Research Articles

Biocomposites based on poly(L-lactic acid) (PLA) and non-woven jute fabrics (NWJF) were fabricated by sandwiching non-woven jute mat between PLA sheets. First, composites were fabricated with various weight proportions of jute fabric (5, 10, 20, and 30 wt.%) with the PLA matrix, and the effect of fabric loading on their mechanical properties was investigated. Higher mechanical properties were found at 10 wt.% fabric-loaded composite. The results show that the tensile, flexural, and impact strengths were increased by 61.7, 52.3, and 47.2%, respectively, as compared with neat PLA. In the second part, the jute fabrics were chemically treated with NaOH, NaClO2, acrylonitrile, acetic anhydride, KMnO4, diphenylmethane diisocyanate, and benzoyl chloride. The effect of chemical treatment on the mechanical and water absorption properties of NWJF/PLA biocomposites was studied. The mechanical properties of these biocomposites were found to be higher than those of untreated biocomposites. Among all the treatments, the combined alkali-benzoylated-treated fabric composite showed higher mechanical properties. The water absorption properties of these composites were found to be remarkably lower than those of untreated fibers. The interfacial adhesion between the fiber and the matrix was shown to increase with surface modification as revealed by SEM analysis.

A photocatalytic fiber was prepared by modifying the surface of jute fiber with a Bi2O3/TiO2 composite. Maleic acid was used as an organic linker, and the coating process was conducted with heat-treatment at 240 °C. At first, the Bi2O3/TiO2 composite was synthesized by incorporating TiO2 nanoparticles onto a Bi2O3 phase. Subsequently, the photocatalytic fiber was prepared by incorporating the Bi2O3/TiO2 composite onto the surface of the fiber. The Bi2O3/TiO2 composite-modified fiber was characterized by field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and UV-visible spectroscopy. The synthesized composite exhibited notably high photocatalytic activity under visible light irradiation of λ up to 420 nm, whereby it could decompose organic pollutants in the aqueous and gaseous phases. Because of increasing environmental concerns, this photocatalytic system could be an important candidate for decomposing organic pollutants.

Manufacturing glued laminated timber (glulam) can help overcome the limited availability of large-sized timber, and the use of bio-adhesives may resolve environmental problems associated with synthetic adhesives containing high formaldehyde contents. Tannin adhesive is a bio-adhesive that can be used as alternative glue in the manufacture of glulam. The purpose of this study was to determine the physical and mechanical properties of glulam made with mahogany (Swietenia sp.) tannin adhesive and wood from three fast-growing species, namely pine (Pinus merkusii), jabon (Anthocephalus cadamba), and sengon (Falcataria moluccana). Glulam (3 cm × 6 cm × 120 cm in thickness, width, and length, respectively) was manufactured with three layers of lamina. The physical and mechanical properties of the glulams were tested based on relevant standards. The results showed that pine glulam fulfilled the standard for the modulus of rupture and modulus of elasticity, while sengon glulam met the standard for shear strength. In the delamination test, sengon glulam was resistant to immersion in cold water and hot water. All glulams had low formaldehyde emission levels and therefore fulfilled the standard requirements. The results showed that the tannin adhesive from mahogany bark was equal in quality to methylene diphenyl di-isocyanate for glulam manufacturing.

In order to improve the whiteness of fly ash, the particles were coated by in-situ precipitation of calcium carbonate. After different mass ratios of calcium oxide to fly ash were mixed into water, a certain amount of carbon dioxide was bubbled into the mixture to form a precipitated calcium carbonate deposit on the surface of fly ash. With the help of scanning electron microscopy (SEM), the process and the coating mechanism of the unmodified and modified fly ash were studied. The results showed that when a 1:1 mass ratio of calcium oxide to fly ash was implemented, the whiteness of fly ash was increased from 30.3 (the original fly ash) to 74.0 (the modified fly ash). After appropriately controlling for the rate of carbon dioxide, the whiteness was improved to meet the standard for filler in the papermaking industry, and also great advantages in paper physical strength were demonstrated.

Extraction of hemicelluloses prior to pulping and conversion of the extracted hemicelluloses to other bioproducts could provide additional revenue to traditional pulp and paper industries. The effect of hemicelluloses pre-extraction with a hydrothermal (HT) process on Pinus radiata chemimechanical pulp (CMP) properties was investigated in this study. The HT extraction resulted in a release of 7% to 58% of the initial amount of hemicelluloses from the wood. The extraction yield increased with temperature and extraction time. This hemicellulosic fraction was in the form of low molar mass oligomers with molecular weights varying from 1.5 to 100 kDa. Compared with the control (unextracted) CMP pulp, the HT pre-extraction significantly reduced the refining energy to obtain a given fibrillation degree (freeness). The pulp yield with the HT/CMP process was in the range of 56% to 75%. Fiber properties of the pulps from pre-extracted wood, such as fiber length, were reduced, while increases in fiber width, fines content, fiber coarseness, and kink index were observed in comparison with the control pulps. The strength properties of CMP pulps decreased with increasing amounts of hemicellulose removal during the stage prior to pulping.

