• Title, Summary, Keyword: EVA

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Strength and Watertightness Properties of EVA Modified High Strength Concrete (EVA 개질 고강도 콘크리트의 강도 및 수밀 특성)

  • Kim, Young-Ik;Sung, Chan-Yong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.49 no.1
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    • pp.45-54
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    • 2007
  • This study was performed to evaluate strength and watertightness properties of EVA modified high strength concrete in order to improve durability of concrete used in agricultural water utilization facilities that are in constant contact with water. Materials used were cement, coarse and fine aggregates, silica fume, EVA and AE water reducing agent. Tests for the slump, compressive and flexural strengths, absorption ratio and permeability coefficient according to curing condition (water and water+dry curing) and content ratio of EVA were performed. The slump results of EVA modified high strength concrete similarly showed in the content ratio of EVA powder less than 4% and decreased in the content ratio of EVA powder more than 6% compared to that of concrete without EVA powder. The compressive strength of EVA modified high strength concrete decreased with increasing the content ratio of EVA powder. The flexural strength of EVA modified high strength concrete increased with increasing the content ratio of EVA powder in the content ratio of EVA powder ratio less than 4% and had similar or slightly decreased in the content ratio of EVA powder more than 6% compared to that of concrete without EVA powder. The absorption ratio and permeability coefficient of EVA modified high strength concrete decreased with increasing the content ratio of EVA powder in the content ratio of EVA powder less than 4% and slightly increased in the content ratio of EVA powder more than 6%.

Experimental study on the effects of EVA(Ethylene Vinyl Acetate) for solar cell's long-term life (EVA(Ethylene Vinyl Acetate) 수지가 태양전지의 장기적인 수명에 미치는 영향에 관한 실험적 연구)

  • Kim, Seon Yong
    • Journal of the Korea Safety Management & Science
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    • v.17 no.4
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    • pp.397-401
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    • 2015
  • In this study, analysed the characteristics of power drop and surface damage in solar cell through high temperature and humidity test in the 3 case of EVA(ethylene vinyl acetate) and 2 case ribbon thickness. The solar cells were tested during the 500hr in $85^{\circ}C$ temperature and 85% relative humidity conditions, that excerpted standard of PV Module(KS C IEC-61215). Through the EL(Electroluminescence) shots, specimen's surface have partialy damaged. Before and after high humidity and high temperature test, ribbon thickness $200{\mu}m$ EVA1 case power drop rate was 8.463%, EVA2 case was 6.667%, EVA3 case was 6.373%. In the ribbon thickness $250{\mu}m$ EVA1 case power drop rate was 6.521%, EVA2 case was 8.517%, EVA3 case was 6.019%. EVA3 case was the lowest power and FF(fill factor) drop rate at the 2 case of ribbon thickness, because EVA3 is laerger than EVA1 and EVA2 in thickness, elongation and tensile strength.

Gas Separation Properties of Poly(ethylene oxide) and Poly(ethylene-co-vinyl acetate) Blended Membranes (Poly(ethylene oxide)와 Poly(ethylene-co-vinyl acetate)의 혼합막에 대한 기체분리 특성)

  • Lee, Hyun Kyung;Kang, Min Ji
    • Membrane Journal
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    • v.27 no.2
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    • pp.147-153
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    • 2017
  • In this study, we investigated permeation properties of single gas ($N_2$, $O_2$, $CO_2$) through membranes composed of poly(ethylene oxide) (PEO) and poly(ethylene-co-vinyl acetate) (EVA) blend. The prepared membranes showed no new absorbance peaks, which indicate the physical blending of PEO and EVA by FT-IR analysis. SEM observation showed that the crystalline phase of PEO decreased with increasing EVA content in the PEO/EVA mixed matrix. DSC analysis showed that the crystallinity of the PEO/EVA blend membrane decreased with increasing EVA content. Gas permeation experiment was performed with various feed pressure (4~8 bar). The permeability increased in the following order: $N_2$ < $O_2$ < $CO_2$. The permeability of $CO_2$ in PEO/EVA blend membranes were increased with increasing feed pressure, However, the permeability of $N_2$ and $O_2$ were independent of feed pressure. On the other hand, the permeability of all the gases in PEO/EVA blend membranes increased with increasing amorphous EVA content in semi-crystalline PEO. In particular, the blend membrane with 40 wt% EVA showed $CO_2$ permeability of 64 Barrer and $CO_2/N_2$ ideal selectivity of 61.5. The high $CO_2$ permeability and $CO_2/N_2$ ideal selectivity are attributed to strong affinity between the polar ether groups of PEO or the polar ester groups of EVA and polar $CO_2$.

