• Title, Summary, Keyword: NR

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Bifunctional Silane (TESPD) Effects on Silica Containing Elastomer Compound Part I: Natural Rubber (NR) (양기능성실란(TESPD)이 실리카함유 복합소재에 미치는 영향)

  • Kim, Kwang-Jea
    • Elastomers and Composites
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    • v.44 no.2
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    • pp.134-142
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    • 2009
  • Organo bifunctional silane (TESPD) is added into silica containing NR and its effects are investigated with respect to the vulcanization properties, the processability, and the physical properties. The addition of the TESPD into silica filled NR compound increases the degree of crosslinking by formation of a strong 3-dimensional network structure with silica surface via coupling reaction, which results in an improved mechanical property. It also improves the processabilities compared to the Control compound.

Abrasion Behaviors of NR/BR Compounds Using Laboratory Abrasion Tester

  • Son, Chae Eun;Yang, Seong Ryong;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.56 no.1
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    • pp.12-19
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    • 2021
  • The abrasion behaviors of NR/BR blend vulcanizates were investigated using NR/BR = 100/0, 80/20, and 60/40 compounds. The abrasion test was performed using a laboratory abrasion tester (LAT) at slip angles of 1° and 7°. The size distributions of the wear particles and the abrasion rates were examined according to the rubber compositions and slip angles. The most abundant wear particles at the slip angle of 1° were sizes above 1,000 ㎛, irrespective of the rubber composition. The most abundant wear particles at 7° slip angle had sizes in the range of 212-500 ㎛, except for the NR = 100 sample. The wear particle size distribution shifted to a smaller size as the slip angle and BR content increased. The abrasion rate at 7° was much larger than that at 1° slip angle. Furthermore, the abrasion rate was notably increased by adding BR to NR.

Preparation and Physical Properties of Blend Films of Natural Rubber and Chloroprene Rubber Latex (NR/CR 라텍스 블렌드 필름의 제조 및 물리적 특성)

  • Kim, Kong Soo;Park, Jun Ha;Eum, Ju Song
    • Applied Chemistry for Engineering
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    • v.7 no.4
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    • pp.691-697
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    • 1996
  • The NR films were prepared with mixing of natural rubber latex(NRL) with various additives, and NR/CR films were prepared by blend ratio of chloroprene rubber latex(CRL). The swelling degree and the mechanical properties of these films were measured according to the procure time. As a result, optimum condition were showed the swelling degree : 80~85%, precure time : 48~60hrs., and tensile strength was reduced but elongation was increased as increasing the blend ratio of CRL. On the mechanical properties of films prepared by different dipping process in these optimum condition, the tensile strength and tear strength of NR/CR films by one dipping process are better than NR-d-CR films by two dipping process. The surface of these films were observed with scanning electron microscopy(SEM). It was found that phase separation was occured as increasing the blend ratio of CRL.

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Effects of temperature on Hardness and Stiffness of NR and SBR Vulcanizates (NR과 SBR 가황물의 경도와 강성도 대한 온도의 영향)

  • Jin, Hyun-Ho;Hong, Chong-Kook;Cho, Dong-Lyun;Kaang, Shin-Young
    • Elastomers and Composites
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    • v.42 no.3
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    • pp.143-150
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    • 2007
  • Hardness of rubbery materials, which is important for dimensional stability and product performance, was investigated upon temperature change in this study. A newly developed IRHD (International Rubber Hardness Degree) tester was used to measure the hardness changes of NR and SBR specimens at various temperatures and the hardness values were compared with the Young's modulus. The harness and Young's modulus of NR and SBR showed an abrupt change near the glass transition temperatures. The hardness and Young's modulus were increased by increasing temperature due to the increased random chain conformation of molecules. The effect of temperature on hardness and Young's modulus of NR and SBR specimens filled with carbon black and silica was decreased by increasing filler content.