Three types of reinforcement materials, a carbon fiber-reinforced polymer (CFRP) sheet, a glass fiber-reinforced polymer (GFRP) mesh, and a composite of the CFRP sheet and GFRP mesh, were used to reinforce poplar laminated veneer lumber (LVL), and the multi-step hot-pressing method was also applied. The mechanical properties, i.e., modulus of rupture (MOR), modulus of elasticity (MOE), and horizontal shear strength (HSS), of the reinforced LVL were investigated, as well as the effects of lay-up location of the CFRP sheet/GFRP mesh composite. The results indicated that applying the multi-step hot-pressing method and incorporating the CFRP sheet, GFRP mesh, and the CFRP sheet/GFRP mesh composite noticeably improved the MOR and MOE under horizontal and vertical loadings. Only the multi-step hot-pressing method was able to greatly improve the HSS of reinforced LVL under both loading modes. The improved effect of the three kinds of reinforcing materials on the mechanical properties was ordered as follows: CFRP sheet/GFRP mesh composite > CFRP sheet > GFRP mesh. Locating the CFRP sheet/GFRP mesh composite closer to the surface veneer layer yielded the best mechanical properties for the reinforced poplar LVL.

Trichoderma species are widely used for the commercial production of cellulolytic enzymes. In the present investigation, medium components were optimized using a central composite design and response surface methodology to produce endoglucanase (EG) from Trichoderma harzianum KUC1716. From the various medium components tested, cellulose, soy peptone, and thiamine HCl were selected as the optimal carbon, nitrogen, and vitamin sources, respectively. The highest EG (1.97 U/mL) production was obtained with 1.85% cellulose, 0.48% soy peptone, and 0.10% thiamine HCl. EG production in the optimized medium was 2.6 fold higher than in the unoptimized medium. In addition, the crude enzyme preparation from T. harzianum KUC1716 supplemented with β-glucosidase from Schizophyllum commune KUC9397 was used to hydrolyze various types of lignocellulosic materials and showed significant saccharification yields on all lignocellulosic materials, surpassing that of a commercial enzyme cocktail. It was verified that the crude enzyme preparation derived from T. harzianum KUC1716 could replace the commercial enzymes. This highlights the potential of the crude enzymes for use in biomass conversion systems.

Liquefied wood-based precursors and carbon fibers were prepared by various chemical curing processes to investigate the effects of curing time and temperature on the thermostability and tensile strength of carbon fibers. The primary fibers can be converted into high-performance precursors by directly heating at a targeted curing temperature. With the temperature and duration increasing, the number of methylene bonds in the precursors increased, resulting in the enhancement of cross-linkages among molecular chains and the improvement of the thermostability of the precursors. Carbon fibers prepared from the precursors (95 °C and curing time 3 h) exhibited the minimum value in the average interlayer spacing (d002); however, they displayed the highest tensile strength, at almost 800 MPa, which can be classified as fibers of general grade.

The process of cooking with solid alkali is a novel and efficient technology. In the present work, milled wood lignin (MWL) and water-soluble milled wood lignin (WMWL) were used as the raw materials to research their properties when cooking with MgO and active oxygen. Before and after cooking, the lignin content of the samples was estimated using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), heteronuclear single-quantum coherence-nuclear magnetic resonance (HSQC-NMR), and gel permeation chromatography (GPC). The results showed that the properties of the MWL and WMWL were different. The G unit and A′structure in WMWL were more easily degraded than that in the MWL, where the G unit could be oxidized into a novel G′ unit. The D structure in the MWL with a weak signal could be thoroughly degraded, and the P structure was only present in WMWL and could be generated during the cooking process.

In this study, a numerical model of the tangential tensioning stress distribution of a circular saw blade tensioned by multi-spot pressure was established using theoretical analysis, and the tangential tensioning stress distribution of the circular saw blade calculated by the model was shown to be true and reliable. The effect of yield strength of the circular saw blade on the distribution of tangential tensioning stress was studied using the numerical model. The research achievements showed that a circular saw blade made with high-strength or ultra-high-strength steel yielded a better tensioning effect during the multi-spot pressure tensioning process, which could promote the application of a circular saw blade made by high-strength or ultra-high-strength steel.