Research Articles

The objective of this study was to transfer benefits of three-layered particleboards to medium density fiberboard (MDF) manufacture by using coarse fibers and, thus use less energy and lower-cost fibers as core layer material. In the first phase of this study, the effect of wood fiber size in the core layer on the properties of MDF was investigated. In the second phase, the effect of surface to core layer ratio (30/70, 40/60, 50/50, 60/40, and 70/30) on the properties of the MDF was investigated. The surface layers of the panels consisted of fine fibers. The wood fibers were produced using a thermo-mechanical refining process. The length and thickness of the fibers considerably increased with increasing defibrator discs distance. The 24-h TS values of the MDF specimens decreased from 36.8 to 34.2% as the fiber length in the core layer was increased from 4.3 to 11.5 mm. However, further increases in the fiber length increased TS values. Similarly, the bending strength, bending modulus, and internal bond strength increased with increasing fiber length (up to 11.5 mm) and thickness (up to 0.73 mm). The bending properties of the MDF specimens improved with increasing surface layer ratio, while the internal bond strength decreased.

Activated carbon monoliths (ACMs) were fabricated by H2O activation using powdered fast pyrolytic char (PFPC) as a raw material and bio-oil phenol-formaldehyde (BPF) resin as a binder. The effects of the ratio of BPF resin to PFPC on textural and chemical-surface properties of the ACMs were investigated using elemental analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and field-emission scanning electron microscopy (FE-SEM). The adsorption capacity and mechanical properties under different conditions were examined by N2 adsorption analysis and compression strength, respectively. The results indicated that the optimal ratio was 20 wt.% BPF resin binder. The compression strength of ACMs with a carbon content of 79.7 wt.% reached 3.74 MPa, while the BET surface area and total pore volume were 731.3 m2/g and 0.589 cm3/g, respectively. ACMs appeared to be mainly mesoporous with low graphitization and contained multiple functional groups such as alkyl, esters, ether, phenol, olefin, etc.

The impact of alkaline copper quat (ACQ) and zinc borate (ZB) on the moisture adsorption and desorption properties and leaching resistance of corn stalk fiber (CSF) reinforced high-density polyethylene (HDPE) composites was investigated. The equilibrium moisture content (EMC) was fitted by the Nelson model, and the interaction between the CSF component and the preservatives was characterized by Fourier transform infrared spectroscopy (FTIR). The effective components of the preservative were successfully immobilized on the CSF, which was observed by FTIR analysis. The leaching resistant analysis showed that the leaching amount of copper and boron elements reached a plateau, and that the leaching resistant performance in the ACQ treatment was better than in ZB. The moisture adsorption of CSF/HDPE composites was significantly reduced with ACQ treatment at low CSF content, but clearly increased in ZB treatment at high CSF content. The moisture adsorption and desorption EMC increased with the increased preservative (ACQ or ZB) embedding at a given CSF/HDPE component ratio. The experimental values were fitted well with the Nelson model; thereby this model could be used to predict the moisture adsorption and desorption EMC of CSF/HDPE composites at various relative humidity.

The goal of this work was to scale up the simultaneous saccharification and fermentation (SSF) of lactic acid using microwave-alkali-pretreated empty fruit bunches (EFB) from a scale of 16 L to a scale of 150 L. To facilitate the scaling-up process of lactic acid production by Rhizopus oryzae NRRL 395, a scaling-up criterion of constant kLa value was applied. Operating conditions, such as aeration rate and superficial velocity, were varied and evaluated on both scales (16-L and 150-L). The highest lactic acid yield of 6.8 g/L was obtained under an operating condition of 1 vvm (0.061 s-1). Parallel aeration rates were determined for the 150-L fermenter system to obtain the same kLa value as the 16-L fermenter. An operational condition of 0.5 vvm dissolved oxygen supply in the 150-L fermenter was optimal to support an identical value of kLa and production rate of lactic acid for both scales.

An orthogonal design was used to optimize the process of making slim medium-density fiberboard modified by a nitrogen-phosphorous series of flame retardants. Mechanical performance was the evaluating criterion. Subsequently, the combustion performances of each type of flame retardant, including in states solid, liquid, and their combination with a ratio of 1:1, were investigated to clarify the corresponding fire-retardant mechanism. The results showed that only physical bonding was responsible for connecting the wood fiber with the retardants, according to the Fourier transform infrared spectrum. Catalytic charring, flame retardancy, and the thermal insulation of three types of retardant were solidified by the results of a cone calorimeter (CONE) analysis, thermogravimetric (TG) analysis, and differential scanning calorimetry (DSC), and the mixture of solid and liquid was demonstrated as the primary choice. It was also found that after the mixture of the solid and liquid retardant was added, the limiting oxygen index of the board reached 43.3%, and it met the requirements of the B1 Class in the Chinese National Standard GB/T8624-2012 (2012).

