• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.65-65
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• 2012

The air texturing공정은 노즐에서 전달되는 초음속 에어기류에 의해 overfeed를 수반하여 yarn속 fiber가 뒤얽혀 loop와 crimp를 발달시키는데, 고강력 고탄성율 고내열성 내절단성 등의 특성을 가지는 아라미드섬유를 에어 가공사로 가공 할 경우 가공 전 필라멘트 상태일 때 보다 표면에 생기는 loop로 인하여 촉감이 좋아지고 또한 타 소재와 접착 시 접착제 담지 성능이 향상 되어 접착력이 상승되고, 이를 통해 보강재로서의 기능이 강화되는 반면 역학물성이 기존의 아라미드 보다 저하되는 약점을 가지고 있어 최근 ATY 공정조건이 ATY 사의 구조와 물성변화에 미치는 영향에 대한 많은 연구결과가 발표되고 있다. 본 연구에서는 Aiki air jet texturing machine에서 $Heracron^{(R)}$ para-aramid(840, 1000d, 1500d)를 사용하여 ATY nozzle의 직경을 0.6, 0.75, 1, 1.2mm로 변화를 주어 12개의 para-aramid ATY 시료를 제조하여 이들의 섬도, 강신도, 초기탄성률, 열수축률 그리고 형태불안정성(instability)등의 물성변화를 분석하여 다음과 같은 결과를 얻었다. 노즐의 직경이 증가함에 따라 사 내의 filament간의 움직임이 자유로워 교락이 증가하고 루프가 형성되어 단위길이 당 mass가 커지므로 섬도가 미세하게 증가하는 것을 볼 수 있다. 또한 직경이 증가할수록 절단강도와 초기탄성률은 감소하고 절단신도가 증가하는 경향을 볼 수 있는데 이는 축 방향으로의 배열이 적어져 하중을 분담하는 portion이 감소하고 사의 loop형성이 많아짐으로서 상대적으로 인장력에 대응하는 fiber의 수가 적어지기 때문으로 사료된다. 이는 현미경 관찰로 확인할 수 있는데 직경이 증가함에 따라 사의 loop의 엉킴이 증가하고 filament가 조밀한 것을 확인할 수 있다. 직경 변화에 따른 건 습열 수축률은 1% 미만의 매우 낮은 값으로 영향을 받지 않는 것을 확인 할 수 있는데 para-aramid의 열적특성의 안정성에 기인하는 것으로 사료되며 ATY의 불안정성은 노즐 직경 증가에 따른 어떤 경향성을 찾아볼 수 없었지만 840d, 1000d, 1500d로 섬도가 증가함에 따라 사의 불안정성이 증가하였다.

• Polymer(Korea)
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• v.38 no.4
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• pp.457-463
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• 2014

In this study, the changes in the chemical structure and the physical property of fluoropolymer films (PTFE, FEP, PFA, PVDF, and ETFE) induced by $Co^{60}$ gamma ray in air, $N_2$, and vacuum environments were investigated. FTIR spectra of the irradiated fluoropolymers indicate that the oxidation proceeded by the reaction of radicals generated by irradiation with oxygen in air. The changes in the heat of fusion and the degree of crystallinity of the irradiated fluoropolymers were investigated using DSC and the results indicate that the scission and crosslinking reactions of the irradiated fluoropolymers were largely influenced by the chemical structure. It was also found that the mechanical property of the irradiated fluoropolymer films under an air atmosphere was significantly decreased.

• Polymer(Korea)
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• v.37 no.4
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• pp.500-506
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• 2013

The effect of compatibilizer types on the properties of polyphenylene sulfide (PPS)/polyethylene terephthalate (PET) blends was investigated. The blends were extruded by a single screw extruder attached with a Maddock mixing zone and their molded properties were examined. As a basic blend composition, a linear PPS/PET (40/60) blend was selected based on cost efficiency. Three types of compatibilizer, SEBS, modified SEBS, and modified PS were added to the basic blend to improve the properties. The thermal, rheological, mechanical properties and the morphology of the ternary blends were analyzed. The maximum mechanical properties of blends was found at 1 phr of m-SEBS or m-PS content, whose values were almost the same as the theoretical values of miscible blend system. It seemed to by the case that the partial reaction between compatibilizer and the basic blend caused the enhancement of compatibility between linear PPS and PET phases. These ternary blends would be applicable as economic linear PPS alloys.

• Composites Research
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• v.35 no.2
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• pp.69-74
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• 2022

In this study, the conductive paste used in a wide range such as wiring in the electronic packaging field, the automobile industry, and electronic products is manufactured under various process conditions due to the simplicity of the process, and then the thermal, mechanical, and electrical characteristics are analyzed and simulation studies are conducted to optimize the process. to establish the conditions of the conductive paste manufacturing process. First, a conductive paste was prepared by setting various types of binder resin, an essential component of the conductive paste, and characteristics such as thermal conductivity, tensile strength, and elongation were analyzed. Among the binder resins, the conductive paste applied with a flexible epoxy material had the best physical properties, and a simulation study was conducted based on the physical property data base of the conductive face. As a result of the simulation, the best physical properties were exhibited when the Ag flake volume fraction was 60%.

