• Polymer(Korea)
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• v.34 no.4
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• pp.294-299
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• 2010

Clay-loaded polypropylene (PP) nanocomposites were fabricated via melt-compounding of two molecular weight ($M_w$) PPs (140 and 410 kg/mol) and octadecylammine-treated clay (C18MMT), with the assistance of maleic anhydride-grafted PP(PP-MAH), respectively, at $170^{\circ}C$ and $190^{\circ}C$. At both melt-compounding temperatures, the low-$M_w$ PP tends to easily diffuse into silicate layers, especially in the presence of the mobile PP-MAH, resulting in a marked increase in silicate layer spacing (above 58 $\AA$), when compared to 27 $\AA$ in the high-$M_w$ PP-based system. Due to relatively lower melt-viscosity of the low-$M_w$ PP-based system, however, there existed quasi-stacked clay aggregates with a thickness of 60~80 nm, while the high-$M_w$ PP-based nanocomposites showed relatively homogeneous dispersion of clays. The different morphologies are mainly related to changes in the viscoelastic properties of PPs, dependent on the processing temperature and their $M_{w}s$. The slight differences in nanocomposites induce discernible crystallization and mechanical behaviors. High-$M_w$ PP-based nanocomposites containing 1~3 wt% C18MMT showed improvement in both tensile strength and modulus, while maintaining the inherent ductility of pure PP.

• Polymer(Korea)
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• v.34 no.5
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• pp.480-484
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• 2010

A series of poly(amic acid)s(PAAs) was prepared by reacting 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride)(BPADA) as the anhydride monomer and 2,2'-bis(trifluoromethyl) benzidine (TFB), bis(3-aminophenyl)sulfone (APS), 4,4'-methylenebis-(2-methylcyclohexylamine) (MMCA), or bis[4-(3-aminophenoxy) phenyl] sulfone (BAPS) as the amine monomer with 5 mol% melamine in N,N-dimethylacetamide (DMAc). Colorless and transparent polyimide (PI) films were obtained by casting the PAAs at various heat treatment temperatures. The thermo-mechanical properties and optical transparency of the PI films were investigated. The thermal properties of the PI films were examined using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and thermomechanical analysis (TMA), and their optical transparency were measured by spectrophotometry. The coefficient of thermal expansion (CTE) and yellow index (YI) values of all samples were in the range of $48.53-64.24ppm/^{\circ}C$ and < 3.0, respectively.

• Polymer(Korea)
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• v.30 no.6
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• pp.545-549
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• 2006

Blends of poly(acrylic acid- co-maleic acid) (PAM) with poly (vinyl alcohol) (PVA) were pre -pared in distilled water PVA/PAM/saponite (PVA/PAM/SPT) nanocomposite films were prepared with various clay contents by using the solution intercalation method. The variations of the dispersion, morphology, and thermo-mechanical properties of the nanocomposites with clay content in the range 0 to 9 wt% were examined. Up to 3 wt% clay loading, the clay particles were homogeneously dispersed in the PVA/PAM blends. However, some agglomerated structures form in the polymer matrix above a clay content of 7 wt%. The thermal stability of the hybrids was increased linearly with increasing the clay loading up to 9 wt%. The maximum strength and modulus were obtained at a clay content of 7 wt%. Thus, the addition of small amounts of clay to the PVA/PAM blends produced PVA/PAM nano-composites with improved the thermo-mechanical properties.

• Polymer(Korea)
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• v.36 no.5
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• pp.617-621
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• 2012

PHEAs [${\alpha}$,${\beta}$-poly(2-hydroxyethyl-DL-aspartamides)], a class of poly(amino acid), have been widely studied as biodegradable and biocompatible polymers for potential biomedical and pharmaceutical applications. In this study, we investigated a homogeneous blend of PHEA with poly(N-vinyl pyrrolidone) (PNVP) and its semi-IPN (semi-interpenetrating polymer network) gels. Blend films were prepared by a solution casting method. The resulting blends were totally transparent over the whole composition ranges and the single $T_g$, changing monotonously with composition, was observed by DSC to confirm the miscibility between these two polymers. FTIR was used to discuss the possible hydrogen-bonding interaction between polymers. In addition, semi-IPN type gels were prepared by chemical crosslinking of PHEA/PNVP blend solution using hexamethylene diisocyanate (HMDI) as a crosslinking reagent. The prepared gel was characterized by their swelling property and morphology.

• Journal of Veterinary Clinics
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• v.24 no.1
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• pp.35-37
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• 2007

Eight dogs were presented with anal sacculitis with purulent exudates and/or open in the right or left anal sac. Patient dogs, ranging in size from 3-to-8 kg, were treated with closed anal sacculectomies, in which the balloon of a Foley catheter (No. 6, 1.5 ml) was used to facilitate surgical dissection of the sac. In all cases, the Foley catheter successfully distended the anal sac during its removal. Clinical signs associated with the diseased anal sac were abated In the all dogs for a follow-up period of one-to-three months. Anal sacculectomy is a good therapeutic option for cases of chronic anal sacculectomy or impaction. The use of a small Foley catheter to distend the anal sacs during surgery was easy, Inexpensive, and successful.

