• Title, Summary, Keyword: crosslink

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Analytical Techniques for Measurement of Crosslink Densities of Rubber Vulcanizates

  • Son, Chae Eun;Choi, Sung-Seen
    • Elastomers and Composites
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    • v.54 no.3
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    • pp.209-219
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    • 2019
  • It is important to analyze crosslink densities of rubber articles because the physical properties are dependent on the crosslink densities. In this paper, analytical techniques for the measurement of crosslink densities of rubber vulcanizates are described. The most widely used method to measure the crosslink density is a swelling method combined with the Flory-Rehner equation. Application of the interaction parameter (${\chi}$) of rubber and swelling solvent is critical because the crosslink density is absolutely dependent on the ${\chi}$ value. Methods for obtaining ${\chi}$ employ not only solubility parameters of the polymer and swelling solvent but also inverse gas chromatography (IGC). The solubilities of rubbers can be obtained using micro differential scanning calorimetry (${\mu}DSC$), intrinsic viscosity measurement, and UV-visible spectroscopy. Nuclear magnetic resonance (NMR) spectroscopy has been also used for the measurement of the crosslink density using the $T_2$ relaxation time, which is determined by spin-spin relaxation in solid-state NMR. For sulfur-cured rubber vulcanizates, crosslink densities according to the crosslink types of mono-, di-, and polysulfides are measured by treating the rubber samples with a chemical probe composed of thiol and amine compounds. Measurement methods of physical crosslinking by filler, crystallization, and ionic bonding have also been introduced.

Influence of Extender Oil on Properties of Solution Styrene-Butadiene Rubber Composites

  • Choi, Sung-Seen;Ko, Eunah
    • Elastomers and Composites
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    • v.50 no.3
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    • pp.196-204
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    • 2015
  • Crosslink density of a rubber vulcanizate determines the chemical and physical properties, while bound rubber is an important factor to estimate reinforcement of a filled rubber compound. Extender oil is added to a raw rubber with very high molecular weight for improving processability of a rubber composite. Influence of extender oil on crosslink density, bound rubber formation, and physical properties of solution styrene-butadiene rubber (SSBR) composites with differing microstructures was investigated. Crosslink densities of non-oil-extended SSBR (NO-SSBR) vulcanizates were higher than those of oil-extended SSBR (OE-SSBR) ones. Bound rubber contents of NO-SSBR compounds were also greater than those of OE-SSBR ones. The experimental results could be explained by interfering of extender oil. The OE-SSBR vulcanizates had low modulus but long elongation at break, whereas the NO-SSBR ones had high modulus but short elongation at break. It was found that the crosslink densities affected the physical properties more than the bound rubber contents. The moduli increased with increase in the crosslink density irrespective of extender oil, while the elongation at break decreased. Each variation of the tensile strengths of NO-SSBR and OE-SSBR vulcanizates with the crosslink density showed a decreasing trend. Tear strength of the OE-SSBR vulcanizate increased with increase in the crosslink density, whereas variation of the tear strength of NO-SSBR vulcanizate with the crosslink density showed a weak decreasing trend.

Influence of Thermal Aging in Change of Crosslink Density and Deformation of Natural Rubber Vulcanizates

  • Choe, Seong Sin
    • Bulletin of the Korean Chemical Society
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    • v.21 no.6
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    • pp.628-634
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    • 2000
  • Crosslink is the most important chemistry in a rubber vulcanizate. Degree and type of crosslinks of the vulcanizate determine its physical properties. Change of crosslink density and deformation of a rubber vulcanizate by thermal aging were studied using natural rubber (NR) vulcanizates with various cure systems (conventional, semi-EV, and EV) and different cure times (under-, optimum-, and overture). All the NR vulcanizates were deformed by the thermal aging at 60-100 $^{\circ}C.$ The higher the aging temperature is, the more degree of the deformation is. The undercured NR vulcanizates after the thermal aging were deformed more than the optimumand overcured ones. The NR vulcanizates with the EV cure system were less deformed than those with the conventional and semi-EV cure systems. The deformation of the NR vulcanizates was found to be due to change of the crosslink density of the vulcanizates. The crosslink densities of all the vulcanizates after the extraction of organic materials were also changed by the thermal ging. The sources to change the crosslink densities of the vulcanizates by the thermal aging were found to be dissociation of the existing sulfur crosslink and the formation of new crosslinks by free sulfur, reaction products of curing agents, and pendent sulfide groups.

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CDDP induces conformational changes in BTV ds RNA rather than forming protein-protein and/or protein-RNA crosslink (cis-Diamminedichloroplatinum(II) (CDDP)에 의한 불루텅 바이러스 이중가닥 RNA의 구조변화)

  • Yang, Jai-Myung
    • Applied Biological Chemistry
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    • v.34 no.2
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    • pp.86-93
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    • 1991
  • cis-Diamminedichloroplatinum(II)(CDDP), an antitumor drug, did not generate crosslink between bluetongue virus (BTV) capsid protein at moderate concentration. Cesium chloride density gradient centrifugation study revealed that protein-RNA crosslink was not detectable in CDDP treated BTV. CDDP treated BTV ds RNA showed remarkable change in the migration pattern in polyacrylamide gel electrophoresis. These results suggest that the reduction of BTV core associated transcriptase activity is most likely by the CDDP adduction to the genomic ds RNA rather than by the protein-RNA crosslink and/or protein-protein cross-link.

