Research Articles

The thermal stabilities of bio-based polyurethane (PU) foams made from liquefaction bio-polyols with and without solid residue were analyzed by thermogravimetric analysis (TGA) and Fourier transform infrared spectrometry (FTIR). Yaupon holly (Ilex vomitoria) was subjected to microwave liquefaction at different reaction temperatures to characterize the variations of bio-polyol and solid residue with temperature. The results indicated that the solid residue decreased when the temperature increased from 120 °C to 160 °C, while it increased slightly when further increasing temperature to 200 °C. The hydroxyl number decreased with increased reaction temperature. The TGA of PU foams demonstrated that the use of liquefaction bio-polyol with and without solid residue to produce PU foam increased the thermal stability of biofoams as compared with petro-based foam. Moreover, the presence of solid residue in bio-polyol enhanced the thermal stability of biofoams. The FTIR analysis of PU foams suggested that the solid residue had a negative effect on the formation of urethane bonds.

The application of wood-plastic composites is growing rapidly in the fields of corrosion and aging. The present study investigated the effect of alkali-treated (with NaOH concentrations of 0.5, 2.5, 4.5, and 6.5%) sorghum straw (SS) fiber on the wear resistance of polyvinyl chloride (PVC) composites under simulated seawater and acid rain conditions. The results showed that the wear resistance of the SS/PVC composites was noticeably improved by the addition of the alkali-treated SS fiber. SS fiber treated with 4.5% NaOH showed low polarity and hydrophilicity with high crystallinity and improved mechanical properties, which endowed the SS/PVC composites with high interfacial bonding and wear resistance. Exposure to simulated seawater and acid rain resulted in the deterioration of physical (including water repellency and hardness), mechanical, thermal, and wear-resistance properties of the composites; the wear mechanism of the SS/PVC composites after corrosion for 12 days was mainly abrasive wear.

Wood is a natural material with great variability in its mechanical properties. This study analyzed the effectiveness of the impulse excitation technique (IET) to characterize the stiffness of 10-year-old Eucalyptus grandis wood at three different heights of 3 m, 6 m, and 9 m from the bottom (height A, B, and C, respectively). A nondestructive testing method—excitation impulse, using Sonelastic® PC-based technology—and a destructive static bending test were used. The mean value for the modulus of elasticity (MOE) in bending was 16.4 GPa and in IET the value was 16.6 GPa. The average values for MOE in static bending were 14.8 GPa at height A, 17.9 GPa at height B, and 17.0 GPa at height C, demonstrating that the greater the height in the trunk of the tree the greater its modulus of elasticity. The correlation equation between static MOE and dynamic MOE was MOESTAT = 0.743.MOEDYN + 4.0983, with the coefficient of determination of R² = 0.85.

The application of causticized calcium carbonate (CCC) from nonwood pulping as a filler in papermaking is restricted by a marked decrease in alkyl ketene dimer (AKD) sizing efficiency. But the reason for this adverse effect has not been clear. In this paper, effect of carbonization on the AKD sizing efficiency was investigated systematically. The results showed that the hydrated calcium silicate (C-S-H) in the original CCC had been converted into silica gel after carbonization, and this caused the carbonized CCC to have a higher specific surface area and larger pore volume. This could explain the reason why the CCC had a worse AKD sizing efficiency than the conventional CaCO3 fillers. In addition, the effect of pH value of carbonization on the AKD sizing efficiency was also studied. It was discovered that the silica gel generated and the AKD sizing efficiency started to decline dramatically at the pH value of 8.5. Based on the research above, it can be included that pH value of 8.5 is an appropriate pH of carbonization end to maintain the AKD sizing efficiency at a good level.

A process is described for developing bio-based foam board using state of the art freeze-casting technology. The bio-based thermal insulation foam board was produced starting from wood-based cellulose nanomaterials (CNs) water suspensions. Its performance properties were compared to the current products on the market: Foamular® 150 (F150), Styrofoam™ brand square edge insulation (SF), and GreenGuard® XPS (GG). The bio-based foam board’s density was 0.1 g/cm3 with an 8.16% coefficient of variation (CV), which was higher than F150’s density (0.03 g/cm3 with 0.35% CV), SF’s density (0.04 g/cm3 with 3.79% CV), and GG’s density (0.04 g/cm3 with 0.03% CV). The insulation value (R-value) was determined as 3.14 (1.47% CV) for bio-based thermal insulation foam board, 4.37 (0.39%) for F150, 4.43 (0.39%) for GG, and 5.59 (1.55%) for SF. The mechanical performance of the bio-based thermal insulation foam board was lower than those of the current products on the market, so that it requires further enhancement before potential commercialization. However, being among the first nanocellulose thermal insulation foam boards currently available, it still has great potential for use in building systems.

