Research Articles

This paper presents the energy consumption differences during the edge milling of various board materials (medium-density fiberboard (MDF), medium-density fiberboard with single-sided lamination (MDF-L), and spruce edge-glued panel (SEGP)). The edge milling was carried out with various parameters: feed rate (4, 8, and 11 m/min); cutting speed (20, 30, 40, and 60 m/s); and blade type (tungsten carbide HW1, HW2, and HW1 coated with CrTiN (HW1 + CrTiN)). The results indicated that the increase in the cutting speed and feed rate cause the increase in cutting power. The highest cutting power values were observed with the milling of MDF; slightly lower values were observed with MDF-L, and the lowest values were observed with SEGP. Very similar cutting power values during milling were noted with HW1 and HW2 blades, whereas milling with the HW1 + CrTiN resulted in slightly higher values (e.g., 1% higher).

Cellulose nanocrystals (CNCs) were modified with triazine derivative in an effort to decrease the hydrophilicity of CNCs and improve their thermal stability. In recent decades, much attention has been given to the modification of CNCs to broaden their use in various applications, such as in nanocomposites, as adsorbents for the disposal of wastewater, and so on. The CNCs with a rod-like shape were obtained from cotton through sulfuric acid hydrolysis. Hydrophobic triazine derivative was synthesized via the reaction between triazine and n-butylamine (BA) and then applied to modify CNCs to improve their thermal stability and diminish the hydrophilicity of the nanoparticles. Results of thermogravimetric analysis (TGA) indicated a 150 °C increase in the initial thermal decomposition temperature of modified nanocrystals compared to the original CNCs. The improved thermal stability of modified CNCs was attributed to a shielding effect of the hydrophobic aliphatic amine layer on the surface of the nanoparticles. The results of the dynamic contact angle measurement revealed a decrease of hydrophilicity of the modified CNCs.

A carbon-based solid acid catalyst (CHACS) derived corncob residual was prepared by incomplete hydrothermal carbonization followed by activation with phosphoric acid impregnation and sulfuric acid sulfonation. The structure of the solid acid catalyst was characterized using Fourier transform infrared spectra (FTIR), thermogravimetric analyzer (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM), specific surface area (SSA), and elemental analysis. The -SO3H, -COOH, and phenolic -OH functional groups were successfully introduced. Phosphoric acid activation facilitated formation of the porous structure in the solid acid catalyst. The specific surface area and acid density were 1569 m2/g and 1.030 mmol/g, respectively. The CHACS exhibited better catalytic activity for hydrolysis conversion of corn stalk in ionic liquid with water as solvent. A total reducing sugars (TRS) yield of 68.3% was obtained in water and a TRS yield of 52.5% was obtained in an ionic liquid of [BMIM][Cl] at 140 °C for 120 min. The CHACS expressed good catalytic activity in each of 4 separate instances of reuse.

Mechanical restraint through the use of clamps was applied as an attempt to prevent drying defects during the heat treatment of high-density wood. Boards of okan (Cylicodiscus gabunensis (Taub.) Harms) with the initial moisture content of 8.99% and 9.68% for sapwood and heartwood, respectively, were prepared. The boards were heat-treated under an oxygen atmosphere at the peak temperatures of 160 °C, 180 °C, 200 °C, and 220 °C with a residence time of 2 h. The occurrence of drying defects as checks (i.e., surface and end checks) and warps (i.e., bow, cup, and twist) were evaluated. Heat treatment stimulated the occurrence of drying defects in okan wood. The results revealed that the surface checks, end checks, and twists increased linearly with increased temperature. The occurrence of warps, such as bow and cup, after heat treatment was relatively low. Heartwood showed a higher degree of drying defects compared to the sapwood. Application of mechanical restraint by clamping efficiently decreased the occurrence of drying defects of okan wood, particularly surface checks, end checks, and twists.

The withdrawal force capacities were compared for T-type furniture joints made from heat-treated Siberian pine (Pinus sibirica), iroko (Chlorophora excelsa), and common ash (Fraxinus excelsior), which are commonly used in the construction of outdoor furniture. A total of 120 specimens that consisted of 3 wood species, 2 treatment processes (untreated and heat-treated), 2 adhesive types (polyurethane and polyvinyl acetate), and 2 joinery techniques (mortise and tenon, and dowel) were tested, with 5 replications for each condition. Half of the specimens were constructed from heat-treated wood materials, while the remaining half were prepared from untreated wood materials (control specimens). The joints constructed from common ash and iroko exhibited the highest withdrawal force capacity values. Overall, heat treatment reduced the withdrawal force capacity of joints by 25% compared with the joints constructed of control specimens. Mortise and tenon joints yielded 4 times higher performance than dowel joints. The polyurethane adhesive gave better results than the polyvinyl acetate adhesive. The best withdrawal force capacity values of heat-treated wood materials were obtained from the Iroko-polyurethane-mortise and tenon joint combination.

