• Composites Research
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• v.31 no.4
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• pp.133-138
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• 2018

Polymer foams were used to fill the void in the structure in addition to flame retardant and heat insulation. Polymer foams such as polyurethane, polyisocyanurate, poly(vinyl chloride), polyethylene terephthalate were used to weight lighting materials. In this study, epoxy foam was used to improve mechanical properties of polymer foam. Acid anhydride type hardener reacts with polyol. Using this phenomenon, if blowing agent was added into epoxy resin using acid anhydride type hardener, formation and compressive properties of epoxy foam was studied. Formation of polymer foam was compared with type of blowing agent and concentration of blowing agent via compressive test. As these results, optimized condition of epoxy foam was found and epoxy foam had better compressive property than other polymer foam.

• Composites Research
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• v.31 no.4
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• pp.122-127
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• 2018

Sandwich composites of carbon fiber reinforced plastic(CFRP) and polymer foam will be used to automobile and aerospace industry according to increasing importance of light weight. In this study, mechanical and heat resistance properties of sandwich composites were compared with type of polymer foam (polyethylene terephthalate(PET), polyvinylchloride(PVC), epoxy and polyurethane). All types of polymer foams were degraded to 30, 60, 120, 180 minutes in $180^{\circ}C$. After heat degradation, the polymer foams were observed using optical microscope and compressive test was performed using universal testing machine(UTM). Epoxy foam had the highest compressive property to 2.6 MPa and after thermal degradation, the mechanical property and structure of foam were less changed than others. Epoxy foam had better mechanical properties than other polymer foams under high temperature. Because the epoxy foam was post cured under high temperature. As the results, Epoxy foam was optimal materials to apply to structures that thermal energy was loaded constantly.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.91-91
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• 2010

본 논문은 펄스 직류전원 (Pulse DC) 플라즈마 소스와 반응성 가스인 $CF_4$와 불활성 가스인 Ar를 혼합하여 산업에서 널리 사용되는 유기고분자인 Polymethylmethacrylate (PMMA), Polyethylene terephthalate (PET), 그리고 Polycarbonate (PC) 샘플을 건식 식각한 결과에 대한 것이다. 각각의 샘플은 감광제 도포 후에 자외선을 조사하는 포토레지스트 방법으로 마스크를 만들었다. 펄스 직류전원 플라즈마 시스템을 사용하면 다양한 변수를 줄 수 있다는 장점이 있다. 공정 변수는 Pulse DC Voltage는 300 - 500 V, Pulse DC reverse time $0.5{\sim}2.0\;{\mu}s$, Pulse DC Frequency 100~250 kHz 이었다. 변수 각각의 값이 높아질수록 고분자의 식각률이 높아졌다. 특히, PMMA의 식각률이 가장 높았으며 PET, PC 순이었다. 샘플 중 PC의 식각률이 가장 낮은 이유는 고분자 결합 중에 이중결합의 벤젠 고리 모양을 포함하고 있어 분자 결합력이 비교적 높기 때문으로 사료된다. 기계적 펌프만을 사용한 공정 전 압력은 30 mTorr이었다. 쓰로틀 밸브를 완전 개방한 상태에서 식각 공정 중 진공 압력은 $CF_4$ 가스유량이 늘어날수록 증가하였다. 식각률 역시 $CF_4$ 가스유량(총 가스 유량은 10 sccm)이 많을수록 증가함을 보여주었다 (PMMA: 10 sccm $CF_4$에서 330 nm/min, 3.5 sccm $CF_4$/6.5 sccm Ar에서 260 nm/min., PET: 10 sccm $CF_4$에서 260 nm/min, 3.5 sccm $CF_4$/6.5 sccm Ar에서 210 nm., PC: 10 sccm $CF_4$에서 230 nm, 3.5 sccm $CF_4c$/6.5 sccm Ar에서 160 nm). 이는 펄스 직류전원 플라즈마 식각에서 $CF_4$와 Ar의 가스 혼합비를 조절함으로서 고분자 소재의 식각률을 적절히 변화시킬 수 있다는 것을 의미한다. 표면 거칠기는 실험 후 표면단차 측정기와 전자 현미경 등을 이용하여 식각한 샘플의 표면을 측정하여 알 수 있었다. 실험전 기준 샘플 표면 거칠기는 PMMA는 1.53nm, PET는 3.1nm, PC는 1.54nm 이었다. 식각된 샘플들의 표면 거칠기는 PMMA는 3.59~10.59 nm, PET은 5.13~11.32 nm, PC는 1.52~3.14 nm 범위였다. 광학 발광 분석기 (Optical emission spectroscopy)를 이용하여 식각 공정 중 플라즈마 발광특성을 분석한 결과, 탄소 원자 픽 (424.662 nm)과 아르곤 원자 픽 (751.465 nm, 763.510 nm)의 픽의 존재를 확인하였다. 이 때 탄소 픽은 $CF_4$ 가스에서 발생하였을 것으로 추측한다. 본 발표를 통해 펄스 직류전원 $CF_4$/Ar의 고분자 식각 결과에 대해 보고할 것이다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.114-123
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• 2013

