• Elastomers and Composites
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• v.59 no.2
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• pp.51-63
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• 2024

Polypropylene (PP) is a commodity plastic that is widely used owing to its cost-effectiveness, lightweight nature, easy processability, and outstanding chemical and thermomechanical characteristics. However, the imperative to address energy and environmental crises has spurred global initiatives toward a circular economy, necessitating sustainable alternatives to traditional fossil-fuel-derived plastics. In this study, we conducted a series of comparative investigations of bio-based polypropylene (bio-PP) blends with current PP of the same and different grades. An extrusion-based processing methodology was employed for the bio-PP composites. Talc was used as an active filler for the preparation of the composites. A comparative analysis with the current petroleum-based PP indicated that the thermal properties and tensile characteristics of the bio-PP blends and composites remained largely unaltered, signifying the feasibility of bio-PP as a potential substitute for the current PP. To achieve a higher Young's modulus, elongation at break (EAB), and melt flow index (MFI), we prepared different composites of PP of different grades and bio-PP with varying talc contents. Interestingly, at higher biomass contents, the composites exhibited higher MFI and EAB values with comparable Young's moduli. Notably, the impact strengths of the composites with various biomass and talc contents remained unaltered. In-depth investigations through surface analysis confirmed the uniform dispersion of talc within the composite matrix. Furthermore, the moldability of the bio-PP composites was substantiated by comprehensive rheological property assessments encompassing shear rate and shear viscosity. Thus, from these outcomes, the fabricated bio-PP-based composites could be an alternative to petroleum-based PP composites for sustainable automobile applications.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.260-265
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• 2024

To synthesize an antistatic material for use in semiconductor wafer transport trays, in-situ polymerization of poly(methyl methacrylate) (PMMA) and polyurethane (PU) incorporating carbon nanotubes was designed and conducted. The newly synthesized composites were evaluated for their thermal and electrical conductivity properties under conditions mimicking commercial device manufacturing processes. Comparative analysis of their respective performances revealed that both PMMA and PU containing carbon nanotubes exhibited enhanced thermal properties and superior electrical conductivity as the nanotube content increased. Morphology of the composites synthesized via in-situ polymerization was confirmed to be excellent through FE-SEM analysis, demonstrating good dispersibility. Both PMMA and PU incorporating carbon nanotubes showed outstanding surface resistance values of 10³ Ω/□, indicating their suitability as antistatic materials for semiconductor applications.

• Applied Chemistry for Engineering
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• v.35 no.4
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• pp.329-334
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• 2024

To improve the UV absorbance and emulsion stability of sunscreen creams prepared using refined seabuckton oil, experimental conditions were designed utilizing the central composite design model-response surface methodology (CCD-RSM). The amount of surfactant, emulsification time, and thickener amount were chosen as independent variables, and the experiment was carried out after the reaction values of ESI, MDS, and UV absorbance at 290 nm were determined. The main effect and interaction effect, which have the most influence on the response value, were analyzed through the F-value and P-value of the regression equation coefficient calculated through RSM, and the statistical significance of the coefficient was evaluated through the P-value. The optimal emulsification conditions using RSM were calculated as follows: amount of surfactant (4.39 wt%), emulsification time (25.42 min), and amount of thickener (1.24 wt%). At these conditions, the reaction value was calculated as ESI (98.5%), MDS (32.9 nm), and UV absorbance (2.73). As a result of conducting an actual experiment under the calculated optimal conditions, the average error rate was measured as ± 2.7%

• Korean Journal of Materials Research
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• v.34 no.8
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• pp.387-394
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• 2024

