Research Articles

D-xylose is a component of sugarcane bagasse that can be used as a renewable resource for the production of a variety of chemicals. By means of catalytic reactions in an aqueous medium, it was determined that D-xylose can efficiently be converted into furfural by the application of microwave as a green synthetic methodology. The highest yields of furfural were obtained at a HCl concentration of 4 mg/mL. When the reaction was performed at 200 °C, an optimum yield of 64% of furfural was observed after 10 min of reaction time, with 95% of the D-xylose being converted.

Microwave and conventional acetylation of wood was carried out to determine its efficacy on the material properties. Beech (Fagus sylvatica L.) and poplar (Populus hybrids) samples with dimensions 14 mm × 14 mm × 14 mm were impregnated using acetic anhydride, and chemical reactions were initiated by microwave and conventional heating. The microwave acetylation process was carried out using laboratory equipment at a frequency of 2.45 GHz in several testing modes to reduce time of the reaction. The uptake of substance, equilibrium moisture content, wood swelling, and dimensional stability were determined in order to evaluate the efficacy and degree of acetylation. Both microwave and conventional heating positively affected the selected material properties. The results showed that no significant differences were found between microwave and conventional heating; therefore, microwave heating can be used as a valid replacement in the acetylation process. Microwave power of 2 kW and 0.1 m∙min-1 conveyor speed were the optimum conditions for microwave acetylation. These process parameters resulted in 39.4% ASE T and 35.2% ASE R for beech and 38.0% ASE T and 16.3% ASE R for poplar samples. This work provides insight into the details of wood acetylation using microwave heating.

A preliminary investigation of chemical and lignin composition was conducted from samples of oil palm trunk of two different genetic backgrounds. A significant difference in percent (%) of standing palms was noted for the two different genetic backgrounds after 24 years of planting. Given that these palms were planted in neighboring fields, the objective of this preliminary study was to compare the chemical composition, as well as the lignin composition of the two palm varieties. When comparing the two populations, significant differences were observed in the structural carbohydrate composition and the lignin composition. This research constitutes the first reporting on the pyrolysis-gas chromatography-mass spectrometer analysis of oil palm trunk lignin composition.

Nuclear magnetic resonance (NMR) relaxation time distributions can provide detailed information about the moisture in wood. In this paper, the bound water content and pore size distributions in swollen cell wall of two kinds of softwoods (Pinus sylvestris and Cunninghamia lanceolata) and three kinds of hardwoods (Populus sp., Fraxinus excelsior L., and Ochroma lagopus) were determined by NMR cryoporometry. The total bound water content of swollen cell wall almost exceeds 35%, based on dry mass, which is obviously higher than the fiber saturation point (FSP) (appr. 30%) measured by the extrapolation method. The bound water content of different species is consistent with the hypothesis that with the decrease of basic density, the more bound water could be contained in wood. The proportion of the pore diameter smaller than 1.59 nm is higher than 70%, and the proportion of the pore diameter larger than 4 nm is no more than 10%.

A method for the production of paper with high strength and grease resistance was developed. Filter paper was impregnated by an aqueous solution of zinc chloride at a fixed temperature for several seconds. Swelling and partial dissolution of the cellulose fibers resulted in strong and compact paper. Various influencing factors were investigated in an attempt to improve the grease resistance of the paper. In addition, the structural properties of the zinc chloride-treated paper were investigated using a Fourier transform infrared (FT-IR) spectrometer, X-ray diffraction (XRD), and a scanning electron microscope (SEM). Paper treated in this manner was completely grease resistant, had greater stretch, and twice as high tensile strength when compared with untreated paper, while its burst strength more than doubled. Paper treated according to this method had the skeleton of un-dissolved cellulose fibers and the matrix of gelled cellulose. The cellulose of the paper was not chemically modified during this process.

