日本ゴム協会誌
Print ISSN : 0029-022X
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選択された号の論文の6件中1~6を表示しています
研究論文
  • 廣瀬 威仁, 福森 健三
    2024 年 97 巻 5 号 p. 111-118
    発行日: 2024年
    公開日: 2024/06/08
    ジャーナル 認証あり

    Multi-walled carbon nanotube (MWCNT) dispersed dynamically crosslinked olefin thermoplastic elastomers (D-TPEs) based on polypropylene (PP) /ethylene-propylene-diene copolymer rubber (EPDM) blends were prepared with paraffin (Par)-coated MWCNTs, showing good affinity with the EPDM phase, as reinforcing nanofillers. In particular, focusing on the reinforcement of the crosslinked and unfilled EPDM dispersed phase, we investigated the effects of the phase structure and MWCNT on the mechanical properties of the D-TPEs. In consequence, we suggest that the structure-controlling factors contributing to a notable enhancement in the mechanical properties of the D-TPEs are as follows: (ⅰ) the refinement of the size of the EPDM phase by compounding zinc dimethacrylate (ZDMA) as a compatibilizer; (ⅱ) preferentially localized dispersion of paraffin-coated MWCNTs in the crosslinked EPDM dispersed phase, contributing to reinforce the EPDM phase, synergistically connected with the controlling factor- (ⅰ) ; (ⅲ) the reinforcement effects due to the dispersion of ZDMA-derived nanoparticles in the EPDM phase.

  • 澤田 諭, 近藤 寛朗, 中西 洋平, 竹中 幹人, 柴田 基樹, 藤波 想, 宮﨑 司
    2024 年 97 巻 5 号 p. 119-124
    発行日: 2024年
    公開日: 2024/06/08
    ジャーナル 認証あり

    Time-resolved X-ray absorption fine structure (XAFS) spectroscopy measurements were conducted to clarify the difference in the formation behaviors of zinc compounds during vulcanization reaction in rubbers with two different vulcanization systems: efficient vulcanization and conventional vulcanization systems. The changes in the ratio of zinc compounds in sample rubbers with time were estimated from the changes in XAFS spectra during vulcanization processes. The results show that the rates of zinc compound formation and consumption were high when the vulcanization accelerator with high accelerating effects were used, and that the formed zinc compounds and the timing of their formation differed greatly depending on the type of vulcanization accelerator.

特論講座
  • 知野 圭介
    2024 年 97 巻 5 号 p. 125-130
    発行日: 2024年
    公開日: 2024/06/08
    ジャーナル 認証あり
    電子付録

    In general, since rubber has a weak interaction between molecular chains, if it is not crosslinked, it will flow and cannot withstand actual use. Covalent crosslinked rubber has high mechanical properties due to the strong bonding force of crosslinking, but it is difficult to be reshaped and recycled because of the difficulty to cleave the crosslink. On the other hand, thermoplastic elastomers use physical interactions between molecular chains (physical crosslinking) to suppress fluidity and express physical properties. Therefore, although it can be reshaped by disconnecting the physical crosslink due to heat, it lacks heat resistance (creep resistance). Heat resistance is very important in industrial materials, but thermoplasticity and heat resistance have a trade-off relationship. As an attempt to break this trade-off, many studies have been reported to use dynamic bonds such as hydrogen bonds, ionic bonds, and dynamic covalent bonds for crosslinking. However, this trade-off has not been resolved. In recent years, for the purpose of improving heat resistance and creep resistance, attempts have been made to introduce static covalent bonds to dynamic bonding crosslinks, which will be explained in this lecture.

  • 深堀 美英
    2024 年 97 巻 5 号 p. 131-138
    発行日: 2024年
    公開日: 2024/06/08
    ジャーナル 認証あり

    A new structure model of cross-linked rubber named “Gel- network structure model of cross-linked rubber” is proposed by the author, which is exactly different from a conventional molecular network structure model(Fig.4), as follows. (1) Gel network structure in cross-linked rubber is produced through a gelation process that gel-balls initiated randomly connect each other to make three-dimensional networks of gel-balls(Fig.12~Fig.14) . The gel network structure consists of three different regions, the gel-balls of very highly cross-linked, the molecular bundles of slightly cross-linked which connect the gel-balls each other and the uncross-linked regions(Fig.11). (2) The rigid gel-ball doesn’t deform under extension, but instead the dynamic behavior to generate the deformation of the system is produced by the extension and retraction of the molecular bundles of slightly cross-linked between the gel-balls, which produces the entropic force of the system. The uncross-linked region surrounded by the gel-balls is regarded as the passage where the uncross-linked rubber molecules flow freely under the extension. (3) The gel-ball network structure model is similar to the beads structure where the rigid gel-balls are connected with soft rubber strings (Fig.15) , such structures being observed in several polymer gels(Fig.16~Fig.18).

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