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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>
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>
A Study on the Friction Behavior of Natural Rubber
W. D. KIM,D. J. KIM,Changwoon Nah,Y. S. LEE 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
The frictional characteristics of natural rubber plates under various conditions including sliding speed, contacted ball size, and lubrication conditions were evaluated experimentally. The frictional force and the normal force were measured by a self-made tester pin and a load cell with strain gages. In the lubrication condition, the effect of sliding speed was not significant over tested speed range. But in the none-lubrication condition, according to increase the sliding speed, the friction coefficient was decreased. The coefficients of friction under various lubrication conditions were varied from 0.03 to 0.32 and under none-lubrication condition was varied from 2.54 to 4.74
( Minsu Lee ),( Junghyun Lee ),( Jihye Jang ),( Changwoon Nah ),( Yang-il Huh ) 한국고무학회 2019 엘라스토머 및 콤포지트 Vol.54 No.4
Poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified with various co-monomers, such as N-vinyl pyrrolidone (NVP), glycidyl methacrylate (GMA), and glycerol monomethacrylate (GMMA), were prepared to investigate the effect of adding a co-monomer on the water contents, surface wettability, and tensile modulus. These polymers were synthesized by thermal- and photo-polymerization in the presence of azobisisobutyronitrile (AIBN) and diphenyl(2,4,6- trimethylbenzoyl)-phosphineoxide (TPO) as the initiators. The characteristics of the hydrogels were analyzed via FTIR and UV/Vis spectroscopies, contact angle measurements, and tensile modulus measurements with UTM. Regarding the properties of water in the hydrogels, the ratio between free to bound water was investigated using differential scanning calorimetry (DSC). The effects of adding the co-monomers on the water content, surface wettability, and tensile modulus for soft contact lenses were also investigated. In the case of p(HEMA-co-NVP) hydrogels, the increase in the equilibrium water content (EWC) was primarily due to the increase in the bound water content. For p(HEMA-co-GMMA) hydrogels, an increase in free water content was the main reason for the increased EWC. In contrast, in the case of p(HEMA-co-GMA) hydrogels, a decrease in bound water content was observed to be the main factor that reduced the EWC. Photo-polymerized PHEMA hydrogels showed enhanced surface wettability and tensile modulus as compared to those produced via thermal polymerization.