• Elastomers and Composites
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• 제43권4호
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• pp.213-220
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• 2008

In this study, the effects of curing system on the hardness of rubber materials at various temperature were investigated. NR and SBR were compounded with various sulfur or peroxide content, in order to obtain various crosslink densities. The changes of hardness and crosslink density were measured as a function of temperature and the relationship was examined. The thermal stresses were also measured in order to investigate the effect of entropy as a function of temperature. The hardness of NR and SBR compounds increased with increasing temperature above room temperature, and the measured thermal stress increased as temperature increased. However, the crosslink densities were not changed by temperature change.

• Elastomers and Composites
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• 제56권4호
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• pp.223-233
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• 2021

In this study, epoxidized liquid isoprene rubber (E-LqIR) was used as a processing aid in a silica-filled natural rubber compound to improve the fuel efficiency, abrasion resistance, and oil migration problems of truck and bus radial tire tread. The wear resistance, fuel efficiency, and extraction resistance of the compound were evaluated according to the molecular weight of E-LqIR. Results of the evaluation showed that the E-LqIR compound had a lower chemical crosslink density than that of a treated distillate aromatic extract (TDAE) oil compound because of the sulfur consumption of E-LqIR. However, the filler-rubber interaction improved because of the reaction of E-LqIR with silica and crosslink with the base rubber by sulfur. As the molecular weight of E-LqIR increased, crosslink with sulfur was facilitated, and the filler-rubber interaction improved, resulting in improved abrasion resistance. The fuel efficiency performance of the E-LqIR compound was poorer than that of the TDAE oil compound because of the low chemical crosslink density and hysteresis loss at the free chain end of E-LqIR. However, the fuel efficiency performance improved as the molecular weight of E-LqIR increased.

• Journal of environmental and Sanitary engineering
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• 제21권4호
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• pp.49-60
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• 2006

The ion exchange resins have been synthesized from chlormethyl styrene - 1,4 - divinylbenzene(DVB) with 1%, 2%, 4% and 8%-crosslinking and 1-aza-18-crown-6 macrocyclic ligand by copolymerization method. Content of chlorine in styrene-DVB copolymer was decreased as crosslink increased and it is because as crosslink increased 1%, 2%, 4% and 8% DVB content increased and crosslink density increased and cavity was reduced. Functional group of resin almost disappeared as C-C1 peak around $700cm^{-1}$ was substituted with 1-aza-18-C-6 macrocyclic ligand and new peak of C-N around $1020cm^{-1}$ appeared, so it was confirmed that styrene-DVB copolymer and ligand were compounded. As crosslink increased in the analysis of element contents, it resulted in the reduction of nitrogen content and it is because as crosslink increased, it led to the reduction of chlorine content in the process of substitution reaction and it affected macrocyclic ligand substituted. Thermo analysis curve of functional synthetic resin decomposed three part of 1-aza-18-C-6, styrene, and DVB. Form of functional synthetic resin showed distortion of its particles as macrocyclic ligand was introduced to styrene-DVB copolymer and hydrogen of ligand caused substitution with chlorine element of styrene molecule.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제25권10호
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• pp.779-785
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• 2012

The epoxy/micro-and nano-mixed silica composites(EMNC) systems were prepared and the AC insulation breakdown strength was evaluated. Glass transition temperature (Tg) and crosslink density were also measured by dynamic mechanical analyzer(DMA) in order to correlate them with the electrical and mechanical properties, and the effect of silane coupling agent on the electrical properties was also studied. Electrical properties and crosslink density of epoxy/micro-silica composite were noticeably improved by addition of nano-silica and silane coupling agent, and the highest breakdown strength was obtained by addition of 0.5~5 phr of nano-silica and 2.5 phr of silane coupling agent, and the highest tensile and flexural strength were obtained by addition of 2.5 phr of nano-silica.

