NIPPON GOMU KYOKAISHI
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Volume 94, Issue 1
Displaying 1-3 of 3 articles from this issue
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Advanced Course on Rubber Science and Technology
  • Unified Physical Concept of Friction and Wear of Rubber Part 3: A New Philosophy and Theory for Rubber Friction
    Yoshihide FUKAHORI
    2021 Volume 94 Issue 1 Pages 3-10
    Published: 2021
    Released on J-STAGE: March 16, 2021
    DOIhttps://doi.org/10.2324/gomu.94.3
    JOURNAL FREE ACCESS
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    The author proposes a new philosophy and theory for rubber friction that are significantly different from the existing classical theories. The total friction coefficient μall incorporates three factors including an adhesion term μadh, a deformation term μdef and a crack formation term μcrac. This generates an equation

    μall=μadh+μdef+μcrac≒μadh [1+K2（ tanδ/√2+√2 Kεc）E−7/6 W1/6 ]

    where η is the viscosity of the uncross-linked phase, E the modulus of the cross-linked rubber, V sliding velocity, C crack length, W normal load, K1, K2, Kε are all coefficients. The adhesion term is the most dominant factor during rubber friction, which roughly contributes about 70～80% of the total friction coefficient as the zeroth approximation. The new theory might prepare a quite reasonable interpretation for the velocity and normal load dependence of the friction coefficient of the rubber, which is related closely to the formation of meniscus in the interface between the rubber and the solid.

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  • Chemistry of Sulfur Chain and Design of Dynamic Soft Materials Using Rotaxane Effect of Rotaxane-Crosslink (1)
    Toshikazu TAKATA
    2021 Volume 94 Issue 1 Pages 11-17
    Published: 2021
    Released on J-STAGE: March 16, 2021
    DOIhttps://doi.org/10.2324/gomu.94.11
    JOURNAL FREE ACCESS
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    In this review, we would like to discuss on the effect of rotaxane-crosslink on the toughening of crosslinked polymer, which is obtained by copolymerization of two-vinyl group-tethering rotaxane crosslinker (RC) with a typical vinyl monomer such as n-butyl acrylate. Rotaxane-crosslinked polymer (RCP) always showed higher mechanical property than covalently crosslinked polymer (CCP). As for the effect of movable distance of the wheel component along the axle component, RCP obtained from longer axle-possessing RC showed higher toughness than that from shorter one. Meanwhile, rotaxane crosslinkers having thickness-different axle components were prepared to evaluate the effect of actual mobility on the mechanical property. RCPs derived from RC consisting of higher mobile components showed toughness stronger than that derived from RC with lower mobile components. The effect of the rotaxane crosslink on the toughening of crosslinked polymer was accounted for the high mobility and freedom of the rotaxane components, while the toughening mechanism was studied on the basis of timing of the transition from Affine deformation to Non-Affine deformation caused by the rotaxane crosslink.

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