• Composites Research
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• v.24 no.4
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• pp.11-16
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• 2011

Retention of interfacial shear strength (IFSS) of polymer composites at cryogenic temperature application is very important. In this work, single carbon tiber reinforced epoxy compositc was used to evaluate IFSS and apparent modulus under room and cryogenic temperatures. The property change of carbon and selected epoxy for particularly cryogenic temperature application were tested in tension and compression. Tensile strength and elongation of carbon fiber decreased at cryogenic temperature, whereas tensile modulus was almost same. On the other hand, epoxy matrix showed the increased tensile strength but decreased elongation. It can be due to maximum thermal contraction existing free volume in cryogenic temperature. IFSS increased up to $-10^{\circ}C$ and then decreased steadily. However, IFSS at cryogenic temperature was still similar to that at room temperature. This result is very useful to cryogenic application since selected epoxy toughness and interfacial adhesion can keep at such low temperature.

• Composites Research
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• v.33 no.5
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• pp.282-287
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• 2020

In the present study, a high-strength polyethylene terephthalate (PET) sheet was fabricated through a densification process of low melting PET fiber (LMF) combined PET sheet. During the thermal heat treatment process of the combined LMF, individual PET fiber was connected, which in turn leads to the improvement of the interfacial bonding force between the fibers. Also, the densification of the PET sheet leads to reduce macrospore density and in return could enhance the binding force between the overlapped PET networks. Consequently, the asprepared LMF-PET sheet showed about 410% improved tensile strength and the same elongation compared to before compression. Besides, the enhanced bonding force can prevent the shrinkage of the PET fiber network and exhibited excellent dimensional stability.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.11
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• pp.885-890
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• 2015

Nanomaterials possess unique mechanical, physical, and chemical properties. They are small, and have an ultrahigh surface area, making them suitable for air filter applications. Electrospinning has been recognized as an efficient technique for fabricating polymer nanofibers. In order to determine the optimum manufacturing conditions, the effects of several electrospinning process parameters on the diameter, orientation, and distribution of polyacrylonitrile (PAN) nanofiber are analyzed. To improve interlaminar fracture toughness and suppress delamination in the form of laminated non-woven fibers by using a heat roller, the performances of filter efficiency and pressure drop achieved with PAN nanofiber air filter are evaluated experimentally.

• Applied Chemistry for Engineering
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• v.28 no.4
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• pp.485-489
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• 2017

Polyethylene terephthalate (PET) has been widely applied in polymers and packaging industries to produce synthetic fibers, films, drink bottles or food containers. Therefore, it has become one of the major plastic wastes. In this article, glycolysis known as one of the main methods in PET chemical recycling was investigated using a glycol to break down the polymer into a monomer. Glycolysis of PET and ethylene glycol was performed in a micro-tubing reactor under various conditions. The effect of glycolysis conditions on the product distribution was investigated at experimental conditions of the EG/PET ratio of 1~4, the reaction time of 15~90 min and the reaction temperature of $250{\sim}325^{\circ}C$ with Mn and Cu catalysts. The highest yield of bis (2-hydroxyethyl) terephthalate monomer (BHET) was obtained as 89.46 wt% under the condition of the reaction temperature of $300^{\circ}C$ and the time of 30 min using 10 wt% $Cu/{\gamma}-Al_2O_3$ catalyst, with the PET and ethylene glycol ratio of 1 : 2.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.104-104
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• 2012

아웃도어용 스포츠웨어 의류분야는 소비자들의 욕구가 기능성, 착용감, 패션성을 매우 중시하는 고감성, 고기능성 제품특성을 요구하고 있으며 이를 가장 충족시킬 수 있는 패션 트랜드로서 보온, 경량화 제품이 가장 급부상하고 있는 아이템이다. 경량성의 쾌적 스포츠 웨어에 사용되는 주요 합섬소재인 PET, Nylon을 이용하여 소재의 세섬화, 중공 소재를 통한 제품 개발이 대부분으로 보온, 경량, 속건 등 의복에서의 쾌적 기능성을 개선하기 위하여 개발되는 소재 및 제품의 경량화, 보온 및 흡한속 건성 부여를 통한 기능 요소와 신질감 발현의 촉감요소를 통한 차별화 된 제품개발이 요구되고 있다. 보온 기능성을 부여하는 기술로써 가장 일반적인 기술은 섬유 내부에 중공을 형성하여 경량성과 보온성을 동시에 가지는 기능성 원사 제조 기술과 섬유 내에 열에너지를 흡수할 수 있는 물질을 넣어 외부의 태양광을 섬유내로 흡수하여 열에너지로 전환, 축적함으로서 보온성을 향상시키는 방식이 있다. 주로 경량 보온의 동시 발현을 위하여 중공 형성을 통한 보온 소재 개발이 활발하게 일어나고 있는 실정이다. 가장 많은 수요를 차지하고 있는 경량 보온성 중공사의 경우, 강도 저하, 염색 불량 등의 공정 애로점이 발생하며, 제직 및 가공 공정 시 원사 내 중공이 찌그러짐이 발생하므로 완제품 제조 후에는 중공의 기능이 제대로 발현되지 못하는 문제가 발생한다. 또한 알칼리 또는 용제를 사용하여 후용출 하는 중공사의 경우, 공정이 복잡함은 물론 환경에 유해한 공정이다. 특히, 감량 후 직물의 인열강도는 감량 전과 비교하여 감소하게 되는데 이는 이용성 polymer가 용출되면서 생긴 중공에 의해 섬도가 감소되어 강도가 저하됨을 알 수 있다. 따라서 Sheath 부분에 최대한 손상을 주지 않으면서 Core 부분을 완전 용출 시킬 수 있는 감량 조건을 확보할 필요가 있다. 이에 보온성, 경량성의 기능을 극대화시키고, 중공률 유지하는 최적 용출 가공 조건을 확립하고자 연구하였다.

