCs manufactured with the same wood powder size but varying polypropylene-to-wood ratios. Results from the accelerated weathering test revealed color changes, and each attribute generally declined with longer weathering times. In terms of mechanical qualities, the preservation of strength and stiffness increased with increasing plastic content. More wood flour led to higher moisture uptake in frequent humidity fluctuations and high temperatures. It also caused swelling as wells as subsequent cracks. Such surface damage could result in faster weathering and worse mechanical qualities. Additionally, the carbonyl index and the functional groups on the surface of WPCs underwent significant changes with increased weathering time.

Decolorization of malachite green (MG) from the aqueous phase was investigated using tea stalk powder. The adsorption efficiency decreased with the initial MG concentration, ionic strength of the solution, and heavy metal content. A suitable initial MG concentration of up to 200 mg/L can be accepted because adsorption efficiency of more than 95% is achieved. Various adsorption kinetic models were used to fit the experimental data, and the data obtained was best explained by the pseudo second-order model. The adsorption capacities calculated with the pseudo second-order model at different initial MG concentrations ranging from 24.27 to 158.7 mg/g were very close to the experimental data. The Langmuir isotherm fitted well, and the thermodynamic investigation showed that the adsorption of MG by tea stalk powder was feasible, endothermic, and spontaneous. The regeneration/adsorption experiments indicated that the tea stalk powder remained more than 95% of efficiency after six cycles using NaOH as desorbent and thus could be used many times. In conclusion, tea stalk has considerable potential as a cost-effective adsorbent for the removal of MG.

The demand for man-made cellulosic fibres is expected to grow in the future. One commercially-available concept to supply fibres is Lyocell manufacturing from dissolving wood pulps using N-Methylmorpholine N-oxide (NMMO) as the solvent. The literature qualitatively indicates that NMMO recycling efficiency is a key factor for profitable operation. Process design information and parameter data are however poorly available publicly to illustrate the cost factors. Therefore, systematic techno-economic analysis of a 50 kt/year Lyocell plant was conducted using steady-state process simulation and cost modeling. With the simulation models, the underlying technical process design and modelling decisions, and economic assumptions were studied. NMMO makeup need is an important cost item. The simulated makeup need is very dependent on the design of the solvent recovery system and the vapor-liquid equilibrium thermodynamic model selection. On the other hand, water use, fibre washing process design, and washing model parameterization have relatively lower impact on the cost of production. Raw material cost and capital expenses are most critical cost items when the NMMO recycling efficiency is high.

The pyrolysis performances and reaction kinetics of pine needles (PN) were investigated by integrating thermogravimetric analysis, Fourier transform infrared spectroscopy, and pyrolysis-gas chromatography/mass spectrometry. The average activation energy of PN was estimated to be 183.2 kJ/mol by Kissinger Akahira Sunose (KAS) and 183.8 kJ/mol by Flynn Wall Ozawa (FWO), respectively at heating rates of 10, 20, and 40 °C/min. The pyrolysis of PN was found to be more efficient at the lower heating rates, while increased heating rates promoted the reaction. Using the King-Kai (K-K) method, the activation energies of hemicellulose, cellulose, and lignin were calculated to be 156, 165, and 172 kJ/mol, respectively. The descending order of evolving gases and functional groups from PN was found to be CO₂, C=C, C=O, H₂O, CH₄, and CO. The main pyrolytic by-products identified were hydrocarbons, phenols, alcohols, ketones, and aldehydes. The determination of kinetic parameters provides fundamental information for predicting the rates at which chemical reactions occur. This study demonstrates the potential of PN as a suitable source for bioenergy.

Samples of agilawood (agarwood), which were studied in this work, were produced in Zhongshan City, Guangdong Province, China. To enhance incense production, a specific concentration of plant hormone is employed for induction. The extraction technology of agilawood essential oil was explored using supercritical carbon dioxide fluid, which exhibited a more pronounced induction effect. The pressure, temperature, and flow rate, respectively, were 8, 16, and 24 MPa; 35, 45, and 55 °C; and 20, 30, and 40 L/h. A Box-Behnken analysis was adopted for experimental data, which involved 33 experiments. The data were fitted with the equation Y = 2.18 + 0.1312X₁ – 0.025X₂ + 0.1236X₃ – 0.0025X₁X₂ – 0.0125X₂X₃ + 0.0175X₁₂ + 0.035X₂₂ – 0.1275X₃₂. Hence, the optimal process parameters in the supercritical extraction of agarwood essential oil were as follows: the pressure, temperature, and flow rate of 24 MPa, 35 °C, and 33 L/h, respectively. An analysis was conducted with the statistical analysis software Design-Expert 11, which indicated that the extraction yield of agarwood essential oil by supercritical carbon dioxide was mainly affected by the pressure and flow rate. The yield was proportional to the pressure and flow, and inversely proportional to the temperature.