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Chlorine Effect on Thermal Aging Behaviors of BR and CR Composites

  • Choi, Sung-Seen;Kim, Jong-Chul
    • Bulletin of the Korean Chemical Society
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    • v.31 no.9
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    • pp.2613-2617
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    • 2010
  • Chloroprene is a chlorine substituent of 1,3-butadiene. Butadiene rubber (BR) and chloroprene rubber (CR) composites were thermally aged at 60, 70, 80, and $90^{\circ}C$ for 2 - 185 days in a convection oven and changes of the crosslink densities by the accelerated thermal aging were investigated. The crosslink densities increased as the aging time elapsed and as the aging temperature became higher. Degrees of the crosslink density changes of the BR composite were on the whole larger than those of the CR one except the short-term thermal aging at 60 and $70^{\circ}C$. The crosslink densities abnormally increased after themal aging at high temperatures for a long time. Activation energies for the crosslink density changes of the rubber composites tended to increase with increase of the aging time and the variation showed a local minimum. The activation energies of the CR composite were lower than those of the BR one. The experimental results were explained with a role of ligand of chlorine atom of CR in a zinc complex, steric hindrance by chlorine atom of CR, and oxidation of rubber chain.

Influence of the Cure Systems on Long Time Thermal Aging Behaviors of NR Composites

  • Choi, Sung-Seen;Kim, Jong-Chul;Lee, Seung-Goo;Joo, Yong-L.
    • Macromolecular research
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    • v.16 no.6
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    • pp.561-566
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    • 2008
  • NR composites with different curing systems were aged thermally at 60, 70, 80, and $90^{\circ}C$ for 2-185 days in a convection oven, and the changes in the crosslink density were investigated as a function of the accelerated thermal aging. The overall crosslink densities increased with increasing aging time irrespective of the aging temperatures and curing systems. The changes in crosslink density were enhanced by increasing the aging temperature. The degree of the increased crosslink density was in the following order: "the conventional cure system > the semi-EV system > the EV system". For short term thermal aging, the change in crosslink density with the aging time was complicated, particularly for low temperature aging. The activation energies of the change in crosslink density with thermal aging using the conventional and semi-EV cure systems increased and then remained relatively constant with increasing aging time, whereas that of the specimen with an EV cure system tended to increase linearly. The experimental results were explained by the dissociation of the existing polysulfidic linkages and the formation of new cross links through the crosslinking-related chemicals remaining in the sample.

Optical and Electroluminescence properties of PPV derivatives including different crosslink unit

  • Kim, Jae-Hong;Jang, Young-Seok;Jeong, Joon-Ho;Joo, Hyeong-Uk;Jung, Woo-Sik;Kim, Bong-Shik
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1383-1385
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    • 2005
  • We synthesized new poly(p -phenylene vinylene) (PPV) derivatives including different portions of crosslink that could interconnect the backbone of PPV for application in optoelectronic devices such as lightemitting-diodes, photovoltaic cells, and lasers. The fluorescence and electroluminescence properties of PPV including crosslink were discussed with respect of their structure and length of crosslink unit.

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Adsorption and Separation of U (VI), Co (II), and Dy (III) Metal Ions on Crown Synthetic Resin

  • Kim, Joon-Tae
    • Journal of the Chosun Natural Science
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    • v.10 no.1
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    • pp.43-50
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    • 2017
  • Synthetic resins were combined 1-aza-12-crown-4 macrocyclic ligand with styrene divinylbenzene copolymer having 1%, 2%, 8%, and 16% crosslink by a substitution reaction. These synthetic resins were confirmed by chlorine content, elementary analysis, SEM, surface area, and IR-spectrum. As the results of the effects of pH, crosslink of synthetic resin, and dielectric constant of a solvent on metal ion adsorption for resin adsorbent, the metal ions showed high adsorption at pH 3 or over. Adsorption selectivity for the resin in ethanol solvent was the order of uranium ($UO_2{^{2+}}$) > cobalt ($Co^{2+}$) > dysprosium ($Dy^{3+}$) ion, adsorbability of the metal ion was the crosslink in order of 1%, 2%, 8%, and 16% and it was increased with the lower dielectric constant. In addition, theses metal ions could be separated in the column with 1% crosslink resin by using nitric acid (pH 2.0) as an eluent.

Resin Synthesis of Adsorbent Uranium(VI) Ion using 1-Aza-18-Crown-6 (1-Aza-18-Crown-6를 이용한 우라늄(VI) 이온 흡착제 수지 합성)

  • Kim, Sun-Hwa;Kim, Hae-Jin
    • Journal of environmental and Sanitary engineering
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    • v.21 no.4
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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.