• 공업화학
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• 제9권4호
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• pp.523-528
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• 1998

본 연구에서는 고체전해질셀 내에서 작업전극으로 사용된 $V_2O_5$의 전기화학적 특성을 알아보기 위해 YSZ를 고체전해질로 사용하여 전기화학셀(1-Butene+$O_2$, $V_2O_5{\mid}YSZ{\mid}Ag$, $O_2$)을 구성하였다. 상대전극인 Ag는 소성에 따라 sintering이 일어나고 $3{\mu}m$ 이상의 기공을 갖는 구조를 얻었다. 작업전극은 소성조건에 따라 부분산화반응에 영향을 주는 (010)면이 발생되었다. $V_2O_5$의 1-부텐에 대한 주요생성물은 부타디엔이었고 SEP (solid electrolyte potentiometry) 기술을 이용하여 작업전극상에 흡착된 화학종의 화학포텐셜을 측정하였다. 가스조성에 따른 개로전위 (OCV; open circuit voltage)를 측정하여 표면 산소종에 혼합전위의 발생을 확인하였다.

• Elastomers and Composites
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• 제38권3호
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• pp.251-261
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• 2003

본 연구에서는 폐타이어 고무분말 (GTR)과 일부 난연제를 포함한 acrylonitrile-butadiene rubber (NBR) 발포체를 제조하고, 난연 및 발포특성에 GTR이 미치는 영향을 조사하였다. 그결과 고무/난연제의 조성비가 $1/1.95{\sim}3.70 wt%$이며, GTR의 함량이 20 wt% 범위 이내에서 원활한 핵의 생성 및 cell의 성장으로 인해 높은 발포율 ($215{\sim}300 %$)과 균일한 닫힌/반 닫힌 셀(closed/semi-closed cell)을 보여주었으며, 높은 LOI ($29.4{\sim}40.0$)와 낮은 (A)-HRR을 보임을 확인하였다. 또한 GTR의 함량이 증가함에 따라 자체적인 난연 특성으로 인해 LOI가 증가하고, HRR이 감소하는 반면에 (A)-COY는 증가함을 확인하였다.

• Korean Chemical Engineering Research
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• 제52권2호
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• pp.266-271
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• 2014

Polycarbonate/Acrylonitrile-Butadiene-Styrene(PC/ABS) 블렌드의 분해효과를 조사하기 위해 고전단 압출 성형기의 스크류 회전속도와 전단시간의 함수로 PC/ABS의 물성변화에 영향을 미치는 산화방지제의 효과를 연구하였다. 인산계 산화방지제로 Tris-(2,4-di-tert-butyl-phenyl phosphate) (이후 A1로 명명) and Bis(2,4-dicumylphenyl) pentaerythritol diphosphite(이후 A3로 명명)가 사용되었고, 페놀계 산화방지제는 Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate(이후 A2로 명명)가 사용되었다. 열적 물성은 TGA를 통해 측정되었고 고속 전단 가공 후 크게 감소하였다. 산화방지제 A3가 포함된 PC/ABS 블렌드는 다른 산화방지제에 비해 스트레스로 유발된 degradation과, 열적 degradation이 지연되었다. 고속 전단 가공 후 UTM을 사용한 기계적 물성 또한 산화방지제 종류에 따라 각각 감소하였고, 특히, 신율의 경우 크게 감소하는 거동이 나타난 것에 비해 인장강도의 변화는 매우 적었다. 스크류 회전속도 1000 rpm, 전단부하 시간 20초 조건에서의 신율로 예를 들면, 고속 전단 가공하기 전 신율인 148%에서 A1은 91.6%, A2는 63%, A3은 131%로 감소하였다. 형태학적 물성을 알기 위해 SEM을 사용하여 PC/ABS의 분산상을 조사하였고, 스크류 회전속도와 하중이 작용한 기간이 증가함에 따라 그 크기 분포가 감소하였다. 따라서, 세 종류 산화방지제 모두 고속 전단 가공에서 스트레스로 유발되는 PC/ABS 블렌드의 degradation을 억제하고, 그 효과는 A3가 가장 뛰어난 것을 확인하였다.

