• 폴리머
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• 제25권1호
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• pp.41-48
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• 2001

폴리카프로락톤디올(PCD) 및 폴리에틸렌글리콜(PEG), 디이소시아네이트 및 1,2,6-헥산트리올을 용액중합 방법으로 반응시켜 폴리우레탄(PU) 마이크로겔을 합성하였다. PCD/PEG의 몰비가 다른 마이크로겔의 임계 겔화농도의 성질과 생성에 영향을 주는 중요한 인자임을 알았다. 디이소시아네이트, PCD/PEG의 몰비 및 PEG의 분자량을 달리하여 제조한 PU 마이크로겔의 물리적 및 열적 성질을 실험하였다. PU 마이크로겔은 300nm 이하의 다분산성 구형의 작은 입자로 분포되어 있으며, 저점도 특성을 나타내었다.

• 한국염색가공학회지
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• 제28권3호
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• pp.164-174
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• 2016

In this study, dye-encapsulated microcapsules were produced by emulsion polymerization using styrene monomer. The study showed that the average size of microcapsules were $2{\sim}5{\mu}m$ in normal distribution. These microcapsules induced pale yellow(A12) and reddish yellow(B24) color by thermochromic fluoran yellow(dye A) and red(dye B). These microcapsules were changed to dark yellow(A12) and scarlet(B24) color depending on temperature change. The weight of microcapsules decreased by 7% to 11% during the heating ranges from $320^{\circ}C$ to $350^{\circ}C$ implying that the styrene microcapsules had thermal stability upto $300^{\circ}C$.

• 공업화학
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• 제19권3호
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• pp.316-321
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• 2008

Styrene과 4-vinylpyridine의 공중합체(poly(st-co-4vp)) 입자를 무유화제 유화중합에 의해 합성하고 이 입자 내부에 iron pentacarbonyl을 침투시킨 후 열분해 시켜 입자의 표면과 내부에 산화철 나노입자를 갖는 자성 poly(st-co-4vp) 입자를 제조하였다. 얻어진 자성 poly(st-co-4vp) 입자의 크기와 분포, 열적 특성 및 자성 특성에 대해서 조사하였다. 자성 poly(st-co-4vp) 입자는 크기가 약 250 nm 정도로 매우 균일하였으며 약 14%의 산화철을 가졌다. 산화철은 XRD 시험에 의해 대부분 $Fe_3O_4$임이 확인되었으며 superconducting susceptometer (SQUID) 시험에 의해 자성 poly(st-co-4vp) 입자가 초상자성을 가짐을 확인하였다.

• Elastomers and Composites
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• 제11권1호
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• pp.54-62
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• 1976

It has been studied the graft copolymerization of glycidyl-methacrylate monomer containing two functional groups (vinyl- & epoxyl-) to chloroprene rubber. The reaction occured in the manner of chain transfer mechanism was carried out by means of solution polymerization in toluene in the presence of benzoyl peroxide as the radical initiator. The graft copolymer obtained from this work was analyzed by using IR spectrum, and the physical properties of the polymer such as the thermal behavior were also studied according to TG-DTA methods, and the potency of adhesiveness for the purpose of commercial application was investigated. Experimental results for the graft copolymerization are summarized as follows. 1) A small amount of initiator (0.5%) and 50% of monomer showed the best result for the grafting of monomer to the polymer chain of rubber while the 15% of rubber solution was found to be most suitable to raise either for the grafting ratio or the polymerization ratio. 2) Optimum temperature for better yield of graft copolymer was proved to he at $75^{\circ}C\sim80^{\circ}C$ while those of reaction time was to be $1\sim2$ hours.

• Bulletin of the Korean Chemical Society
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• 제18권3호
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• pp.318-323
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• 1997

ο-(2-Vinyloxyethoxy)benzylidenemalononitrile (3a) and methyl ο-(2-vinyloxyethoxy)-benzylidenecyanoacetate (3b), m-(2-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl m-(2-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of ο-(2-vinyloxyethoxy)benzaldehyde (1) and m-(2-vinyloxyethoxy)benzaldehyde (2) with malononitrile or methyl cyanoacetate, respectively. Bifunctional vinyl ether monomers 3a and 3b polymerized quantitatively with radical initiators in γ-butyrolactone solution at 65 ℃, while meta-isomers 4a and 4b gave lower yields of polymers under the same conditions. The polymers 5-6 obtained from the monomers 3-4 were insoluble in common solvents due to cross-linking. Under the same polymerization conditions ethyl vinyl ether polymerized well with model compounds ο-methoxybenzylidenemalononitrile 7a, methyl ο-methoxybenzylidenecyanoacetate 7b, m-methoxybenzylidenemalononitrile 8a, and methyl m-methoxybenzylidenecyanoacetate 8b, respectively, to give 1:1 alternating copolymers 9-10 in high yields. Cross-linked polymers 5-6 showed a thermal stability up to 300 ℃, and showed a double phase degradation pattern in their TGA thermograms. Polymers 5-6 showed broad endothermic bands around 75-110 ℃ without any characteristic Tg peaks in DSC thermograms. Alternating copolymers 9-10, except copolymer 9b were soluble in common organic solvents. The inherent viscosities of polymer 9-10 were in the range of 0.35-0.62 dL/g. Polymer films cast from acetone solution were cloudy and tough and Tg values obtained from DSC thermograms were in the range of 118-165 ℃.

