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Sung-seen Choi - One of the best experts on this subject based on the ideXlab platform.
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Analytical Techniques for Measurement of Crosslink Densities of Rubber Vulcanizates
2019Co-Authors: Chae Eun Son, Sung-seen ChoiAbstract: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 (χ) of rubber and swelling solvent is critical because the Crosslink Density is absolutely dependent on the χ value. Methods for obtaining χ 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 (μDSC), 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 T2 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.
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Considering factors for analysis of Crosslink Density of poly(ethylene-co-vinyl acetate) compounds
Polymer Testing, 2018Co-Authors: Sung-seen Choi, Yu Yeon ChungAbstract:Abstract Relationship between Crosslink densities of peroxide cured poly(ethylene-co-vinyl acetate) (EVA) and delta torques of EVA compounds in cure curves was examined, and considering factors for analysis of Crosslink densities of EVA articles were investigated. The relationship between Crosslink densities and delta torques of EVA samples was not found to be correlated when EVAs with different VA contents and co-Crosslinker (triallyl isocyanurate, TAC) were used. Though the delta torques of EVA compounds with the different VA contents were nearly the same, Crosslink Density of the EVA sample with the low VA content was greater than that with the high one. And the delta torques of EVA compounds containing the co-Crosslinker were much larger than those without the co-Crosslinker though Crosslink densities of the EVA samples were nearly the same irrespective of the co-Crosslinker. From the experimental results, considering factors for analysis of Crosslink densities of EVA articles were found to be formation of semi-Crosslink points by crystalline structure of the ethylene sequences of EVA and long Crosslink points formed by the co-Crosslinker and VA moiety. Increase of the crystalline structure increased the Crosslink Density, whereas formation of long Crosslink points led to higher swelling ratio.
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Lifetime prediction and thermal aging behaviors of SBR and NBR composites using Crosslink Density changes
Journal of Industrial and Engineering Chemistry, 2012Co-Authors: Sung-seen Choi, Jong-chul KimAbstract:Abstract SBR and NBR composites were thermally aged and the Crosslink Density changes were investigated. The Crosslink Density changes of the SBR composite after thermal aging were larger than those of the NBR one. This could be explained by the allylic proton contents and the role of phenyl or nitrile group as a ligand in a zinc complex. The activation energies of the SBR composite were slightly lower than those of the NBR one. The lifetime to reach 50 and 100% increase of Crosslink Density of the NBR sample was shorter than that of the SBR one.
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A simple NMR method to measure Crosslink Density of natural rubber composite
Polymer Testing, 2010Co-Authors: Young Kee Chae, Woo-young Kang, Joong-hee Jang, Sung-seen ChoiAbstract:Abstract The Crosslink Density of carbon black-reinforced natural rubber (NR) was correlated with 1H chemical shift by liquid-state 1H NMR spectroscopy. Instead of observing the rubber directly with the solid-state NMR technique, we used toluene molecules in the liquid state as probes to explore the inner cavities of the rubber sample. Four NR composites with different carbon black contents of 20, 40, 60, and 80 phr were tested. The toluene signals were split into two: one from the bulk solvent and the other from inside the rubber. The chemical shift difference between those two split signals was observed to be in linear relationship with the carbon black content. The samples thermally aged at 70 °C for 100 days showed larger chemical shift differences than the unaged sample. Furthermore, the chemical shift difference was directly proportional to the apparent Crosslink Density obtained independently by the conventional swelling method. This result offers by far the simplest method to measure the apparent Crosslink Density in rubber.
