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Volume 77, Issue 10
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[in Japanese]2004 Volume 77 Issue 10 Pages 335
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSDownload PDF (151K) -
Shigeki TAKISHIMA2004 Volume 77 Issue 10 Pages 336-342
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSSolubility, diffusivity and viscosity in supercritical fluid and polymer systems are reviewed. Supercritical fluids such as carbon dioxide dissolve in polymers at high pressures and plasticize them. The increase in diffusivity and the decrease in viscosity of polymers with dissolved supercritical fluids are due to the plasticizing effect of supercritical fluids. In this article general tendency, data source and theoretical calculation methods of solubility, diffusivity and viscosity are presented for supercritical carbon dioxide and nitrogen in polymers.View full abstractDownload PDF (1140K) -
Shigeo NISHIKAWA2004 Volume 77 Issue 10 Pages 343-347
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSSupercritical carbon dioxide is an environmentally friendly material and has great potential for the modification and processing of polymers. Addition of supercritical carbon dioxide to various polymers may lower the glass transition temperature, melt viscosity, and interfacial tensions. The aim of this study is to contribute to the development of the new processes and new products of high value and conserving the global environment. We have studied processes of foaming, reactive processing, and impregnation using supercritical carbon dioxide. The results from our work indicate that the solubility and diffusivity of carbon dioxide in polymers are key parameters for control of these processes.View full abstractDownload PDF (1020K) -
Hiromu SAITO2004 Volume 77 Issue 10 Pages 348-352
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSWe found characteristic morphologies of polymers having various shape and size by annealing under supercritical carbon dioxide. Mosaic crystals consisting of regularly arranged straight and thick lamellae were obtained in polypropylene by crystallization under supercritical carbon dioxide due to local ordering in the melt state. On the other hand, interconnected porous structure was obtained by liquid-liquid phase separation of polycarbonate and supercritical carbon dioxide via spinodal decomposition. Nano-porous structure with various shape of layer type and network one was also obtained by annealing polypropylene/clay nanocomposite, polyethylene, aramid, and polyimide gel under supercritical carbon dioxide.View full abstractDownload PDF (1473K) -
Idzumi OKAJIMA, Takeshi SAKO2004 Volume 77 Issue 10 Pages 353-358
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSPlastic recycling using supercritical fluids was investigated to develop promising future techniques. Supercritical water (Tc=374°C, Pc=22.1MPa) and supercritical methanol (Tc=239°C, Pc=8.09MPa) were used mainly because they are chemically stable, cheap and environmentally friendly. Here we introduced the several hopeful applications: decomposition and recovery of constituent monomers from polyethylene telephthalate and polyethylene naphtalate using supercritical methanol, breaking of bridging point and subsequent material recycling of cross-linked polyethylene using supercritical methanol, separation and recovery of constituent monomer and plastic from laminate films composed of polyamide and polyethylene using subcritical water, decomposition of thermosetting plastic without solid residue using supercritical water, decomposition of plastics and recovery of fibers in CFRP and GFRP with supercritical water, decomposition and debromination of flame-resistant polymer containing bromine atoms by using subcritical water and gasification and hydrogen production of plastics by use of supercritical water.View full abstractDownload PDF (1189K) -
Toshiharu GOTO, Takanori YAMAZAKI2004 Volume 77 Issue 10 Pages 359-364
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSThe material recycling of cross-linked polymer is difficult because of its low fluidity born of cross-linking element. There are several researches that decompose the cross-linked polymer to improve the fluidity of cross-linked polymer using share stress or heat. But it is hardly to sever the cross-linking element of Si-XLPE (silane cross-linked polyethylene) selectively by these technique. So, recycling rate of Si-XLPE was not improved drastically because of the poor processability and mechanical properties of the recycled PE.
We found out that the cross-linking element of Si-XLPE could be severed selectively by supercritical alcohol. The efficient process for reforming the Si-XLPE by supercritical alcohol is necessary to industrialize this technique. This is the common problem for the application of supercritical fluid. We suggested the continuous process using extruder for supercritical fluid. It was indicated that the twin-screw extruder could be used as the continuous reactor of the supercritical alcohol.
The properties of the products satisfy the standard of the insulation of 600V cross-linked polyethylene cable. More research for industrializing this technique will be prosecuted.View full abstractDownload PDF (1202K) -
Masaru NAKAHARA2004 Volume 77 Issue 10 Pages 365-371
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSThis review on supercritical water reactions of rubbers is composed of the following chapters: 1) Introduction, 2) Synthetic Processes in Hot and Supercritical Water Complementary to Photosynthesis, 3) What Is Supercritical Water? 4) Rate-Controlling Factors of Supercritical Water Reactions, 5) Chemical Bonds Composing Rubbers and Their Reactivity, 6) Reactions of Synthetic Rubbers Studied in Supercritical Water, and 7) Future Problems. The importance of the development of science and technology of supercritical water reactions are emphasized in relation to green chemistry. It is shown that hydrothermal reactions of used rubbers and other organics is investigated in order to conserve chemical bonds, such as C-C, C-H etc. contained in rubbers, instead of their oxidative degradation by burning. Learning from chemical evolution on the primitive earth, thus we hope that hydrothermal synthesis can replace photosynthesis as much as possible to avoid the energy crisis of the 21st century. For recycling styrene-butadiene and ethylene-propylene rubbers, several works have been carried out in sub- and supercritical water. Used rubbers can be converted to useful organic compounds. Ethylene-propylene rubbers are cracked to paraffin oils, while styrene-butadiene rubbers are transformed into benzene and its derivatives.View full abstractDownload PDF (1495K) -
[in Japanese]2004 Volume 77 Issue 10 Pages 372-373
Published: 2004
Released on J-STAGE: May 28, 2007
JOURNAL FREE ACCESSDownload PDF (355K)
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