Key Engineering Materials Vol. 914

Abstract: Oxypeucedanin hydrate is a furanocoumarin widely found in various fruits and vegetables so it may interact with prescribed drugs leading to pharmacokinetic interaction. This study was conducted using in vitro cell culture model to investigate the role of oxypeucedanin hydrate on P-gp function. To evaluate the role of oxypeucedanin hydrate as a P-gp substrate, the bidirectional transport studies of oxypeucedanin hydrate were performed in LLC-PK₁ and LLC-GA5-COL300. The corrected efflux ratio of oxypeucedanin hydrate was 3.3 ± 0.7, indicating that it was a P-gp substrate. Calcein AM uptakes performed in comparison between LLC-PK₁ and LLC-GA5-COL300 as well as daunorubicin transport across Caco-2 cell monolayer were conducted to examine the inhibition effect of oxypeucedanin hydrate on P-gp. The results exhibited that oxypeucedanin hydrate significantly increased calcein accumulation in LLC-GA5-COL300 in a concentration dependent manner and, moreover, the b-a daunorubicin transport across Caco-2 cell monolayer was decreased from 7 to 5, implying the role of the compound on P-gp inhibition, although the effect was quite minimal. Collectively, the results suggested that oxypeucedanin hydrate could act as P-gp substrate and be likely to inhibit P-gp function.

Abstract: Senna alata leaf is used as an active ingredient in various Ayurvedic preparations due to its bioactive components. This study examined the effect of extracting solvents on total phenolic and rhein contents as well as antioxidant and anti-inflammatory capacities in S. alata leaf extracts. 95% v/v and 50% v/v ethanol (EtOH) solutions were used as extracting solvents. In spite of its lower extraction yield, 95% EtOH extract with a lower moisture content should be considered more microbiologically stable than 50% EtOH extract. As a result of the analysis using thin-layer chromatography (TLC), Fourier-transform infrared (FTIR) spectrophotometry, and high performance liquid chromatographic diode array (HPLC-DAD), phytochemicals including anthrones, coumarins, and anthraquinones were found in both extracts. Additionally, the 95% EtOH extract possessed higher phytochemical contents and biological activities than the 50% EtOH extract. Thus, the 95% v/v EtOH was a powerful extracting solvent for preparation of S. alata leaf extractscontaining high contents of phenolics and rhein, together with antioxidant and anti-inflammatory activities.

Abstract: Benzhydrol derivatives 2a-c were synthesized, and evaluated for antituberculosis activities. These compounds were prepared from corresponding phenyl benzoates through Fries rearrangement and reduction reaction. Fries rearrangement reaction was chosen to use due to its convenient non-solvent method for synthesis. In order to determine the effective temperature for Fries rearrangement reaction, the reaction mixtures of phenyl benzoates 4a-c and AlCl₃ heated at constant rates were studied using DSC analysis. DSC curves of those mixtures showed that the reactions started at endothermic temperature ranging from 130 to 140 °C. The optimum temperatures for the synthesis of Fries rearrangement products 5a-c with high %yields were observed at 130, 140, and 130 °C, respectively. The DSC data were effectively applied for the estimation of the optimal reaction temperatures to attain high %yields for the synthesis of benzhydrols. The final benzhydrol derivatives 2a-c were structurally elucidated by FT-IR, ¹H NMR, and LC-MS and evaluated for antituberculosis activities by agar-dilution method. It was found that 4-hydroxy-α-(4ʹ-fluorophenyl) benzyl alcohol 2a possessed the highest activity in the series with the minimum inhibitory concentration (MIC) of 40 µg/mL.

Abstract: The (Zn_0.5Cu_0.5)Al₂O₄ pigments were synthesized by solid state processing with an aim to examine the kinetics of phase formation. The calcining temperature was 1100 °C with firing times of 2, 12, 24, 48 and 96 hours during which intermediate grinding was carried out. All five obtained pigment samples appeared to be single-phase as probed by XRD. However, lattice refinement revealed differences in the lattice constant which kept decreasing and reached constancy after 24 hours of firing. Such reduction in the lattice constant was associated with incorporation of smaller copper cations into the Zn-sites. FTIR spectra also supported this result as the relevant peaks still got broadened and shifted for the calcination times of less than 48 hours. Elemental analysis of the 2-hour sample showed small presence of starting precursor particles, though not detected by XRD, suggesting an incomplete reactivity at a minute scale. These structural changes were resultantly reflected by small but significant alterations in the color parameters. A higher degree of solid solution for the samples fired for longer times, as judged by lowering in the lattice constant, resulted in detectable changes in both a and b parameters. Longer calcination times yielded a brighter (higher L values) brownish tone likely due to both diminution in the averaged particle size from pulverizing and completion of solid solution. The first would be useful for good dispersion in glazes whereas the latter could be directly related to the degree of cationic substitution, confirming the expected “true” color for this specific doping level at a particular calcination temperature.