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Influence of internal strain on change of Crosslink Density of natural rubber vulcanizates by thermal ageing
Polymer International, 2001Co-Authors: Sung-seen ChoiAbstract:Change of Crosslink Density of natural rubber (NR) vulcanizates by thermal ageing at 60 °C has been studied under swollen conditions in solvents to investigate the influence of internal strain applied to the vulcanizate on the Crosslink Density change. The internal strain was controlled by swelling with various solvents such as n-hexane, toluene, tetrahydrofuran (THF), methanol and water. The order of degree of the swelling is toluene THF > n-hexane > methanol > water. The influence of curing system has been investigated with the vulcanizates cured by the conventional and EV cure systems. After thermal ageing, the apparent Crosslink densities of the swollen vulcanizates in n-hexane, toluene and THF decrease irrespective of the cure systems, while that of the swollen vulcanizate in water increases. For the swollen vulcanizates in methanol, the apparent Crosslink Density of the vulcanizate with the conventional cure system after thermal ageing increases while that of the vulcanizate with the EV cure system decreases. The decrement of the apparent Crosslink Density of the vulcanizate after thermal ageing becomes larger and larger upon increasing the internal strain.
Xiaogang Li - One of the best experts on this subject based on the ideXlab platform.
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degradation characterization of ethylene propylene diene monomer epdm rubber in artificial weathering environment
Journal of Failure Analysis and Prevention, 2010Co-Authors: Quanlin Zhao, Jianwen Hu, Xiaogang Li, Zhengfang YeAbstract:Ethylene-propylene-diene monomer containing 5-ethylidene-2-norbornene as diene was exposed to artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different periods of time. The changes of surface color and mechanical properties were monitored by spectrophotometer, computer-controlled tensile testing and hardness measurements. Crosslink Density of ethylene-propylene-diene monomer specimens was measured by the solvent swell method. The results showed that the surface of ethylene-propylene-diene monomer became yellower due to the form of carbonyl group. The degradation process proceeded predominantly via cross-linking. With increase in Crosslink Density, the tensile strength increased and the elongation at fracture decreased.
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degradation evaluation of ethylene propylene diene monomer epdm rubber in artificial weathering environment by principal component analysis
Materials Letters, 2009Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene were conducted in a xenon lamp light exposure and weathering equipment for different time periods. Principal component analysis (PCA) was used to evaluate the 12 degradation parameters of EPDM including surface properties, Crosslink Density and mechanical properties. The results showed that the combined evaluating parameter Z of EPDM degradation increased quickly in the first 12 days of exposure and then leveled off. After 45 days, it began to increase rapidly again. Among the 12 degradation parameters, the Crosslink Density is strongly associated with tensile stress at 300% elongation and tear strength. The surface tension is also well correlated with the color aberration.
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Degradation evaluation of ethylene–propylene–diene monomer (EPDM) rubber in artificial weathering environment by principal component analysis
Materials Letters, 2009Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene were conducted in a xenon lamp light exposure and weathering equipment for different time periods. Principal component analysis (PCA) was used to evaluate the 12 degradation parameters of EPDM including surface properties, Crosslink Density and mechanical properties. The results showed that the combined evaluating parameter Z of EPDM degradation increased quickly in the first 12 days of exposure and then leveled off. After 45 days, it began to increase rapidly again. Among the 12 degradation parameters, the Crosslink Density is strongly associated with tensile stress at 300% elongation and tear strength. The surface tension is also well correlated with the color aberration.
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aging of ethylene propylene diene monomer epdm in artificial weathering environment
Polymer Degradation and Stability, 2007Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Ethylene–propylene–diene monomer (EPDM) containing ENB as diene was exposed to artificial weathering environment for different periods of time. The changes of appearance, morphology, mechanical properties and chemical structures were monitored by spectrophotometer, glossmeter, microscope, computer-controlled tensile testing, hardness measurements and Fourier Transform Infrared (FTIR) spectroscopy. Crosslink Density of EPDM specimens was measured by the solvent swell method. The results showed that the surface of EPDM became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The specular gloss reached a maximum when the sample was exposed for 18 days and then decreased. The aging process proceeded predominantly via Crosslinking. The tensile strength increased with increase in Crosslink Density up to an optimum value and thereafter decreased with further increase in Crosslink Density. FTIR spectra confirmed the formation of carbonyl groups in an artificial weathering environment.
