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Volume 76, Issue 12
Displaying 1-6 of 6 articles from this issue
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Changes in Molecular Mobility and Crosslinking Density Caused by Carbon BlackHitoshi IWABUKI, Kazuya NAGATA, Toru NOGUCHI, Eisuke YAMADA2003 Volume 76 Issue 12 Pages 429-435
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSPeroxide-crosslinked EPDMs filled with various kinds of carbon black (CB) were examined by 1H pulsed NMR. The signal of spin-spin relaxation time (T2) measured by Hahn echo method was resolved into two components, T2n and T2nn, which correspond to the network molecules and the non-network molecules respectively. For the non-crosslinked EPDMs filled with CB, T2n and T2nn became shorter with the increase in the specific surface area of CB, though the degree of the decrease in the molecular mobility was smaller in the case of the network component. For the crosslinked EPDMs, T2n and T2nn became longer with the increase in the specific surface area of CB, suggesting that the presence of the CB obstructs the crosslinking. The crosslinking density of rubber phase (νR) were calculated from the relationship between the apparent crosslinking density (νS) and the reciprocal of T2n (1/T2n) for unfilled EPDMs. The crosslinking density related to CB (νF) were obtained from the difference betweenνS and νR for CB-filled EPDMs. The νF values showed good correlation with the tensile stress at 100% elongation.View full abstractDownload PDF (1171K) -
Yoshihiro SOEDA, Atsushi SUGITA, Shigeru TASAKA2003 Volume 76 Issue 12 Pages 436-440
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSThe structure of interphase between nylon 11 and brominated Isobutylene/p-methylstyrene copolymer(BIMS)containing the small amount of halogen moieties at the mixing temperature of dynamic vulcanization was discussed. The graft-reaction between nylon 11 and BIMS occurred below the melting temperature of nylon 11. The lower contact angle and the better adhesion properties of this system were observed at the mixing temperature at 200-220°C. The surface of the copolymer, after the thermal elimination of bromine atom, may rapidly react with nylon 11 to make chemical bonds and to promote the formation of a micro-dispersion system.View full abstractDownload PDF (847K) -
Toshihiro TADAKI2003 Volume 76 Issue 12 Pages 441-445
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSHigh cis-polybutadienes(poly BD) are widely used in the industrial field such as materials for tire or golf ball.
High cis-poly BD prepared from Ziegler-type catalyst system are effective to take a cis configuration in high levels, however, the molecular weight distributions (Mw/Mn) of obtained poly BDs are fairly broad. Poly BD having both narrow Mw/Mn and high cis configuration levels are desirable for the purpose of better abrasion resistance, higher resilience and lower heat build-up, and so on.
Recently, the new polybutadiene rubbers polymerized by Nd catalyst (Nd-poly BD) has been developed. Nd-poly BDs have higher 1, 4-cis bond content, lower 1, 2-vinyl bond content, narrower Mw/Mn and higher linearity than the conventional Ziegler-type Ti, Co or Ni catalyzed poly BD.
Evaluation on polybutadiene only and carbon black system for tire application was carried out. Nd-poly BD showed better processability, lower hysteresis loss and higher abrasion resistance. Furthermore, evaluation on golf ball formulation was carried out. Nd-poly BD had the potential of higher resilience property than Ni catalyzed poly BD from the results of lower tanδ value at -20°C. These results indicate that Nd-poly BD is a much for industrial application such as tire, golf ball and so on.View full abstractDownload PDF (1007K) -
An Approach from Prenyltransferase Gene AnalysisSeiji TAKAHASHI, Tanetoshi KOYAMA2003 Volume 76 Issue 12 Pages 446-452
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSLinear prenyl diphosphates whose carbon chain length varies widely from geranyl diphosphate (C10) to natural rubber (C>105) are biosynthesized by the catalytic function of a group of enzymes called prenyltransferases. Prenyltransferases are classified in two major groups, trans- or (E)-prenyltransferases and cis- or (Z)-prenyltransferases. From the year of 1987, many genes encoding (E)-prenyltransferases have been cloned and characterized well. However, the structure and detailed mechanism of (Z)-prenyltransferase had been completely unknown until our identification of a gene encoding the undecaprenyl diphosphate synthase (UPS) from Micrococcus luteus B-P 26. Not only the primary structure but also the tertiary structure of the UPS is quite different from those of (E)-prenyltransferases. Multiple alignment of primary structures of (Z)-prenyltransferases identified from various organisms reveals that there are five highly conserved regions among (Z)-prenyltransferases. In order to elucidate the biosynthetic pathway of natural rubber which is composed of cis-1, 4-polyisoprene, we isolated and characterized two genes encoding (Z)-prenyltransferases from the latex in Hevea brasiliensis by using sequence information on the conserved regions of (Z)-prenyltransferases. In vitro rubber transferase assay using the recombinant gene product revealed that the enzyme catalyzed the formation of polyprenyl products with approximate sizes around 1×104 Da. Moreover, in the presence of washed bottom fraction from latex, the rubber transferase activity and the size of the major product was increased, suggesting a possible requirement of certain activation factors in the washed bottom fraction for the production of high molecular weight rubber.View full abstractDownload PDF (1465K) -
Hiroyuki KOYAMA2003 Volume 76 Issue 12 Pages 453-459
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSIt is paid attention the odor that occur from several engineering manufactures made polymers to set more value, and the estimation of odor is important by reason of the advance as the comfortable life environment. It is explained about the mechanism of human odor detection and the analysis methodology of odor, and is introduced about the solution for the odor include of vehicle cabin and polymers.View full abstractDownload PDF (1210K) -
No 1, General Rules of ReinforcementYoshihide FUKAHORI2003 Volume 76 Issue 12 Pages 460-465
Published: 2003
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSAddition of carbon black significantly improves physical and mechanical properties of elastomers. That is, it greatly increases modulus, tensile strength, tear strength, fatigue resistance and wear resistance of unfilled elastomers. This improvement is called“Carbon black reinforcement”, and has been widely discussed. Nevertheless, most of theories, ideas and models proposed deal only with a part of the above phenomena, rather than addressing the overall phenomena to give an unified and synthetic concept.
In this paper, we would like to generalize the fundamental concept of reinforcement and apply it to the carbon black reinforcement of rubber. That will be the basic of a new concept and theory being proposed by the author.View full abstractDownload PDF (1044K)
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