• Title/Summary/Keyword: Polymer Material

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Effects of Calcinations Temperature on the Electrochemical Properties of Li[Ni0.6Co0.2Mn0.2]O2 Lithium-ion Cathode Materials (리튬 이차전지용 양극활물질 Li[Ni0.6Co0.2Mn0.2]O2의 소성 온도가 전기화학적 특성에 미치는 영향)

  • Yoo, Gi-Won;Jeon, Hyo-Jin;Son, Jong-Tae
    • Journal of the Korean Electrochemical Society
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    • v.16 no.2
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    • pp.59-64
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    • 2013
  • Using $Na_2CO_3$ and $MeSO_4$ (Me = Ni, Co and Mn) as starting materials, the precursor of $[Ni_{0.6}Co_{0.2}Mn_{0.2}]CO_3$ has been synthesized by carbonate co-precipitation. The precursor was mixed with $Li_2CO_3$, and calcined at 750, 850, and$950^{\circ}C$ in air. Effect of calcinations temperature on characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ cathode materials was investigated. The structure and characteristics of $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ were determined by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and electrochemical measurements. The X-ray diffraction (XRD) results show that the intensity ratio of $I_{(003)}/I_{(104)}$ increased and the R-factor ratio decreased with the increase of calcinations temperature. And Scanning electron microscopy (SEM) result show that the primary particle size increased. Especially, the $Li[Ni_{0.6}Co_{0.2}Mn_{0.2}]O_2$ calcined at $950^{\circ}C$ for 24 H shows excellent electrochemical performances with reversible specific capacity of $165.3mAhg^{-1}$ [cut-off voltage 2.5~4.3 V, 0.1 C($17mAhg^{-1}$)] and good capacity retention of 95.4% after 50th charge/discharge cycles[cut-off voltage 2.5~4.3 V, 1 C($170mAhg^{-1}$)].

Enhancement of Skin Permeation of Pyrus serotina var Leaf Extract Using Polymer Micelle and Liposome Containing Cell Penetrating Peptide (세포투과 펩티드를 함유한 고분자 미셀 및 리포좀을 이용한 배나무 잎 추출물의 피부 흡수 증진)

  • An, Gyu Min;Park, Su In;Kim, Min Gi;Heo, Soo Hyeon;Shin, Moon Sam
    • Journal of the Korean Applied Science and Technology
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    • v.36 no.3
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    • pp.685-699
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    • 2019
  • Antioxidant, antibacterial, and skin penetration tests were conducted to investigate the skin absorption of Pyrus serotina var leaf extracts using polymer micelles and their applicability to cosmetic ingredients. Total polyphenol content was found to be $118.83{\pm}9.39mg/g$ in Pyrus serotina var leaf ethanol extract and $106.89{\pm}4.45mg/g$ in Pyrus serotina var leaf hydrothermal extract. The DPPH radical scavenging activity was found to be the highest radical scavenging activity of $74.39{\pm}7.48%$ of the Pyrus serotina var leaf ethanol extract at the concentration of 500 mg/L. The SOD-like activity was $91.62{\pm}0.43%$, the highest value at the concentration of 1,000 mg/L in the hydrothermal extract. After the experiment, antioxidation, wrinkle improvement and whitening activity were confirmed, and the Pyrus serotina var leaf extract was highly likely to be realized as antioxidant and antibacterial material. In the skin penetration experiment with the Pyrus serotina var leaf ethanol extract, the permeation amount of total accumulated tannic acid was found to be Formulation 2 ($55.45{\mu}g/cm^2$), Formulation 1 ($46.43{\mu}g/cm^2$), Formulation 0 ($34.36{\mu}g/cm^2$). In the liposome's skin penetration experiment containing pear leaf hydrothemal extract, the total amount of accumulated tannic acid permeation was found to be Formulation 5 ($75.01{\mu}g/cm^2$), Formulation 4 ($64.01{\mu}g/cm^2$) and Formulation 3 ($36.60{\mu}g/cm^2$). Through this study, we confirmed the possibility of antioxidant and wrinkle effects of Pyrus serotina var leaf extract. In addition, as a result of skin penetration through the production of polymer micelles and liposome containing Pyrus serotina var leaf extract, It will be more usable in cosmetic industry.

