NIPPON GOMU KYOKAISHI
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Volume 96, Issue 1
Displaying 1-6 of 6 articles from this issue
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Regular Papers
  • Influence of Mastication of NBR on Dispersion of Carbon Black
    Koji OKAMOTO, Michiharu TOH, Ken NAKAJIMA
    2023 Volume 96 Issue 1 Pages 3-10
    Published: 2023
    Released on J-STAGE: March 28, 2023
    DOIhttps://doi.org/10.2324/gomu.96.3
    JOURNAL FREE ACCESS
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    In this study, we investigated the effects of different mastication on dispersion of carbon black (CB) and mixing using NBR with different raw material rubber viscosity and acrylonitrile content. In addition, the effects of rheological unit on the order of ?m, which are considered to be caused by mastication, on them were discussed. In NBR, CB dispersion is improved by sufficient mastication and mastication at low temperature. Furthermore, CB is easily dispersed in the case of NBR with low viscosity or high acrylonitrile content. On a microscopic scale, if CB incorporation is completed with large rheological unit remaining due to insufficient mastication, these large rheological unit remain until the end of mixing, which contributes to CB dispersion reduction. We found that the subdivision of NBR on the micro-scale has a greater effect on CB dispersion than the viscoelasticity of masticated NBR on the macro-scale. On the other hand, for BIT, temperature of masticated NBR on the macro-scale has a greater effect than the subdivision of NBR on the micro-scale.

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  • Material Modulus Estimation for Drop Impact of Viscoelastic Body onto Plate
    Hiroyuki IWAMOTO, Muneharu SAIGO, Kohei YUGE, Hiroshi KATO
    2023 Volume 96 Issue 1 Pages 11-16
    Published: 2023
    Released on J-STAGE: March 28, 2023
    DOIhttps://doi.org/10.2324/gomu.96.11
    JOURNAL FREE ACCESS
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    This paper deals with the material modulus estimation for the impact of dropped viscoelastic material bodies. A bar model was investigated firstly as it is easy to understand the impact phenomena. Besides the fundamental material modulus of impact, Young's modulus and density, two dimensionless viscoelastic material parameters, the ratio of the long-term elastic modulus to the short-term one and the relaxation modulus to the wave propagation time along a bar, were found to be the other key parameters. The dropped viscoelastic spheres were investigated secondly and shown to have similar impact characteristics to bars regarding these two key parameters. We can estimate the material modulus very quickly in the computation analysis by tuning these parameters. And this approach is very useful to design the impact source of dropped sphere from the point of view of the viscoelastic materials.

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