Medium density fiberboard (MDF) is an industrial product manufactured from lignocellulosic fibers. It has homogeneity, dimensional stability, and mechanical strength compared with solid wood. Milling is a machining method widely used in the furniture industry; despite the relevance of the subject, there are few works dealing with the specific MDF milling process using computerized numerical control (CNC) machines. This study evaluated MDF milling in CNC machining centers by analyzing roughness. The MDF panels were front direction with the machined cut depth of 3 mm with six replicates, four cutting speeds of 804 m/min, 603 m/min, 402 m/min, and 201 m/min, and one forward speed of 4 m/min. The parameter of roughness average (Ra) was analyzed. The results showed that the surface roughness showed lower values for the cutting speeds of 603 m/min and 804 m/min, and cutting depths of 3 mm exhibited satisfactory results for the front surface. In conclusion, the parameters studied here significantly influence the finish, resulting in uneven surfaces that can reduce the quality of products.

Crude enzyme secreted from Trametes sp. lg-9 was applied in bio-mechanical pulping of poplar. The Canadian Standard Freeness (CSF) of the pulp pretreated with crude enzyme by a charge of 8 IU g^-1 pulp was 215 mL. However, the CSF of untreated pulp was 235 mL at the same refining revolutions of 15,000. Also, the energy consumption during refining was significantly lowered. The brightness of enzyme-pretreated pulp was increased by 2%, and the light absorption coefficient and opacity were decreased slightly. The effect of H₂O₂ (P) and CH₃COOOH-H₂O₂ (PaP) bleaching were reinforced, and the brightness of pulp was further enhanced when the dosage of crude enzyme was great than 8 IU g^-1 pulp. However, the content of fines was decreased, and the lowest value was 6.99% when the dosage of crude enzyme was 8 IU g^-1 pulp. The results of this work will be valuable for future possible commercialization.

Biochar, a carbon-rich product, can be obtained from crop residues via pyrolysis. Its properties may vary widely depending upon the pyrolysis conditions and feedstock type. Physicochemical properties were studied for biochars produced from rice straw, wheat straw, corn stover, rape stalk, and cotton stalk pyrolyzed at 300 °C to 700 °C. At higher pyrolysis temperatures, the carbon content, pH, and electrical conductivity of the biochars slightly increased, while the O/C and H/C ratios decreased. The pH values had a strong negative linear correlation with the H/C ratio. Higher carbonization temperatures resulted in larger pores and increased the aromatic/aliphatic carbon ratio in the biochars. The oxygen functional groups in the biochars, such as -COOH and -OH, decreased with an increasing carbonization temperature. The combustion performance of the biochars varied with the carbonization temperature because of the differences in the physicochemical compositions of the biochars. Additionally, the crop residue types also influenced the physicochemical properties. The cotton stalk biochar had the highest fixed carbon content and lowest H/C ratio, and thus can be used as a solid biofuel. The rice straw biochar, which had the highest N and O contents, may be a potential soil amendment.

Rice straw fibers are potential raw materials that can be used to produce biogas and reinforcing fibers for composites. In order to ascertain the effects of anaerobic digestion on the structural properties of the fibers, the structure of fibrous residuals with different digestion time, including 0, 10, 20, and 30 days, were investigated. The normalized biogas production volume was 224 mL/g volatile solid of substrate, of which the methane content was about 50%. Fiber detergent analyses of the straw before and after 10 days digestion indicated that the cellulose levels increased from 34.3% to 41.3%, and cellulose crystallinity index ranged from 44.9% to 49.9%, respectively. After the rice straw had been digested for 30 days, the cellulose and hemicelluloses of the rice straw were partially degraded; the crystallinity index of the cellulose decreased from 44.9% to 40.1% based on XRD analyses, and the amount of hydroxyl groups were observed to decrease based on FT-IR analyses. Consequently, the polarity and hygroscopicity of the rice straw fibers were speculated to be lowered based on these observed changes. Furthermore, the relative amount of lignin in the straw residuals increased as digestion time increased, which increased the thermal stability of the resulting fibers. As a result of anaerobic digestion, the properties of the rice straw fibers for their use in plastic composites were enhanced.