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Chen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Applied Polymer Science, 100(6), p.4565 - 4574, 2006/06
Times Cited Count：44 Percentile：75.8(Polymer Science)This study concerns a comparative study of three crosslinkers, divinylbenzene (DVB), 1,2-bis(p,p-vinylphenyl)ethane (BVPE) and triallyl cyanurate (TAC) crosslinked poly(ethylene-co-tetrafluoroethylene) (ETFE)-based radiation-grafted membranes, which were prepared by radiation grafting of p-methylstyrene (MeSt) onto ETFE films and subsequent sulfonation. The effect of the different types and contents of the crosslinkers on the grafting and sulfonation, and the properties such as water uptake, proton conductivity and thermal/chemical stability of the resulting polymer electrolyte membranes was investigated in detail. Introducing crosslink structure into the radiation-grafted membranes leads to a decrease in proton conductivity due to the decrease in water uptake. The thermal stability of the crosslinked radiation-grafted membranes is also somewhat lower than that of the noncrosslinked one. However, the crosslinked radiation-grafted membranes show significantly higher chemical stability characterized in the 3% H
O at 50
C. Among the three crosslinkers, the DVB shows a most pronounced efficiency on the crosslinking of the radiation-grafted membranes, while the TAC has no significant influence; the BVPE is a mild and effective crosslinker, showing the moderate influence between the DVB and TAC crosslinkers.
Sawada, Shinichi; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Yoshida, Masaru
Transactions of the Materials Research Society of Japan, 30(4), p.943 - 946, 2005/12
We synthesized crosslinked-polytetrafluoroethylene (PTFE) electrolyte membranes by a radiation grafting technique under different conditions, and then investigated their proton conduction properties at controlled temperatures and relative humidities (R.H.) by an AC impedance method. The density and length of graft chains were controlled by varying the pre-irradiation dose and grafting time, respectively. When the pre-irradiation dose was fixed at 15 kGy to make the graft chains an uniform density, the elongation of the graft chain increased the ion exchange capacity (IEC), there by enhancing their proton conductivity. The membrane with an IEC of 2.8 meq/g possessed the maximum conductivity reaching 0.20 S/cm at 80 C and R.H. 95%. At almost the same IEC, membranes with more and shorter graft chains showed higher conductivity than those with less and longer chains. This result was probably related to the different structures of hydrophilic domains as proton-conducting pathways.
O
ceramics from precursor polymers by radiation curingWach, R.; Sugimoto, Masaki; Lam, N. D.; Yoshikawa, Masahito
Proceedings of 8th SPSJ International Polymer Conference (IPC 2005) (CD-ROM), 60 Pages, 2005/07
no abstracts in English
-poly(alkyl vinyl ether) membranes for polymer electrolyte membrane fuel cells by radiation processingChen, J.; Asano, Masaharu; Yamaki, Tetsuya; Yoshida, Masaru
Journal of Membrane Science, 256(1-2), p.38 - 45, 2005/06
New polymer electrolyte membranes having sulfonic acid groups for polymer electrolyte membrane fuel cell applications were prepared by simultaneous radiation-induced grafting method. The poly(tetrafluoroethylene) (PTFE) films, crosslinked by electron-beam radiation at molten temperature, were used as substrates for grafting of two alkyl vinyl ether monomers, propyl vinyl ether (nPVE) and isopropyl vinyl ether (iPVE), under controlled grafting conditions followed by sulfonation reactions. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), water contact angle and Fourier transform infrared (FTIR) were used to characterize the crosslinked PTFE (cPTFE) and grafted cPTFE films. The degree of grafting was found to be dependent on the grafting parameters such as irradiation temperature and Lewis acid catalyst, in which in the presence of Lewis acid catalyst or at a temperature close to the boiling point of each monomer, the grafting reaction significantly accelerated even when the relatively low dose was irradiated. Finally, the grafted cPTFE films were sulfonated in a chlorosulfonic acid solution. In spite of the lower ion-exchange capacity (0.75 mmol/g), the membrane synthesized in this study showed a proton conductivity as high as the Nafion 112.
Nagasawa, Naotsugu; Yagi, Toshiaki; Kume, Tamikazu; Yoshii, Fumio
Carbohydrate Polymers, 58(2), p.109 - 113, 2004/11
Times Cited Count：116 Percentile：96.06(Chemistry, Applied)A new biodegradable starch derivative hydrogel, carboxymethyl starch (CMS) hydrogel, was synthesized by irradiation in high concentrated solution (in the so-called paste-like condition). The effect of the solution concentration on the crosslinking of CMS, the properties of formed hydrogel and the biodegradability were investigated. The crosslinking of CMS was induced by irradiation at concentration range from 20 to 50 %. 1 g of the dry gel formed from the solution at concentration of 40 % crosslinked at dose of 2 kGy was able to absorb about 500 and 26 g of distilled water and 0.9 % NaCl, respectively. Biodegradation of crosslinked CMS (irradiated in 50 % solution at a dose of 5 kGy) by controlled composting was about 40 % after 2 weeks which was faster than standard cellulose powder. The contribution of crosslinking in CMS was elucidated from crosslinking behaviors of carboxymethyl amylopectin (CMAP) and carboxymethyl amylose (CMA). The crosslinked CMAP (irradiated at a concentration range from 10 to 50 %) reveal higher gel fraction and water-uptake than that of CMA. The amylopectin region in CMS is predominantly responsible for crosslinking of CMS.