Mechanical properties were evaluated for pulp delignified by four deep eutectic solvents (DES). The DES systems were based on choline chloride and lactic acid (1:9), oxalic acid:dihydrate (1:1), malic acid (1:1), and the system alanine:lactic acid (1:9). The results indicated that the type of DES system used influenced the delignified pulp’s mechanical properties including tensile, burst and tear indexes, tensile length, and stiffness. The most suitable DES systems were choline chloride:malic acid (1:1) and alanine:lactic acid (1:9), which achieved the best aforementioned mechanical properties compared to the other DES systems. The weakest performance in the process of pulp delignification was the system with choline chloride and oxalic acid dihydrate (1:1).

Bamboo curtain and poplar veneers, which are used as decorative building materials, were impregnated using two types of fire retardants (A and B) at atmospheric pressure in order to investigate fire retardancy using a cone calorimeter. When the impregnation time was longer, the fire retardancy was enhanced in the decorative material samples. When poplar veneer was treated by fire retardant A with impregnation times of 8 h, 16 h, and 24 h, the peak of heat rate release (pk-HRR) decreased by 41%, 51%, and 50%; the total heat release (THR) values decreased by 61%, 69%, and 75%; the total suspended particulates (TSP) values decreased by 90%, 82%, and 72%; and mass residues increased by 39%, 41%, and 43%, respectively. Treated bamboo curtain veneer had a lower fire retardancy when compared to poplar veneer. When bamboo curtain impregnation times were 8 h, 16 h, and 24 h, their pk-HRR values decreased by 37%, 45%, and 51%; the THR values decreased by 32%, 39%, and 44%; the TSP values decreased by 69%, 57%, and 78%; and the mass residues increased by 26%, 28%, and 29%, respectively. The results from this research should help to develop bamboo curtain veneer as an indoor decorative material.

Sweet sorghum bagasse (SSB) and citric acid (CA) were used as sustainable raw materials in the development of environmentally friendly particleboard. Sucrose was added to improve the mechanical and physical properties of the particleboard. The effects of the weight ratio between CA and sucrose on the physical properties of the particleboards were investigated. The mechanical properties of particleboards bonded with adhesives at 15/85 and 10/90 wt.% ratios of CA to sucrose were superior to particleboard with other ratios. The thickness swelling of the particleboard increased with an increasing sucrose ratio. Moreover, the physical properties of the particleboard were comparable to those of particleboard bonded using phenol formaldehyde (PF) resin and satisfied the requirements of the type 18 JIS A 5908 (2003) standard. Also, the brittleness of the particleboard was decreased by adding sucrose. Low formaldehyde emission and biological durability against termites and decay were obtained by particleboard under suitable ratios of CA to sucrose. According to the results from thermal analysis and infrared spectra measurement, reactions leading to ester linkages occurred among the CA, sucrose, and SSB components.

Southern yellow pine (Pinus sp.) wood cubes were vacuum-pressure treated with nano-SiO2 solution and different concentrations of amine copper quaternary (ACQ)/wax (0.5%, 2.5%, and 5.0% wax)-modified solutions. The effects of wax concentration and nano-SiO2 addition on water absorption, air drying shrinkage, and moisture swelling stabilities were investigated. The results showed that during the whole process of water absorption and air drying shrinkage, better stability of nano-SiO2 modified ACQ-treated wood could only be obtained with the ratio of wax addition equal to 2.5%. However, the best moisture swelling resistance was found in the samples modified with the highest wax addition (5.0%). Both wax and nano-SiO2 could be useful for keeping the dimensional stability of the treated wood.

Four kinds of carbon-based magnetic solid acid catalysts (CBMSACs) were prepared from rice husk, wood chips, peanut shells, and corn straw. The structure was investigated via x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), elemental Analysis (EA), scanning/transmission electron microscope (SEM/TEM), and BET analyses. The catalysts were used to hydrolyze cellulose, and the hydrolysis efficiencies were determined. The catalysts were all comprised of a disordered carbon structure with random polycyclic aromatic hydrocarbons similar to graphite layers. This structure had a large number of -SO3H groups and the alkyl side chain, which increased the electron cloud density of the carbon carrier, relative to the other catalysts; this was advantageous to the adhesion of the -SO3H group to increase the activity of catalysts. The product also contained a large number of magnetic particles, making it easy to separate the catalysts from the reaction residue. The properties of the catalyst derived from corn straw as the carbon source appeared to be the best. Although it could be further recycled many times, the catalyst activity decreased due to the loss of -SO3H groups. At the same time, the catalyst had a high specific surface area of 755 m2/g.