• Korean Chemical Engineering Research
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• v.46 no.1
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• pp.63-68
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• 2008

We investigated the recycling method to re-plasticize cross-linked polyethylene by using supercritical methanol. The cross-linked polyethylene is successfully fragmented to thermoplasticized polyethylene with little degradation reactions in supercritical fluids. The thermo-plasticization reaction was accelerated with increase in temperature in the range from $360^{\circ}C$ to $400^{\circ}C$, resulting in decrease in crosslinking density, molecular weight and mechanical properties. However, the thermoplasticized polyethylene at $360^{\circ}C$ showed comparable tensile strength and impact strength with a raw resin of crosslinked polyethylene. Chemical structure of main chain of polyethylene was not affected by reaction condition.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.11a
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• pp.50-50
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• 2011

국내 섬유산업은 해외로부터의 저가 섬유제품이 대량으로 유입되는 속에서도 수출의 상당한 부분을 차지하며, 꾸준히 양에서 질로의 전환을 도모해 왔으며, 특히 최근에는 섬유 전반에 걸쳐 고부가 가치화를 지향하고 있다. 이러한 소비자의 요구에 부응하여 섬유소재에도 다양한 신개념과 이를 충족시킬 수 있는 기술이 요구되고 있으며, 그 가운데 하나의 영역을 구축해 나가고 있는 분야가 면 리플가공과 같은 표면 형태 가공이며, 최근 들어 폴리에스테르 입체(3D)가공제의 개발 및 가공 방법도 이런 흐름에 부응하여 업계에서 절실한 개발을 요구하고 있는 분야이다. 기존의 폴리에스테르 및 합성섬유의 입체 가공에 적용된 화학제품보다 성능은 우수하면서, 가공 공정이나 완성된 섬유제품에 전혀 잔존하지 않아 인체친화적(기존의 제품들은 인체에 유해한 재료이면서 가공 후 잔존함)이며, 환경적인 측면에서도 친환경을 유지하면서 새로운 폴리에스테르섬유, 좀 더 폭넓게는 열가소성인 모든 합성섬유의 입체가공이 가능한 약품의 개발 및 이를 이용한 가공방법의 개발은 매우 중요한 의의를 가지게 된다. 본 연구에서는 폴리에스테르의 3D입체 디보싱을 부여하는 합성바인더가 물에 의한 용해도를 확인하기 위하여 용액의 PH에 따른 용해성 시험을 진행하였으며, 합성한 발포제의 양에 따른 3D입체형성 정도를 이미지로 형상화 하였다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.36 no.6
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• pp.663-669
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• 2007

The solvent extracts of Sargassum muticum, which were extracted by using several solvents with different polarities, were prepared for use as natural preservatives. The S. muticum extract with 80% ethanol was sequentially fractionated with n.hexane, dichloromethane, ethylacetate, and butanol. In order to effectively screen for natural preservatives agents, we first investigated the antioxidant activities such as DPPH radical scavenging capacity, superoxide radical scavenging capacity, and xanthine oxidase inhibitory activity of the S. muticum extracts. Through the screening system, we found that dichloromethane and ethylacetate fraction had high antioxidant activity with increments of the extract concentration. The antimicrobial activities and cell growth inhibition were investigated for each strain with the different concentrations of S. muticum extracts. Antimicrobial activities were shown in ethanol, dichloromethane, and n.hexane fractions of S. muticum. However, butanol, ethylacetate and water fractions showed weak antimicrobial activity against the tested microorganisms. Among the five fractions, dichloromethane fraction showed the highest antimicrobial activities against microorganisms tested, such as Bacillus sublitis, Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, Salmonella Enteritidis and Pseudomonas aeruginosa. The polyphenolic compounds from ethanol, n.hexane, dichloromethane, ethylacetate, butanol, and water fractions were 63.96 mg/g, 8.49 mg/g, 28.11 mg/g, 172.64 mg/g, 114.56 mg/g, and 34.91 mg/g, respectively. The dichloromethane fraction could be suitable for development as a food preservative.

• Journal of the Korean Ceramic Society
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• v.41 no.9
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• pp.690-695
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• 2004

In this study, inorganic (steel, asbestos and carbon) and organic (polyacryl and polyamide) fibers were used to investigate their reinforcing effects of the physical properties of Portland cement. From the load-displacement curve of each reinforced specimen, fracture strength, Young's module, fracture energy and fracture toughness were computed and compared with each other. In addition, the experiment of their impact toughness was carried out and compared with the fracture energy. For the improvement of fracture strength the inorganic (asbestos) fiber reinforcement was most effective, while the best reinforcing effect of impact toughness was achieved by organic (polyacryl) fiber. And steel fiber proved to be most adequate for improvement of both fracture strength and impact toughness. Steel fiber also showed the highest fracture energy and fracture toughness among all of the fibers.

• Polymer(Korea)
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• v.24 no.6
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• pp.770-776
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• 2000

The effect of unreactive coupling agent on mechanical and thermal properties of talc-filled polypropylene (PP) composites was studied. Stearic and oleic acids were introduced as coupling agents, and tensile, flexural, and impact strength, thermal stability and melting transition temperature were measured and analyzed according to the types and concentration of coupling agents. Tensile and flexural strength were enhanced by introduction of coupling agent and the maximum effect was observed at the concentration of 3 wt% of coupling agent. Tensile and flexural strength of PP treated with oleic acid were higher than those of PP treated with stearic acid. but impact strength vice-versa. The reasons for these results were postulated by analyzing morphologies of talc-filled PP observed by SEM.