Preparation and Characterization of Rubber/Clay Nanocomposite Using Skim Natural Rubber Latex (스킴천연고무 라텍스를 이용한 고무/점토 나노복합체의 제조 및 특성)

  • Alex, R.;Kim, M.J.;Lee, Y.S.;Nah, C.
    • Elastomers and Composites
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    • v.41 no.4
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    • pp.252-259
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    • 2006
  • A new route for making rubber/clay nanocomposites was suggested based on skim natural rubber latex (SNRL), which is a protein rich by-product obtained during the centrifugal concentration of natural rubber (NR) latex. NR/acrylonitrile butadiene rubber (NBR) based nanocomposites were prepared from SNRL and NBR latex of 26 % acrylonitrile content by blending of aqueous dispersion of organoclay (OC) followed by coagulation, drying, mill mixing and vulcanization. X-ray diffraction(XRD) studies revealed that NR/NBR blend nanocomposites exhibited a highly intercalated and exfoliated structure, especially for NBR-rich blends. Dynamic mechanical studies showed that more compatible behavior was observed for NBR-rich blends. The 25/75 NR/NBR blend nanocomposite showed the best mechanical properties.

Effects of Nrogen Form and Light Conditions on the Nitrate Reductase Activity of Ulva pertusa (Chlorophyta) and Ecklonia cava (Phaeophyta) (구멍갈파래 (Ulva pertusa Kjellman)와 감태 (Ecklonia cava Kjellman)의 질산환원요소 활성에 미치는 질소원 형태와 빛의 효과)

  • Hwang, Jae-Ran;Kang, Yun-Hee;Oak, Jung-Hyun;Lee, Sang-Rae;Chung, Ik-Kyo
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.44 no.1
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    • pp.64-70
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    • 2011
  • Nitrate reductase (NR) is activated by nitrogen sources (${NO_3}^-$ and ${NH_4}^+$) and irradiance. This study investigated the effects of these factors on the NR activity of Ulva pertusa (Chlorophyta) and Ecklonia cava (Phaeophyta). In addition, the ammonium (${NH_4}^+$) and nitrate (${NO_3}^-$) uptake rates of the two species were examined. U. pertusa took up most of the ${NO_3}^-$ and ${NH_4}^+$ in the medium during a 3hour incubation, while E. cava had a relatively high uptake rate after 3 hours. The NR activities of the two species were affected by the nitrogen source and irradiance and were highest when they were exposed to ${NO_3}^-$-rich medium and high irradiance. However, the patterns of NR activity differed between the two species. In ${NO_3}^-$-rich medium and high irradiance, U. pertusa achieved the highest NR activity ($2.01{\pm}0.07\;{\mu}mol$ ${NO_2}^-$ $g^{-1}$ DW $h^{-1}$) within the first 3 hours and then this activity decreased drastically. By contrast, the NR activity of E. cava ($0.36{\pm}0.04\;{\mu}mol$ ${NO_2}^-$ $g^{-1}$ DW $h^{-1}$) was constant for 12 hours. When exposed to darkness, the NR activity of U. pertusa decreased dramatically, while that of E. cava increased gradually for 12 hours. Therefore, E. cava is able to maintain NR activity during the dark because of its adequate carbohydrate reserves and substrate.

Effects of Iron, Chelators and Nitrate Concentration on in vivo Fluorescence and Nitrate Reductase of the Red Tide Organism Amphidinium carterae

  • Yang, Sung-Ryull;Song, Hwan-Seok;Pae, Se-Jin;Huh, Sung-Hoi
    • Journal of the korean society of oceanography
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    • v.34 no.1
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    • pp.49-57
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    • 1999
  • A red tide organism, Amphidinium carterae was incubated under different iron/chelator and nitrate concentrations to investigate the factors controlling the growth. The chelation capacity played a critical role in regulating the nitrate reductase (NR) activity and in vivo fluorescence of this organism. However, there was a significant difference between the NR activity and in vivo fluorescence in response to trace metals and chelator treatments. In vivo fluorescence was the highest in FeEDTA 10 ${\mu}$M treatments and the lowest in DTPA 10 ${\mu}$M treatments. This indicates that the availability of the trace metal is important in regulating the in vivo fluorescence of this photosynthetic microalgae In contrast, NR activity showed the highest values in trace metal enriched treatments, and trace metal + DTPA treatments showed fairly high NR activities. This suggests that DTPA treatment did not hinder the NR activity as much as it did in vivo fluorescence. In vivo fluorescence and NR activity increased with nitrate concentration of up to 50 ${\mu}$M and remained relatively constant or the rate of increase decreased above that concentration, indicating that initial nitrate concentration of higher than a certain level would not accelerate the growth of A. carterae. Further investigation is needed to elucidate the reason for the difference in timing sequence between the NR and in vivo fluorescence in response to different metal treatments and chelation capacity.