• Journal of environmental and Sanitary engineering
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• 제19권3호
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• pp.52-57
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• 2004

Content of chlorine in s쇼rene-DVB copolymer was decreased as crosslink increased and it is because as crosslink increased $1\%,\;2\%,\;5\%\;and\;10\%$ DVB content increased and crosslink density increased and cavity was reduced. Functional group of resin almost disappeared as C-C1 peak around $700cm^{-1}$ was substituted with 1-aza-12-C-4 macrocyclic ligand and new peak of C-N around $1020cm^{-1}$ appeared, so it was confirmed that styrene-DVB copolymer and ligand were compounded. As crosslink increased in the analysis of element contents, it resulted in the reduction of nitrogen content and it is because as crosslink increased, it led to the reduction of chlorine content in the process of substitution reaction and it affected macrocyclic ligand substituted. Form of functional synthetic resin showed distortion of its particles as macrocyclic ligand was introduced to styrene-DVB copolymer and hydrogen of ligand caused substitution with chlorine element of styrene molecule.

• Journal of the East Asian Society of Dietary Life
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• 제15권3호
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• pp.264-270
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• 2005

This study was performed to evaluate the effect of red-yeast-rice on blood lipids and also to investigated the relation of blood lipids, bone related hormones, and bone mineral density in overiectomized rats. Forty female rats (body weight $210\pm5$g) were divided into two groups. The rats in the first group were ovariectomized which the others received sham operation (SHAM). And then each rat group was further divided into control diet $(casein\;20\%)$ and red-yeast-rice powder supplemented $(0.1\%)$ diet group. All rats were fed on experimental diet and deionized water ad libitum for 9 weeks. Bone mineral density (BMD) and bone mineral content (BMC) were measured using PIXImus in spine and femur. Bone formation and bone resorption were measured by serum osteocalcin and urinary deoxypyridinoline (DPD) crosslinks value. Serum growth hormone, IGF-1 and calcitonin were analyzed using radioimmunoassay kits. The red-yeast-rice group had significantly lower the blood triglyceride concentration and had lower the blood total cholesterol concentration than casein group did in ovariectomized rats. And the red-yeast-rice group than casein group in ovariectomized rats. The red-yeast-rice group had significantly lower the atherogenic index than control group within the ovariectomized groups. In the experimental rats, serum total cholesterol concentration was negatively correlated with femur BMC and crosslink value. Crosslink value was negatively correlated with spine BMC and IGF-1. Osteocalcin concentration was negatively correlated with crosslink value. Growth hormone was negatively correlated with crosslink value and positively correlated with spine BMC. The findings of this study suggest that red-yeast-rices are beneficial for blood lipid in ovariectomized rats. And when considering a population-based public health approach to lowering cholesterol and bone loss, and preventing coronary heart disease and osteoporosis, the red-yeast-rice dietary supplement could provide a new approach for the maintenance of healthier cholesterol and bone.

• Elastomers and Composites
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• 제27권3호
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• pp.183-193
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• 1992

Compared with NR and HNBR compounds, the blend properties of NR/HNBR were studied. The heat, oil and ozone resistance of NR compounds were improved by blending HNBR, and these effects were more clearly revealed with elevating temperatures. For the overall stabilities of the compounds, it was resonable to use the carbon black under the 60phr. In the EV systems, high-saturated NR/HNBR and HNBR compounds showed similar total crosslink density in comparison with NR compounds. Interaction parameters calculated by stress-strain method showed widely varied value.

• Corrosion Science and Technology
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• 제16권1호
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• pp.49-49
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• 2017

• Applied Chemistry for Engineering
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• 제2권4호
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• pp.356-362
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• 1991

The physico-mechanical properties of NR/BR blend were measured, and the results were interpreted in terms of the crosslink density with cure system. The cure rate, maximum torque and crosslink density increase with the content and ratio of curative for cure system. Hardness, 300 % tensile modulus, rebound and wear resistance increase with crosslink density of the vulcanizate but heat build-up and tan $\delta$ at $60^{\circ}C$ decrease. It is expected that semi-EV(efficient vulcanization) cure system is appropriate for application in tire tread of truck/bus in which load bearing property is impotant.

• Elastomers and Composites
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• 제42권2호
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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.