• 한국안광학회지
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• 제5권2호
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• pp.87-90
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• 2000

Poly(HEMA)는 소프트 콘택트렌즈의 재료로써 널리 사용되어 왔다. $phSiH_3$, $phMeSiH_2$, $ph2SiH_2$와 같은 다양한 hydrosilane들과 hydroxyethyl methacrylate(HEMA)와의 열중합은 Phenylsilyl 말단기를 포함하는 poly(HEMA)를 생성시켰다. 열중합 반응 동안에는 Phenylsilane의 농도가 증가함에 따라 고분자의 분자량과 고분자 수득률이 감소됨을 보였으며 광중합 반응에서 보다 중합 수득률, 고분자의 분자량, TGA 잔여 수율 등이 더 높았다.

• 한국염색가공학회지
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• 제33권3호
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• pp.147-152
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• 2021

Bulk polymerization was used to produce poly(vinyl acetate) with different molecular weights, which were then saponified to prepare poly(vinyl alcohol) (PVA) with different molecular weights. With P_n of 2,060 and 3,240, the optimum film formation concentrations of PVA were found 7.5wt.% and 6.5wt.%, respectively. The drawing characteristics of the PVA film prepared at the optimum film formation concentrations were experimented, as well as the thermal characteristics of the PVA film based on the drawing ratio were observed. When the drawing velocity was fixed, it was found that the drawing ratios of all samples decreased as the heat band gap increased, and the melting temperature of the PVA film slightly increased as the drawing ratio increased regardless of the P_n of PVA.

• Korea-Australia Rheology Journal
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• 제17권2호
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• pp.41-45
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• 2005

As an effort to explore the effective use of carbon nanotubes as a reinforcing material for advanced nano-composites with polymer matrices, multi-walled carbon nanotubes (MWNTs) were successfully incorporated into polystyrene (PS) via in-situ bulk polymerization. Various experimental techniques revealed that the covalent bonds formed between PS radicals and acid-treated carbon nanotubes are favorable resulting in an effective load transfer. The enhanced storage modulus of the nanocomposites suggests a strong possibility for the potential use in industrial applications.

• Fibers and Polymers
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• 제7권3호
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• pp.217-222
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• 2006

Propargyl alcohol was coupled to 2,4-hexadiyne-1,6-diol (HDD) and crystallized in the process of ultraviolet irradiation-induced topochemical polymerization. The HDD polymer crystals were used as one component in the fabrication of organic photovoltaic cells, in combination with fullerene as the electron acceptor. The various structures of the produced photovoltaic cells included bilayer, trilayer, and bulk heterojunction structures. Their photovoltaic properties were analyzed in relation to crystal structure, electrochemical properties, and band structure of the HOD polydiacetylene polymers.

• Restorative Dentistry and Endodontics
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• 제25권1호
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• pp.91-108
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• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• 대한소아치과학회지
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• 제44권3호
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• pp.335-340
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• 2017

복합 레진은 소아치과 영역에서 대중적으로 사용되는 재료가 되었다. 하지만 복합 레진은 중합 수축을 최소화하기 위하여 적층 충전을 해야 하기 때문에 긴 시술 시간이 필요하다. 이러한 문제를 극복하기 위하여 임상가들은 bulk-filling 재료에 관심을 돌리기 시작하였고, 최근 bulk-base 복합 레진이 새로 출시되었다. 본 연구는 bulk-base 복합 레진의 깊이별 미세경도 측정값을 비교, 평가하였다. 실험군으로 1종의 저점도 bulk-base 복합 레진과 1종의 고점도 bulk-base 복합 레진을 사용하였고 대조군으로 1종의 전통적 복합 레진을 사용하였다. 각 깊이별 재료들의 미세경도에 대한 결과로 대조군의 경우는 중합 깊이가 깊어질수록 미세경도의 유의한 차이를 보였다(p < 0.05). 이에 반해 실험군 인 HFB는 0 mm와 4 mm에서, 그리고 MFB는 0 mm와 2 mm, 0 mm와 3 mm에서 각각 유의한 차이를 보였으나 높이에 따른 유의한 감소 경향을 보이지는 않았다. 각각의 깊이에서 시편들의 미세경도를 비교하였을 때 표면과 2 mm에서는 대조군이 실험군보다 큰 미세경도를 보였다(p < 0.05). 3 mm에서는 저점도 실험군이 대조군보다 미세경도가 크게 나왔으나 통계적으로 유의한 차이는 아니었다. 하지만 4 mm에서는 모든 실험군이 대조군보다 통계적으로 유의하게 큰 미세경도 값을 보였다(p < 0.05). 이번 실험을 통하여 bulk-base 복합 레진이 4 mm에서 기존의 복합 레진보다 더 높은 미세경도를 보였고 표면과 2 mm에서는 더 낮은 미세경도를 보이는 것을 관찰하였다. 그러므로 bulk-base 레진의 기계적 성질의 향상을 통해 표면의 낮은 미세경도 특성이 극복된다면 소아 환자의 수복 치료 시 적용이 고려되어 질 만 할 것이다.