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수평 구조 Zinc Oxide Nanorods 기반 센서의 전극 금속별 특성 비교

  • Lee, Jae-Hyeok;Kim, Seon-Min;Lee, Su-Min;Kim, Seong-Hyeon;Kim, Tae-Geun;Jo, Jin-U
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.377-377
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    • 2012
  • 반도체 물질로서 Zinc oxide (ZnO) nanorod (NR)는 Hydrothermal growth method로 제작 시 고가의 장비가 필요치 않기에 저비용 대면적 박막을 제작하는데 적합하지만 NR들의 array 조절과 각각의 rod와 전극 간의 연결에서 어려움을 가지고 있다. 최근 연구에서는 이러한 NR array 형상 조절과 소자의 성능 향상을 위하여 tilted sputtering method를 이용해 seed layer를 lateral 하게 형성하여 성장시켜 표면적을 극대화함으로서 응용되는 센서의 성능을 향상시키는 연구가 진행되고 있다. 본 연구에서는 이렇게 향상된 수평구조의 ZnO NR과 다양한 전극 금속 간의 schottky barrier의 높이 차이에 따라 sensitivity와 response time의 차이를 측정하였다. NR들을 전계방출형 전자현미경과 XRD로 분석 NR의 lateral structure 및 결정성을 확인하였다. 그리고 이렇게 형성한 NR을 소자화하여 Au, Ag, Al을 전극 금속물질로 사용한 경우에 대하여 sensing performance와 전극 금속의 schottky barrier의 상관관계를 확인하였다.

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Effects of CR Contents on Rubber Vulcanization and Mechanical Properties of NR/CR Blends (NR/CR 고무블랜드에서의 CR조성비가 가황 및 물성에 미치는 영향)

  • Ahn, Won-Sool;Park, Dong-Ryul
    • Elastomers and Composites
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    • v.46 no.2
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    • pp.152-157
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    • 2011
  • Effects of CR contents in NR/CR blends on the vulcanization kinetics and miscibility were studied by dynamic DSC and TGA, as well as the mechanical properties. While the vulcanization activation energy showed a constant value of $77.5{\pm}2.5$ kcal/mol regardless of CR contents, reaction rate, however, was observed to be somewhat lowered at increased CR contents. Partial miscibility was found between NR and CR phases at lower CR content of 3 wt%, but immiscibility was observed at higher CR content of 21 wt%. Mechanical properties were also affected by this miscibility, showing linear increase of compression set but decrease of tensile strength with CR contents in the blends.

Cloning and Sequence Analysis of Spinach (Spinacia oleracea L. cv Ace) Nitrate Reductase cDNA (시금치 nitrate reductase cDNA 클로닝 및 염기서열 분석)

  • Park, Nu-Ri;Chung, Jong-Bae;Park, Sang-Gyu
    • Applied Biological Chemistry
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    • v.45 no.3
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    • pp.129-133
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    • 2002
  • Suppression of nitrate accumulation in spinach and lettuce through foliar application of chitosan formula containing micronutrients is related with the increase of the nitrate reductase (NR) activity. If NR in spinach were highly expressed to increase the assimilatory activity, nitrate content could be reduced. For this, NR cDNA was cloned from the isolated mRNAs of spinach using reverse transcriptase-PCR. Nucleotide sequence of cloned spinach NR cDNA showed highly deduced amino acid sequence identity ($71{\sim}82%$) with other known plant NR genes. Only two nucleotide-base differences were observed in the cloned NR cDNA compared with that of the published spinach NR cDNA.