• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.115-119
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• 2008

The raw materials of permalloy were processed the ball-mill for 30 hours and the shape of permalloy particles was changed from sphere to flake type, which was observed using scanning electron microscope. The complex permittivity and permeability spectra and reflection loss of permalloy-rubber composite was measured using Network Analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake type permalloy-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of -6.1 dB was observed in $1.65\;GHz{\sim}1.86\;GHz$ for a 1.3 mm thickness.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1999.10a
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• pp.19-19
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• 1999

KSR 3단 AKM Motor Case를 개발하기 위해 추진기관 경량화에 가장 유리하고 비강도 및 비강성이 뛰어난 복합재 연소관을 고려하여 직경 300mm급의 축소형 모델을 선행 개발하였다. Netting 이론에 의해 연소관 두께를 결정하고 체적을 최소화 하기 위해 구형으로 연소관 형상을 설계하였다. 연소관을 제작하기 위한 맨드렐은 분리, 조립식으로 설계, 적용하였고 연소관 기밀 유지 및 추진기관 연소시 연소관을 보호하기 위한 삭마성 재료로 EPDM base의 고무 내열재 조성을 개발하였다. 고무 내열재는 맨드렐 위에 적층하고 Vacuum bagging 상태로 Autoclave에서 가황하여 적용하였다. 국내 최초로 Prepreg를 사용하는 Dry process로 고무 내열재가 적층된 맨드렐 위에 Winding하고, Vacuum bagging 상태에서 경화하여 연소관을 제작하였으며, 이 때 사용한 Carbor/Epoxy Perpreg 재료의 기계적 성질 및 열특성 시험을 병행하였다. 제작된 연소관은 수압 시험을 통하여 구조적 안정성을 입증하였고, NDT 검사를 통해 재료간 계면 상태를 분석하였다. 시험이 끝난 연소관은 향후 점화기 개발을 위하여 점화제 종류 및 약량을 변경하여 점화 시험을 수행하여 점화기 개발을 위한 기초 데이터를 확보하였다.

• Elastomers and Composites
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• v.39 no.4
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• pp.294-300
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• 2004

Mechanical properties of the commingled waste plastics filled with ground rubber tire were studied. To improve adhesion at the interface, trans-octylene rubber(TOR) was added. With increasing the rubber level, first, due to their inherent incompatibility, the tensile and the compressive strength decreased but tensile strain and impact strength increased. Then, as TOR added, the samples showed still the same strain but the tensile, impact, and compressive strength as well increased markedly Variation of the properties by addition of TOR seemed to be attributed to the dual character of TOR.

• Polymer(Korea)
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• v.25 no.2
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• pp.233-239
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• 2001

The ethylene propylene diene terpolymer (EPDM) blends with acrylonitrile butadiene rubber (NBR) were prepared by mechanical mixing method. Mooney viscosity, cure behaviors, compression set and dynamic mechanical properties were subsequently examined. Dynamic characteristics of the entire blends determined from a Rheovibron generally showed two glass transitions (T'$_{g}$s), -43$^{\circ}C$ and -4$^{\circ}C$ for NBR and EPDM, respectively. The tan $\delta$ peak monotonically shifted toward the higher temperature with increasing NBR content. It was also found that the optimum cure time was significantly decreased with loading of NBR.

• Elastomers and Composites
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• v.43 no.2
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• pp.72-81
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• 2008

Nowadays, modifying asphalt to improve the resistancy of plastic deformation or rutting on roads has been drawing attention. In this study, asphalts were modified with modifying agents and ground rubber from waste tire (GRT), and the effects of modifier and GRT on the properties of asphalt were analyzed. The Marshall stability of modified asphalt was increased by 98% and the tensile strength increased by 43% compared to straight asphalt. GRT played an important role in enhancing these properties. Viscosity tests, penetration tests and TMA analysis showed the deformation resistancy of modified asphalt. IR and GPC tests indicated that asphalt and modifier have similar chemical structures to each other, and chemical bonding between asphalt and modifier have occurred so that the molecular size lengthened.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.622-629
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• 2003

Generally, a silicone rubber and a chloride polyethylene(CPE) have been used for the development of high-performance composite EM(ElectroMagnetic) wave absorber. In this study, the EM wave absorption abilities for natural lacquer which is newly suggested in this study as a binder for composite EM wave absorber were investigated to develop an improved EM wave absorber In addition, MnZn ferrite composite EM wave absorber mixed with the natural lacquer were prepared and their absorption ability was also investigated. MnZn ferrite composite EM wave absorber which employs the natural lacquer as a binder showed an improved EM wave absorption characteristics in comparison with the conventional binder such as a silicone rubber and a chloride polyethylene(CPE). The matching frequency and the absorption ability of EM wave absorber mixed with natural lacquer can be controled the change of the thickness of them.