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Aging of ethylene–propylene–diene monomer (EPDM) in artificial weathering environment
Polymer Degradation and Stability, 2007Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Ethylene–propylene–diene monomer (EPDM) containing ENB as diene was exposed to artificial weathering environment for different periods of time. The changes of appearance, morphology, mechanical properties and chemical structures were monitored by spectrophotometer, glossmeter, microscope, computer-controlled tensile testing, hardness measurements and Fourier Transform Infrared (FTIR) spectroscopy. Crosslink Density of EPDM specimens was measured by the solvent swell method. The results showed that the surface of EPDM became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The specular gloss reached a maximum when the sample was exposed for 18 days and then decreased. The aging process proceeded predominantly via Crosslinking. The tensile strength increased with increase in Crosslink Density up to an optimum value and thereafter decreased with further increase in Crosslink Density. FTIR spectra confirmed the formation of carbonyl groups in an artificial weathering environment.
Quanlin Zhao - One of the best experts on this subject based on the ideXlab platform.
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degradation characterization of ethylene propylene diene monomer epdm rubber in artificial weathering environment
Journal of Failure Analysis and Prevention, 2010Co-Authors: Quanlin Zhao, Jianwen Hu, Xiaogang Li, Zhengfang YeAbstract:Ethylene-propylene-diene monomer containing 5-ethylidene-2-norbornene as diene was exposed to artificial weathering environment produced by a xenon lamp light exposure and weathering equipment for different periods of time. The changes of surface color and mechanical properties were monitored by spectrophotometer, computer-controlled tensile testing and hardness measurements. Crosslink Density of ethylene-propylene-diene monomer specimens was measured by the solvent swell method. The results showed that the surface of ethylene-propylene-diene monomer became yellower due to the form of carbonyl group. The degradation process proceeded predominantly via cross-linking. With increase in Crosslink Density, the tensile strength increased and the elongation at fracture decreased.
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degradation evaluation of ethylene propylene diene monomer epdm rubber in artificial weathering environment by principal component analysis
Materials Letters, 2009Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene were conducted in a xenon lamp light exposure and weathering equipment for different time periods. Principal component analysis (PCA) was used to evaluate the 12 degradation parameters of EPDM including surface properties, Crosslink Density and mechanical properties. The results showed that the combined evaluating parameter Z of EPDM degradation increased quickly in the first 12 days of exposure and then leveled off. After 45 days, it began to increase rapidly again. Among the 12 degradation parameters, the Crosslink Density is strongly associated with tensile stress at 300% elongation and tear strength. The surface tension is also well correlated with the color aberration.
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Degradation evaluation of ethylene–propylene–diene monomer (EPDM) rubber in artificial weathering environment by principal component analysis
Materials Letters, 2009Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) containing 5-ethylidene-2-norbornene (ENB) as diene were conducted in a xenon lamp light exposure and weathering equipment for different time periods. Principal component analysis (PCA) was used to evaluate the 12 degradation parameters of EPDM including surface properties, Crosslink Density and mechanical properties. The results showed that the combined evaluating parameter Z of EPDM degradation increased quickly in the first 12 days of exposure and then leveled off. After 45 days, it began to increase rapidly again. Among the 12 degradation parameters, the Crosslink Density is strongly associated with tensile stress at 300% elongation and tear strength. The surface tension is also well correlated with the color aberration.
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Evaluation of ethylene–propylene–diene monomer (EPDM) aging in UV/condensation environment by principal component analysis (PCA)
Materials Letters, 2009Co-Authors: Quanlin Zhao, Jin Gao, Zhijun JiaAbstract:Abstract Artificial weathering tests on ethylene–propylene–diene monomer (EPDM) were conducted in UV/condensation environment for different time periods up to 90 days. Principal component analysis (PCA) was used to evaluate the 11 aging parameters of EPDM including surface properties, Crosslink Density and mechanical properties. The results showed that EPDM aged quickly in the first 18 days of exposure and then slowed up. Among the 11 evaluating parameters, tensile stress at 100% elongation, surface tension and carbonyl content are strongly associated. The Crosslink Density is also well correlated with the hardness.