Transition metal oxide-based materials have mainly been studied as electrodes for energy storage devices designed to meet essential energy demands. Among transition metal oxide-based materials, hydrated vanadium pentoxide (V₂O₅·nH₂O), a vanadium oxide material, has demonstrated great electrochemical performance in the electrodes of energy storage devices. Graphene oxide (GO), a carbon-based material with high surface area and high electrical conductivity, has been added to V₂O₅·nH₂O to compensate for its low electrical conductivity and structural instability. Here, V₂O₅·nH₂O/GO nanobelts are manufactured with water without adding acid to ensure that the GO is uniformly dispersed, using a microwave-assisted hydrothermal synthesis. The resulting V₂O₅·nH₂O/GO nanobelts exhibited a high specific capacitance of 206 F/g and more stable cycling performance than V₂O₅·nH₂O without GO. The drying conditions of the carbon paper electrodes also resulted in more stable cycling performance when conducted at high vacuum and high temperature, compared with low vacuum and room temperature conditions. The improvement in electrochemical performance due to the addition of GO and the drying conditions of carbon paper electrodes indicate their great potential value as electrodes in energy storage devices.

• Composites Research
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• v.37 no.4
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• pp.350-355
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• 2024

Boron nitride nanotubes (BNNT) are materials of significant interest in next-generation technological fields due to their outstanding physicochemical properties, including excellent chemical and thermal stability. However, for effective utilization, dispersion of BNNT is essential. Unfortunately, BNNT exhibit hydrophobic surfaces and strong van der Waals forces, making their dispersion challenging. Current dispersion methods include the addition of surfactants and surface functionalization, but these chemical treatments often damage BNNT and involve cumbersome processes. In this study, we dispersed BNNT in water under various tip ultrasonication conditions and identified conditions that do not affect BNNT using FT-IR spectroscopy, Raman spectroscopy, and X-ray diffraction analysis. Subsequently, enhanced dispersibility was confirmed through turbidity measurements, and the solubility range in 15 different solvents was evaluated using the Hansen solubility parameter.

• Journal of Climate Change Research
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• v.34 no.22
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• pp.9093-9113
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• 2021

This study examines the role of the relative wind (RW) effect (wind relative to ocean current) in the regional ocean circulation and extratropical storm track in the south Indian Ocean. Comparison of two high-resolution regional coupled model simulations with and without the RW effect reveals that the most conspicuous ocean circulation response is the significant weakening of the overly energetic anticyclonic standing eddy off Port Elizabeth, South Africa, a biased feature ascribed to upstream retroflection of the Agulhas Current (AC). This opens a pathway through which the AC transports the warm and salty water mass from the subtropics, yielding marked increases in sea surface temperature (SST), upward turbulent heat flux (THF), and meridional SST gradient in the Agulhas retroflection region. These thermodynamic and dynamic changes are accompanied by the robust strengthening of the local low-tropospheric baroclinicity and the baroclinic wave activity in the atmosphere. Examination of the composite life cycle of synoptic-scale storms subjected to the high-THF events indicates a robust strengthening of the extratropical storms far downstream. Energetics calculations for the atmosphere suggest that the baroclinic energy conversion from the basic flow is the chief source of increased eddy available potential energy, which is subsequently converted to eddy kinetic energy, providing for the growth of transient baroclinic waves. Overall, the results suggest that the mechanical and thermal air-sea interactions are inherently and inextricably linked together to substantially influence the extratropical storm tracks in the south Indian Ocean.

• Composites Research
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• v.37 no.4
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• pp.265-274
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• 2024

This study reviews previous research on various coating materials and methods designed to improve the adhesion and durability of steel pipes exposed to real-world marine environments, with the goal of identifying optimal solutions. The results concerning the adhesion and corrosion resistance of the pipes were categorized and analyzed based on exposure tests in extreme marine conditions to evaluate their stability. Furthermore, a detailed microstructural analysis of the coatings applied to the pipes was performed to assess surface damage, including peeling and delamination. The findings confirmed that coatings effectively prevent corrosion and provide sufficient adhesion and durability. Based on these results, we have proposed suitable coating materials, types, and application methods for steel pipes used in marine environments and offered recommendations for future exposure tests.

