• 분석과학
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• 제12권5호
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• pp.436-440
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• 1999

축중합조에 제전제를 첨가하여 중합한 폴리에틸렌테레프탈레이트(PET)의 제전성과 결정화 거동에 대하여 연구하였다. 제전제 성분중 폴리에틸렌글리콜(PEG) 성분에 의해 제전 PET의 유리전이온도와 용융 온도가 낮아졌다. 제전PET의 결정화속도는 결정화온도가 감소함에 따라 억제되었다. 제전PET의 열적성질과 결정화 거동은 제전제 성분중 알킬나트륨설포네이트 보다는 PEG 함량에 영향을 받았다. 따라서 제전성은 발현하는 주요 성분은 PEG였다. 알킬나트륨설포네이트는 제전폴리에스터 폴리머의 용융점도를 향상시키는 역할을 하는 것으로 판단된다.

• Elastomers and Composites
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• 제51권1호
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• pp.56-62
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• 2016

The isothermal crystallization behaviors of blends of poly(ethylene naphthalate) (PEN) and a thermotropic liquid crystalline polymer (TLCP) were investigated by differential scanning calorimetry (DSC) as functions of crystallization temperature and blend composition. Avrami analyses were applied to obtain information on the crystal growth geometry and the factors controlling the rate of crystallization. The crystallization kinetics of the PEN/TLCP blends followed the Avrami equation up to a high degree of crystallization, regardless of crystallization temperature. The calculated Avrami exponents for PEN/TLCP revealed three-dimensional growth of the crystalline region in each blend. The crystallization rate of each blend increased as the crystallization temperature decreased, and decreased as the TLCP content increased. The crystallization of PEN in the blend was affected by the addition of TLCP, which acts as a nucleating agent.

• Macromolecular Research
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• 제10권2호
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• pp.127-134
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• 2002

Microporous polypropylene hollow fiber membrane was fabricated from isotactic polypropylene-soybean oil system by melt spinning process. Addition of nucleating agent accelerated the crystallization rate and elevated the crystallization temperature. Nucleating agent increased the number of nuclei and spherulites, which offered more inter-spherulitic amorphous sites for stretching. Benzoic acid, adipic acid, and dibenzylidene sorbitol were selected as nucleating agents, and their characteristics and effects were investigated by thermal and optical analyses. Spherulite growth and micropore formation characteristics were correlated with the kind of nucleating agent. Benzoic acid and adipic acid showed the remarkable nucleating effect, while dibenzylidene sorbitol was less effective than those. Nucleating agents also helped the sample have uniform microporous structure. Increase of nucleating agent composition enhanced the nucleation effect to some extent. Nucleating agents played very important roles in enhancing the membrane porosity and water flux.

• 한국결정성장학회지
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• 제30권4호
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• pp.136-142
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• 2020

아연결정유약은 결정생성의 요건을 맞추기 위해서는 조핵제의 생성 - 조핵제의 양 조절 - 결정의 성장 등의 까다로운 소성과정을 거쳐야 한다. 소성온도 폭이 좁고 아연의 상태에 따라 결정에 영향을 미치는 등 사용이 용이하지 않다. 아연결정생성을 촉진시켜 이를 Frit화하여 폭넓은 소성조건에서 안정적으로 재결정화도록 하여 상용유약으로 유약을 개발할 수 있다.

• Carbon letters
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• 제7권2호
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• pp.87-96
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• 2006

This paper describes the physical properties of filled Nylon6 composites resin with nano-sized carbon black particle and graphite nanofibers prepared by melt extrusion method. In improving adhesions between resin and fillers, the surface of the carbon filler materials were chemically modified by thermo-oxidative treatments and followed by treatments of silane coupling agent. Crystallization temperature and rate of crystallization increased with increases in filler concentration which would act as nuclei for crystallization. The silane treatments on the filler materials showed effect of reduction in crystallization temperature, possibly from enhancement in wetting property of the surface of the filler materials. Percolation transition phenomenon at which the volume resistivity was sharply decreased was observed above 9 wt% of carbon black and above 6 wt% of graphite nanofiber. The graphite nanofibers contributed to more effectively in an increase in electrical conductivity than carbon black did, on the other hand, the silane coupling agent negatively affected to the electrical conductivity due to the insulating property of the silane. Positive temperature coefficient (PTC) phenomenon, was observed as usual in other composites, that is, temperature increase results conductivity increase. The dispersity of the fillers were excellently approached by melt extrusion of co-rotational twin screw type and it could be illustrated by X-ray diffraction and SEM.

• 한국포장학회지
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• 제21권3호
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• pp.107-113
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• 2015

This work focused on the study of thermal properties and kinetic behavior of LDPE-nanoclay composite films. The effect of nanoclay content (0.5, 1, 3, and 5 wt%) on thermal stability and crystallization characteristics of the nanocomposites were investigated by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The results from endothermic curve showed that the nanoclay played an important role in the crystallization of nanocomposites by acting as nucleating agent. From exothermic curve, there was a crystallization temperature shift which was attributed to crystallization process induced by nanoclay. The TGA results showed that the addition of nanoclay significantly increased the thermal stability of LDPE matrix, which was likely due to the characteristic of layered silicates/clays dispersed in LDPE matrix as well as the formation of multilayered carbonaceous-silicate char. A well-known Coats-Redfern method was used to evaluate the decomposition activation energy of nanocomposite. It was demonstrated that introducing of nanoclay to LDPE matrix escalated the activation energy of nanocomposite decomposition resulting in thermal stability improvement.