• Journal of Korean Society of Steel Construction
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• v.24 no.3
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• pp.349-360
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• 2012

This paper describes a detailed assessment of the structural safety, serviceability, capacity rating and long-term performance of a glass fiber-reinforced polymer (GFRP) slab bridge superstructure. This first all-GFRP slab bridge was installed in Korea on May 2002. The GFRP slab bridge is a simply supported, its length is 10.0 m, and is designed to carry two-lane traffic and has an overall width of 8.0m. The GFRP slab bridge is a sandwich structure with a corrugated core, fabricated by hand lay-up process with E-glass fibers and vinyl ester resins. The assessment of long-term performance for the GFRP slab bridge in 2004, 2011 includes a field load testing identical to that performed in 2002. The assessment indicates that the GFRP slab bridge has no structural problems and is structurally performing well in-service as expected. The assessment may provide a baseline data for the capacity ratings assessment of the GFRP slab bridge and also serve as part of a long-term performance of all-GFRP bridge superstructure.

• Carbon letters
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• v.16 no.3
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• pp.147-170
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• 2015

In recent decades, there has been an increasing interest in the use of carbon fiber reinforced plastic (CFRP) in aerospace, renewable energy and other industries, due to its low weight and relatively good mechanical properties compared with traditional metals. However, due to the high cost of petroleum-based precursors and their associated processing costs, CF remains a specialty product and as such has been limited to use in high-end aerospace, sporting goods, automotive, and specialist industrial applications. The high cost of CF is a problem in various applications and the use of CFRP has been impeded by the high cost of CF in various applications. This paper presents an overview of research related to the fabrication of low cost CF using polyethylene (PE) control technology, and identifies areas requiring additional research and development. It critically reviews the results of cross-linked PE control technology studies, and the development of promising control technologies, including acid, peroxide, radiation and silane cross-linking methods.

• Composites Research
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• v.29 no.5
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• pp.243-248
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• 2016

Although thermoset carbon fiber composite bipolar plates not only have high mechanical properties but also high corrosion resistance in acid environment, high manufacturing cost and low bulk electrical conductivity are the biggest obstacle to overcome. In this research, thermoplastic polymer is employed for the matrix of carbon composite bipolar plate to increase both the manufacturing productivity and bulk electric conductivity of the bipolar plate. In order to increase the electrical conductivity and strength, plain type carbon fabric rather than chopped or unidirectional fibers is used. Also nano particles are embedded in the thermoplastic matrix to increase the bulk resistance of the bipolar plate. The area specific resistance and the mechanical strength of the developed bipolar plate are measured with respect to the environmental temperature and stack compaction pressure.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.751-756
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• 2009

In the perspective of saving energy in buildings, the high performance of insulation and air tightness for improving the heating and the cooling efficiency, has brought economically positive effects. However, these building energy saving technologies cause the lack of ventilation, which is the direct cause of increasing the indoor contaminants, and is also very harmful to the residents, because they spend over 90% of their time indoors. Therefore, the ventilation is important to keep the indoor environment clean and it can also save the energy consumption. In this study, a HEPA type nano ceramic filter is designed as a passive ventilation system to collect airborne particles and to supply fresh outdoor air. The double layer filter, which has $30{\mu}m$ in diameter at the conditions of 10wt% of concentration and 3kV/cm of the electric intensity, is produced by electrospinning. The filtration coating technology is confirmed in the solution with $SiO_2$ nano particles using polymer nano fibers. Also double layer filters are coated with $SiO_2$ nano particles and finally the porous construction materials are made by sintering in the electric furnace at $200{\sim}1400^{\circ}C$. The efficiency is measured 96.67% at the particle size of $0.31{\mu}m$, which is slightly lower than HEPA filter. However the efficiency is turned out to be sufficient.

• Composites Research
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• v.24 no.5
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• pp.39-43
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• 2011

For the last twenty years, nanocomposites composed of polymer matrices reinforced with carbon nanotubes (CNTs) have been an active research area. Also, the polymeric nanocomposites reinforced with CNTs are being investigated to be used matrices of carbon fiber composites. Carbon tiber composites have achieved advanced properties in the direction of carbon fibers due to enhanced carbon fiber properties. However, the matrix dominated properties need to be improved further to fully utilize the advanced carbon fiber properties. In particular, delamination is a typical and critical reason for fracture of carbon fiber composites. Mode I fracture toughness test which is also often called double cantilever beam (DCB) test shows the resistance to delamination of carbon fiber composites and this test is performed on carbon fiber composite samples incorporated with carbon nanotubes functionalized with various functional groups. The specimens with mat-like CNT layers showed the increased fracture toughness by 10.6%.