• Composites Research
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• v.36 no.4
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• pp.275-280
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• 2023

Because polymer-based composites are lightweight and have excellent properties, their demand is growing rapidly as a way to fulfill properties that are difficult to achieve with a single material. As a result, there has been a lot of research on polymer nanocomposites, which are made by dispersing particles with a size of 1-100 nm in a polymer matrix. In addition, many nanocomposites using thermoplastic resins as matrix materials are being studied. In this study, poly(ethylene terephthalate) (PET)-based nanocomposites containing organic nanoclays modified with cetyltrimethylammonium bromide (CTAB) as interlayer materials were prepared. Among various nanoclays, vermiculite (VMT) has been studied to increase the mechanical and thermal properties of polymeric materials due to its low cost, abundant reserves and unique properties. However, the strong interlayer bonding of VMT has limited its utilization due to its poor exfoliation and dispersion performance within polymer matrices. In this study, the mechanical properties of the VMT content were confirmed by tensile tests, the dispersion of VMT particles in the PET matrix was evaluated by TEM cross-sectional images, and the nitrogen gas barrier properties were evaluated.

• Clean Technology
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• v.19 no.3
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• pp.272-278
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• 2013

Ethylene propylene diene terpolymer (EPDM) has been usually used for various applications. Bottom ash generated in thermoelectric power plant is hardly recycled. In this study, EPDM/bottom ash/talc composites were prepared by using roll-mill. Bottom ashes obtained from thermoelectric power plant were modified using surfactant. The processing materials used in this study were antioxidant, processing oil, cross-linking co-agent and softening agent. Morphology and physical properties of EPDM composites are investigated by using SEM, TGA, UTM and Rheometer. As a result, when modified ash and talc are added to EPDM composites, the tensile strength and modulus of EPDM composites were remarkably enhanced.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.285-290
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• 2016

To improve properties of epoxy composites, surfaces of the illite and carbon nanotube (CNT) were treated by fluorine gas. The fluorinated illite and CNT were then characterized by X-ray photoelectron microscopy (XPS) and the mechanical and thermal properties of their composites were evaluated. The tensile and impact strengths and thermal stability of the composites increased upto about 59%, 18% and 124%, respectively compared to those of the neat epoxy. Improvements of mechanical and thermal properties in the composites were attributed that the fluorination of illite and carbon nanotube helps to enhance the dispersion in epoxy resin and interfacial interaction between them.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.339-346
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• 1997

Liquid crystalline polyurethanes were prepared from 1,4-bis(6-hydroxyhexoxy)benzene (BHB6) and 2,5-tolylene diisocyanate (2,5-TDI) solution polymerization in dimethylformamide produced intrinsic viscosities in the range 0.26 and $0.42d{\ell}/g$. The polyurethanes were investigated by DSC, Polarizing microscopy, X-ray, $^1H$-NMR and IR spectroscopy. Polyurethanes of two different molecular weights were studied in detail and these will be referred to as low molecular weight and high molecular weight. Polyurethane 2,5-TDI/BHB6 with $[{\eta}]=0.26d{\ell}/g$ prepared from BHB6 and 2,5-TDI, exhibited monotropic liquid crystallinity, although these polyurethanes contained no mesogenic core unit. For example, LCPU-L(low molecular weight) exhibited $T_{I-LC}$ of $122^{\circ}C$ $T_{LC-K}$ $89^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.200-204
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• 2011

In this paper, we deposited the tungsten carbon nitride (W-C-N; nitrogen gas flow of 2 sccm) and tungsten carbon (W-C) thin film on silicon substrate using rf magnetron sputter. Then the thin films annealed at $800^{\circ}C$ during 30 minute ($N_2$ gas ambient) for thermal damage. Nano-indenter was executed 16 points on thin film surface to measure the thermal stability, and we also propose the elastic modulus and the Weibull distribution, respectively. This nanotribology method provides statistically reliable information. From these results, the W-C-N thin film included nitrogen gas flow is more stable for film uniformities, physical properties and crystallinities than that of not included nitrogen gas flow.

• Composites Research
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• v.31 no.6
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• pp.371-378
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• 2018

In this study, the thermoelastic properties of poly lactic acid (PLA) based nanocomposites are predicted by molecular dynamics (MD) simulation and a micromechanics model. The stereocomplex mixed with L-lactic acid (PLLA) and D-lactic acid (PDLA) is modeled as matrix phase and a single walled carbon nanotube is embedded as reinforcement. The glass transition temperature, elastic moduli and thermal expansion coefficients of pure matrix and nanocomposites unit cells are predicted though ensemble simulations according to the hydrolysis. In micromechanics model, the double inclusion (D-I) model with a perfect interface condition is adopted to predict the properties of nanocomposites at the same composition. It is found that the stereocomplex nanocomposites show prominent improvement in thermal stability and interfacial adsorption regardless of the hydrolysis. Moreover, it is confirmed from the comparison of MD simulation results with those from the D-I model that the interface between CNT and the stereocomplex matrix is slightly weak in nature.