• Macromolecular Research
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• 제15권2호
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• pp.154-159
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• 2007

Polyaniline (PANI) nanospheres, 4 run in diameter, were fabricated by the microemulsion polymerization of octyltrimethyl ammonium bromide (OTAB). The size of the PANI nanoparticles could be controlled as functions of the surfactant concentration, surfactant spacer length and polymerization temperature. The diameter of the PANI nanospheres decreased with increasing surfactant concentration and decreasing temperature. The PANI nanoparticles revealed enhanced conductivity compared to conventional bulk PANIs. In addition, the PANI nanoparticles could be applied as optically transparent conducting materials due to their high conductivity and the nanosize effect. With 9 wt% PANI in the PC matrix, the PANI/PC film exhibited a conductivity of $8.9\times10^{-3}S/cm$ and transparency exceeding 95% over the entire visible light range.

• 한국응용과학기술학회지
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• 제35권2호
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• pp.502-508
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• 2018

코팅, 발수 및 접착특성이 우수한 불소함유 아크릴계 공중합체를 설계, 제조하였다. 공중합체용 모노머로 methyl methacrylate(MMA), 2,2,2-trifluoroethyl acrylate(FMA) 그리고 2-hydroxyethyl methacrylate(HEMA)를 사용하여 괴상 중합 및 유화 중합으로 반응하여 > 95 %이상 고수율로 공중합체를 제조하였다. $^1H-NMR$로 화학구조를 확인하였고 DSC와 DMA로 물성분석을 한 결과, FMA의 함량이 5 %에서 10 %로 증가함에 따라 유리전이온도는 $3^{\circ}C$ 감소하였으며 HEMA의 경우에는 감소폭이 $2{\sim}8^{\circ}C$로 나타났다. Instron 및 TGA를 이용한 분석에서는 FMA 혹은 HEMA 함량이 10 % 증가함에 따라 괴상 및 유화 중합체 모두에서 인장강도는 29 MPa에서 22 MPa로 감소하였고 Td는 $200^{\circ}C$에서 $180^{\circ}C$로 감소하는 경향을 나타내었다. 접촉각은 친수성인 HEMA의 함량이 증가함에 따라 상대적으로 감소하였다.

• 한국응용과학기술학회지
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• 제33권4호
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• pp.771-776
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• 2016

내열, 코팅 및 접착특성이 우수한 아크릴계 공중합체를 설계, 제조하였다. 공중합체용 모노머로 methyl methacrylate(MMA), isobornyl methacrylate(IBMA) 그리고 2-hydroxyethyl methacrylate(HEMA)를 사용하여 괴상 중합 및 유화 중합으로 반응하여 > 95%이상 고수율로 중합체를 제조하였다. $^1H$-NMR로 화학구조를 확인하였고 DSC, DMA, TGA분석으로 내열성을 확인한 결과 유리전이온도가 $123^{\circ}C$이상 $140^{\circ}C$까지 높게 나타났다. 또한, IBMA성분이 증가함에 따라 저장 탄성율, 열분해온도 모두 증가하였다. 인장강도는 IBMA의 함량이 전체 모노머 조성물중 10%에서 30%로 증가함에 따라 괴상 및 유화 중합체 모두에서 22에서 30 MPa로 강도가 증가하였으며 IBMA의 소수성 특성으로 접촉각은 70도에서 88도까지 증가함을 확인하였다.

• Macromolecular Research
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• 제17권4호
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• pp.221-226
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• 2009

The present study firstly describes the synthesis of novel, thermo-latent initiators based on xanthenyl phosphonium salts with different counter anions and phosphine moieties and secondly examines their efficiency in the bulk polymerization of glycidyl phenyl ether(GPE). The polymerization was performed with phosphonium salt initiators($I_{SbF6}$, $I_{PF6}$, $I_{AsF6}$ and $I_{BF4}$) at ambient temperature to $200^{\circ}C$ for 1 h. The order of initiator activity was $I_{SbF6}>I_{PF6}>I_{AsF6}>I_{BF4}$. To examine the effect of the phosphine moiety on the initiator activity, polymerization was carried out with $I_{SbF6}(Ph_{3}P)$ and $II_{SbF6}(Bu_{3}P)$ at ambient temperature to $170^{\circ}C$ for 1 h. The order of reactivity was $I_{SbF6}>II_{SbF6}$. In general, the conversion percentage increased with increasing polymerization temperature. The thermal stability of these salts was measured by thermo gravimetric analysis(TGA). The solubility of phosphonium salts in various organic solvents and epoxy monomers was also investigated.