Physical Properties of the Hydrogel Using Alginate (Alginate가 포함된 하이드로겔의 물리적 특성)

  • Woo, Chul-min;Heo, Seongin;Lee, Hyun Mee
    • Journal of Korean Ophthalmic Optics Society
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    • v.20 no.4
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    • pp.463-469
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    • 2015
  • Purpose: A hydrogel including alginate and $CaCl_2$ extracted from seaweed was manufactured, and their physical properties were investigated. Also, its applicability as contact lenses was examined. Methods: A film-type sample used in this experiment was manufactured using 2-hydroxyethyl methacrylate (HEMA), which is the raw material of hydrogel contact lenses; azobisiobutyonitile (AIBN), which is an initiator and ethylenglycoldimethacrylate (EGDMA), which is a cross-linking agent. It was hydrated in a PBS solution for 24 hours, and an interpenetrating polymer network (IPN) was formed in 1% and 2% alginate and 1%, 3%, and 5% $CaCl_2$ solutions for 24 hours, respectively. Results: The measurement of the physical properties of the film after the IPN showed that the moisture content was 30.89~36.89%, the refractive index was 1.431~1.441, the contact angle was $62.98{\sim}80.45^{\circ}$, and the tensile strength was 2.378~4.215 ($gf/mm^2$). Also, the physical properties hardly changed as the content of alginate increased, and the moisture content decreased as the content of $CaCl_2$ increased. As a result of the IPN, the moisture content and contact angle decreased compared to those of basic HEMA, but the tensile strength increased. The tensile strength of the second IPN was higher than that of the first IPN. In the case of $CaCl_2$, for the sample polymerized for 24 hours and the second IPN sample with 2% alginate, the contact angle decreased as the content of $CaCl_2$ increased. Conclusions: In this study, the tensile strength increased as the content of $CaCl_2$ increased, and the wettability increased as a result of IPN of alginate and $CaCl_2$. The hydrogel containing the alginate and $CaCl_2$ was confirmed possible utilization as contact lens material.

Case Study on Determination of the Level of New RoHS II Substances in Domestic Electronic and Electrical Equipments (국내 전기전자 제품에 함유된 신규 RoHS II 물질 검출 사례 연구)

  • Song, Moon-Hwan;Son, Seung-Hwan;Cho, Young-Dal;Choe, Eun-Kyung
    • Clean Technology
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    • v.17 no.2
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    • pp.124-133
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    • 2011
  • In addition to six substances regulated in EU RoHS including lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE), priority substances are identified in new RoHS II as hexabromocyclododecane (HBCDD), dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and diethylhexyl phthalate (DEHP). In this study, 20 plastic samples were collected from 12 domestic electrotechnical companies and levels of four restricted substances were determined by gas chromatography-mass spectrometry, Among 20 parts that compose washer, refrigerator or microwave oven, HBCDD was detected in three samples of NBR material with the amount of 42~381 mg/kg while DBP and BBP was not detected in any samples collected respectively, implying that these substance may not be used widely in plastic materials for EEE. However, DEHP was detected in all samples of NBR, PP, PBT, EPDM and PVC materials with the amount of 42 up to 59,400 mg/kg that exceeds the limit value of 0.1 wt% (1,000 mg/kg). Presence of a restricted substance in polymer material makes a great negative influence on a number of final product. To cope with coming RoHS II as well as REACH, action not to use DEHP in plastic material or the relevant notification in case of REACH seems to be needed. Screening test of Arsenic compounds such as diarsenic pentaoxide, diarsenic trioxide, lead hydrogen arsenate, triethyl arsenate that are included in REACH SVHC was done by ICP measurement Arsenium was detected in four samples made of NBR and PBT materials in the level of 15~700 mg/kg. By considering the screening method used in this study, the amount of arsenium compounds in the thermistor made of PBT material has a high chance of exceeding the regulated limit value.