Thermally modified wood is widely used in cladding, decking, and other construction projects that are meant for outdoor exposure. The purpose of this study was to investigate changes in the color, microstructure, and chemical composition of heat-treated, Larix spp. wood that was exposed to artificial weathering. In this study, accelerated weathering tests (UV and moisture) were conducted over a period of 3000 h. Photodegradation of both heat-treated and untreated wood was evaluated in terms of color, microstructure, and chemical changes that were characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. Ultra-violet radiation caused the degradation of lignin and extractives of wood, resulting in an immediate color change of the wood. The SEM observation of the heat-treated wood showed deformations and cracks in both treated and untreated samples. Irradiation resulted in a pronounced reduction in the absorption intensity and broadening of the FTIR spectra. It was found that the industrial heat-treatment of wood products resulted in more color stability than untreated wood during the early stages of weathering. Thermal modification was found, however, was ineffective in improving the UV resistance wood over long-term photodegradation conditions.

The pyrolysis of waste newspaper (WP) and co-pyrolysis of waste newspaper with high-density polyethylene (HDPE) (1:1 wt%) were carried out in a quartz tube at 500 °C to obtain biochars. The biochars were characterized in detail by X-ray diffraction (XRD), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), elemental analysis, scanning electron microscopy (SEM), automated specific surface area and pore size analyzer, and Raman spectroscopy to determine their physical and chemical properties. The analysis results for WP/HDPE-derived biochar (CWH) were compared to WP-derived biochar (CWB). The CWH had lower oxygen-containing groups, increased aromatic structure, higher calorific value, higher fuel ratio, and greater porosity development. CWH is more appropriate as solid fuel, soil adsorbent, or activated carbon precursor as compared to CWB.

In the present study, oil palm empty fruit bunch (OPEFB) fibers were taken from a 25-year-old oil palm tree. The cellulosic nanofiber (CNF) was isolated from the OPEFB using a chemo-mechanical process and utilized as reinforcement in an epoxy matrix. Various CNF loading percentages (0 to 0.75%) were applied in the epoxy matrix to explore the potential of using OPEFB-CNF as reinforcement. The morphological, mechanical, physical, and thermal characteristics of the OPEFB nanofiber-reinforced epoxy composites were evaluated. Results showed that the 0.25% and 0.5% CNF loadings were homogenously distributed and well-dispersed in the composite matrix. Conversely, agglomeration was detected in the matrix with 0.75% CNF loading. Determination of the water absorption behavior of CNF-reinforced epoxy composites at various loadings revealed that the physical properties of the composites increased with reinforcement loading. Furthermore, the analyses of the mechanical and thermal properties of the CNF-reinforced composites revealed that the incorporation of OPEFB-CNF enhanced the mechanical performance and thermal stability up to 0.5% loading.

This paper investigates the effect of heat treatment temperature on the stiffness and strength properties of Douglas fir (Pseudotsuga menziesii Franco) and common alder (Alnus glutinosa Gaertn.) woods. Two temperatures of heat treatment were used: 165 and 210 °C. The effects of dynamic elasticity modulus, static elasticity modulus, impact toughness, bending strength, and density were evaluated. It is already understood that the mechanical properties, primarily the bending strength, decreases with increasing temperature. In contrast to the favorable stability in shape and dimension that was achieved, the changes in the woods’ properties with temperature were mostly negative. Higher heat treatment temperatures corresponded with lower stiffness and strength properties. For higher temperature treatments, above 200 °C, deterioration of the tested properties was noticable as a result of the significant changes in the wood chemical structure. Even the positive effect of the equilibrium moisture decrease was not able to counterbalance the unfavorable changes. Moreover, it was observed that as the hemicellulose content is higher in alder wood, density, static bending strength, and toughness all decreased steadily at high temperatures, compared to Douglas fir wood.

The ability to increase the filler content of paper without significantly sacrificing its mechanical strength is of high interest for papermakers. In this work, three samples of ground calcium carbonate (GCC), differing in size and in brightness, modified with silica via the sol-gel method, were used as fillers in papermaking. Handsheets were produced using a eucalyptus kraft pulp furnish and with a filler amount near 20%. It was found that not only were the strength properties of the handsheets produced with the modified GCCs always significantly better than those obtained with the unmodified GCCs (e.g., the tensile index exhibited improvements of 16 to 20%), but bulk also was increased (by 7 to 13%). Some decreases in the light scattering and opacity values were noted when using the modified GCC, but the brightness was roughly the same. The enhanced fiber-to-filler bonding may be attributed to the hydrogen bonding between the cellulosic fibers and the hydroxyl groups of the silica coating the calcium carbonate particles.