This study was performed to verify the structural reinforcing effect of recycled polyethylene terephthalate (PET) fiber. In order to verify the structural reinforcing capacity of RPET fiber, recycled PET fiber added RC slab specimens were prepared to examine the flexural capacity while those of plain concrete and those of added with PP fiber, and the behavior of the specimens were also evaluated. The result shows that the compressive strength reduces as the fiber volume fraction increases, and the rate of reduction varies from 2% to 7%. The result of the flexural capacity shows that the ultimate capacity of plain specimens is the highest compare to those fiber reinforced specimens, but it has shown that specimens reinforced by 5% PET fiber has the highest energy absorption and the ductility index. In the application of PET fiber in slab specimens has shown that ductility capacity have increased where the ultimate capacity decreasing. That is the different tendency of beam specimens, which the ultimate capacity and the ductility of those have both shown the improvement compare to plain concrete specimens, which means the reinforcing effect of PET fiber in slab is less strong than in beam. Therefore, the application of PET fiber in slab structures as reinforcement needs the proper mix proportion of concrete and volume fraction of PET fiber with deep consideration of the structures.

• Journal of Life Science
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• v.25 no.12
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• pp.1445-1449
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• 2015

The pinewood nematode Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) poses a serious threat to pine forests in Europe and East Asia, leading to a debilitating pine wilt disease. Infected pine trees in Korea are generally fumigated or crushed to small wood chips after felling. Although pine wilt disease often recurs in pest management sites, there are no adequate means to monitor the effectiveness of pest control measures in those sites. Recently, a male-produced aggregation pheromone, 2-(undecyloxy)ethanol, was shown to be useful for attracting several Monochamus species, which are vectors for the pinewood nematodes. In this study, we investigated the abilities of 2-(undecyloxy)ethanol at three different doses (175, 350, and 700 mg), as well as host plant volatiles (α-pinene and ethanol), to attract M. alternatus (Coleoptera: Cerambycidae) at a pine forest in Pohang, Korea where infected pine trees had been cut down and fumigated. Twenty-seven M. alternatus were captured in cross-vane panel traps made of polyethylene terephthalate bottles and acrylic sheets. The results indicate that a high dose of 2-(undecyloxy)ethanol (700 mg per trap) is the most effective for attracting M. alternatus. The aggregation pheromone could be used to monitor the effectiveness of pest control measures as well as M. alternatus populations.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.202-202
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• 2012

