Volume 15 Issue 2

The pods of Acacia nilotica were successfully utilized for the extraction of tannins using a methanol/water extraction medium. The experimental design employed for the extraction was a central composite design that enabled the evaluation of the effects of time, temperature, and methanol concentration on the dependent variables of extraction yield, total phenolic contents (TPC, as gallic acid equivalents (GAE)), and antioxidant activity (AA, as millimoles of ascorbic acid equivalents (AAE)). Response surface models were developed for the three responses, and statistical analysis of variance was performed to determine the optimum values of the independent variables and the coefficients of determination. The maximum extraction yield of 46.2 wt% (pod extract) was achieved at 200 min, 85 °C, and 40% methanol concentration. Similar conditions also led to the attainment of 50.7 wt% TPC and 51.3 mmol AAE/100 g pod. The coefficients of determinations were 0.9750 for extraction yield, 0.9626 for TPC, and 0.9774 for AA, which indicated that the model equations obtained fitted the experimental data. The result of the retanning of the leather using the extracted A. nilotica tannins also showed that the tear and tensile strength, as well as the elongation at break, of the leather samples were within the range obtained when chestnut extract and chrome tannin were used.

The aim of this study was to produce mahogany (Swietenia macrophylla) wood flour filled polypropylene (both recycled and virgin) composites and to determine the effects of maleic anhydride-grafted polypropylene (MAPP) on the interfacial compatibility, density, and other mechanical properties of the resulting composites. Approximately 40 wt% of mahogany wood flour, and 60 wt% of polypropylene, 3 wt% of MAPP, 1.5 wt% of zinc stearate, and 1.5 wt% of wax were used during composite manufacturing. Test specimens were manufactured using extrusion and injection molding processes. The flexural, tensile, impact, and hardness properties of all specimens were determined. Scanning electron microscopy was used to study the morphology and interfacial compatibility of the filler in prepared composites. The test results showed that MAPP use and the filler rates affected the density and mechanical properties of test specimens.

The growth of coarse roots is complex, leading to intricate patterns of root systems in three dimensions. To detect and recognize coarse roots, ground-penetrating radar (GPR) was used. According to the GPR theory, a clear profile hyperbola is formed on the GPR radargrams when electromagnetic waves travel across two surfaces with different dielectric constants. First, the forward models (different root orientations) were built with simulation software (GprMax3.0) based on the finite-different time-domain method (FDTD). As the radar moved forward, the signal reflection curve was generated in different root orientations. An algorithm was proposed to obtain the coordinates of a single coarse root and analyze the influence of root direction on the hyperbola of coarse root through a symmetry curve and relative error (RE). Based on GPR datasets from the simulation experiment, the controlled experiment evaluated feasibility and effectiveness of the simulation experiment. To demonstrate the effect of the root orientation, the algorithm was applied to in situ recognition of the Summer Palace. The results showed that the localization of root orientation was relatively accurate. However, the proposed algorithm was unable to implement automatic detection, and the results still required human intervention. This research provides a solid basis for the biomass measurement, diameter estimation, and especially the three-dimensional reconstruction of ancient and famous trees.

The largest mechanical pulp production units are high-consistency refiners. In the high-consistency refiners, in-situ measurements of pulp quality are rare. Temperature profile is one of the measurements that is industrially applicable to estimate pulp quality. It measures the steam temperature in the refining area – but how it can detect deteriorated pulp quality will be shown. This paper analyzed the high-consistency refiner plate temperature and its correlation to pulp quality in a 1.34 MW pilot-scale Sunds RGP-44 variable speed refiner in a variety of operating conditions and particularly at production rates close to maximum refiner capacity. The study showed that there was a narrow band of optimal refining conditions at the maximum refiner production level just before pulp quality drastically decreased. When the refiner was pushed above this optimal point of operation, the plate temperature rapidly increased above normal refining temperature, causing reduction of fiber length and consequently lower pulp strength and quality. Thus, refiner plate temperature measurement was found to be a quick way and an effective tool for preventing low-quality pulp production through overloading the refiner.

Particleboards were manufactured using coconut fibers (Cocos nucifera). The panels were made using different green adhesives, i.e., native potato starch, citric acid, and glutardialdehyde modified potato starch, that were applied at 10%, 12%, and 15% based on oven-dry particle weight for each green adhesive type. The properties of the panels were determined according to the Japanese industrial standard. The results showed that the panels that were bonded with the 15% citric acid-modified starch green adhesive yielded the best mechanical properties (the modulus of elasticity, modulus of rupture, and internal bonding strength). The modified potato starch had potential as a green adhesive used for the production of particleboards from coconut fibers.

