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Some Considerations in Measurement of Cutting and Chipping Resistance of Rubber Compounds
Nah, Changwoon,Choi, Byung Soon,Kook, Seung Uk,Kim, Hae-Jin 東新大學校 1998 論文集 Vol.10 No.-
The cutting and chipping resistance of the blend compound of natural rubber (NR) and polybutadiene (BR) was investigated using the B. F. Goodrich tester [1]. A set of field tire tests was performed by applying two selected tread compounds with WR and NR/BR= 80/20 in order to correlate its performance with that of the laboratory tests. An opposite trend was found between the laboratory and field tests. The discrepancy was discussed by considering two factors: frictional characteristics, especially the frictional work exerted on the surface of rubber specimen by the cutting and chipping indentor, and the resilience of rubber compounds. The strength of NR/BR blends was also reported in this study.
Nah, Changwoon,Kim, Seung Gyeom,Shibulal, Gopi Sathi,Yoo, Yong Hwan,Mensah, Bismark,Jeong, Byeong-Heon,Hong, Bo Ki,Ahn, Jou-Hyeon Elsevier 2015 International journal of hydrogen energy Vol.40 No.33
<P><B>Abstract</B></P> <P>Ethylene-propylene-diene-termonomer (EPDM) rubber based fuel cell gasket compounds have been designed and explored the effects of various vulcanization systems on different properties. Three types of sulphur-accelerated vulcanization systems such as conventional vulcanization (con), semi-efficient vulcanization (sev) and efficient vulcanization (ev) and also a peroxide vulcanization system were employed in this study. The curing characteristics, tensile, hardness and compression set properties of the cured compounds were evaluated. The crosslink density was assessed by equilibrium swelling method in dodecane. The chemical stability of the cured EPDM compounds was also evaluated through an accelerated durability test (ADT) using a solution (1 M H<SUB>2</SUB>SO<SUB>4</SUB> + 10 ppm HF) very close to the fuel cell atmosphere. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), energy dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) were employed to investigate the chemical and physical changes of the cured EPDM compounds before and after exposure to the ADT solution over time. The results indicate that the EPDM compounds cured with peroxide exhibit the highest crosslink density with lowest compression set value at both room temperature and at elevated temperature. The FTIR and the corresponding SEM results show no significant chemical degradation of the peroxide cured EPDM compounds due to ADT ageing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We examine the long-term ageing resistance of rubber vulcanizates in a simulated fuel cell environment. </LI> <LI> We monitor the chemical and physical change during ageing. </LI> <LI> The peroxide cure system shows much enhanced resistance to ageing than sulphur cure system. </LI> <LI> The cure additive such as ZnO in the sulphur cure system can negatively affect the performance of fuel cell. </LI> </UL> </P>
폴리페닐렌옥사이드/에폭시 수지 블렌드의 경화거동 및 파괴인성에서 폴리페닐렌옥사이드가 미치는 영향
박수진,정효진,나창운 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.4
본 실험에서는 4관능성 에폭시 수지(4EP)와 Poly (phenylene oxide) (PPO) 블렌드의 경화거동, 열 안정성 그리고 기계적 계면특성을 알아보았다. PPO의 조성비는 0, 5, 10, 15, 20 phr로 하였다. 4EP/PPO 블렌드물의 경화거동은 근적외선 분광법과 시차주사열량계를 통해 관찰하였고, 열 안정성은 열분해 개시온도(IDT), 열안정성 인자 그리고 적분 열분해 진행온도(IPDT)에 의해 관찰하였다. 시편의 기계적 계면특성을 고찰하기 위해서 파괴인성 실험을 수행하였고, 시편의 파괴단면을 주사전자현미경으로 분석하였다. 그 실험결과, 전화율은 5 phr에서 높은 값을 나타내었고, 경화 활성화 에너지(E_(a))는 5 phr에서 PPO에 의해 경화가 가속화되어 감소되는 경향을 나타내었다. 열안정성은 분자내 PPO의 페닐그룹의 존재로 인해 PPO의 함량이 증가함에 따라 증가하였다. 또한 파괴인성 인자(K_(IC), G_(IC))는 5 phr에서 고분자 사슬 분자사이의 계면 결합력의 향상으로 인해 가장 높은 값을 나타내었다. In this work, the effect of poly (phenylene oxide) (PPO) in tetrafunctional epoxy resin (4EP) was investigated in terms of cure kinetics, thermal properties, and mechanical interfacial properties of the blends. The content of PPO was varied within 0, 5, 10. 15, and 20 phr to neat 4EP. The cure kinetics of 4EP/PPO blend system are examined by near-IR and DSC measurements. And the thermal stabilities were determined by initial decomposed temperature (IDT), thermal stability factors, and integral procedural decomposition temperature (IPDT) of the blends. For the mechanical interfacial properties of the casting specimens, the fracture toughness test was performed, and their fractured surfaces were examined by SEM. As a result, the conversion (a) is indicated in high value at 5 phr of PPO and, the cure activation energy (E_(a)) is decreased at 5 phr PPO, due to the plasticized PPO polymer molecule in epoxy resins. The thermal stabilities were increased, which can be explained by the presence of phenyl group of PPO in intermolecular chains. Also the fracture toughness parameters (K_(IC), G_(IC)) show high values at 5 phr PPO. This result is interpreted in the development of interfacial adhesion force between intermolecules of the polymer chains.