유연성 투명 전도막은 현대 전자산업의 발전에 있어 필수적인 부품소재로서, 가시광선의 투과율이 80% 이상이고 면저항이 $100{\Omega}/sq.$ 전후이며 휘거나 접히고 나아가 두루마리의 형태로도 응용이 가능한 소재를 일컫는다. 이러한 유연성 투명 전도막은 차세대 정보디스플레이 산업 및 유비쿼터스 사회의 중심이 되는 유연성 디스플레이, 터치패널, 발광다이오드, 태양전지 등 매우 다양한 분야에 응용이 기대된다. 이러한 이유로 고 신뢰성 유연성 투명 전도막 개발기술은 차세대 산업에 있어서의 핵심기술로 인식되고 있다. 현재로서는 인듐 주석 산화물(indium tin oxide; ITO) 및 전도성 유기고분자를 사용하여 투명 전도막을 제조하고 있으나, ITO 박막의 경우 인듐 자원의 고갈로 인한 가격상승 및 기판과의 낮은 접착력, 열팽창계수의 차이로 인한 공정상의 문제, 산화물 특유의 취성으로 인한 유연소자로서의 내구성 저하 등의 문제가 제기되고 있다. 전도성 유기고분자의 경우는 낮은 전기전도도와 기계적강도, 유기용매 처리 등의 문제점이 지적되고 있다. 따라서 높은 전기전도도와 투광도 뿐만 아니라 유연성을 지니는 재료의 개발이 요구되고 있는 실정이다. 최근 이러한 재료로서 그래핀(graphene)과 탄소나노튜브(carbon nanotube; CNT)를 중심으로 하는 탄소나노재료가 주목받고 있으며 많은 연구가 활발히 진행되고 있다. 본 연구에서는 열화학기상증착법(thermal vapor deposition; TCVD)으로 합성된 그래핀 및 CNT를 이용하여 탄소나노재료 복합체 기반의 유연성 투명 전도막을 제작하고 그 특성을 평가하였다. 그래핀과 CNT합성을 위한 기판으로는 각각 300 nm 두께의 니켈과 1 nm 철이 증착된 실리콘 웨이퍼를 이용하였으며, 원료가스로는 메탄(CH4)과 아세틸렌(C2H2)등의 탄화수소가스를 이용하였다. 그래핀의 경우 원료가스의 유량, 합성온도, 냉각속도를 변경하여 대면적으로 두께균일도가 높은 그래핀을 합성하였으며, CNT의 경우 합성시간을 변수로 길이 제어합성을 도모하였다. 합성된 그래핀은 식각공정을, CNT는 스프레이 증착공정을 통해 고분자 기판(polyethylene terephthalate; PET) 위에 순차적으로 전사 및 증착하여 탄소나노재료 복합체 기반의 유연성 투명 전도막을 제작하였다. 제작된 탄소나노재료 복합체 기반의 유연성 투명 전도막은 물리적 과부하를 받았을 때 발생할 수 있는 유연성 투명 전도막의 구조적결함에 기인하는 전도성 저하를 보상하는 특징이 있어, 그래핀과 탄소나노튜브 각각으로 제조된 유연성 투명 전도막보다 물리적인 하중이 반복적으로 인가되었을 때 내구성이 향상되는 효과가 있다. 40% 스트레인을 반복적으로 인가하였을 때 그래핀 투명 전도막은 20 사이클 이후에 면저항이 $1-2{\Omega}/sq.$에서 $15{\Omega}/sq.$ 이상으로 급증한 반면 그래핀-CNT 복합체 투명 전도막은 30사이클까지 $1-2{\Omega}/sq.$ 정도의 면저항을 유지하였다.

• Polymer(Korea)
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• v.30 no.2
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• pp.140-145
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• 2006

The mort commonly available substrate material is glass in the display fibrication process. However, glass is not desirable due to its heaviness and fragility. Recently, plastics such polysulfone (PSF), polyethesulfone (PES), polycarbonate (PC), polyethylene terephthalate (PET) and cyclic olefin polymers (COP) have been investigated to replace glass as a substrate material for display fibrication. Plastic substrates are advantageous in that they are lightweight, huh impart resistance, flexibility, and ability for roll to roll manufacturing process. But many plastics have poor chemical resistance in organic solvent. The chemica resistance is also lequired because they are exposed to solvents for various chemical treatments din the manufacturing process. So, we have an interest in the chemical modification of PSF to improve chemical resistance. We introduced crosslinkable imide moieties using chloromethylation method for the modification of PSF which could be overcome above shortcomings for display substrate based on plastic film. We prepared the cross-linked polysulfone films which were represented chemical resistance in HeOH, THF, DMSO and NMP. The thermal properties were measured by TGA, DSC and TMA. As the results, we have confirmed to enhance of the thermal property. They had low coefficient of thermal expansion (CTE) which decreased to 15% and had increased $T_g\;from\;180^{\circ}C\;to\;252^{\circ}C$. Cross-linked polysulfone films with imide side-chain had good optical properties and chemical resistance so that they could be used as flexible display substrate.