Ni-xLa/Al2O3-MgO-sawdust char catalysts were prepared by modifying the Ni/Al2O3 catalyst from two aspects of support and active components. The effect of Al2O3, MgO, sawdust char molar ratio, and La content of catalysts on syngas (H2 + CO) production in the catalytic pyrolysis of rice straw was investigated in a horizontal fixed-bed quartz tube reactor. Furthermore, the stability of catalysts with the optimum catalytic performance was tested and compared with that of the Ni/Al2O3 catalysts. X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, energy disperse X-ray, and Brunauer-Emmett-Teller analyses were applied to understand the physiochemical properties of the supports and catalysts. The study revealed that the supports were composed of many irregular flaky particles and thus formed many pores. Moreover, the addition of La decreased the particle size of NiAl2O4 and increased the active metal surface of the Ni/Al2O3-MgO-sawdust catalysts. When the molar ratio of Al2O3, MgO, and sawdust char was 1:1:1 and the La content was 10 wt% (dry weight basis), the catalysts presented the highest syngas concentration of 78.9 vol% and the most stable performance during the catalytic pyrolysis process.

The objective of this study was to evaluate the relationship of growth characteristics to compression properties from commercially available southern pine lumber. The in-grade No. 2 southern pine lumber was collected from retail stores across the Southeast United States. For this specific project, 797 samples of 2 × 8 and 2 × 10 boards were examined. The samples were subjected to static bending following ASTM D 198 to determine mechanical properties. The 2 × 8 samples averaged 4.78 growth rings per inch (RPI) and the 2 × 10s averaged 3.95. Average density (ρ) was 477 kg·m-3 in the 2 × 8 and 487 kg·m-3 for the 2 × 10 specimens. From small clear samples from the parent boards, compression parallel to grain averaged from 43.78 MPa for the 2 × 8 to 46.77 MPa for the 2 × 10. Correlations were run to test significance among growth rings per inch and compressions parallel to grain, across both sizes: 2 × 8 and 2 × 10. Slight significance was found in those correlations and increased in measure from 2 × 8 to 2 × 10. The segmentation of RPI into three distinct groups helped strengthen the findings of effect on compression parallel to grain. Moreover, the addition of density as another test variable further strengthened in relationship per those RPI categorizations. Statistically significant findings for density per RPI segments, R2 values: for 2 × 8 equal 0.31 (3 or less RPI) to 0.60 (more than 5 RPI). For the 2 × 10 lumber per the same segments, R2 values: 0.39, 0.46 and 0.25, respectively. The results suggest ρ is a better predictor than RPI alone for compression parallel to grain values.

The use of ultrasonic tools in paper forming results in highly dynamic mechanical alternating stress, which causes a changed material load. This work aimed to determine the influence of the ultrasonic process parameters of amplitude, ultrasonic time, and static contact pressure and to characterize the material compression during the ultrasonic-assisted forming of paperboard. To achieve this, a method was developed to determine the static, dynamic, and irreversible material compression during the gap-controlled forming of paper. The results showed that the ultrasonic amplitude, the gap pressure, and their second-order interactions had an important influence on the irreversible material compression. With the new method, the irreversible material compression could be increased up to 480% compared to the equivalent static load case.

Melamine, polyvinyl alcohol, and adipic acid dihydrazide as modifiers were added to urea-formaldehyde (UF) resin for reducing the free formaldehyde. The influence of addition amount and addition stage of modifiers on the physicochemical property and free formaldehyde content of UF resin was tested. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA) were used to determine the structural change and thermal stability of the resins. The results revealed that the UF resin added with 6% melamine had the lowest free formaldehyde content of 0.31%. Among all modified resins added with equal amount of modifier in different stages, the UF resin added with 3% polyvinyl alcohol in the second alkaline stage achieved the lowest free formaldehyde content of 0.33%. More importantly, the comprehensive effect of melamine, polyvinyl alcohol, and adipic acid dihydrazide on the free formaldehyde content of resin was studied. The free formaldehyde content in the UF resin added with the comprehensive modifiers achieved 0.24% content, and formaldehyde emission of this kind of adhesive was just 0.21 mg/g. Coupling the experimental results with the characterization data, comprehensive modifiers can reduce the formation of chemical bonds (methylene and ether bonds) in the resin and improve thermal stability of UF resin effectively.

Fast-growing poplar has become an extensively planted fast-growing forest tree species because of its short plantation rotation, lightweight character, and strong adaptability. However, fast-growing poplar usually exhibits some disadvantageous properties, such as inferior mechanical properties, high hygroscopicity, and poor dimensional stability, which limits its applications to a great extent. Herein, a simple method for improving the water resistance and mechanical properties of fast-growing poplar wood using the biobased monomer isobornyl methacrylate (IBOMA) was investigated. Wood/PIBOMA composites were prepared by impregnating the wood matrix with IBOMA ethanol solution, and then the IBOMA in the wood matrix was heated to initiate in situ polymerization. Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were used to investigate the properties of fast-growing wood/PIBOMA composites. The results showed that the IBOMA successfully penetrated the wood structure and polymerized in the cell walls and cell lumens. Thereby, the water resistance and mechanical properties of the fast-growing poplar were effectively improved. In addition, the water uptake of the wood decreased from 168.3% to 35.8% after impregnation with the 90% IBOMA solution. The modulus of rupture (MOR), modulus of elasticity (MOE), and compression strength (CS) of the 90% wood/PIBOMA composites were increased by 82.7, 28.6, and 2.3%, respectively.