Basuli, Utpal,Chattopadhyay, Santanu,Nah, Changwoon,Chaki, Tapan Kumar Wiley Subscription Services, Inc., A Wiley Company 2012 Polymer composites Vol.33 No.6
<P><B>Abstract</B></P><P>Electrical and electromagnetic interference shielding effectiveness (EMI SE) properties of the ethylene methyl acrylate (EMA)/multiwalled carbon nanotube (MWNT) nanocomposites have been studied. High resolution transmission electron microscope (HRTEM) was used to validate the MWNTs dispersion state and network connections of its microstructure. The electrical resistance of the nanocomposites decreases significantly with MWNTs content. DC resistivity and AC conductivity measurement on the nanocomposite samples showed that the insulator to conductor transition took place within 10 wt% MWNTs concentration. It has been found that as MWNT concentration increased network connections improved. The EMI SE of the nanocomposites has also been investigated. The highest SE (∼20 dB) of these nanocomposites is realistic for an industrial application. EMA/MWNT nanocomposites provide sufficient intrinsic EMI shielding capability which may be hopeful for electrical and electronic applications. The morphology correlates well with the electrical and electromagnetic behavior of these nanocomposites. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers</P>
Kim, Dae-Yoon,Nah, Changwoon,Kang, Shin-Woong,Lee, Seung Hee,Lee, Kyung Min,White, Timothy J.,Jeong, Kwang-Un American Chemical Society 2016 ACS NANO Vol.10 No.10
<P>The preparation of materials exhibiting structural colors has been intensively studied in biomimetic science and technology. Utilizing a newly synthesized cholesteric liquid-crystal (CLC) monomer (abbreviated as BP1CRM), we have prepared CLC films. Photoinitiated copolymerization of this monomer with a common achiral liquid-crystalline monomer produced free-standing films with homogeneous and nanoscale pitch distributions. Employing the thermal sensitivity of the CLC monomer, chirophotonic crystal reflectors were prepared exhibiting a range of colors. The free-standing and circular-polarizing chirophotonic crystal films maintain excellent thermal, mechanical, and chemical stabilities, and the composition can readily be applied as polarized optical films and smart paints.</P>
Kang, Dong-Gue,Kim, Namil,Park, Minwook,Nah, Changwoon,Kim, Jin Soo,Lee, Cheul-Ro,Kim, Youngsu,Kim, Chae Bin,Goh, Munju,Jeong, Kwang-Un American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.4
<P>To develop an advanced heat, transfer composite a deeper understanding of the interfacial correlation between matrix and filler is of paramount importance. To verify the effect of interfacial correlations on the thermal conductivity, the conductive fillers such as expanded graphite (EG) and boron nitride (BN) are introduced in,the discotic liquid crystal (DLC)-based polymeric matrix. The DLC matrix exhibits better interfacial affinity with EG compared to BN because of the strong pi-pi interactions between EG and DLC. Thanks to its excellent interfacial affinity, the EG-DLC composites show a synergistic increment in thermal conducting performance.</P>
최성신,나창운,Choi, Sung-Seen,Nah, Changwoon 한국접착및계면학회 2002 접착 및 계면 Vol.3 No.2
실리카로 보강된 천연고무 가황물에서 가황촉진제의 양이 열노화에 의한 가교밀도의 변화에 미치는 영향에 대해 연구하였다. 또한 실란커플링제의 영향도 조사하였다. 가황촉진제로는 N-tert-butyl-2-benzothiazole sulfenamide(TBBS)를 실란 커플링제로는 bis-(3-(triethoxysilyl)-propyl)-tetrasulfide(TESPT)를 사용하였다. 가황물을 열노화 시키면 가교밀도는 증가하였고 노화 온도가 높을수록 그 변화 정도는 컸다. 실란 커플링제가 포함되지 않은 가황물의 가교밀도 변화가 실란 커플링제를 포함한 것에 비해 더 크게 나타났다. 실란 커플링제가 포함되지 않은 가황물의 경우에는 가교밀도의 변화에 대한 활성화 에너지가 가황촉진제의 함량이 증가할수록 순차적으로 낮아지는 경향을 보였다. The effect of cure accelerator content on the change in crosslink density by thermal aging was studied for silica-filled natural rubber (NR) vulcanizates. Influence of silane coupling agent was also investigated. N-tert-Butyl-2-benzothiazole sulfenamide (TBBS) and bis-(3-(triethoxysilyl)-propyl)-tetrasulfide (TESPT) were used as a cure accelerator and a silane coupling agent, respectively. The crosslink density increased by thermal aging and the increasing level became larger as the aging temperature increased. The degree of crosslink density change of the vulcanizates without the silane coupling agent was larger than that of the vulcanizates containing the silane coupling agent. For the vulcanizates silane coupling agent, the activation energy for the crosslink density change decreased with increase of the cure accelerator content in the vulvanizate.