• Journal of Korean Society on Water Environment
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• v.30 no.2
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• pp.199-205
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• 2014

The knowledge on the migration of antimony (Sb) from PET bottles into the water is of greate concern. Antimony in all bottled water marketed in korea and in raw water was analyzed. The detection rate of antimony in total bottled water was 88 % and 100% in PET (Polyethylene terephthalate, PET), 55% in PC (Polycarbonate, PC) bottled water. 55% of raw water contained antimony. The average concentration of Sb in PET bottled water was $0.39{\mu}g/L$, higher than PC bottles ($0.20{\mu}g/L$) and the raw water ($0.22{\mu}g/L$). The migration of Sb into water that is stored in different conditions (room temperature, $45^{\circ}C$, and direct sunlight exposure) was investigated for 180 days. The migration tendency increased with the storage time and temperature. PET bottles showed a sharp increase of Sb concentration at $45^{\circ}C$, but there was no differences between the room temperature and sunlight exposure. The Sb migration in all simulated solution(deionized water, 4% acetic acid, and 20% ethanol) also increased with storage time and temperature. The Sb migration values ranged from 0.35 to $0.49{\mu}g/L$ in all simulated solution, which was far below the permissible korean migration level of $40{\mu}g/L$. There was a tendency that the number of re-use of a bottle and the amount of leaching were in inverse proportion.

• Journal of the Korean Society of Food Science and Nutrition
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• v.37 no.2
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• pp.231-238
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• 2008

Quality attributes of fresh-cut sesame leaf (Perilla frutescens var. japonica) as affected by hydrocooling and packing were investigated in terms of weight loss, respiration, vitamin C content, total chlorophyll content, microbial load and sensory properties during storage at 4 and $10^{\circ}C$. Fresh sesame leaf was trimmed and washed with cold water (1, $5^{\circ}C$) as well as tap water ($13^{\circ}C$) for 30 sec 3 times and then packaged in PP (polypropylene) film bag and PETE (polyethylene terephthalate) tray, and stored for 9 days at 4 and $10^{\circ}C$. Weight loss was decreased by washing and packing. Respiration rate was increased slowly over the storage at $4^{\circ}C$. Vitamin C content and total chlorophyll contents of sesame leaf packaged within PETE tray decreased gradually during storage. Hydrocooling and packing within PETE tray treatments resulted in approximately $1{\sim}2\;log\;CFU/g$ reduction of microbial load.

• Food Science and Preservation
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• v.15 no.1
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• pp.1-8
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• 2008

Quality attributes of fresh-cut pak-choi (Brassica campestris var. chinensis) as affected by hydrocooling and packing were investigated in terms of weight loss, respiration, vitamin C content, total chlorophyll content, microbial load and sensory properties during storage at 4 and $10^{\circ}C$. Fresh pak-choi was trimmed and washed with cold water $(1^{\circ}C)$ as well as tap water $(6^{\circ}C)$ for 30 sec 3 times and then packaged in PP (polypropylene) film bag and PETE (polyethylene terephthalate) bay, and stored for 9 days at 4 and $10^{\circ}C$. Weight loss was decreased by washing and packing generally. Respiration rate was increased slowly over the storage at $4^{\circ}C$. Vitamin C content and total chlorophyll contents of pak-choi packaged within PETE bay decreased gradually during storage. Hydrocooling and packing within PETE bay treatments resulted in approximately 1-2 log CFU/g reduction of microbial load.