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aging of ethylene propylene diene monomer epdm in artificial weathering environment
Polymer Degradation and Stability, 2007Co-Authors: Quanlin Zhao, Xiaogang LiAbstract:Abstract Ethylene–propylene–diene monomer (EPDM) containing ENB as diene was exposed to artificial weathering environment for different periods of time. The changes of appearance, morphology, mechanical properties and chemical structures were monitored by spectrophotometer, glossmeter, microscope, computer-controlled tensile testing, hardness measurements and Fourier Transform Infrared (FTIR) spectroscopy. Crosslink Density of EPDM specimens was measured by the solvent swell method. The results showed that the surface of EPDM became redder, yellower and lighter in the first stage of aging and then remained almost unchanged. The specular gloss reached a maximum when the sample was exposed for 18 days and then decreased. The aging process proceeded predominantly via Crosslinking. The tensile strength increased with increase in Crosslink Density up to an optimum value and thereafter decreased with further increase in Crosslink Density. FTIR spectra confirmed the formation of carbonyl groups in an artificial weathering environment.
K Sekhar - One of the best experts on this subject based on the ideXlab platform.
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scanning electron microscopy study on the influence of temperature on tear strength and failure mechanism of natural rubber vulcanizates
Polymer Testing, 2005Co-Authors: K Agarwal, D K Setua, K SekharAbstract:Abstract Scanning Electron Microscopy (SEM) analysis of tearing of natural rubber (NR) vulcanizates has been carried out with respect to, (1) nature of Crosslinks [e.g. –C–C– (peroxide) or-S x -(sulphur) type], (2) extent of Crosslinking (inadequate, optimum and excess Crosslink Density level), (3) effect of addition of reinforcing carbon black filler (HAF N330), and (4) effect of temperature. All these parameters exert profound influence on the failure pattern, as obtained in the SEM photographs of the vulcanizates subjected to tear fracture. The peroxide cured vulcanizate gives rise to stick-slip type of tear with striations and microfolds on the surface, while sulphur curing of the vulcanizate generates a failure pattern which indicates an origin of multiple fracture paths and their subsequent conversion into shear planes at a higher Crosslink Density. In the case of carbon black filled samples, a coarse fracture surface with convergence of tear paths and formation of many short rounded tear lines are observed. The vulcanizates show maximum tear resistance at the level of achieving optimum Crosslink Density. However, the strength drops sharply at elevated temperatures.
Ki-sook Cho - One of the best experts on this subject based on the ideXlab platform.
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Filler–elastomer interactions: influence of silane coupling agent on Crosslink Density and thermal stability of silica/rubber composites
Journal of Colloid and Interface Science, 2003Co-Authors: Soojin Park, Ki-sook ChoAbstract:In this work, the Crosslink Density and thermal stability of the silica/rubber composites treated by silane coupling agents, i.e., gamma-aminopropyl triethoxysilane (APS), gamma-chloropropyl trimethoxysilane (CPS), and gamma-methacryloxypropyl trimethoxysilane (MPS), were investigated. The chemical structures of modified silicas were studied in term of solid-state 29Si NMR spectroscopy. The Crosslink Density of the composites was determined by swelling measurement. The development of organic functional groups on silica surfaces treated by coupling agents led to an increase in the Crosslink Density of the composites, resulting in increasing final thermal stability of the composites. The composites treated by MPS showed the superior Crosslink Density and thermal stability in these systems. The results could be explained by the fact that the organic functional groups of silica surfaces by silane surface treatments led to an increase of the adhesion at interfaces between silicas and the rubber matrix.