Research Articles

Though there has been a great deal of work concerning the development of natural fibers in reinforced starch-based composites, there is still more to be done. In general, cellulose fibers have lower strength than glass fibers; however, their specific strength is not far from that of fiberglass. In this work, alpha-fibers were obtained from alpha-grass through a mild cooking process. The fibers were used to reinforce a starch-based biopolymer. Composites including 5 to 35% (w/w) alpha-grass fibers in their formulation were prepared, tested, and subsequently compared with those of wood- and fiberglass-reinforced polypropylene (PP). The term “high-performance” refers to the tensile strength of the studied composites and is mainly due to a good interphase, a good dispersion of the fibers inside the matrix, and a good aspect ratio. The tensile strength of the composites showed a linear evolution for fiber contents up to 35% (w/w). The strain at break of the composites decreased with the fiber content and showed the stiffening effects of the reinforcement. The prepared composites showed high mechanical properties, even approaching those of glass fiber reinforced composites.

Three aerobic lignin-degrading bacterial strains were isolated from palm oil plantation soils. The bacterial isolates were screened using a selective nutrient medium of minimum salt media (MSM), with kraft lignin as lignin substrate and methylene blue as the ligninolytic dye indicator. The newly isolated bacterial strains SHC1, SHC2, and SHC3 were found to have the potential to tolerate high concentrations of kraft lignin and produced all three main ligninolytic enzymes (lignin peroxidase, manganese peroxidase, and laccase); these strains may therefore be useful in the degradation of lignin in oil palm empty fruit bunch biomass. The production of ligninolytic enzymes was carried out by means of submerged fermentation for 7 days using 2 mm of oil palm empty fruit bunch (OPEFB) fiber as a substrate. These bacterial isolates were characterized using biochemical tests from Biolog and identified using 16S rRNA gene sequencing analysis, which identified the strains SHC1, SHC2, and SHC3 as Bacillus sp., Ochrobactrum sp., and Leucobacter sp., respectively with 99% sequence similarity. Bacillus sp. SHC1 produced the highest manganese peroxidase (MnP) of 2313.4 U/L on the third day and the highest lignin peroxidase (LiP) of 209.30 U/L on the fifth day of fermentation. The optimum pH and temperature for the production of ligninolytic enzymes by Bacillus sp. SHC1 were pH 8 and 30 °C.

In this study, oil palm empty fruit bunch (OPEFB) was treated with sodium hydroxide at room temperature and produced pulps with acceptable quality suitable for the making of commercial serviettes. The cold soda pulping of OPEFB was performed using various NaOH concentrations (1, 3, 5, 7, and 10%) for 24 hours using a liquor/OPEFB ratio of 8/1. The treated pulps were refined in 4 stages under atmospheric conditions by means of a Sprout Bauer disk refiner. The refined pulps were then screened and evaluated for their physical characteristics. The main pulp properties obtained were related to the caustic concentrations; higher caustic concentrations gave better properties. The measured pulp characteristics were: freeness 550-750 mL, sheet density 0.18-0.34 g/cm³, tear index 4.2-5.8 mN*m²/g, tensile index 3-20 N*m/g, and burst index 1.3-2.5 kPa*m²/g. In most cases the refining had little impact on pulp properties. The resulting cold soda OPEFB pulp treated with 3% caustic charge or higher showed good quality for serviette making.

A simple, green method was developed for the synthesis of silver nanoparticles (AgNPs) by using Dialdehyde Chitosan (D-CTS) as the reducing and stabilizing agent. D-CTS was prepared from the oxidation of chitosan by sodium periodate, and its degree of oxidation was determined by 1H-NMR and elemental analysis. The synthesized AgNPs were characterized by UV-Vis spectroscopy, dynamic light scattering (DLS), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The morphology and size distribution of the AgNPs were found to vary with the dialdehyde content of D-CTS and the pH value of the reaction solution. FT-IR spectra revealed that the aldehyde groups and the amino groups were the major agents that stabilized the AgNPs. XRD results indicated the presence of nano-silver having a face-centered cubic structure. SEM results showed that nano-silver particles of 30 to 40 nm in size were homogeneously dispersed in the solution. The possible mechanism of D-CTS on the reduction and stabilization of AgNPs may be due to the formation of four-coordinate complexes. The synthesized AgNPs remained stable for more than three months.

Preprocessing of biomass at or near the growing site has considerable advantages over transporting to distant fermentation refineries equipped to process cellulosic material. The alkali-cellulase (Alkcell) process converts biomass to glucose using materials and methods that can be implemented at or near a growing site. This study has shown that the Alkcell process can be configured to run continuously. The use of carriers to contain the biomass allows continuous movement along a treatment train starting with alkali pretreatment and ending with glucose release. Conditions for pretreatment with NaOH, washing, and pH adjustment have been determined. Immersion of the carriers in a cellulase bath at optimal temperature and duration follows. The carriers are then submerged in a large volume of buffer at pH and temperature that allows release of glucose. Finally, the residual solids are returned to the start of the process to be mixed with fresh biomass and the treatment cycle is repeated. The glucose solution can be concentrated locally to reduce volume and enhance transportation savings. The local operation can be done at farms or near regional centers prior to being transported to distant existing conventional fermentation facilities.

