Volume 15 Issue 3

The effects of pH on residual solids (RS), total dissolved solids (TDS), carbohydrates, and lignin in eucalyptus during hydrothermal pretreatment were studied. The balance between RS and TDS was obtained at pH 4.0 in hydrothermal pretreatment with pre-adjustment pH. The yield of hemicellulose increased, and oligosaccharides dominated. Hemicellulose had the highest dissolution rate, and cellulose and lignin had the lowest dissolution rate at pH 4.0. The crystallinity index (CrI) and structural transformation of lignin was analyzed by X-ray diffraction (XRD) and nuclear magnetic resonance spectroscopy (NMR) with or without pretreatment. The CrI at pH 4.0 was 64.2% higher than that with the traditional hydrothermal pretreatment (62.1%). The β-O-4 bonds, OMe, and phenylcoumarane of lignin were protected. The highest hemicellulose extraction and minimal physicochemical structural changes were obtained at pH 4.0.

The effect of different mechanical force application methods was investigated relative to the structure and properties of nanofibrillated cellulose (NFC) from sugarcane bagasse. The NFC was prepared by grinding, high pressure homogenization, and ultrasonication with chemical pretreatment. Fiber morphology, crystalline, chemical structures, and tensile property were analyzed to reveal the mechanisms of NFC production behind different mechanical treatments. The results showed that compared with grinding treatment, high pressure homogenization and ultrasonic treatment can obviously increase the aspect ratio and size uniformity of NFC. Ultrasonic treatment gave the best results. The combination of grinding, high pressure homogenization, and ultrasonic treatment resulted in NFC with the average diameter of 23.18 nm. With the shearing action of grinding, high pressure homogenization, and ultrasonic treatment, the mechanical properties, crystallinity and thermal stability of NFC were gradually enhanced. This results demonstrated that a very low-value agricultural waste product can be easily converted to a high performance nanocomposite with tensile strength of 153.6 MPa and strain at break of 8.83%.

The wooden columns in timber structures of ancient buildings have column foot tenons of various sizes. The main reason for these differences is their use for different roof loads. Six full-scale specimens with different sizes of column foot tenon were designed and manufactured. The tree species used for the specimens was larch. The quasi-static test was conducted on the specimens that were used in timber structures of ancient buildings. The effects of column foot tenon size on the mechanical properties of larch wooden columns were studied. The moment-rotational angle hysteretic curves, moment-rotational angle skeleton curves, ductility, stiffness degradation, energy dissipation capacity, slippages between the wooden column and the plinth, and the damage of the column foot tenons were examined. The test results showed that the column foot tenon played an important role in the mechanical behavior of the wooden column under low-cycle reversed cyclic loading. The rotation of the column foot tenon improved the energy dissipation capacity of the wooden column. As the rotational angle of the column base increased, the column foot tenon had different degrees of damage. Different sizes of column foot tenon had their own advantages and hysteretic behavior.

The physicochemical properties of dissolved and colloidal substances (DCS) in the old corrugated containers’ (OCC) whitewater were studied. Then, the colloidal substances (CS) were separated from dissolved substances (DS) and the effect of inorganic salts on the stability of CS (not DCS) was studied for the first time. The results showed that many DCS aggregated and attached to the fiber surface when pulping. The primary sources were resin, lignin, adhesives, coating fixatives, and fillers. The colloidal stability of DCS and solids of whitewater differed because the DCS contained less filler. Both Ca2+ and Na+ can affect the stability of CS, but Ca2+ led to more CS instability and aggregated into larger flocculent precipitates. The surprising discovery in the experiment was that when Ca2+ and Na+ were added together, the instability degree of the system was between the addition of Ca2+ and Na+ alone. Ca2+ played a dominant role in affecting the stability of CS, and Na+ competed for adsorption sites.

Based on the effects of stress wave propagation in larch (Larix gmelinii) wood, the propagation mechanism of stress wave was explored, and a theoretical model of the propagation velocity of stress waves in the three-dimensional space of wood was developed. The cross and longitudinal propagation velocities of stress wave were measured in larch wood under different moisture contents (46% to 87%, 56% to 96%, 20% to 62%, and 11% to 30%) in a laboratory setting. The relationships between the propagation velocity of stress waves and the direction angle or chord angle with different moisture contents were analyzed, and the three-dimensional regression models among four parameters were established. The analysis results indicated that under the same moisture content, stress wave velocity increased as the direction angle increased and decreased as chord angle increased, and the radial velocity was the largest. Under different moisture contents, stress wave velocity gradually decreased as moisture content increased, and the stress wave velocity was more noticeably affected by moisture content when moisture content was below the fiber saturation point (FSP, 30%). The nonlinear regression models of the direction angle, chord angle, moisture content, and the propagation velocity of stress wave fit the experiment data well (R2 ≥ 0.97).

