NIPPON GOMU KYOKAISHI
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Volume 85, Issue 5
Displaying 1-5 of 5 articles from this issue
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Regular Papers
  • Influence of Side Group Contents of Polycarbonate Glycol on Aggregation Structures and Mechanical Properties of Polyurethane Elastomers
    Ken KOJIO, Mutsuhisa FURUKAWA, Suguru MOTOKUCHO, Motonori MIZOKAMI, Ko ...
    2012 Volume 85 Issue 5 Pages 151-156
    Published: 2012
    Released on J-STAGE: August 02, 2013
    DOIhttps://doi.org/10.2324/gomu.85.151
    JOURNAL FREE ACCESS
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    Polycarbonate (PC) glycol synthesized from 1,6-hexanediol and 2-butyl-2-ethyl-1,3-propanediol (BEPD) with various ratios were employed to control the mechanical property of PC-glycol-based polyurethane elastomers (PUEs). The PUEs were synthesized from PC-glycol, 4,4’-diphenylmethane diisocyanate and 1,4-butanediol by a one-shot method. The degree of microphase separation became weaker with an increase in the BEPD content. This trend results in a decrease in Young’s modulus due to the lack of the formation of crystallized hard segment domains in the PUEs. Tensile strength and strain at break decreased and increased with increasing BEPD content, respectively. This result clearly suggests that butyl and ethyl groups of the BEPD part suppressed the packing of the soft segment under elongation.
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  • Methanolysis of the Polyurea in Subcritical or Supercritical Carbon Dioxide
    Suguru MOTOKUCHO, Shingo MUKAI, Mutsuhisa FURUKAWA, Ken KOJIO, Kohji Y ...
    2012 Volume 85 Issue 5 Pages 157-161
    Published: 2012
    Released on J-STAGE: August 02, 2013
    DOIhttps://doi.org/10.2324/gomu.85.157
    JOURNAL FREE ACCESS
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    Methanolysis of polyurea (PUA) in the subcritical carbon dioxide was investigated. PUA was synthesized from 4,4'-diphenylmethane diisocyanate and water in the N,N-dimethylformamide. The methanolysis were performed in the temperature range from 160 to 190 °C and under supercritical state of carbon dioxide at pressures from 3.5 to 13.8 MPa. The methanolysis of PUA at 190 °C in the pressure range from 4.3 to 7.3 MPa gave methanol soluble products composed of dimethyl-carbamate, diamine and carbamate-amine compounds in 97-99 % conversion.
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  • A Visualizing Study of Blister Fracture in Rubber O-rings
    Atsushi KOGA, Tadahisa YAMABE, Hiroyuki SATO, Kenichi UCHIDA, Junichi ...
    2012 Volume 85 Issue 5 Pages 162-167
    Published: 2012
    Released on J-STAGE: August 02, 2013
    DOIhttps://doi.org/10.2324/gomu.85.162
    JOURNAL FREE ACCESS
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    In order to establish a hydrogen energy system, the reliability of sealing rubber for high-pressure hydrogen has been required. The rubber O-ring for hydrogen energy system is used with pressurized-decompress cycle of high-pressure hydrogen. It causes internal cracks referred as blister fracture. Degradation of seal performance originated from blister fracture is one of the important issues to improve the reliability. This study focused on the blister initiation behavior and the effect of materials, gas species and decompression rate on blister fracture in terms of visualizing O-ring behavior under high-pressure gas. For the visualizing evaluation, a transparent ethylene-propylene rubber (EPDM) and vinyl-methyl silicone rubber (VMQ) O-rings were molded, and a special viewable high-pressure vessel with a glass viewport was developed. The O-ring specimens were exposed to high-pressure hydrogen, helium, and nitrogen at 10 MPa until gas solubility content in O-ring was saturated; afterwards, these gases were decompressed with some rate. It was obviously visualized that the blister fracture did not occur in VMQ O-ring but occurred in EPDM. The blister fracture of the EPDM O-ring in nitrogen was the most serious in the tested gases. These blister behaviors are considered to be related to gas diffusivity of hydrogen, helium and nitrogen.
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