Mesoporous activated carbons were prepared from coconut shells by the method of chemical activation with H3PO4. Effects of main influence factors on the yield and adsorption properties of activated carbon were studied via orthogonal experiments. Experimental results under the optimum conditions were as follows: the yield of the activated carbon was 36.90%; methylene blue adsorption was 21.5 mL/0.1 g; and the iodine number was 889.36 mg/g. The surface area of the activated carbon prepared was 891 m2/g, as determined by the BET method. Horvath-Kawazoe equations (H-K) and density functional theory (DFT) were introduced to analyze the porous structures of the activated carbon. It was shown that the activated carbon was mesoporous, with a total pore volume of 0.7233 mL/g, a micropore volume of 37.06%, a mesopore volume of 62.85%, and a macropore volume of 0.07%. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies demonstrated the results of the pore structure analysis.

Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was employed to investigate the primary pyrolysis product distribution of the pyrolysis of wood-plastic composites (WPCs) and the mutual effects of poplar wood (PW) and high-density polyethylene (HDPE). The PW, HDPE, and WPCs were pyrolysed at 475, 550, and 625 °C. The effect of temperature on the WPC pyrolysis products was examined. The comparison of the degradation composition results for HDPE, PW, and WPCs indicated that thermal degradation of WPCs comprised individual poplar wood and HDPE pyrolytic decompositions, and the pyrolytic products of PW and HDPE did not react with each other. The experimental results demonstrate that the pyrolytic product distribution of HDPE changed apparently in the presence of PW during pyrolysis. The PW decomposed at lower temperature during pyrolysis provided radicals, enhancing the scission of polymer chains to obtain more light paraffins. Further, the proposed pathway for the evolution of the main volatile organic products was probed. This study provides insights into the fundamental mechanisms of WPC pyrolysis and a basis for developing more descriptive models of WPC pyrolysis.

This study investigated the effects of various solvents on cypress liquefaction in the range of 180 to 300 °C. The solid residues and bio-oils obtained from cypress liquefaction were characterized to investigate the mechanism of the liquefaction process. Results obtained using FT-IR, sugar analysis, and elemental analysis showed that the solvent could affect both the formation of various compounds in the bio-oil and the product distribution during the cypress liquefaction process. Considering the bio-oil yield, the solvent efficiency in cypress liquefaction was as follows: water > methanol > ethanol. The decomposition velocities of cellulose, hemicelluloses, and lignin were different in the solvents, and hemicellulose decomposition preceded cellulose and lignin in all solvents. Water had the most pronounced effect on the higher heating value (HHV) of residues among the three tested solvents; the highest HHV was 26.3 MJ/Kg. This study suggests that characterization of products provides a promising approach for investigating the mechanism of solvent effects on biomass liquefaction.

The present paper aims to determine values of the modulus of elasticity (MOE) and modulus of rupture (MOR) of particleboards made from specially prepared particles from willow (Salix viminalis L.) and black locust (Robinia pseudoacacia L.) to enable formulation of an orthotropic material model for use in computer numerical simulations (FEM; finite element method). The mean densities of the panels were 600 and 660 kg·m^-3 for the willow and black locust, respectively. The MOE was used to test entire particleboards as well as their individual layers. The willow and black locust particleboards were compared with commercially available particleboards that met the requirements of the EN 312 standard. The modulus of rupture (MOR) of the particleboards was also determined according to the requirements of the EN 312 standard. The commercial particleboards showed the effects of different manufacturing directions, which resulted in changes in properties. No influence from manufacturing direction was found for the laboratory-made experimental panels. The impact of the thickness of the face layer of the specimens on MOE was also investigated. These tests indicated that the 2.1-mm sample showed no detectable distortive impact from the core layer. The tests confirmed the impact of manufacturing direction on the MOE of the commercial panels, which moreover was higher for the face layer. The highest MOE was found for the commercial panels, although the experimental panels met the requirements of the EN 312 standard, excluding the black locust at a mean density of 600 kg·m^-3.

Aluminum oxide nanoparticles were used as nanofillers in urea-formaldehyde (UF) resin and prepared for medium density fiberboards (MDF). The nanofillers composed weight percentage of the UF resin. The thermal and viscoelastic properties were studied using differential scanning calorimetry and dynamic mechanical analysis. The DH value of the UF resin showed an increase with increasing nanoparticle concentration. The core temperature during hot pressing increased with the addition of nanofillers. The formaldehyde emissions from MDF decreased with an increase in the concentration of nanofillers. The internal bonding strength and the modulus of rupture of boards were improved significantly after nanoparticle loading.