NIPPON GOMU KYOKAISHI
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Volume 88, Issue 3
Displaying 1-6 of 6 articles from this issue
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Regular Papers
  • Studies on the Deterioration of EPDM by Hypochlorous Acid
    Part 3 Influence of Surface-deteriorated Layer on Tensile Strength of Black Filled EPDM System
    Hitoshi IWABUKI, Takuya ISHIDA, Satoshi FUKUZAKI
    2015 Volume 88 Issue 3 Pages 75-79
    Published: 2015
    Released on J-STAGE: June 16, 2015
    DOIhttps://doi.org/10.2324/gomu.88.75
    JOURNAL FREE ACCESS
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    The change in tensile strength of black-filled ethylene propylene diene terpolymer (EPDM) in sodium hypochlorite (NaOCl) solution of pH 4.5 was studied. At pH 4.5, free available chlorine mainly exists as undissociated hypochlorous acid (HOCl), which can diffuse into EPDM and cause the occurrence of corrosion pits, blisters, cracks,and precipitations of rubber powders. Analysis of transverse relaxation measured by 1H pulsed-NMR showed that the immobilized rubber phase increased after being immersed in NaOCl solution at higher temperatures, at which surface morphological change became remarkable. This indicates the hardening of EPDM and the formation of brittle surface layer. However, the decrease in tensile strength occurred regardless of the detection of the brittle layer. The diffusion behaviors of Cl and O atoms were investigated by electron probe micro analysis. At low temperatures close to the freezing point, only Cl atoms were diffused into EPDM, whereas no significant decrease in tensile strength was observed. The tensile strength of EPDM decreased with the increase in the depth of diffusion of O into EPDM. These results indicate that during elongation process of EPDM specimen, the cracking which occurs in the surface-oxidized layer acts as a notch of the specimen. It appears that the cracks formed in the brittle layer cannot develop into the inner EPDM.
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General Reviews
Advanced Course on Rubber Science and Technology
  • Fracture Reveals Real Structure and Characters of Rubber
    Part 4: Viscosity to Characterize the Friction and Wear of Cross-linked Rubber
    Yoshihide FUKAHORI
    2015 Volume 88 Issue 3 Pages 86-92
    Published: 2015
    Released on J-STAGE: June 16, 2015
    DOIhttps://doi.org/10.2324/gomu.88.86
    JOURNAL FREE ACCESS
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    The surface of cross-linked rubber gives a sticky touch in general. Its frictional coefficient is quite high and very sensitive to velocity and temperature, in addition to generating stick-slip motion and Schallamach wave during frictional sliding. Similar behaviors are also observed in gel and uncross-linked rubber, which seems to indicate that a meniscus is formed in common on the surface of these materials in frictional sliding. Such a component spreading over a surface of cross-linked rubber may be an uncross-linked rubber phase, which governs the friction and wear of cross-linked rubber.
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Report
  • On the Renewed Possibility of Natural Rubber Yielding Plants (Part II)
    Shinzo KOHJIYA
    2015 Volume 88 Issue 3 Pages 93-97
    Published: 2015
    Released on J-STAGE: June 16, 2015
    DOIhttps://doi.org/10.2324/gomu.88.93
    JOURNAL FREE ACCESS
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    It has been known that lots of plants are rubber yielding besides Hevea brasiliensis. Among them, only Hevea brasiliensis has been actively cultivated to produce rubber. Recently, studies on non-Hevea rubber yielding plants are focused, which seem to become more and more important in this century. In this part, revival of guayule and koksaghyz is specifically noted together with new biotechnological studies, genome engineering, in particular. Based on the analysis of the scientific and industrial trends, several measures for more natural rubber production are proposed from the sustainability viewpoint.
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Activity Report
Technical Note
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