• 한국산업보건학회지
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• 제32권2호
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• pp.153-162
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• 2022

Objectives: Fused deposition modeling (FDM) 3D printer which is one of the material extrusion (MEX) technologies is an additive manufacturing (AM) process. 3D printers have been distributed widely in Korea, particularly in school and office, even at home. Several studies have shown that nanoparticles and volatile organic compounds (VOCs) were emitted from an FDM 3D printing process. The objective of this study was to identify types of chemicals possibly emitted from FDM 3D printing materials such as PLA (polylactic acid), ABS (acrylonitrile butadiene styrene), nylon, PETG (polyethylene terephthalate glycol), PVA (polyvinyl alcohol), PC (polycarbonate) filaments. Methods: 19 FDM 3D printing filaments which have been distributed in Korea were selected and analyzed VOCs emitted of 3D printing materials by headspace gas chromatography mass spectrometry (headspace GC-MS). Subsamples were put into a vial and heated up to 200℃ (500 rpm) during 20 minutes before analyzing FDM 3D printing filaments. Results: In the case of PLA filament, lactide and methyl methacrylate, the monomer components of one, were detected, and the volume ratio ranged 27~93%, 0.5~37% respectively. In the case of ABS filaments, styrene (50.5~59.1%), the monomer components of one, was detected. Several VOCs among acetaldehyde, toluene, ethylbenzene, xylene, etc were detected from each FDM 3D printing filaments. Conclusions: Several VOCs, semi-VOCs were emitted from FDM 3D printing filaments in this study and previous studies. Users were possibly exposed to ones so that we strongly believe that we recommend to install the ventilation system such as a local exhaust ventilation (LEV) when they operate the FDM 3D printers in a workplace.

• Environmental Engineering Research
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• 제14권4호
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• pp.212-219
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• 2009

Emission characteristics of air pollutants from three commercially operating cement kilns co-burning waste were investigated. The major heavy metals emitted were mercury (Hg), zinc (Zn), nickel (Ni), chromium (Cr), lead (Pb), cadmium (Cd), and arsenic (As) Removal efficiency of the bag filter was above 98.5% for heavy metals (except Hg), and above 60% for Hg. Higher fractions of heavy metals entering the bag filter were speciated to cement kiln dust. On average, 3.3% of the -heavy metals of medium and low toxicity (Pb, Ni, and Cr) entering the bag filter were released into the atmosphere. Among highly toxic heavy metals, 0.14% of Cd, 0.01% of As, and 40% of Hg entering the bag filter were released into the atmosphere. In passing through the bag filter, the proportion of oxidized Hg in all cases increased. Emission variations of hazardous air pollutants in cement kilns tested were related to raw materials, fuel, waste feed and operating conditions. Volatile organic compounds detected in gas emissions were toluene, acrylonitrile benzene, styrene, 1,3-butadiene, and methylene chloride. Although hazardous air pollutants in emissions from cement kilns co-burning waste were within the existing emission limit, efforts are required to minimize their levels.

• Environmental Analysis Health and Toxicology
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• 제17권2호
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• pp.95-107
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• 2002

This study was designed to investigate the characteristics of atmospheric concentrations of toxic volatile organic compounds (VOCs) in Korea. Target compounds included 1,3-butadiene, aromatics such as BTEX, and a number of carbonyl compounds. In this paper, as the first part of the study, the performance of sampling and analytical methods was evaluated for the measurement of selected VOCs and carbonyl compounds in the ambient air. VOCs were determined by the adsorbent tube sampling and automatic thermal desorption coupled with GC/MSD analysis, while carbonyls by the DNPH-silica cartridge sampling with HPLC analysis. The methodology was investigated with a wide range of performance criteria such as repeatability, linearity. lower detection limits, collection efficiency, thermal conditioning, breakthrough volume and calibration methods using internal standards. In addition, the sampling and analytical methods established in this study were applied to real field samples duplicately collected in various ambient environments. Precisions for the duplicate samples appeared to be comparable with the performance criteria recommended by USEPA TO-17. The overall precision of the sampling and analytical methods was estimated to be within 20 ∼ 30% for major aromatic VOCs such as BTEX, whereas the precision for major carbonyl compounds such as formaldehyde and acetaldehyde was within 10 ∼ 20% for field samples. This study demonstrated that the adsorbent sampling and thermal desorption method can be reliably applied for the measurement of BTEX in ppb levels frequently occurred in common indoor and ambient environments.