Physical Properties of Functionalized Graphene Sheet/Poly(ethylene-co-vinyl acetate) Composites (관능화 그래핀 쉬트/에틸렌-비닐아세테이트 공중합체 복합재료의 물성)

  • Lee, Ki Suk;Kim, Jeong Ho;Jeong, Han Mo
    • Polymer(Korea)
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    • v.38 no.3
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    • pp.307-313
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    • 2014
  • The physical properties of functionalized graphene sheet (FGS)/poly(ethylene-co-vinyl acetate) (EVA) was examined with various kinds of EVA, having vinyl acetate (VA) contents in the range of 0 to 40 wt%. The compatibility between FGS and EVA was enhanced as the polar VA content of EVA increased. Thus, the dispersion of FGS in EVA became finer, and the decrease of surface resistivity and the increase of tensile modulus by the added FGS became more effective when the VA content of EVA was high. When the VA content was low, the elongation at break was reduced drastically by added FGS due to the poor adhesion of FGS/EVA interface. The crystallization of EVA was generally retarded by the interaction with dispersed FGS. However, when both the VA content of EVA and the added amount of FGS were low, the crystallization of EVA was enhanced, probably due to the predominant nucleating effect by FGS.

Studies on the Surface Changes and Adhesion of EVA Foam by Plasma Treatment (플라즈마 처리에 의한 EVA Foam의 표면변화 및 접착특성에 관한 연구)

  • Choi, Myung Jin;Kim, Dong Ho;Kim, Gu Ni
    • Journal of Adhesion and Interface
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    • v.9 no.1
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    • pp.9-15
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    • 2008
  • EVA foam was treated by oxygen plasma under a various treatment time for surface modification. The effect of plasma treatment on surface properties of EVA foam was investigated in terms of FT-IR ATR, XPS, contact angle, and SEM analysis and the adhesion characteristic of the EVA foam was studied in peel strength. As a results, EVA foam treated by plasma led to an elimination of organic compound, an increase of oxygen content, and an increase of surface roughness, resulting in improving the adhesion properties of the EVA foam. As the plasma treatment time increased, the hydrophilicity and physical change of surface of the EVA foam were increased and showed maximum value at 180 s and 420 s, respectively. The maximum adhesion strength appeared at plasma treatment time of 420 s and therefore, in this study the physical change was thought to be a major factor for improving the adhesion of the EVA foam.

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투자성과지표로서 EVA의 유용성에 관한 실증연구

  • Kang, Hyo-Seok;Nam, Myeong-Su
    • The Korean Journal of Financial Management
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    • v.14 no.3
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    • pp.1-21
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    • 1997
  • 본 연구는 가치창조 경영의 중심지표인 EVA가 우리나라에서도 올바른 주주가치 평가지표로서 활용될 수 있을지를 살펴보고 있다. 실증분석 결과를 보면 연구기간(1986년${\sim}$1995년)중 대부분의 기업은 주당 EVA가 음(陰)이였고, 주당 EVA는 주당영업 이익, 주당순이익, 자기자본이익률등 기존 성과 척도들에 비해 주가와 상관관계가 가장 높았다. 연도별 EVA를 기준으로 매년 포트폴리오를 재구성하는 방법으로 10년간의 초과 수익률을 계산한 결과 EVA가 양(陽)인 포트폴리오는 음(陰)경우보다 초과수익률이 거의 140%정도 높았다. 또한 당해연도 뿐 아니라 전년도 주당 EVA가 주가변동의 주요결정 요인인것도 발견되었다. 이러한 연구결과는 EVA의 극대화가 주가의 극대화 곧 기업가치 및 주주가치 극대화를 의미하므로 성과지표로서 EVA를 성과측정 및 보상등 기업의 모든 의사결정에 활용할 수 있다는 것을 시사해 준다. 또한 EVA를 포트폴리오 관리를 위한 새로운 투자지표로 활용한다면 증권시장에서 수익률을 재고할 수 있다는 것을 입증해줌으로써 증권시장의 활성화에 크게 기여할 수 있을 것이다.

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Early Strength and Properties of EVA Powder Modified High Strength Concrete (EVA Powder 개질 고강도 콘크리트의 초기강도 및 수밀특성)

  • Kim, Young-Ik;Sung, Chan-Yong
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • pp.123-127
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    • 2005
  • EVA Powder modified high strength concretes were prepared by varying polymer/binder mass ratio with a constant water/binder mass ratio of 0.3. The effect of EVA powder on the slump, hydration heat, compressive and flexural strength, toughness and water absorption ratio was studied. In hydration heat test, temperature of hydration reaction displayed almost fixed level regardless of containing rate of EVA powder, but peak time of hydration reaction displayed late inclination as containing rate of powder increases. With the same water/binder mass ratio, the compressive strength and water absorption of EVA powder modified concretes decreased slightly when EVA powder was added and the flexural strength of EVA powder modified concretes rised slightly when EVA powder was added. Also, the toughness of the modified concretes can be improved markedly. The interpenetrating structure between the polymeric phase and cement hydrates formed at a $2{\sim}6%$(containing rate of EVA powder). The properties of the polymer modified concretes were influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases.