• 융복합기술연구소 논문집
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• 제12권1호
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• pp.13-18
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• 2022

Polyacrylonitrile was synthesized through suspension polymerization and then sieved to obtain spherical beads with a size of 200~510 ㎛. PAN was copolymerized with 2 mol% MMA monomer which is known to promote cyclization and crosslinking of nitrile group. The resonance cyclization reaction of the nitrile group in the synthesized PAN beads was observed near 170℃ with thermal analysis and FT-IR. The reaction conversion of the nitrile group in spherical beads was 23% during heat treatment, which was lower than that of the well-oriented PAN fiber used as a precursor of carbon fiber. This is because the stereo-regularity of molecular chains in the form of a random coil (spherical bead) is much lower than that of PAN fiber. It was confirmed that the compressive strength of the spherical PAN bead was greatly improved through the resonance cyclization and shrinkage according to the heat treatment, and it was also observed that the pores in PAN beads were formed after the heat treatment.

• 대한치과기공학회지
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• 제44권4호
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• pp.111-117
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• 2022

Purpose: This study was conducted to compare the Vickers hardness on the denture acrylic resins using the glaze color system. Methods: The specimens (20×2 mm) were prepared by mixing according to the manufacturer's protocols through thermal polymerization and self-polymerization. The surface roughness was measured using a testing machine after water-soaking for 48 hours. For the Vickers hardness measurement, the completed specimen was soaked in water for 48 hours and then applied at 200 gf for 30 seconds. Was the specimen immersed after being soaked in water for 48 hours at temperatures of 5℃ and 55℃, respectively, for 30 seconds for the thermos-cycling treatment, and it was carried out 5,000 times. Results: Surface roughness was higher in the more glazing group than in the control group. A significant difference was observed in all groups, except for the Retec Don 2000 and Luciton 199 groups (p<0.05). As a result of measuring the Vickers hardness, the treatment by glaze color showed slightly lower but the thermo-cycling treatment group appeared higher than control group in all. Conclusion: Therefore, the glaze color was found to affect the surface roughness and showed a significant difference. The surface glaze color showed a very high Vickers hardness after the thermo-cycling treatment, indicating that the surface-strengthening effect is greater in the oral environment.

• 한국응용과학기술학회지
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• 제25권3호
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• pp.341-346
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• 2008

Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity ($X_c$) and molecular weight ($M_w$) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and $M_w$ of MFC by HBr hydrolysis considerably decreased, but $X_c$ showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.

• 공업화학
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• 제3권2호
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• pp.280-287
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• 1992

테레프탈산, 비페닐 디카르복시산과 히드로퀴논을 용액중합하여 전방향족 액정 폴리에스테르를 합성하고 테레프탈산과 비페닐 디카복시산의 몰비가 액정중합체의 열적성질, 열안정성 및 메소상의 구조에 미치는 영향을 DSC, TGA, 편광현미경 및 X선회절기로 조사하였다. 본 연구에서 합성한 중합체는 모두 열방성 액정중합체였고 네마틱 액정상을 나타내었으며, 용융온도 및 등방화온도는 중합체중의 비페닐렌구조가 증가함에 따라 약간씩 증가하였다. 또한 중합체의 열안정성은 중합체중의 비페닐렌구조가 증가함에 따라 개선되었으며, 비페닐렌구조를 가지는 중합체의 결정도는 상당히 높아서 약 33%정도로 나타났다.

• Food Science and Biotechnology
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• 제18권6호
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• pp.1392-1397
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• 2009

This study was aimed at developing a low cost cold storage system for agricultural products. Three kinds of slurries: $K_1$, $K_2$, and $K_3$ slurries were developed using phase change materials (PCMs) such as tetradecane, octadecane, and sodium polyacrylate to maintain the desired temperature ranges. The slurries were manufactured by in-situ polymerization. Tetradecane and octadecane were capsulated in a core with melamine at the surface. The thermodynamic characteristics of the slurries were measured and analyzed. The latent heats of the $K_1$, $K_2$, and $K_3$ slurries at the melting points were 206.41, 186.88, and 147.91 kJ/kg, respectively. A transportable cold storage container was built to investigate the performance of the slurries as thermal storage media. The temperatures at the insides of the container could be maintained in the ranges of 0-5, 5-10, and $10-15^{\circ}C$ for more than 23, 27, and 60 hr with the $K_1$, $K_2$, and $K_3$ slurries, respectively.