Preparation and Properties of Crosslinked Thermo-responsive Poly(N-isopropylacrylamide) Gel Materials For Smart Windows - Effect of Glycerol Content in Water/Glycerol Solvent - (스마트 윈도우용 가교 열감응성 폴리(N-이소프로필아마이드) 겔 소재의 제조 및 특성 - 물/글리세롤 혼합용매 중의 글리세롤 함량의 영향 -)

  • Park, Jae-Hyong;Kim, Il-Jin;Lee, Dong-Jin;Sim, Jae-Hak;Song, Min-Seop;Lee, Young-Hee;Yoo, Jung-Whan;Kim, Han-Do
    • Clean Technology
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    • v.24 no.2
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    • pp.112-118
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    • 2018
  • Thermo-responsive polymers that exhibit phase transition in response to temperature change can be used as materials for smart windows because they can control solar light transmission depending on the outside temperature. The development of thermo-responsive polymers for smart windows that can be used over a wide temperature range is desirable. To obtain high performance smart windows materials, three-dimensional thermo-responsive poly(N-isopropylacrylamide) (PNIPAm) gels were prepared by free radical polymerization from monomer N-isopropylacrylamide, N, N'-methylenebis acrylamide (MBAm) as a crosslinking agent, ammonium persulfate (APS) as a strong oxidizing agent/tetramethylene diamine as a catalyst, and a mixture of two solvents (water/glycerol). This study examined the effect of glycerol content on the lower critical solution temperature (LCST), freezing temperature and the solar light transmittance of crosslinked PNIPAm gel films. The LCST and freezing temperature of PNIPAm gel films were found to be significantly decreased from 34.3 and $6.3^{\circ}C$ to 28.2 and $-6.5^{\circ}C$ with increasing glycerol content from 0 wt% to 10 wt%, respectively. It was found that the transparent PNIPAm gel films at $25^{\circ}C$ (temperature < LCST) were converted to translucent gels at higher temperature ($45^{\circ}C$) (temperature > LCST). These results suggested that the crosslinked PNIPAm gel materials prepared in this study could have high potential for application in smart glass materials.

Development of Optimum Grip System in Developing Design Tensile Strength of GFRP Rebars (GFRP 보강근의 설계 인장강도 발현을 위한 적정 그립시스템 개발)

  • You Young-Chan;Park Ji-Sun;You Young-Jun;Park Young-Hwan;Kim Keung-Hwan
    • Journal of the Korea Concrete Institute
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    • v.17 no.6 s.90
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    • pp.947-953
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    • 2005
  • Previous test results showed that the current ASTM(American Standard for Testing and Materials) grip adapter for GFRP(Glass Fiber Reinforced Polymer) rebar was not fully successful in developing the design tensile strength of GFRP rebars with reasonable accuracy. It is because the current ASTM grip adapter which is composed of a pair of rectangular metal blocks of which inner faces are grooved along the longitudinal direction does not take into account the various geometric characteristics of GFRP rebar such as surface treatment, shape of bar cross section as well as physical characteristics such as poisson effect, elastic modulus in the transverse direction and so on. The objective of this paper is to provide how to proportion the optimum diameter of inner groove in ASTM grip adapter to develop design tensile strength of GFRP rebar. The proportioning of inner groove in ASTM grip adapter is based on the force equilibrium of GFRP rebar between tensile capacity and minimum frictional resistance required along the grip adapter. The frictional resistance of grip adapter is calculated based on the compressive strain compatibility in radial direction induced by the difference between diameter of GFRP rebar and inner groove In ASTM grip. All testing procedures were made according to the CSA S806-02 recommendations. From the preliminary test results on round-type GFRP rebars, it was found that maximum tensile loads acquired under the same testing conditions is highly affected by the diameter of inner groove in ASTM grip adapter. The grip adapter with specific dimension proportioned by proposed method recorded the highest tensile strength among them.

Long-Term Behavior of CFRP Strips under Sustained Loads (지속하중을 받는 탄소섬유판의 장기 거동)

  • You, Young-Chan;Choi, Ki-Sun;Kim, Keung-Hwan
    • Journal of the Korea Concrete Institute
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    • v.21 no.2
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    • pp.139-146
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    • 2009
  • Experimental study was performed to evaluate the long-term behavior of CFRP (carbon fiber reinforced polymer) strips under sustained loads including prestressing force in strengthening RC members with post-tensioned CFRP strips. Two types of CFRP strip such as unidirectional CFRP strip and hybrid CFRP strip which is composed of carbon fiber and steel plate were considered. Also two types of loading scheme were included in this study. Direct sustained loading test had been carried out to estimate the creep deformation and relaxation of CFRP strips including slip deformation at both mechanical anchorages for over 700 days. Also, flexural sustained loading test had been conducted to estimate the initial prestress losses on clamping the CFRP strips at jacking anchorages for over 90 days. From the sustained loading tests, it was observed that stress losses of unidirectional CFRP strips due to the creep deformation and relaxation of material itself and slip deformation at mechanical anchorage were ignorable. On the other hand, significant stress losses caused by the yielding of steel embedded in CFRP strips were found in case of hybrid CFRP strips due to the initial jacking force over steel yielding stress. Also, initial prestress losses during setting of CFRP strips on mechanical anchorage were about 10% of intial jacking force, which must be considered in the design.