• Journal of the Korean Society of Food Science and Nutrition
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• v.44 no.4
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• pp.592-601
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• 2015

Rubus coreanus is known as Korean black raspberry, native to Korea, Japan, and China. Preliminary studies evaluating their potential for cancer treatment in mammalian test systems are ongoing. In recent years, interest has been renewed due to their high levels of anthocyanins. Anthocyanins in black raspberry are important due to their potential health benefits as dietary antioxidant, anti-inflammatory compound, and as a chemopreventive agent. In the present study, Saccharomyces cerevisiae BA29 was isolated from black raspberry fruit and fruit juice as a biogenic amine non-producing strain for manufacturing of black raspberry wine, after which we investigated its characteristics: biogenic amine-producing ability, cell growth ability, alcohol-fermentation ability, and resistance to alcohol, glucose, and sulfur dioxide. Based on preliminary experiments, we optimized culture medium compositions for improving dried cell weight of S. cerevisiae BA29 by response surface methodology (RSM) as a statistical method. Design for RSM used a central composite design, and molasses with the industrial applicability was used as a carbon source. Through statistical analysis, we obtained optimum values as follows: molasses 200 g/L, peptone 30 g/L, and yeast extract 40 g/L. For the model verification, we confirmed about 3-fold improvement of dried cell weight from 6.39 to 20.9167 g/L compared to basal yeast peptone dextrose medium. Finally, we manufactured black raspberry wine using S. cerevisiae BA29 and produced alcohol of 20.33%. In conclusion, S. cerevisiae isolated from black raspberry fruit and juices has a great potential in the fermentation of black raspberry wine.

• Food Science and Preservation
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• v.16 no.6
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• pp.908-914
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• 2009

A central composite design was used to optimize extraction of propolis materials using ethanol. The independent variables in extraction experiments were ethanol concentration (50, 60, 70, 80, 90%, v/v) and extraction time (1, 2, 3, 4, and 5 h). Higher ethanol concentration and shorter extraction time increased total polyphenol content, but total polyphenol concentration began to decrease when ethanol concentration was higher than 80% (v/v). Ethanol concentration was more important than extraction time in optimization of total polyphenol content in propolis extracts. Electron-donating ability increased with ethanol concentration and shorter extraction time, with ethanol concentration being of greater significance. Antioxidant ability in extracts was optimal at an ethanol concentration of 65 - 75% and with an extraction time of 2.2 - 3.6 h. Nitrite-scavenging ability was increased with use of higher ethanol concentration and shorter extraction time. Total flavonoid content was maximized with an ethanol concentration of 68 - 82% and an extraction time of 2.4 - 3.7 h. Total flavonoid content was affected by both ethanol concentration and extraction time. By superimposition of contour plots, an ethanol concentration of 72 - 82% and an extraction time of 2.2 - 3.3 h were optimal for preparation of propolis extracts.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.26-35
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• 2013

Outbreak of animal infectious diseases such as foot-and-mouth disease, avian influenza are becoming prevalent worldwide. For prevent the further infection, tremendous numbers of the infected or culled stocks are buried around farm. This burial method can generate a wide range of detrimental components such as leachate, nutrient, salt, and pathogenic bacteria, consequently. In this study, for the stabilization of livestock carcasses leachate, advanced oxidation processes utilizing the Fenton reaction was investigated in lab-scale experiments for the treatment for $COD_{Cr}$ of livestock carcass leachate. $COD_{Cr}$ reduction by the Fenton oxidation was investigated response surface methodology using the Box-Begnken methods were applied to the experimental results. A central composite design was used to investigate the effects of the independent variables of pH ($x_1$), dosage of $FeCl_2{\cdot}4H_2O$ ($x_2$) and dosage of $H_2O_2$ ($x_3$) on the dependent variables $COD_{Cr}$ concentration ($y_1$). A 1 M NaOH and $H_2SO_4$ was using for pH control, $FeCl_2{\cdot}4H_2O$ was used as iron catalyst and NaOH was used for Fenton reaction. The optimal conditions for Fenton oxidation process were determined: pH, dosage of $FeCl_2{\cdot}4H_2O$ and dosage of $H_2O_2$ were 3, 0.6 g (0.0151 M) and 7 mL(0.259 M), respectively. Statistical results showed the order of significance of the independent variables to be pH > initial concentration of ferrous ion > initial concentration of hydrogen peroxide.