The pretreatment of a high lignin substrate, coconut coir dust, was studied by chemical techniques (NaOH solution, ionic liquid, and NaOH followed by ionic liquid) and by a physical method (subcritical water, SCW). Following substrate pretreatment and a washing step, structural analyses were performed by scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy. It was found that all substrates pretreated by chemical methods had more amorphous structures than the untreated substrate. The XRD patterns of the chemically treated substrates shifted toward higher angles by 0.50° to 1.00°. However, the XRD peak symmetry of the SCW-treated substrate did not shift, but its crystallinity index decreased. The results revealed that lignocellulose treated with NaOH followed by ionic liquid at 120 °C for 30 min showed the greatest extent of structural transformation.

Acoustic and thermal properties were determined for boards made from Washingtonia palm tree pruning waste. Three types of boards with different particle sizes (0.25 to 1.00 mm, 1.00 to 2.00 mm, and 2.00 to 4.00 mm) were obtained from the rachis of the palm fronds. To bind the particles, 8% urea formaldehyde resin was used via hot pressing at 120 ºC for 6 min at 1.6 MPa. Three types of panels were generated to evaluate the influence of particle size. Analysis of their physico-mechanical properties showed that their mechanical performance was superior to the existing insulating boards used in the building industry. The average thermal conductivity of the panels was 0.062 W/(K·m) and did not depend on the size of the particles. At frequencies of 125 and 250 Hz, the experimental boards were classified as class D acoustic panels. The manufactured panels had high values of sound transmission loss (TL), despite the thinness of the panels, which indicates that they have good acoustic insulation capacity. Acoustic properties could be improved by increasing the thickness of the boards. Due to their mechanical, thermal, and acoustic properties, these panels could be used as lining and as false ceilings.

Lignophenol was separated from bamboo (Sinocalamus affinis) using a phase separation system. Different concentrations of a lignophenol-acetone solution were used to impregnate hardwood pulp fiber sheets (80 g/m2). The results showed that the tightness, tensile index, tear index, and burst index properties of sheets impregnated with a lignophenol acetone solution (80 g/L) increased 5.66%, 160.08%, 93.66%, and 140%, respectively, compared with sheets prepared without lignophenol. The lignophenol-hardwood pulp fiber composites were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and total reflectance Fourier transform infrared spectroscopy. The results indicated that lignophenol uniformly adhered to the pulp fibers but no chemical bonding occurred. Additionally, both virgin and recycled softwood pulp fiber sheets (80 g/m2) were tested using the same method. Although the strength of all composites increased after impregnation, the most obvious improvement was observed in the hardwood pulp-based composite. This simple method improved the physical strength and hydrophobicity of the composite sheets.

Citric acid has been investigated as a good adhesive for particleboard. This research studied the effect of starch addition on the properties of citric acid-bonded particleboard. Starch provides hydroxyl groups that can react with the carboxyl group in citric acid. Three kinds of starches were used in this research, i.e. corn, ganyong (Canna edulis Ker-Gawl), and garut (Maranta arundinacea L.) starches. Petung (Dendrocalamus sp.) bamboo particles were used as raw material. The mixture ratios of citric acid/starch were set at 100/0, 87.5/12.5, and 75/25 (w/w), while the resin content was set at 30 wt.% based on air-dried particles. The boards were then manufactured under pressing conditions of 180 °C for 10 min. Based on the physical and mechanical properties of the particleboards, it was concluded that the addition of starch tended to enhance the mechanical properties, while decreasing the physical properties of the boards. An addition of 12.5 wt.% starch in citric acid was the optimum resin ratio for manufacturing bamboo particleboard. Maranta and canna starches provided higher mechanical properties compared to corn starch. A FTIR analysis clearly showed that the intensity of carbonyl groups increased with increasing of starch content, which indicated that crosslinking between starch and citric acid occurred.

The process for producing activated carbon from peat was optimized. The peat was impregnated with different ratios of ZnCl2, and the impregnated biomass was activated at different temperatures. The specific surface area, pore size distribution, total carbon content, and yield of the activated carbon were investigated. The best results for the specific surface area and mesoporosity of the activated peat were obtained by using a high impregnation ratio (2) and high activation temperature (1073 K). Highly porous activated carbon was produced that had a specific surface area of approximately 1000 m2/g and total pore volume that was higher than 0.5 cm3/g for most samples. The activated carbon had a high degree of mesoporosity. The adsorptive properties of the activated carbon were determined with methylene blue and orange II dyes.