The Experts below are selected from a list of 159 Experts worldwide ranked by ideXlab platform
Seiichi Kawahara - One of the best experts on this subject based on the ideXlab platform.
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HIGH-RESOLUTION LATEX-STATE 13C-NMR SPECTROSCOPY FOR NATURAL Rubber Vulcanizates
Rubber Chemistry and Technology, 2007Co-Authors: Seiichi Kawahara, Jinta Ukawa, Junichiro Sakai, Yoshimasa Yamamoto, Yoshinobu IsonoAbstract:Crosslinking junctions of natural Rubber Vulcanizates were characterized by high-resolution latex-state 13 C-NMR spectroscopy. Vulcanized natural Rubber latex was prepared by two methods: i.e., vulcanization of the Rubber latex and cryogenic crushing of a Rubber sheet vulcanized on a hot press. High-resolution latex-state 13 C-NMR spectroscopy was attained even after vulcanization of the Rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEFT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1 H- 1 H correlation (H-H COSY), 2-dimensional 1 H- 13 C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.
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HIGH-RESOLUTION LATEX-STATE 13C-NMR SPECTROSCOPY FOR NATURAL Rubber Vulcanizates
Rubber Chemistry and Technology, 2007Co-Authors: Seiichi Kawahara, Jinta Ukawa, Junichiro Sakai, Yoshimasa Yamamoto, Yoshinobu IsonoAbstract:Crosslinking junctions of natural Rubber Vulcanizates were characterized by high-resolution latex-state 13 C-NMR spectroscopy. Vulcanized natural Rubber latex was prepared by two methods: i.e., vulcanization of the Rubber latex and cryogenic crushing of a Rubber sheet vulcanized on a hot press. High-resolution latex-state 13 C-NMR spectroscopy was attained even after vulcanization of the Rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEFT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1 H- 1 H correlation (H-H COSY), 2-dimensional 1 H- 13 C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.
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Structural Characterization of Crosslinking Points of Rubber Vulcanizates
NIPPON GOMU KYOKAISHI, 2006Co-Authors: Seiichi KawaharaAbstract:Crosslinking points of Rubber Vulcanizates have been investigated by nuclear magnetic resonance (NMR) spectroscopy. Several signals in 13C-NMR spectrum appearing after vulcanization of the Rubber were assigned by solution-, solid- and latex-states 13C-NMR spectroscopy. The assignments of the signals, which have been reported by recent research works, are summarized in this article, and they are compared with each other to propose the most probable crosslinking points. The signals at 44ppm and 57ppm for natural Rubber Vulcanizates are rationally assigned to secondary, tertiary and quaternary carbons.
Yoshinobu Isono - One of the best experts on this subject based on the ideXlab platform.
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HIGH-RESOLUTION LATEX-STATE 13C-NMR SPECTROSCOPY FOR NATURAL Rubber Vulcanizates
Rubber Chemistry and Technology, 2007Co-Authors: Seiichi Kawahara, Jinta Ukawa, Junichiro Sakai, Yoshimasa Yamamoto, Yoshinobu IsonoAbstract:Crosslinking junctions of natural Rubber Vulcanizates were characterized by high-resolution latex-state 13 C-NMR spectroscopy. Vulcanized natural Rubber latex was prepared by two methods: i.e., vulcanization of the Rubber latex and cryogenic crushing of a Rubber sheet vulcanized on a hot press. High-resolution latex-state 13 C-NMR spectroscopy was attained even after vulcanization of the Rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEFT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1 H- 1 H correlation (H-H COSY), 2-dimensional 1 H- 13 C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.
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HIGH-RESOLUTION LATEX-STATE 13C-NMR SPECTROSCOPY FOR NATURAL Rubber Vulcanizates
Rubber Chemistry and Technology, 2007Co-Authors: Seiichi Kawahara, Jinta Ukawa, Junichiro Sakai, Yoshimasa Yamamoto, Yoshinobu IsonoAbstract:Crosslinking junctions of natural Rubber Vulcanizates were characterized by high-resolution latex-state 13 C-NMR spectroscopy. Vulcanized natural Rubber latex was prepared by two methods: i.e., vulcanization of the Rubber latex and cryogenic crushing of a Rubber sheet vulcanized on a hot press. High-resolution latex-state 13 C-NMR spectroscopy was attained even after vulcanization of the Rubber latex, as is evident from no background in spectrum and narrow half width of signals independent of vulcanization time. Small signals at 44 ppm and 57 ppm in the aliphatic carbon region were assigned by measurements of both Distortionless Enhancement by Polarization Transfer (DEFT) and Attached Proton Test (APT) to secondary and tertiary carbons of crosslinking points. The assignment was proved by high-resolution solution-state NMR spectroscopy of vulcanized liquid cis-1,4-polyisoprene as a model, in which DEPT, APT, 2-dimensional 1 H- 1 H correlation (H-H COSY), 2-dimensional 1 H- 13 C correlation (H-C COSY) and 2-dimensional heteronuclear multiple bond correlation (HMBC) measurements were applied.
Yuko Ikeda - One of the best experts on this subject based on the ideXlab platform.
