• Polymer(Korea)
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• v.36 no.2
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• pp.196-201
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• 2012

Electrospinning is a versatile process used to prepare micro or nano sized fibers from various materials dissolved in volatile solvents. This study reports electrospun pullulan fibrous webs fabricated through electrospinning using water as a solvent. The electrospinning conditions such as pullulan (PUL) concentration and applied voltage were optimized in order to obtain smooth electrospun fibers. The concentration of PUL greatly influenced the viscosity and surface tension of PUL solution. PUL beaded electrospun fibers were obtained from PUL solutions with concentrations lower than 5 wt%, while homogenous electrospun fibers were prepared from solutions with high concentration and high viscosity. The average diameters of PUL fibers were decreased to 200 nm when the polymer concentration was kept at 10 wt% and the applied voltage was fixed at 15 kV during electrospinning. PUL electrospun fiber exhibited higher solubility, flexibility, softness and adhesive strength.

• Polymer(Korea)
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• v.33 no.4
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• pp.307-312
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• 2009

The fabrication of PHBV nanofibers containing various plant polyphenols by electrospinning has been examined. It has been found that the average diameters of fibers increased by the adding of polyphenols. The resulting fibers exhibited a uniform diameter ranging from 340 to 450 nm. As the concentration of polyphenols increased, the diameter of fibers increased due to the hydrogen bonding interaction between the ester groups of PHBV and hydroxyl groups of polyphenols. The interaction between PHBV and polyphenols, which forms a complex together in solution, was verifed by UV measurement. ATR-FTIR analysis confirmed the existence of the hydrogen bonding interaction. The semicrystalline structure of the PHBV nanofiber was observed from XRD pattern. The crystallinity of PHBV nanofibers was increased by the adding of polyphenols. PHBV nanofibers containing polyphenols showed superior antimicrobial activities.

• Polymer(Korea)
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• v.35 no.3
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• pp.228-231
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• 2011

The rate of vulcanization of nonpolar ethylene-propylene-diene terpolymer(EPDM)/carbon black compounds was investigated by using hot air and microwave as a heating source. The present study parameters such as heating source, sample thickness, and loading of an additive. The compound thickness was the main factor in the hot air vulcanization. It was due to the poor thermal conductivity of EPDM; that is, the thicker thickness, the lower vulcanization rate. For 100% vulcanization, the compound with 3 mm thickness required 7 min at $250^{\circ}C$ in the hot air system. However, the vulcanization of EPDM compounds by microwave system was not affected by the thickness while strongly dependent on the amount of a polar additive, carbon black. A compound with 80 phr of carbon black was perfectly vulcanized within 30 sec. These results suggest that the use of microwave as a heating source is an effective method for the vulcanization of compounds including a polar component.

• Polymer(Korea)
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• v.35 no.3
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• pp.210-215
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• 2011

Rutin (R) exhibits a wide range of biological activities including anticarcinogenic, antiinflammatory and antiviral actions. The purpose of this study is to investigate the effect of rutin concentrations (1 and 3 wt%) on the antibacterial activity of poly(3-hydroxybutylate-co-hydroxyvalerate) (PHBV) scaffolds. Antibacterial activity was evaluated by using Staphylococcus aureus and Klebsiella pneumoniae. Furthermore, the qualitative ongrowth of human KB endothelial cells was done to study in vitro cytotoxicity of the scaffolds. As the results, PHBV scaffolds containing 3 wt% rutin completely inhibited the proliferation of Staphylococcus aureus and Klebsiella pneumoniae. In addition, the PHBV/R scaffolds used in this study did not show any cytotoxicity when evaluated them with KB endothelial cells.

• Polymer(Korea)
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• v.33 no.1
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• pp.1-6
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• 2009

We report the template-based synthesis of well-dispersed CdS nanoparticles (NPs) in the interior of poly (2-acetamidoacrylic acid) (PAAA) hydrogel as a novel type of nanocomposite without particle aggregation via ion exchange in a aqueous system. As revealed by the TEM image analysis, the mean crystallite diameter of CdS NPs embedded in hydrogel composite was 4.5 nm, and the composite did not suffer any observable change after 6 months. Desorption/decomposition of CdS/PAAA hydrogel composite was studied by evolved gas analysis-gas chromatography-mass spectrometry (EGA-GC-MS), and thermogravimetric analysis (TGA) methods. From the TGA data, the thermal stability of the composite system increased by ca. 100 $^\circ$C and the content of CdS NPs in a dry composite gel was over 70 wt%. In addition, the chemical pathway was proposed for the entire decomposition process.

