Volume 13 Issue 2

In terms of manufacturing cost and weight, current bulletproof vests are simply not optimized. This means that consumers and manufacturers alike desire a bulletproof vest that is more user-friendly, cheaper, and lighter. This study considered the tensile and flexural characterization of new lighter and cheaper hybrid composite materials to replace the existing insert panel for the currently available bulletproof vest. The materials chosen included a natural fibre, i.e., kenaf fibre, chemically treated with sodium hydroxide solution, and, as a means of recycling, used x-ray films with a surface treatment. Using the traditional hand lay-up method, the materials were fabricated into seven layers of different configurations, which were then subjected to tensile and flexural tests. The findings showed that one of the configurations that consisted of both treated materials had a tensile strength of 396.9 MPa, which is quite strong, and a flexural modulus of 6.24 GPa, which makes it flexible enough to be made into wearable equipment. This configuration was then chosen to be the base design for the specimen subjected to impact test. The interfacial bond between the two distinct materials proved to be a major issue, even with the help of fibre treatment. Therefore, some improvements need to be made for the material to be comparable to existing materials performance-wise hence making this configuration suitable for ballistic application. However, the design did show promising results by stopping a bullet with speed up to 230 m/s.

A mesoporous carbon as solid acid catalyst was prepared from kraft lignin via one-step phosphoric acid activation. The catalyst was characterized by acid–base titration, N2 adsorption–desorption, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and thermal gravity analysis (TGA). The results showed that the prepared solid acid catalyst had high thermal stability, large specific surface area (850 m2/g), and a mesopore structure with the average pore diameter of 4.7 nm. The acid-base titration result of the catalyst revealed high surface acidity (5.36 mmol/g), indicating high catalytic activity. The prepared solid acid catalyst was used to catalyze dehydration of fructose to 5-hydroxymethylfurfural (HMF). The influence of reaction temperature and reaction time on HMF yield was investigated. The results indicated that a HMF yield of 80.1% was obtained with a reaction time of 3 h at 140 °C.

The synthesis of TEMPO-oxidized bamboo cellulose nanofibrils (TOBCNs) was attempted using two locally available species in Thailand (Dendrocalamus asper and D. membranaceus). Bamboo powder was first delignified with NaClO2. The obtained bamboo holocelluloses (BHs) were then oxidized via a TEMPO/NaBr/NaClO system in water at pH 10 for 2 h. The effects of NaClO addition level on the weight recovery ratio, carboxylate content, and nanofibrillation yield were studied. At a higher level of NaClO addition, the weight recovery ratio of TEMPO-oxidized bamboo holocelluloses (TOBHs) decreased from 90% to 70%, while the carboxylate content of TOBHs increased up to 0.8 mmol/g to 0.9 mmol/g for both species. Fourier transform infrared spectra indicated that C6-hydroxyl groups of cellulose were converted to negatively-charged carboxylate groups. After a gentle mechanical treatment with water, transparent liquid of TOBCNs were obtained after the removal of unwanted fraction, which gave a nanofibrillation yield of more than 90% at a NaClO addition level of 7.5 mmol/g to 15.0 mmol/g-BHs. Well individualized TOBCNs were successfully prepared and had a length of several microns and an average width of 5 nm to 7 nm under transmission electron microscopy. Thus, ultra-long TOBCNs are applicable for use as nano-reinforced polymer composites in non-food industries.

The effects of three heavy metals on hydrogen production via syngas fermentation were investigated within a metal concentration range of 0 to 1.5 mg Cu/L, 0 to 9 mg Zn/L, 0 to 42 mg Mn/L, in media with initial pH of 5, 6, and 7, at 55 °C. The results showed that at lower metal concentration, pH 6 was optimum while at higher metal concentrations, pH 5 stimulated the process. More specifically, the highest hydrogen production activity recorded was 155% ± 12% at a metal concentration of 0.04 mg Cu/L, 0.25 mg Zn/L, and 1.06 mg Mn/L and an initial medium pH of 6. At higher metal concentration (0.625 mg Cu/L, 3.75 mg Zn/L, and 17.5 mg Mn/L), only pH 5 was stimulating for the cells. The results showed that the addition of heavy metals, contained in gasification-derived ash, can improve the production rate and yield of fermentative hydrogen. This could lead to lower costs in gasification process and fermentative hydrogen production and less demand for syngas cleaning before syngas fermentation.