• 한국산업융합학회 논문집
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• 제2권1호
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• pp.69-75
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• 1999

Intending to develop a new rubber curing process using only microwave, the both the characteristics of cure and the mechanical properties of rubbers for the tire tread, for which a green styrene-butadiene compounds had been cured with 2.45 GHz microwave, have been compared with those of the custom thermal cured rubber. The unintentional hot spot formation in the compound during the microwave curing has not found where the compound has a microwave absorbing ceramic powders in 4.18 weight percents and the supplying voltage has been adjusted to 90 volts. The new microwave process accomplished preheating to 418K in a quarter of the thermal cure time. The average tensile strength of the microwave-cured rubber indicating $190kg/cm^3$ was compatible to that of the thermal cure. In conclusion, the new microwave cure had approved to be applicable in a commercial plant.

• Food Science and Biotechnology
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• 제16권2호
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• pp.290-293
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• 2007

Cassumunar ginger (Zingiber montanum Roxb.) was grown in the experimental field at the Department of Horticulture, Kasetsart University, Thailand. The antioxidant activity and volatile oil content of rhizomes of varying age were measured. Antioxidant activity as determined using the DPPH (diphenyl-2-picrylhydrazyl) method differed significantly between samples of different ages. Antioxidant activity and rhizome age were positively correlated, with 22-month old rhizomes showing the highest radical scavenging activity (79.19%). Volatile oil was obtained by steam distillation of fresh rhizomes. The extraction yield of volatile oil was highest in l6-month old rhizomes (13.02 mL/kg). GC-FID data indicated the presence of three major compounds, sabinene, terpinen-4-ol and (E)-1-(3',4'-dimethylphenyl) butadiene (DMPBD), however none of the major components were correlated with the age of rhizome.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.651-655
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• 2004

This paper studies the designing method and application for grommets, rubber material used to absorb vibration on the air conditioner compressor. The existing grommet with hardness 40 degrees, EPDM, has the high transmissibility on the compressor that causes additional structure born sound. The problem for EPDM is transformation over long time usage possibly due to its design in which stress is concentrated on a certain position. In order to resolve it, silicon material was previously used with the same design in some models. The vibration performance did improve, but the cost became high. Below are the major developments regarding improvements in compressor rubber material, vibration performance and durability through design change, and new grommet to attain cost reduction. 1 The optimum grommet design for stress even distribution through FEM methods. 2. Comparison for grommet material and design for improved transmissibility. 3. Assess for grommets durability and product applications.

• Elastomers and Composites
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• 제42권1호
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• pp.9-19
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• 2007

본 연구에서는 카본블랙과 유기화 클레이(C18-MMT) 로 보강된 SBR 나노 복합재료를 라텍스법(latex method)으로 제조하였다. 필러의 함량은 50 phr로 고정하였으며, 카본 블랙/C18-MMT의 함량비를 50/0, 49/1, 48/2, 47/3, 45/5, 44/6, 40/10 phr로 정하고 함량비에 따른 가황 특성 및 기계적 물성을 비교하였다. 각 컴파운드의 가황 특성 및 기계적 물성을 비교 평가한 결과 carbon black(49phr)/C18-MMT(1phr) 컴파운드가 ODR에서 가장 높은 최대 토크 값을 나타내었으며, 높은 인장 강도 및 모듈러스, 인열 에너지를 나타내었다. 이러한 기계적 물성 증가는 클레이의 박리 정도 및 분산도의 향상으로 인한 C18-MMT의 우수한 보강 효과 때문이라고 판단된다.