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Shin, Mu-Hak;Bae, Bong-Jin;Kim, Myeong-Hwan
- Journal of Technologic Dentistry
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- v.2 no.1
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- pp.21-24
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- 1980
This experiment was intended to obtain a prefect casting body the same as the original wax patterns by melting metal into the opening of the ring. The investment ring was dried to the temperature between 600 and 700, when the wax pattern would be completely melted to leave an empty mould made in the ring. The main point to studied was the investing process for perfect casting body. This process was experimented on several important factors: the size and spatulation of investment particles, purity of wax patterns, investing time after the completion of model, and investing temperature. The results obtained from the above experiment were as follows: A desirable cast body with no fissure or pore would be mode by investing with smaller particles in the first time and with larger onces in the second, both at the temperature between 180.
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장원철;공명선
- Bulletin of the Korean Chemical Society
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- v.20 no.10
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- pp.1195-1199
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- 1999
2-(2,4,5-Trimethoxyphenyl)-4-methylene-1,3-dioxolane (1b), 2-(2,4,6-trimethoxyphenyl)-4-methylene-1,3-di-oxolane (2b), and 2-(3,4,5-trimethoxyphenyl)-4-methylene-1,3-dioxolane (3b) were prepared and polymerized with boron trifluoride. Boron trifluoride catalyzed reaction proceeded via mainly ring-opening polymerization and cyclization reaction to yield poly(keto ether) and 3(2H)-dihydrofuranone. The yields of polymer and cyclized product exhibited a dependency on the position of the methoxy substituents in the benzene ring of 2-phenyl-4-methylene-1,3-dioxolane derivatives. Electrophilic attack of methylene or oxygen atom on 4-meth-ylene-1,3-dioxolane ring were suggested for the polymerization and cyclization.
https://doi.org/10.5012/bkcs.1999.20.10.1195 인용 PDF

Yoon, Kyung-Hwan;Park, Seung-Beom;Park, In-Sook;Yoon, Do-Y.
- Bulletin of the Korean Chemical Society
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- v.32 no.spc8
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- pp.3074-3080
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- 2011
We synthesized three novel poly(norbornene bisimide)s by ring opening metathesis polymerization (ROMP) and subsequent hydrogenation. Their thermal, mechanical and optical properties were investigated with TGA, DMA, UV-Vis spectrometer, and optical reflectometer. The new polymers showed high glass transition temperatures over $260^{\circ}C$ and good thermal stability with 5% wt-loss temperature higher than $390^{\circ}C$. When solvent casted, they yielded optically transparent and dimensionally stable films with a relatively low coefficient of thermal expansion of about 50 ppm $K^{-1}$. Therefore, the bisimide moieties substantially enhanced thermal and dimensional stabilities, as compared with normal ROMP-prepared polynorbornene films. Though the water uptake was increased to 0.6 wt-%, this water uptake is still considerably lower than that for polyethersulfones (1.4 wt-%) or polyimides (2.0 wt-%). Hence, the new poly(norbornene bisimide)s may become attractive candidates for flexible substrates of optoelectronic devices such as displays and photovoltaic solar cells.
https://doi.org/10.5012/bkcs.2011.32.8.3074 인용 PDF KSCI

Park, Gyo Ik;Lee, Wha Young;Song, In Kyu
- Applied Chemistry for Engineering
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- v.9 no.7
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- pp.1018-1022
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- 1998
Characteristics and catalytic activities of 12-molybdophosphoricacid catalysts modified by ring opening polymerization of tetrahydrofuran (THF) were studied in this work. 12-Molybdophosphoricacid catalysts modified by THF showed higher conversions and product yields than the mother acid in the vapor-phase ethanol conversion. It was believed that the enhanced catalytic activities of modified 12-molybdophosphoricacids were due to structural flexibility of heteropolyanions and weakened hydrogen bond around heteropolyanions. THF interacted with protons and crystalline water molecules of heteropolyacids. The interaction between THF and heteropolyanoins, which crystalline water molecules act as intermediary, was the dominant factor deciding the catalytic activities of modified 12-molybophosphoricacids.
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