• Polymer(Korea)
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• v.36 no.1
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• pp.16-21
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• 2012

Organic-inorganic hybrid coating film using 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene (BTHFC) as a photochromic material was prepared under various reaction conditions such as the amounts of tetramethoxysilane (TMOS), various silane coupling agents, and solvent. It was found that color-fading speed and absorbance of the coating film was strongly dependent upon the polarity of silane coupling agent and solvent. In addition, the mole ratio of TMOS and methacryloyloxypropyltrimethoxysilane (MPTMS) was an important factor to determine color-fading speed and absorbance of the coating film. With increasing TMOS contents in coating film, the pencil hardness was increased. On the other hands, the transmittance of coating film was relatively decreased with the increase of TMOS.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.389-398
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• 2019

Hydrogen energy is not only a solution to climate change problems caused by the use of fossil fuels, but also as an alternative source for the industrial power generation and automotive fuel. Among hydrogen production methods, electrolysis of water is considered to be one of the most efficient and practical methods. Compared to that of the fossil fuel production method, the method of producing hydrogen directly from water has no emission of methane and carbon dioxide, which are regarded as global environmental pollutants. In this paper, the alkaline water electrolysis (AWE) and polymer electrolyte membrane water electrolysis (PEMWE), which are one of the hydrogen production methods, were discussed. Recent research trends of hydrocarbon electrolyte membranes and the crossover phenomenon of electrolyte membranes were also described.

• Membrane Journal
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• v.31 no.6
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• pp.384-392
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• 2021

Growing pollution due to industrialization leads to difficulties in survival of mankind. Generation of clean water from wastewater by membrane separation process is emerging cost efficient technology. Membrane prepared from renewable resources are in lots of demand to reduce burden on synthetic polymers which is one of the source of environmental pollution. Bacterial cellulose (BC) is very pure and distinct form of cellulose nanofibrils (CNF). Nanopapers prepared from CNF are used ad ultrafiltration (UF) and nanofiltration (NF) membrane for different applications. High crystallinity of BC gives rise to excellent mechanical property, an essential criterion for wastewater treatment membrane. In this review, BC based membrane for application in dye, oil, heavy metal and chemical removal from wastewater is discussed.

• Applied Chemistry for Engineering
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• v.33 no.6
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• pp.618-623
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• 2022

The bipolar plate is a key component of the polymer electrolyte membrane fuel cell (PEMFC) that transfers reactants and electrons, discharges water and heat as by-products, and serves as a mechanical support for the membrane electrode assembly (MEA). Therefore, the flow field structure of the bipolar plate plays an important role in improving fuel cell performance. In this study, PEMFC performance was investigated with copper foams with different compressibility ratios applied to cathode bipolar plates using a 25 cm² unit cell. The total resistance decreased as the compressibility ratio of the metal foams increased, and, in particular, the charge transfer and mass transfer resistance were significantly improved compared to the serpentine flow field, lowering voltage loss in medium and high current density region. In the case of pressurized air reactant flow with serpentine structure, fuel cell performance was similar to that of a compressed metal foam flow field (S3) up to the medium current density region, but low performance appeared in the high current density region due to flow field structure limitations.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.250-256
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• 2013

Gasoline generates organic acid and polymer (gum) by hydrocarbon oxidation depending on the storage environment such as temperature and exposure to sunlight, which can cause metal corrosion, rubber and resin degradation and vehicle malfunction caused by accumulation in fuel supply system. The gasoline which has not been used for a long time in bi-fuel (LPG-Gasoline) vehicle causes problems, and low octane number gasoline have evaporated into the field, but the exact cause has not been studied yet. In this study, we suggest a plan of quality management by investigating the gasoline oxidation behavior. In order to investigate the oxidation behavior of gasoline, changes of gasoline properties were analyzed at various storage conditions such as storage time, storage vessel type (vehicle fuel tank, PE vessel and Fe vessel) and storage circumstances (sunlight exposure and open system, etc.). Currently distributing gasoline and bioethanol blended fuel (blended 10%) were stored for 18 weeks in summer season. The sample stored in PE vessel was out of quality standard (octane number, vapor pressure, etc.) due to the evaporation of the high octane number and low boiling point components through the vessel cap and surface. Especially, the sunlight exposure sample stored in PE vessel showed rapid decrease of vapor pressure and increase of gum. Bioethanol blended fuel showed similar results as gasoline.