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Biaxial tensile behavior of Rubber Vulcanizates: I. Silica and gum stocks
Rubber Chemistry and Technology, 2004Co-Authors: Kanji Kajiwara, Yuko Ikeda, Yoshihiro Kameda, Hiroshi Urakawa, Takanobu Kawamura, Kenji Urayama, Shinzo KohjiyaAbstract:We have studied the strip biaxial tensile behavior of natural Rubber Vulcanizates filled with silica by the conventional milling method and by the in-situ silica filling method. The rapid increase of both stresses along the stretching and the fixed axes after the initial stretching was observed on samples filled with a conventional silica by the milling method. Low strain dependence of stresses in the successive strain regions was followed by the rapid increase of the stresses at the higher deformation region. On the other hand, we did not observe such behavior for the samples filled with silica generated in-situ in the Rubber matrix before curing. The transmission electron microscopic measurements showed that a highly developed aggregated structure of silica particles was suggested in the conventional silica filled samples and just a simple aggregation was suggested in the case of the in-situ silica filled samples. The differences between samples reinforced with two different filling methods in low tensile region are mainly attributed to the aggregate structure of the silica particles dispersed in the Rubbery matrix. We estimated the functional form of the strain energy density function for the samples filled with silica in intermediate and large deformation regions: W = C 10 (I 1 - 3) + C 01 (I 2 - 3) + C 20 (I 1 - 3) 2 The estimated W was found to reproduce the experimental stress-strain curves in intermediate and large deformation region. The relative contributions of three terms in the estimated W for the samples prepared by the in-situ method show the different dependence on the silica content from those of the samples containing silica mixed by the conventional method.
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Preparation and properties of graded styrene‐butadiene Rubber Vulcanizates
Journal of Polymer Science Part B: Polymer Physics, 2002Co-Authors: Yuko IkedaAbstract:Styrene-butadiene Rubber (SBR) Vulcanizates with graded network-chain densities in the thickness direction were prepared by layering and heat pressing the compounding sheets. The effect of the gradient of network-chain density on the mechanical properties of the graded Rubber Vulcanizates was investigated in comparison with those of SBR Vulcanizates that were prepared from the homogeneous compounding sheets. The matrix with a high network-chain density exclusively affected the mechanical properties of the graded Rubber Vulcanizates when the gradient was given in the thickness direction. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 358–364, 2002; DOI 10.1002/polb.10096
Kyong-hwan Chung - One of the best experts on this subject based on the ideXlab platform.
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Effect of silica reinforcement on natural Rubber and butadiene Rubber Vulcanizates by a sol–gel reaction with tetraethoxysilane
Journal of Applied Polymer Science, 2008Co-Authors: Kyong-hwan ChungAbstract:The effect of silica reinforcement was studied for natural Rubber (NR) and butadiene Rubber (BR) Vulcanizates by a sol–gel reaction with tetraethoxysilane at different temperatures. The formation of silica in the Rubber Vulcanizates was investigated analytically with Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. The variations of the mechanical and dynamic properties were measured in the NR and BR Vulcanizates with silica filling. The hardness of the Rubber Vulcanizates increased with silica filling in the Rubber matrix. The tensile strength and elongation at break decreased with silica filling in the NR Vulcanizates. The moduli at 50, 100, and 300% elongation increased with silica filling in the Rubber matrix. The storage modulus of silica-filled Rubber Vulcanizates became higher than that of pure Rubber Vulcanizates. The temperature dependence of the loss modulus also increased with silica filling. The temperature dependence of the loss tangent was maintained, regardless of silica filling in the BR Vulcanizates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
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effect of silica reinforcement on natural Rubber and butadiene Rubber Vulcanizates by a sol gel reaction with tetraethoxysilane
Journal of Applied Polymer Science, 2008Co-Authors: Kyong-hwan ChungAbstract:The effect of silica reinforcement was studied for natural Rubber (NR) and butadiene Rubber (BR) Vulcanizates by a sol–gel reaction with tetraethoxysilane at different temperatures. The formation of silica in the Rubber Vulcanizates was investigated analytically with Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. The variations of the mechanical and dynamic properties were measured in the NR and BR Vulcanizates with silica filling. The hardness of the Rubber Vulcanizates increased with silica filling in the Rubber matrix. The tensile strength and elongation at break decreased with silica filling in the NR Vulcanizates. The moduli at 50, 100, and 300% elongation increased with silica filling in the Rubber matrix. The storage modulus of silica-filled Rubber Vulcanizates became higher than that of pure Rubber Vulcanizates. The temperature dependence of the loss modulus also increased with silica filling. The temperature dependence of the loss tangent was maintained, regardless of silica filling in the BR Vulcanizates. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008
Toshio Tada - One of the best experts on this subject based on the ideXlab platform.
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in situ dilatometry and x ray microtomography study on the formation and growth of cavities in unfilled styrene butadiene Rubber Vulcanizates subjected to constrained tensile deformation
Polymer, 2020Co-Authors: Eric Euchle, Ricardo Ernhard, Konrad Schneide, Ge Heinrich, Sve Wiesne, Toshio TadaAbstract:Abstract It is known, that under constrained tensile deformation the mechanical response and the failure behavior of Rubber Vulcanizates reveal unlikely features. Due to multiaxial stress concentrations, the formation of internal cracks can be initiated. For the first time, fundamental investigations on unfilled styrene-butadiene-Rubber pancake specimens were performed. Via in situ dilatometry and X-ray microtomography experiments, the damage process under constrained tensile deformation is studied and discussed. Although cavitation has been often discussed for filler reinforced Rubber Vulcanizates, the results of this study demonstrate how it occurs also in unfilled Rubbers. In fact, the stronger the geometrical constraints are, the higher is the number of small cavities. However, the integral cavity volume is not affected. Moreover, micrographs of fracture surfaces indicate that cavitation is controlled by an omnidirectional growth of radial side-cracks. Finally, an energy-based approach to describe the cavitation onset criterion initiating the damaging process is presented to revise Gent's theory.