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金海珍,羅昌運 東新大學校 工業技術硏究所 1996 工業技術硏究 Vol.2 No.-
Various mechanical properties of natural rubber/butadiene-acrylonitrile rubber (NR/NBR) blend compounds were investigated. A typical NBR having 34% of acrylonitrile was selected in the study. The NBR content in the blend was varied from 0 to 100 phr. Mooney viscosity increased linearly but stress relaxation time and green tack decreased with increasing NBR content. Tensile modulus, heat build-up and rate of crack propagation increased while strain at break, rebound and rate of wear decreased as the NBR content was increased. Tensile stress at break stayed constant up to about 60 phr of NBR and thereafter increased with increasing NBR content. Based on tan a peak, the glass transition temperature of NR and NBR were found to be -55°C and -10°C respectively. In the case of NR/NBR blend compounds, two distinct transition points were observed and each transition temperature was found to be independent of NBR level indicating an incompatible characteristics of NR/NBR blend system.
Jeong, Young-Il,Seo, Dong-Hyuk,Kim, Don-Gon,Choi, Chang-Yong,Jang, Mi-Kyeong,Nah, Jae-Woon,Park, Yoon-Kyung The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.7
In this study, methotrexate (MTX)-encapsulated polymeric micelles using methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymer were prepared. The MIX-incorporated polymeric micelles of ChitoPEG copolymer has a particle size of around 50-100 nm. In 1H nuclear magnetic resonance (NMR) study, the specific peaks of MTX disappeared in heavy water ($D_2O$) and only the specific peak of MPEG was observed, while all of the peaks were confirmed in dimethyl sulfoxide (DMSO). These results indicated that MTX was complexed with chitosan and then formed an ion complex inner-core of the polymeric micelle in an aqueous environment. The drug contents of the polymeric micelle were around $4{\sim}12%$ and the loading efficiency of MTX in the polymeric micelles was higher than 60% (w/w) for all of the formulations. The cytotoxicity of MIX and MTX-incorporated polymeric micelle against CT26 tumor cells was not significantly changed.
나창운(Chang Woon Nah),김대훈(Dai Hoon Kim),김동진(Dong Jin Kim),김완두(Wan Doo Kim),장영욱(Young Wook Chang) 한국공업화학회 2002 공업화학 Vol.13 No.4
염소화 처리에 따른 천연고무 쉬트(sheet)의 마찰특성을 새로운 형태의 마찰시험기를 이용하여 조사하였다. 아울러 염소화에 따른 표면의 분자구조, 표면 모폴로지 및 경도의 변화를 조사하였다. 천연고무 쉬트의 표면은 염소화 반응으로 분자구조의 변화가 확인되었고, 장시간 처리조건에서는 고리화 반응도 관찰되었다. 염소화 처리시간에 따라 마찰계수는 큰 폭으로 감소하였고, 염소화 초기단계에서 보다 급격한 감소를 보였다. 염소화에 따른 마찰계수 감소의 주요 원인은 경도와 표면 거칠기로 설명되었다. 경도의 증가는 접촉면적과 고무의 변형을 감소시킴으로써 각각 접착마찰과 히스테리시스 마찰을 감소시키고, 거칠기의 증가는 접촉면적을 감소시켜 접착마찰을 감소시킨 것으로 설명되었다. Using a new friction tester, the frictional property of chlorinated-natural rubber sheet was investigated as a function of the chlorination time. The changes in molecular structure, morphology, and hardness on the surface of the rubber sheet were also investigated with the chlorination time. It was confirmed that the molecular structure on the surface of natural rubber sheet has changed due to the chlorination reaction, and with a longer chlorination treatments a cyclization reaction was observed. The frictional coefficient decreased significantly with increasing the chlorination time, and the decrease rate was the highest at the initial stage of the chlorination reaction. Such rapid drop in the frictional coefficient--upon chlorination--can explained by two main parameters: surface roughness and hardness. The increase in the hardness caused a reduction in both the contact area and deformation of rubber, thereby decreasing the adhesive and hysteresis frictions. The increase in the surface roughness reduced the contact area, which in turn decreased the adhesive friction.
Natural Rubber / Acrylonitrile - Butadiene Rubber 블랜드의 기계적 물성과 강선과의 접착거동
나창운(Chang Woon Nah),손봉영(Bong Young Sohn) 한국고무학회 2001 엘라스토머 및 콤포지트 Vol.36 No.2
N/A Mechanical properties and their adhesion behavior with zinc- and brass-plated steel cords of natural rubber/acrylonitrile-butadiene blend compounds were investigated as a function of blend ratio. The Mooney viscosity and stress relaxation time were found to be lowered with increasing NBR content. Tensile modulus generally increased with increasing NBR content. Tensile stress at break stayed constant up to about 40 phr and showed minimum at 50∼60 phr, and thereafter increased with increasing NBR content. Strain at break decreased linearly below 50 phr, and above the level it showed nearly constant value. Based on the abrupt drops in elastic modules and tan8 peak, the glass transition temperature of NR and NBR were found to be -55 and -10℃ respectively. In the case of NR/NBR blend compounds, two distinct transition points were observed and each transition position was not affected by NBR level indicating an incompatible nature of NR/NBR blend system. The pullout foroe and rubber coverage decreased to the level of about 40% to that of pure NR compound, when the 50 phr of NR was replaced by NBR. However, the pure NBR compound showed the comparable adhesion performance with NR(∼90%). The sulfur concentration was found to become lower with the increased NBR content at the adhesion interface based on the Auger spectrometer results, representing a lack of adhesion layer formation, and this was explained for a possible cause of low adhesion performance with adding NBR.
나창운(Chang Woon Nah),김현재(Hyeon Jae Kim),강신영(Shin Young Kaang) 한국고무학회 1998 엘라스토머 및 콤포지트 Vol.33 No.4
N/A Tensile properties including Young`s modulus and tear strength were measured for four different rubber compounds; natural rubber(NR), styrene-butadiene copolymer(SBR), ethylene-propylene dime monomer(EPDM), and brominated isobutylene-p-methyl-styrene copolymer(BIMS) as a function of temperature and degree of cure. To see the effect of over cure, a measurement was made of the tensile strength and swelling behavior of the over-cured rubber compounds. Young`s modulus, E, was found to have linear dependency on the degree of cure for all rubber compounds. EPDM and BIMS showed the highest and lowest slopes, respectively. The slope of NR and SBR lay between EPDM and BIMS. Tear strength, Gc, decreased in the order of NR$gt;BIMS$gt;SBR$gt;EPDM. As the cure time was extended the degree of cure of NR and SBR decreased, while that of BIMS increased. EPDM showed little change in the degree of cure.