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Predecessor
Volume 72, Issue 5
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[in Japanese]1999 Volume 72 Issue 5 Pages 239-246
Published: 1999
Released on J-STAGE: July 09, 2007
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[in Japanese]1999 Volume 72 Issue 5 Pages 247-256
Published: 1999
Released on J-STAGE: July 09, 2007
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[in Japanese]1999 Volume 72 Issue 5 Pages 257-262
Published: 1999
Released on J-STAGE: July 09, 2007
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[in Japanese], [in Japanese], [in Japanese]1999 Volume 72 Issue 5 Pages 263-270
Published: 1999
Released on J-STAGE: July 09, 2007
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[in Japanese]1999 Volume 72 Issue 5 Pages 271-277
Published: 1999
Released on J-STAGE: July 09, 2007
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STUDY OF DEVULCANIZATION PROCESS FOR EPDMMakoto MOURI, Norio SATO, Hirotaka OKAMOTO, Mitsumasa MATSUSHITA, Hide ...1999 Volume 72 Issue 5 Pages 278-282
Published: 1999
Released on J-STAGE: July 09, 2007
JOURNAL FREE ACCESSWe studied devulcanization process by measuring rubber state, viscosity, gel fraction, its effective network chain density and average molecular weight of sol. When passing through grinding zone, vulcanized rubber was ground by screw rotation and its size became small. Next, devulcanization proceeded in the devulcanizing zone and viscosity of rubber decreased. Gel fraction and its effective network chain, density decreased too. Finally, gel fraction of devulcanized rubber was 45% and its effective network chain density was one twentieth of virgin vulcanized rubber. On the other hand, average molecular weight of sol part did not change and its value was nearly equal to virgin raw rubber. Devulcanization process depended on shear stress by screw rotation. Gel fraction and its effective network chain density decreased by increasing screw rotation. Devulcanization rate depended on reaction temperature and became high by raising temperature.View full abstractDownload PDF (752K) -
DEVULCANIZATION MECHANISM FOR EPDMMakoto MOURI, Norio SATO, Hirotaka OKAMOTO, Mitsumasa MATSUSHITA, Hide ...1999 Volume 72 Issue 5 Pages 283-287
Published: 1999
Released on J-STAGE: July 09, 2007
JOURNAL FREE ACCESSMechanism of devulcanization by shear flow stage reaction control technology for sulfur vulcanized EPDM rubber has been studied based on network structure of devulcanized rubber and behavior of crosslinking bond breakage. Sulfur crosslinking bonds of vulcanized rubber are broken selectively during the devulcanization reaction. There are three types of crosslinking bonds such as monosulfide, disulfide and polysulfide bond. At the initial stage of reaction, polysulfide and disulfide bonds are changed to monosulfide bond by heat. Furthermore, monosulfide bond is broken by addition of shear stress and devulcanized rubber is obtained finally. Residual sulfur atom at the broken crosslinking bonds are stabilized by reaction of adjacent hydrogen atom and change into less reactive sulfur functional groups.View full abstractDownload PDF (651K) -
EFFECT OF MIXED FATTY ACID ON THE CRYSTALLIZATION OF CIS-1, 4 POLYISOPRENESeiichi KAWAHARA, Naoyuki NISHIYAMA, Ai MATSUURA, Takashi KAKUBO, Yasu ...1999 Volume 72 Issue 5 Pages 288-293
Published: 1999
Released on J-STAGE: July 09, 2007
JOURNAL FREE ACCESSCrystallization behavior of synthetic cis-1, 4 polyisoprene (IR), used as a model for natural rubber, was investigated by dilatometry at -25°C. The rate of crystallization increased in the presence of fatty acid. The acceleration effect of fatty acid on the rate of crystallization was explained with respect to the transition temperature, Tc, at which fatty acid crystallized during cooling after melting at 120°C. The crystallization rate of IR was accelerated at Tc. A similar dependence of crystallization behavior of IR on Tc of fatty acid was also shown for a mixture of saturated fatty acids or saturated fatty acid esters and unsaturated fatty acids. A mixture of stearic acid and methyl linoleate also promoted the crystallization of IR, despite that stearic acid was not miscible with methyl linoleate. The most rapid crystallization of IR was found when the ratio of stearic acid to methyl linoleate was 1:3, being consistent with the ratio of saturated to unsaturated fatty acids in natural rubber.View full abstractDownload PDF (850K) -
EFFECT OF LINKED FATTY ACID ON THE CRYSTALLIZATION OF CIS-1, 4 POLYISOPRENESeiichi KAWAHARA, Takashi KAKUBO, Ai MATSUURA, Eng Aik-Hwee, Yasuyuki ...1999 Volume 72 Issue 5 Pages 294-300
Published: 1999
Released on J-STAGE: July 09, 2007
JOURNAL FREE ACCESSThe effect of fatty acid linked to cis-1, 4 polyisoprene on the crystallization of polymer chain was investigated by differential scanning calorimetry (DSC) and dilatometry at -25°C. Synthetic cis-1, 4 polyisoprene (IR) was esterified with stearic acid selectively at 3, 4 isoprene units after introduction of OH group by hydroboration (IR-C 18). The rate of crystallization of IR-C 18 was increased by the addition of saturated fatty acids. The addition of methyl linoleate promoted the crystallization of IR-C 18, whereas it suppressed the crystallization of IR. This was explained to be due to a synergistic effect of mixed and linked fatty acids on the crystallization of IR. Stearic acid was introduced into natural rubber (NR) by esterification after purification of NR by deproteinization followed by acetone extraction and transesterification with NaOCH3. The content of stearic acid in the esterified NR (DPNR-C 18) was about 1/2 compared to the ester content in untreated NR. The rate of crystallization of DPNR-C 18 was similar to that of DPNR-TE and was not increased by the addition of methyl linoleate. Precooling of the rubber at 0, 10 and 30°C before crystallization at -25°C resulted in a significant difference in the crystallization rate between untreated NR, DPNR-TE and DPNR-C 18, where the crystallization of only untreated NR was promoted by precooling. This demonstrates the presence of a critical concentration of linked fatty acid on the crystallization of NR, at which the synergistic effect was promoted with mixed fatty acids.View full abstractDownload PDF (899K) -
[in Japanese]1999 Volume 72 Issue 5 Pages 302-303
Published: 1999
Released on J-STAGE: July 09, 2007
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