Salix psammophila has been extensively used as a sand barrier material in many desertification control applications. Thus, understanding its degradation processes with long-term environmental moisture changes is essential. In this paper, via alternated desorption-absorption treatment of the S. psammophila sand barrier, damage of differing degrees occurred, and moisture variation was simulated. Through FTIR, X-ray diffraction, SEM, and other characterization methods, changes in macroscopic morphology and physical-mechanical properties of S. psammophila sand barrier were tracked, evaluated, and compared, and the causes were analyzed. The results showed that the alternated desorption-absorption accelerated aging treatment weakened the physical-mechanical properties of the S. psammophila sand barrier. The microscopic manifestation was the decrease in space between the tracheids, which caused the formation of cracks on the macroscopic level. Carbohydrates (cellulose, hemicellulose, and lignin) degraded, which reduced the crystallinity of cellulose, and cracks appeared on the surface of the S. psammophila sand barrier. As the aging degree increased, the number of cracks increased, and the cracks continued to extend to both ends. Therefore, the degradation of the S. psammophila sand barrier was mainly caused by shrinkage cracking in the alternated desorption-absorption aging process, which reduced the ability of the S. psammophila sand barrier to resist lodging damage.

Rice husk has a water repellent wax layer on its surface and has high pH and buffering capacity, which inhibit surface adhesion and result in the poor strength and water resistance of rice husk particleboard bonded with water-borne urea formaldehyde (UF) resin. In this work, rice husks were pretreated with liquid hot water at different temperatures (130, 140, 150, and 160 °C) and residence times (10 and 20 min). Pretreated rice husks were used to produce particleboard with UF resin. The effects of liquid hot water pretreatment temperature and residence time on the wax contents and pH values were investigated. In addition, the buffering capacities of the rice husks and the mechanical properties and the water resistance of the rice husk particleboards were investigated. The results indicated that liquid hot water pretreatment remarkably reduced the wax contents, pH values, and buffering capacities of the rice husks. In addition, it improved the mechanical properties and water resistance of the rice husk particleboards. Liquid hot water pretreatment effectively improved bondability between rice husks and water-borne UF resin, and it enhanced the performance of the rice husk particleboard.

Polylactic acid (PLA)-based composites with wood filler were 3D-printed using fused deposition modeling (FDM) at different infill settings (i.e., 10 to 100%) to evaluate their strength and biodegradation properties. Microvoids were present in the commercial wood-filled PLA filaments. Wood-PLA filament had reduced thermal stability compared with mineral-filled PLA filament due to the presence of thermally degradable wood flour. The printed composites had a denser internal structure with increased infill. The flexural modulus of elasticity and modulus of rupture also increased with infill value. Sixteen-week fungi test performed using a brown rot, Postia placenta, and a white rot, Irpex lacteus, did not lead to significant sample weight loss and strength reduction for composites at various infill values. Therefore, 3D printed composites with PLA-based filament containing 30 wt.% wood fiber were shown to be resistant to biodegradation by common decay fungi.

The invention of spindleless lathe technology has enabled veneers to be produced from small logs, such as logs from short rotation Hevea plantations, with low recovery loss. However, for structural laminated products, such as laminated veneer lumber (LVL), manufacturers are highly selective regarding the veneers for their conventional production. During the peeling process of small logs (< 18 cm), deeper and higher frequency of lathe checks were induced on veneer surface compared to the common log size used (> 30 cm). In this study, spindleless rotary-peeled veneers made from small rubber logs were processed into LVL using different lamination pressures: 7, 8, 9, and 10 kgf/cm2. The effects of lamination pressures on the physical and mechanical properties of the produced LVL were evaluated. Based on the findings, the specific gravity increased from 0.73 to 0.83 with increased lamination pressure. In terms of mechanical properties, all the values increased with lamination pressure, but with a sudden drop with 10 kgf/cm2. Understanding the effect of lamination pressure on the physical and mechanical properties can shed light on optimizing the usage of spindleless rotary-peeled veneers from small logs for the production LVL and other lamination products.

Computer simulation methods are currently used to simulate production processes and optimize production systems. Computer simulation is one of the most effective tools for implementation of Industry 4.0 principles in industrial practice. This research focused on the optimization of production processes in furniture production using simulation, which is an innovative method of production optimization for furniture manufacturers. The aim of this research was to improve the production system of Slovak furniture manufacturing enterprise by creating a discrete event simulation model of production based on the analysis of its current state. Improvement indicators are specific parameters of the production system, which primarily include material flow, productivity, and workload utilization. First, with the use of Tecnomatix Plant Simulation software and the collected real production data, the original production system processes were simulated and analyzed. Second, the incorporation of more powerful devices was proposed to improve the production line. Third, the proposed improvements were simulated and analyzed. The result of this research was a statistical comparison of the parameters of the current production line and the proposed production improvements.