• Elastomers and Composites
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• v.42 no.2
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• pp.107-111
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• 2007

Adhesion of NR and BR composites with different initial states of precured or uncured conditions was studied. Adhesion between the NR and BR sheets as well as adhesion between the same rubber sheets was investigated. Adhesion forces of the uncured/uncured specimens were larger than those of the cured/uncured and cured/cured ones. The cured/cured samples and uncured NR/cured BR specimen were fully peeled out by the peel test. When one sheet was broken during the peel test, the sheet having the higher crosslink density was broken irrespective of the rubber types. Adhesion forces of the same rubber sheets were higher than those of the different ones and adhesion force of the cured NR/uncured BR sample was higher than that of the uncured NR/cured BR one. The experimental results were explained with the crosslink density and interdiffusion of rubber chains.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.508-515
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• 2002

The characterization of adhesive property in multi-layer materials has been hot issue for a long time. In order to evaluate adhesive properties, we constructed fully automated system for the backward radiation of leaky Lamb wave. The backward radiation profiles were obtained for the bare steel plate and plates with rubber-loading. The rf waveforms and frequency spectra of backward radiation show the characteristics of involved leaky Lamb wave modes. As the thickness of rubber-loading increased, the amplitude of profile at the incident angle of $13.4^{\circ}$ exponentially decreased. Scanning the incident position over the partially rubber-loaded specimen shows good agreement with the actual rubber-loading. The backward radiation of leaky Lamb wave has great potential to evaluate the adhesive condition as well as material properties of plates.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.350-353
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• 2008

과산화물 가교제의 농도가 헬리콥터 연료탱크의 자기밀폐층 소재로 적용시키기 위한 천연고무 스폰지의 팽윤에 미치는 효과를 조사하였다. 천연고무 콤파운드를 Kneader와 Roll-Mill을 활용하여 제조하고, 고압조건의 프레스에서 부분 가교시킨 후 대기압의 금형에서 발포와 완전가교를 실시하였다. 얻어진 스폰지의 겉보기밀도를 측정하고 스폰지의 셀구조를 주사전자현미경을 통하여 관찰하였다. 톨루엔, 이소옥탄과 항공유를 사용하여 실온에서 팽윤실험을 실시하였다. 용매에 2분 동안 침적 후 얻어지는 부피팽윤비 값은 과산화물 농도가 감소함에 따라 증가하다가 감소하는 경향을 보였다. 스폰지의 겉보기밀도와 셀구조는 과산화물 함량에 매우 민감하였으며 이는 또한 천연고무 스폰지의 팽윤거동에 영향을 미쳤다. 천연고무 스폰지가 연료와 접촉하여 신속한 팽윤이 얻어지기 위하여 금형에서 동시에 발생하는 두 가지 반응인 발포제의 분해반응과 천연고무의 가교반응을 적절히 조절하는 것이 중요하다.

• Elastomers and Composites
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• v.36 no.3
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• pp.169-176
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• 2001

Ethyl-branched polyethylene[PE(2)] containing 2mole% ethyl branch and three ethylene-propylene rubbers(EPR's) haying the same ethylene(E)-propylene(P) molar ratio(E/P=50/50) with different stereoregularity, that is, random EPR(r-EPR), alternating-EPR(alt-FPR) and isotactic-alternating-EPR(iso-alt-EPR) were mixed for the investigation of their properties depending on the stereoregurarity. The three blends were immiscible at room temperature, and showed the simple additivity effect in density behavior. The melting point depression with blend composition increased in order of PE(2)/r-EPR>PE(2)/alt-EPR>PE(2)/iso-alt-EPR. In the tensile test, this blend systems have the lowest value or the breaking strength at FE(2) fraction of 0.5. This phenomenon results from the greastest separated phase morphology at this blend composition.