Abstract: In this work, PLA/lignin composite films have been developed for packaging films. The composite films were prepared by a solution casting method. The lignin was prepared from black liquor from the paper industry, by extracting with acetic acids at 50°C. The lignin contents in PLA matrix were 0.5, 1, 3 and 5 phr. Fourier-transformed infrared spectroscopy (FTIR) analysis demonstrated similar structure of lignin precipitation when compared with the standard lignin. The addition of lignin reduced the tensile strength of PLA/lignin films, whereas the composite film at 1 phr of lignin was more elongation than neat PLA. Scanning electron microscopy (SEM) micrographs showed the roughness surface and voids in the composite films, except 1 phr and 5 phr of lignin with a better interface between PLA and lignin. UV-Vis analysis indicated reduced light transmission with increasing lignin contents in UV region.

Abstract: This research studied the effect of tin (Sn) on the surface dullness of ENAC44300 aluminum alloy commercial grade for die casting applications.Tin impurities in the alloy composition led to surface dullness which degraded the quality of the alloy. This investigation found that bulk structure as well as microstructure were affected by the presence of high Sn content. Porosity increased in the amount and size and microstructural change was evident when the alloy containing high Sn (0.67%) was homoginized at 550°C.

Abstract: Disposable face masks which are used to prevent the massive spreading of Covid-19 infection, will be new plastic wastes, causing environmental problems. The purpose of this study was to investigate the potential processability of recycling disposable masks, composing of structural layers of nonwoven polyolefin fabrics by compression molding and grinding before melt recycling. It was found that the disposable masks used in this research, composed of 3 layers of polypropylene nonwoven with different fabrication methods but they had a similar melting temperature (T_m) thus provided the possibility of melt processing after removing accessories such as rubber strap and metal wire. The compressed mask sheets made from 1, 3 and 10-stacking sheets of disposable masks were subjected to the grinding analysis by ImageJ program to investigate the particle size distribution. Mechanical and physical properties as well as morphology study of the compressed mask sheets were further analyzed. The tensile strength and elongation at break of compressed mask sheets in horizontal direction were higher than that of the compress mask sheets by vertical direction due to a folding pattern of the disposable masks. The fracture surface of the compressed mask sheets was hard and brittle thus they were suitable for grinding process. Image analysis histogram showed that the grinding condition of 5 minute-cutting time of the compressed 10-stacking mask sheets provided smaller and uniform particles while the 1-stacking mask sheets had larger particle size after grinding due to their thinness which causes them slip through cutting blade. Grinded compressed masks had potential recyclability for melt blending with neat polypropylene at various blending ratios.

Abstract: This research studied the preparation of luminescent glasses using 18SiO₂-35B₂O₃-22ZnO-20K₂O glass frits. The glass frits were first mixed with 15 wt.% of commercial SrAl₂O₄:Eu²⁺,Dy³⁺ phosphors and different B₂O₃ concentrations of 0-15 wt.%. The raw materials were then melted at 750-800°C for 1 hr. The results showed that the addition of B₂O₃ as a flux induced the crystallization of α-Zn₂SiO₄ phase and suppressed the luminescent properties of phosphor-in-glasses. This could be due to the dissociation of SrAl₂O₄ by the reaction of SrAl₂O₄ and B₂O₃. The higher sintering temperature at 800°C also further degraded the luminescent properties as a result of further phosphor degradation and the oxidation of Eu²⁺.

Abstract: Poly(lactic acid) or PLA is one of the most important biodegradable plastics that replaces petroleum-based plastics for transparent disposable packaging. For circular economy, the accumulated PLA waste is required to recycle to produce high-quality recycled PLA grades. This research was aimed to simulate the influence of PET contamination (0.5, 1.0 and 2.0 wt%) on properties of the recycled PLA. Two grades of PLA; extrusion and injection molding, were used, and two temperature conditions (180 and 250°C) were used to evaluate the influence of mechanical recycling condition. Mechanical and thermal properties of the recycled PLA were investigated using tensile and impact testing, and differential scanning calorimeter, respectively. It was found that the mechanical recycling at 180°C produced the transparent specimens having unmolten white PET defects, which the mechanical properties were still intact with the PET contamination up to 1 wt%. The mechanical recycling at 250°C produced the opaque specimens with significantly lower mechanical properties due to the chain scission of PLA molecules, and the impact strength was slightly improved due to transesterification. The results could be used to emphasize the importance of the sorting step that the PLA recycling process should be performed with the PET contamination less than 1 wt%.

Abstract: Microwave pyrolysis combined with CO₂ and steam environment is investigated for its feasibility as an alternative method for waste disposal. The combined use of CO₂ and steam under microwave radiation created a synergistic effect in enhancing the thermal cracking of waste material during pyrolysis. The motivation of using CO₂ is to replace N₂ as carrier gas during pyrolysis as an effort to reduce the production of potent greenhouse gas. In this study, different types of microwave pyrolysis are performed including conventional, CO₂ and CO₂+steam on waste particleboard. It was found that the utilization of steam and CO₂ affect the final pyrolytic products yield and composition. Incorporating CO₂ and steam in microwave pyrolysis decreased the yield of char by 33% but increased the yield of bio-oil by 108%. Biochar obtained under CO₂ showed well-developed and cleaner pore structure compared to biochar produced under N₂. Our results demonstrate that the utilization of CO₂ and steam in microwave pyrolysis shows great potential to convert wastes into value-added char and bio-oil with desirable properties.