• Macromolecular Research
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• 제17권7호
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• pp.476-482
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• 2009

The crystallization behavior of poly(vinyl alcohol) (PVA) in the presence and absence of polypyrrole nanoparticles (PPy NPs) was investigated in terms of the heterogeneous nucleation effect of PPy NPs using FTIR, X-ray diffraction, differential scanning calorimeter and polarized optical microscope analysis. PPy NPs were prepared by dispersion polymerization method stabilized by PVA in aqueous solution. A polymer nanocomposite with uniform dispersity could be readily obtained due to the enhanced compatibility between the filler and matrix. Compared with the PPy NP-absent PVA, the PPy NP/PVA nanocomposite exhibited an enhanced degree of crystallinity. The degree of crystallinity increased up to 17% at the PPy NP concentration of 1 wt%, compared to the pristine PVA. The PPy NP acted as an effective nucleating agent during the crystallization process, thereby enhancing the degree and rate of crystallization. The kinetics study of the crystallization also revealed the decreased value of the Avrami coefficient in the case of the PPy NP/PVA nanocomposite.

• 한국결정성장학회지
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• 제12권5호
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• pp.229-233
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• 2002

유기화학적 방법인 착체중합법을 이용하여 나노사이즈의 ZnO 분말을 저온에서 합성하였다. 고분자 전구체는 Zn nitrate hexahydrate를 사용하였고, chelating agent로서 citric acid를 reaction medium으로서 ethylene glycol을 혼합하여 제조하였다. 고분자 전구체를 300~$700^{\circ}C$의 온도범위에서 3시간 동안 하소하였으며, 열분해와 결정화 과정을 TG-DTA, FI-IR과 XRD 등을 이용하여 분석하였다. 결정화 온도에 따른 입자의 형상이나 크기를 SEM, TEM의 분석 및 Scherrer's equation을 이용한 계산을 통하여 관찰 및 비교를 하였다. ZnO의 결정화는 $300^{\circ}C$부터 시작되었고, $400^{\circ}C$에서 완전히 합성되었음을 알 수 있었다. 400~$700^{\circ}C$에서 하소된 ZnO 입자들은 대부분 둥근 형태로 균일하게 분포되었으며, $400^{\circ}C$에서 하소된 분말의 평균입도는 약 30~40nm를 보였다. 일반적으로 온도의 상승에 따라 입경이 증가되는 일반적인 경향이 관찰되었다.

• 한국결정성장학회지
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• 제19권1호
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• pp.25-32
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• 2009

화력발전소로부터 발생된 석탄 바닥재(coal bottom ash)에 융제로 $Na_{2}O$ 및 $Li_{2}O$를, 핵 형성제로 $TiO_2$를 첨가하여 결정화유리를 제조한 뒤 그 미세구조를 분석하였다. 시편내 주결정상은 nepheline이었고, $TiO_2$가 첨가됨에 따라 nepheline 결정상 분율이 증가되었다. $TiO_2$가 첨가되지 않은 시편은 표면 결정화 기구에 수지(dendrite) 형태의 결정상이 성장되었으며, 내부 모상에는 결정이 거의 생성되지 않았다. 그러나 $TiO_2$ 첨가량이 4% 이상으로 증가되면, 표면결정화 기구는 억제되어 표면결정층의 두께가 얇아졌고 내부 모상은 결정질로 전이되었으며 동시에 $1{\mu}m$ 이하 크기의 미립자도 함께 생성되었다. 특히 6%의 $TiO_2$가 첨가된 결정화유리 내부에는 길이가 $5{\mu}m$인 수지상 결정들이 서로 얽혀진 형태를 보였으며, 이러한 미세구조는 외부로부터 하중을 가해졌을 때 발생되는 균열의 전파를 효과적으로 억제할 수 있을 것으로 예상된다.

• Fibers and Polymers
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• 제7권4호
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• pp.367-371
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• 2006

Thermal properties of copolyetherester/silica nanocomposites were examined by using DSC and TGA. The segmented block copolyetheresters with various hard segment structures and hard segment contents (HSC) were synthesized and their silica nanocomposite films were prepared by solution casting method. The nano-sized fumed silica particles were found to act as a nucleating agent of the copolyetheresters. The nanocomposites always showed reduced degree of supercooling or faster crystallization than the corresponding copolyetheresters. The nanocomposites also showed increased hard segment crystallinity except HSC 35 sample which had short hard segment length. In case of 2GT [poly(ethylene terephthalate)] copolyetheresters, which were not developed commercially because of their low crystallization rate, the hard segment crystallinity increased considerably. The copolyetherester/silica nanocomposites showed better thermal stability than copolyetheresters.