Yamaki, Tetsuya; Kobayashi, Kazuhiro; Asano, Masaharu; Kubota, Hitoshi*; Yoshida, Masaru
Polymer, 45(19), p.6569 - 6573, 2004/09
Times Cited Count：56 Percentile：82.78(Polymer Science)We prepared proton exchange membranes by the 
-ray-induced post grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. The degree of grafting was controlled in the range of 7-75% by the crosslinking density of the PTFE matrix as well as the grafting conditions. Under our preparation conditions, the films at the grafting yield of 
30% were found to produce ion exchange membranes with a homogeneous distribution of sulfonic acid groups. The resulting membranes showed a large ion exchange capacity up to 2.9 meq g
, which exceeded the performance of commercially-available perfluorosulfonic acid films such as Nafion; nevertheless, they appeared to be dimensionally stable in water. These should undoubtedly result from the use of the crosslinked PTFE films as graft substrates and make our ion exchange membranes promising for applications to polymer electrolyte fuel cells.
Oshima, Akihiro; Udagawa, Akira; Morita, Yosuke
Radiation Physics and Chemistry, 60(4-5), p.467 - 471, 2001/03
Times Cited Count：12 Percentile：64.73(Chemistry, Physical)Plain-woven carbon fber-filled polytetrafluoroethylene (PTFE)composites were fabricated by radiation-crosslinking under selective conditions.High mechanical and frictional properties are found in the composite materials compared with crosslinked PTFE without fiber.The composite materials with optional shapes,which are laminated after electron beam (EB) crosslinking treatment of each mono-layer could also be fabricated.
Oshima, Akihiro; Udagawa, Akira; Morita, Yosuke
Radiation Physics and Chemistry, 60(1-2), p.95 - 100, 2001/01
Times Cited Count：8 Percentile：52.36(Chemistry, Physical)no abstracts in English
Yamazaki, Takanori*; Seguchi, Tadao
Journal of Polymer Science, Part A; Polymer Chemistry, 38(17), p.3092 - 3099, 2000/09
no abstracts in English
Oshima, Akihiro; Udagawa, Akira; Morita, Yosuke
Proceedings of International Symposium on Prospect for Application of Radiation towards the 21st Century, p.83 - 84, 2000/00
no abstracts in English
Seguchi, Tadao
Radiation Physics and Chemistry, 57, p.367 - 371, 2000/00
Times Cited Count：29 Percentile：85.04(Chemistry, Physical)no abstracts in English
*; Udagawa, Akira; Morita, Yosuke
Conference Proceeding RadTech Asia'99, p.507 - 512, 1999/08
no abstracts in English
Oshima, Akihiro; Seguchi, Tadao; Tabata, Yoneho
Polymer International, 48, p.996 - 1003, 1999/00
Times Cited Count：24 Percentile：68.24(Polymer Science)no abstracts in English
*; Seguchi, Tadao; *
Radiation Physics and Chemistry, 54(6), p.575 - 581, 1999/00
Times Cited Count：26 Percentile：85.59(Chemistry, Physical)no abstracts in English
*; *; *; Tabata, Yoneho*; Seguchi, Tadao; *
Radiation Physics and Chemistry, 54(2), p.165 - 171, 1999/00
Times Cited Count：78 Percentile：97.56(Chemistry, Physical)no abstracts in English
*; Seguchi, Tadao; Tabata, Yoneho*
Radiation Physics and Chemistry, 55(1), p.61 - 71, 1999/00
Times Cited Count：77 Percentile：97.51(Chemistry, Physical)no abstracts in English
Oshima, Akihiro; Seguchi, Tadao; Tabata, Yoneho*
Proceedings of IUPAC World Polymer Congress 37th International Symposium on Macromolecules (MACRO 98), P. 56, 1998/00
no abstracts in English
Seguchi, Tadao
Isotope News, (521), p.10 - 13, 1997/10
no abstracts in English
Oshima, Akihiro; Ikeda, Shigetoshi*; Seguchi, Tadao; Tabata, Yoneho*
Preprints of 6th SPSJ International Polymer Conference, P. 237, 1997/00
no abstracts in English
*; Seguchi, Tadao; Tabata, Yoneho*
Radiation Physics and Chemistry, 50(6), p.601 - 606, 1997/00
Times Cited Count：68 Percentile：96.84(Chemistry, Physical)no abstracts in English
