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Predecessor
Volume 79, Issue 10
Displaying 1-8 of 8 articles from this issue
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[in Japanese]2006 Volume 79 Issue 10 Pages 465
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (164K) -
Ken NAKAJIMA, Hiroyuki WATABE, Naoto OHNO, Satoshi NAGAYAMA, Kenji WAT ...2006 Volume 79 Issue 10 Pages 466-471
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSTwo parts of the physics of rubber elasticity have not been fully verified experimentally to date. The first one is the entropic elasticity of a single polymer chain. The second one is Affine deformation hypothesis, the bridge between molecular bases of rubber elasticity and phenomenological deformation mechanics of polymer chain network. Atomic force microscopy (AFM) was employed to find a cue to experimental evidence for them. Therefore, we did not give much attention to AFM's high-resolution feature, while its nanometer-scale palpatbility was specially utilized instead. The technique, so-called, nanofishing revealed the entropic elasticity of a single polystyrene chain in good, or theta solvent conditions. The entanglement inside a single polymer chain was detected by nanometer-scale stress-relaxation experiment with quick stepwise strain excitation. The breakdown of Affine deformation was also observed in uniaxially elongated natural rubber vulcanizate, which showed a very wide modulus distribution. We concluded tentatively that the plateau region observed in macroscopic stress-strain curve could be attributed to the remaining of the local region that had sufficiently low modulus even after stretched at the elongation ratio of around 4.View full abstractDownload PDF (8234K) -
Shigeyuki TOKI2006 Volume 79 Issue 10 Pages 472-479
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSRubber is composed of flexible chains and network points. Theory of rubber elasticity succeeds to elucidate stress-strain relation of rubber using the inverse Langevin equation of entropy modulus. However, actual rubber is much different from ideal networks composed of ideal rubber chains. Network points may not distribute homogeneously and the molecular weight between two network points may show wide distribution. Flexible chains show. strain-induced crystallization. Recent synchrotron X-ray and simultaneous stress-strain measurements reveal that strain-induced crystallization reduces the stress by increasing the length of molecules along the stretching direction. Also, strain-induced crystals are created not at the middle of the network points, but at the close location to the network points. The hybrid structure of strain-induced crystallites and network points may be stronger than network points alone. Therefore, strain induced crystallization may increase the tensile strength of rubber by two mechanisms, they are, increase of elongation at break and reinforcement of network points. Natural rubber has biotic network points in nature. After vulcanization, the biotic network may contribute the superior toughness of NR, comparing to IR. Carbon filled NR also shows strain induced crystallization. In order to acquire high tensile strength, molecules should have higher flexibility to perform strain induced crystallization by selecting a kind of carbon blacks, an accelerator and a curing condition.View full abstractDownload PDF (10520K) -
Wonmun CHOI2006 Volume 79 Issue 10 Pages 480-486
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe reactivities of hydrocarbon, the radical reactions through the allylic radicals, the results of model compound vulcanization, and the cross-link structures of vulcanizates are comprehensively reviewed and discussed to understand the main reaction for accelerated sulfur vulcanization. Through this review, the author's view on the main mechanism and cross-linking structure for accelerated sulfur vulcanization are discussed.View full abstractDownload PDF (2658K) -
Seiichi KAWAHARA2006 Volume 79 Issue 10 Pages 487-493
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSCrosslinking 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.View full abstractDownload PDF (4798K) -
Shin HORIUCHI2006 Volume 79 Issue 10 Pages 494-499
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSEnergy-filtering transmission electron microscopy (EFTEM) was employed for investigating accelerated vulcanized rubber nanostructures. The principle of EFTEM was outlined and the investigation of rubber nanostructures by combining elemental mapping and EELS was demonstrated. We showed that EFTEM allows us to create elemental distribution images and to perform quantitative elemental analysis of rubbers with the spatial resolutions of approximately 10nm and with 0.5 atomic % detection sensitivity. Rubber/ZnO interfaces in the accelerated rubber mixtures were investigated and it was found that ZnS were generated around ZnO particles as a byproduct in the vulcanization process. This provides valuable information on the mechanism of the accelerated vulcanization.View full abstractDownload PDF (13068K) -
Asahiro AHAGON2006 Volume 79 Issue 10 Pages 500-506
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSThe phenomena in rubber abrasion reported in the literature are reviewed from chemical aspect, as suggested by the formation of oily and roll-shaped debris, the variations of the effects of antioxidant with frictional force and the oxygen content in the environment, the high oxygen absorption by wear debris, etc. The phenomena can be consistently explained in terms of mechanochemical degradation taking place in the surface layer under frictional force. Although the mechanochemical feature is most apparent at lower frictional forces where wear is slow, it appears to exist latently even at larger frictional forces where wear is fast. The bimodal size distribution of wear debris is considered as the indication such that the larger debris are formed by the fracture in the depths and the smaller ones are formed by the detachment of the mechanochemically degraded layer from the surface. Nevertheless, the wear rate is determined by fracture or crack growth at larger frictional forces, and by mechanochemical degradation at lower frictional forces. It is considered important to select a proper condition to reflect the major mechanism, which would be operative for the products, when simulation of wear in the field is to be made in the laboratory.View full abstractDownload PDF (6484K) -
[in Japanese]2006 Volume 79 Issue 10 Pages 507-508
Published: October 15, 2006
Released on J-STAGE: March 12, 2010
JOURNAL FREE ACCESSDownload PDF (309K)
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