Measurement of Space Dose Distribution during Exposure Micro Computed Tomography (μ-CT) for Scattering Rays (Micro-CT 촬영 시 발생되는 산란선에 관한 공간선량률 측정)

  • Jung, Hongmoon;Won, Doyeon;Kwon, Taegeon;Jung, Jaeeun
    • Journal of the Korean Society of Radiology
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    • v.7 no.1
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    • pp.45-50
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    • 2013
  • Non-invasive technique CT, called automated computed tomography, is used to detect lesion of a patient when diagnosing human body. Information obtained from CT plays an important role in assembling 3 dimensional images. Recently, new equipment, operated by CT, is required which can be appliable to physical and biological research. In accordance to this quest, micro-CT is invented that produce more detail and concrete information. Images supplied by CT are even more detailed and concrete, so it contributes much to the development of biology and polymer material engineering field. However, there has been little reliable reports regarding measuring information of space dose distribution about exposure dose limit of users operating micro-CT. In addition, little reports regarding space dose distribution of exposure has been known about unwanted diffraction light produced by usage of micro-CT. The exterior of micro-CT is covered by lead, which is for removing exposure of diffraction light. Thus, even if it is good enough to prevent exposure of diffraction light, consistent management of equipment will be required as time goes by and equipment are getting old as well. We measured space dose distribution regarding exposure of diffraction light of users operating micro-CT directly. Therefore, we suggest that proper management should be necessary for users operating micro-CT not to be exposed by unwanted diffraction light.

International Trends in Development, Commercialization and Market of Bio-Plastics (국내외 바이오 플라스틱의 연구개발, 제품화 및 시장 동향)

  • You, Young-Sun;Oh, Yu-Sung;Hong, Seung-Hoi;Choi, Sung-Wook
    • Clean Technology
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    • v.21 no.3
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    • pp.141-152
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    • 2015
  • As environmental issues are emerging, bio-plastic suppliers in leading countries have been foreseeing the strong needs for environment-friendly materials such as eco-packing materials due to increased attention and regulation on recycle. To catch up with the demand, various types of bio-plastics based on natural feedstocks were developed and released on a market. These bio-plastic products drew the great attention even in domestic industries. At present, international oil price fluctuation and heavy charge on waste raise the unit cost of production and disposal expense of conventional plastic materials. These conditions make bio-plastic an alternative, because it is not restrained by oil prices and problem in the disposal. It is also expected that bio-plastic will be applied to various types of products including containers, industrial supplies, disposables, and medical supplies. However, the bio-plastic is still in its infancy, thus more research and understanding should be followed to put it to application. Bio-plastic is considered as environment-friendly material with high potential which has the advantages of production and disposal.

Simulation-Based Design of Shear Mixer for Improving Mixing Performance (혼합효율 개선을 위한 Shear Mixer의 시뮬레이션 기반 형상 설계)

  • Kim, Tae-Young;Jeon, Gyu-Mok;Ock, Dae-Kyung;Park, Jong-Chun
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.20 no.2
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    • pp.107-116
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    • 2017
  • When drilling operation is being performed, many physical and chemical changes are occurred near wellbore. To handle various changes of well condition and keep drilling process safe, additives of bulk, such as bentonite for increasing density of drilling mud, barite for increasing viscosity of drilling mud, polymer for chemical control, or surfactant, are added into drilling mud through a mud shear mixer. Because the achievement of the required material property through mud mixing system is essential to stabilize drilling system, it is of importance to analyze multi-phase flow during mud mixing process, which is directly related to increase mixing performance of the system and guarantee the safety of the whole drilling system. In this study, a series of liquid-solid flow simulation based on a computational fluid dynamics (CFD) are performed with comparing to solid concentration in experiment by Gilles et al. [2004] to understand the characteristics of liquid-solid mixing in a mud shear mixer. And then, the simulation-based design of shear mixer are carried out to improve mixing performance in a mud handling system.