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Effect of Metal Ionic Crosslinking Agents on the Water Resistance and Mechancial Properties of EVA Emulsion (EVA 에멀젼의 내수성 및 기계적 특성에 미치는 금속 이온 가교제의 효과)

  • Lee, Eun-Kyoung;Choi, Sei-Young
    • Journal of Adhesion and Interface
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    • v.9 no.2
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    • pp.24-31
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    • 2008
  • In this work, calcium hydroxide and magnesium carbonate as metal ionic crosslinking agents were used to introduce ionic crosslinking points to the ethylene vinylacetate (EVA) emulsions for the enhancement of water resistance and mechanical properties of emulsion films. The properties of EVA emulsion film were investigated in crosslinking density, thermal features, surface energy, and mechanical properties, such as tensile strength, elongation at break and tear strength. With the increasing content of metal ionic crosslinking agent, the crosslinking density of the EVA emulsion film increases, resulting into the improvement of water resistance. The surface energy and mechanical properties of the EVA emulsion film, however, showed somewhat different behaviors. The highest surface energy, tensile strength, and tear strength were observed when 0.4% for calcium hydroxide and 0.5% for magnesium carbonate was added respectively, because the EVA emulsion containing carboxylic acid forms strong carboxylate-metal bond of ionically-crosslinked system. Therefore, it can be concluded that metal ionic crosslinking agents, such as magnesium carbonate and calcium hydroxide are considered to improve water resistance and mechanical properties of the EVA emulsion.

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우리 나라 주식시장에서 투자지표로서 경제적 부가가치(EVA)의 유용성에 관한 연구

  • Gu, Maeng-Hoi;Kim, Byeong-Gon
    • The Korean Journal of Financial Studies
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    • v.4 no.1
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    • pp.1-38
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    • 1998
  • 미국의 증권시장에서는 EVA가 주요한 주자지표로 주목을 받고 있다. 그동안 주요 투자지표로 사용되던 EPS, ROA, ROE, PER 등의 회계적 이익지표들에 비해 EVA의 활용도가 점차 높아지고 있다. 우리 나라에서도 투자지표로서, 경영관리지표로서의 활용 가능성에 대해 관심이 증가하고 있다. 본 연구에서는 우리 나라 주식시장에서 EVA가 유용한 투자지표로 활용될 수 있는가를 살펴보고자 하였다. 1991년부터 1995년의 분석기간에 걸쳐 첫째, 주당EVA가 회계적 이익지표보다 주식수익률을 더 잘 설명하는가, 둘째, 주당EVA가 높은 기업이 더 높은 초과수익률을 실현하는가, 셋째, 주당EVA는 개별 종목 초과수익률의 선행지표로 활용될 수 있는가를 EPS, ROA, ROE, PER 등의 회계적 이익지표와 비교하여 분석하였다. 분석결과 첫째, 우리 나라 주식시장에서 주식수익률은 주당EVA보다 회계적 이익지표인 EPS, ROA, ROE가 더 잘 설명하는 것으로 나타났다. 둘째, EPS, ROA, ROE를 기준으로 포트폴리오를 구성하는 경우 유의적인 초과수익률을 획득할 수 있는 것으로 나타난다. 주방EVA를 기준으로 포트폴리오를 구성하는 경우에는 3월 이후에 포트폴리오간 유의적인 초과수익률 차이가 발생하여 초과수익률 획득이 가능한 것으로 나타났다. 셋째, 주당EVA, EPS, ROA 등은 초과수익률에 대해 동행적 투자지표로 유용하고, ROE는 동행적 지표와 선행적 지표로 모두 유용하고, PER는 선행지표로 유용한 것으로 나타났다. 이와 같은 분석결과는 우리 나라 주식시장에서 EVA는 회계적 이익지표인 EPS, ROA, ROE, PER보다 더 우월한 투자지표라고 말하기는 어렵지만, 회계적 이익지표와 보완적으로 활용하는 경우에는 유용한 투자지표로 활용될 수 있음을 나타내고 있다.

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Preparation of Sulfur Crosslinkable EVA and Blend With Rubbers (황가황형 EVA의 제조 및 고무와의 블렌드)

  • Jin, Je-Yong;Choi, Sei-Young
    • Elastomers and Composites
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    • v.34 no.3
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    • pp.229-238
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    • 1999
  • In this study, double bond, unsaturated group was introduced to the main chain of EVA by chemically treating EVA, nondiene polymer. Benzene sulfonic acid, ENB and DCPD were used as a third element. Also, from blending CR and SBR, conventional synthetic rubber we prepared vulcanizates and examined their physical properties. The datum lead to the following conclusion that some problems were modified; limited temperature in use and mechanical properties like hardness, tensile strength, tensile stress, and elongation rate of thermoplastic EVA, keeping the following advantages of original EVA; green strength, injection molding by Pressure, adhesion, tackiness, dimensional stability, and ozone resistance, etc. It is expected that continuous research of the modification between nondiene and diene polymer will improve what were shown disadvantages in synthetic polymer; processing, oxidation resistance, and adhesion. In addition, it will be possible to continue process of rubber products by utilizing possible fluidity for fusion of EVA.

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