The complexes produced by mixing oppositely charged starches containing aldehyde groups (cationic aldehyde starch, CAS, and anionic aldehyde starch, AAS) were compared with complexes consisting of polyamidoamine epichlorohydrine (PAE) and AAS regarding adsorption properties and efficiency in providing paper strength. Quartz crystal microbalance with dissipation (QCM-D) studies showed that the complex of CAS and AAS adsorbed less on the model film of nanofibrillated cellulose (NFC) than CAS by itself due to the acetal and hydrogen bonds formation in the complex structure blocking available groups to be adsorbed. The wet tensile index of the paper produced with CAS-AAS complex also decreased, and this was attributed to less adsorption on the cellulose surface, as indicated by the QCM-D results. At a higher concentration, the aldehyde starch complexes provided better tensile strength than the CAS addition. The adsorbed amount of PAE-AAS complex onto cellulose model film was more than PAE. This complexation decreased PAE efficiency in giving the wet tensile strength while dry strength of the paper increased at further complex addition. Atomic force microscopy (AFM) results showed that CAS-AAS complexes filled gaps between fibrils making a more flattened layer due to the higher adsorption and bigger particle size compared to the PAE-AAS complex.

Fast pyrolysis is a promising method that is being investigated for application in the degradation of lignin into phenolic chemicals. In this study, enzymatic/mild acidolysis lignin (EMAL) isolated from eucalyptus (E-EMAL) and wheat straw (W-EMAL) were characterized by pyrolysis-gas chromatography/mass spectrometry. The results showed that the compositions and yields of the products were determined by the lignin type and pyrolysis temperature. The identified products from the E-EMAL and W-EMAL pyrolysis mainly included G-phenols such as 2-methoxy-4-vinylphenol and guaiacol, S-phenols such as syringol and 2,6-dimmethoxy-4-(2-propenyl)-phenol, and H-phenols such as phenol, 2-methylphenol, and 4-vinylphenol. The overall yield of these phenolics varied with the investigated conditions. The G- and S-phenols were the primary products during the E-EMAL pyrolysis, while more H-phenols were produced during the W-EMAL pyrolysis. A compromise mild pyrolysis temperature of 450 °C to 650 °C resulted in a high phenolics yield, while a temperature greater than 650 °C led to the production of more aromatic hydrocarbons.

Four fusion enzymes were expressed in Escherichia coli BL21 (DE3), and their properties against sodium carboxymethyl cellulose (CMC-Na) and microcrystalline cellulose were characterized. When endoglucanase cel12B genes fused with the cellulose binding domain (CBD) of the N-terminal of xylanases from Thermotoga maritima and Thermotoga thermarum, CBD1, CBD2, CBD3, and CBD4 fusion proteins were obtained. The four fusion proteins exhibited a certain adsorption of microcrystalline cellulose, and CBD4 showed the best performance. In addition, the optimum pH and temperature of fusion proteins were all somewhat decreased, and they became more sensitive to cations. The CBD1, CBD2, CBD3, and CBD4 displayed some enzyme activity towards microcrystalline cellulose; however, the CMC-Na enzyme activity was remarkably reduced.

Knots are inevitable components found in wood that can adversely affect the mechanical properties of the lumber. The objective of this study was to investigate the effect of knots on the horizontal shear strength of southern yellow pine. Knot condition (sound/unsound) and shear plane (radial/tangential face) were studied as the factors of shear strength. The standard ASTM D143-94 (2014) was used to compare 120 pairs of clear shear blocks and shear blocks containing knots. Paired t-test results showed that regardless of the direction of the grain compared with the shear plane (perpendicular or parallel), sound knots increased the shear strength and the unsound knots decreased shear strength. Based on this study, the unsound knot volume was found to be a significant factor in decreasing the shear strength in the radial or tangential face direction. Furthermore, no significant relationship between the knot angle and shear strength was found. Shear failure occurred in the wood when an encased knot sample was tested and shear failure occurred in the knot when an intergrown knot sample was tested.

This paper applies a corporate accounting standard approach for measuring greenhouse gas emissions for a particular entity, the GHG Protocol, for a specific type of company in the primary sector. The main goal was to measure the total carbon footprint and carbon balance of the School Forest Enterprise of the Czech University of Life Sciences Prague. The total carbon footprint for Scope 1, Scope 2, and Scope 3 of the forestland managed by the SFE in 2017 was 686 t CO₂-eq or 3.5 t/employee, and 3.8 CZK/1000 CZK of turnover or 99 kg CO₂-eq/ha. These findings suggested a specific role of forest management in terms of climate change, where, in contrast with other companies in the secondary and tertiary spheres, the sinks outweigh the greenhouse gas production.

This study aimed to determine the physical and chemical properties of Kelampayan wood. Three Kelampayan trees were sampled at the bottom, middle, and top and partitioned into sections described as near pith, intermediate, and near bark. The TAPPI standard T258 om-94 (1995) was followed to determine the physical properties including moisture content and specific gravity. Overall, the moisture content decreased from the bottom to the top portions and from near pith to near bark. The specific gravity increased with height and when moving from the inside to the outside of the stem. No significant variations were found among tree portions with cold water extractable content and ash content. The properties of Kelampayan in this study were comparable to rubberwood, which is the most common species used to make wood-based products in Malaysia.