Sound elements were studied for a six strings sape, a traditional instrument. The frequency was evaluated using a frequency spectrum and a time frequency plane. PicoScope oscilloscopes and Adobe Audition version 3 were used to record the acoustic spectra. Fast Fourier Transform (FFT) analysis was used for the Fourier spectra (using PicoScope) and time frequency analysis (TFA) spectrograms (using Adobe Audition). The Fourier spectra identified the partial frequencies up to 10^th overtone. The sape have an acoustic spectrum pattern with a constant harmonic overtone. Open strings 1 through 6 have notes F3, F3, A3, Bb3, G3, and C4, respectively. String 1 has 17 frets. Strings 2 through 6 are for drone purposes with no fret. The open string 1 and frets 1 through 17 have notes F3, G3, A3, Bb3, C4, D4, E4, F4, G4, A4, Bb4, C5, D5, E5, F5, G5, A5, and C6. String 1 has 2 octaves in the F major key with a jumping note in the third octave, which consists of F5, G5, A5, and C6 only.

Plastic used in food packaging causes permanent damage to living things. Therefore, biodegradable packaging has gained importance. In this study, biodegradable composite plates made from cross-linked wheat starch and cellulose-based fibers were examined for their physical and mechanical properties. The mechanical and physical properties were significantly altered when the obtained composite plates were examined. According to texture analysis, the plate with the lowest brittleness and with the highest crushing toughness value was produced from 7% carboxymethylcellulose. The densities of the composite plates obtained from cross-linked wheat starch were found to be 0.171 g/cm³, and their densities were found to be lower than the composite plates produced from natural wheat starch. It was determined that the plate with the highest water resistance was produced from 7% carboxymethyl cellulose. Added cellulosic fibers (commercial cellulose, linter fiber, hemp fiber) reduced moisture absorption from the air, reducing the average moisture content to 8.71. All of the plates produced with 7% linter fiber, which has the lowest moisture content, completely disappeared from nature within 40 days.

The aim of the conducted experiments was to determine the effect of selected machining parameters on power consumption and surface quality obtained during the milling of beech wood using a computerized numerical control woodworking machine. Surface roughness was tested using the contact roughness measurement method, while roughness parameters R_a and R_z were recorded and cutting energy was determined. Tests were conducted for two variants of cutting speed (7.5 and 15 m·s^-1) as well as three variants of chip thickness (0.10, 0.06, and 0.02 mm); additionally, the tests examined different cross-sections of wood. It was found that greater chip thickness and feed speed caused an increase in surface roughness and cutting power. In turn, cutting speed had no effect on surface roughness, whereas its increase resulted in increased cutting power. Surface roughness at the radial and tangential cross-sections was comparable, while it was greater at the transverse cross-section. It was also found that cutting power was lowest at the radial cross-section, while it was greater at the tangential and the greatest at the transverse cross-section.

Parallel-strand lumber was manufactured with bamboo (Phyllostachys bambusodies). A polyol compound was added to modify the adhesive (pMDI). Bamboo culms were used to manufacture strands 3 mm thick, 19 mm wide, and 65 cm long. Adhesive was applied to the strands at 200 g/m² with pressing at 110 °C, 15 kg/cm², and 30 min. Panels were made with width 600 mm, length 600 mm, and thickness 20 mm. Some physical properties (oven-dry density, air-dry density, moisture content, thickness swelling, and water absorption percentage) and mechanical properties (bending resistance, modulus of elasticity, impact resistance, screw-holding capacity in tangential, radial, and transverse directions) of parallel-strand lumber for both adhesive types were determined. Both resin types improved some physical and mechanical properties of parallel-strand lumber. Additionally, the modulus of rupture and flexural modulus of elasticity of the test specimens using pMDI+5%MP adhesive were higher than those of the test specimens using pMDI. The average screw-holding capacity values of the test specimens were affected by the fiber aspect of the specimens rather than the adhesive type. Parallel-strand lumber produced from both pMDI and pMDI+5%MP adhesives can be used in structural applications, especially in places exposed to the disturbing effects of weather.