• Applied Chemistry for Engineering
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• v.7 no.3
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• pp.496-503
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• 1996

Aromatic and aliphatic copolyesters for the dispersing agent were synthesized by two stage reaction, esterification and polycondensation. Copolyesters were blended with PET in the melt state and their thermal and rheological properties were investigated. From GPC analysis Mn's and Mw's of copolyesters were about 30000 and 65000g/mol, respectively. From DSC experiment copolyesters had melting range of $90{\sim}150^{\circ}C$. Copolymer composition was in good agreement with comonomer feed ratio from $^1H$-NMR analysis. Copolyesters and SPA (standard sample) were blended with PET in the melt state. From DSC experiment, copolyesters and SPA were miscible with PET. From the dynamic melt viscosity experiment, melt viscosity of blended sample was increased as the content of aromatic copolyester was increased, while it was decreased as the content of aliphatic and SPA were increased. As for volume resistivity of dry color containing carbon black and copolyesters with dispersing time, aromatic copolyester showed highest value. It was conferred from this result that aromatic copolyester was the best dispersing agent for carbon black in PET resin.

• Solar Energy
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• v.11 no.2
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• pp.41-50
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• 1991

Heat transfer phenomena and temperature characteristics in heat storage and release process in the heat storage system using PCM(Phase Change material) were studied experimentally. The melting points of Octacosane paraffin($C_{28}H_{58}$) and sodium pyrophosphate decahydrate ($Na_4P_2O_7{\cdot}10H_2O$) used for phase change materials are $62^{\circ}C$ and $79^{\circ}C$ respectively. Experiments were performed in order to investigate temperature distributions, the heat storage quantity and the release quantity on octacosane paraffin and sodium pyrophosphate decahydrate for heat storage and release in the heat storage system. Furthermore the comparison of these characteristics between paraffin and $Na_4P_2O_7{\cdot}10H_2O$ were evaluated. In case of the paraffin, temperature slowly increased at early heat storage process by natural convection, while temperature of $Na_4P_2O_7{\cdot}10H_2O$ rapidly increased the dominant role played by conduction at early heat storage processing Also, during the heat storage and release process in case of the paraffin, it was observed that the variation of temperature of the neighborhood of wall and center in the top and bottom of the tube exhibited a great difference, however in $Na_4P_2O_7{\cdot}10H_2O$, it was observed that the variation of temperature exhibited a little difference. And heat storage quantity of each PCM of identity mass in heat storage process was shown that $Na_4P_2O_7{\cdot}10H_2O$ exhibited more by 16 percents than paraffin.

• Analytical Science and Technology
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• v.12 no.5
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• pp.436-440
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• 1999

Antistatic property and crystallization behavior of antistatic poly(ethylene terephthalate) (PET) were studied by feeding antistatic agents into polycondensation reactor. Glass transition and melting temperature of antistatic PET were decreased by poly(ethylene glycol) (PEG) component of antistatic agent. The crystallization rate of antistatic PET was inhibited by decreasing crystallization temperature. Thermal properties and crystallization behavior was affected POAG content of antistatic agent rather than sodium alkylsulfonate of it. The main antistatic component of antistatic agent was POAG. The main role of sodium alkylsulfonate was increasing melt viscosity of antistatic poly(ethylene terephalate) polymer.

• Polymer(Korea)
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• v.31 no.1
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• pp.25-30
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• 2007

The characteristics of crosslinking and physical properties in partially crosslinked waste high density polyethylene (HDPE) were studied by introducing reactive melt processing with perbutyl peroxide (PBP). It was found that impurities in waste HDPE affected the crosslinking kinetics. Decrease in density and heat of fusion were observed in partially crosslinked HDPE while its melt viscosity increased. It was explained that impurities in waste HDPE enhanced the crosslinking compared to pure HDPE As a result, dramatic mechanical property improvement was achieved in the waste HDPE by crosslinking reaction.

• Solar Energy
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• v.12 no.1
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• pp.48-58
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• 1992

In the present investigation, experimental analysis was performed to research heat transfer phenomena generated by means of conduction and natural convection at a succession of tube-inclimations relative to the vertical tube during inward melting process of a phase change material. The phase change material used in the experiments is 99 percent pure n-docosane paraffin($C_{22}H_{46}$). When the tube is vertical, the dominant mode of energy transfer between the tube wall and the melting interface is natural convection. On the other hand, when the tube is inclined to the vertical, the melting solid is brought into direct contact with the tube wall by the action of gravity. In the experimental results, direct contact gave rise to substantial enhancements in the amount of melted mass, relative to those for natural-convection-dominated melting.

• Analytical Science and Technology
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• v.28 no.5
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• pp.347-352
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• 2015

Chemical properties such as heat of formation and density of methylnitroimidazole derivatives were predicted and analyzed by using density functional theory (DFT). Successive addition of energetic nitro groups into an imidazole ring increases both the heat of formation and the density. Using the chemical property values computed by DFT, explosive performance was analyzed with the Cheetah program, and compared with those of TNT, RDX, and HMX, which are currently used widely in military systems. When both C-J pressure and detonation velocity were used as explosive performance, methyldinitroimidazole derivatives show better performance than TNT, while methyltrinitroimidzole is almost close to RDX. Since methylnitroimidazole derivatives have a good merit, i.e. low melting point for melt loading, they are forecasted to be used widely in various military and civilian application.

• New & Renewable Energy
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• v.1 no.4 s.4
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• pp.6-11
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• 2005

본 고에서는 태양전지 모듈 원가의 60% 이상을 차지하는 실리콘 기판의 생산성을 향상시키고 그에 따라 제조단가를 저감시키기 위한 일환으로 최근 들어 일본과 프랑스를 중심으로 중점적으로 기술개발이 이루어지고 있는 EMCC법 (Electro Magnetic Continuous Casting)에 의한 다결정 실리콘 잉고트의 제조기술에 관하여 연구하였다. 특히, 태양전지급의 고순도 잉고트로 제조하기 위해 높은 용융점과 낮은 전기전도도를 갖는 실리콘의 용해 및 주조 공정이 수냉되는 cold crucible 내에서 이루어지게 됨에 따라 발생하는 종래의 EMCC법의 문제점을 해결하고자, 코일전류 및 도가니 구조 등이 Joule 가열 효과 및 pinch 효과에 미치는 영향을 체계적으로 조사하였다. 연구 결과 대용량의 전원장치나 별도의 2차 가열원을 사용하지 않고서도 실리콘 원료의 가열 및 용해 효율을 현격히 향상시키며 용탕의 전 구간에 걸쳐 전자기력을 용탕의 정수압보다 큰 상태로 유지할 수 있는 EMCC용 무접촉성 도가니의 설계기술 및 이를 활용하는 전자기연주공정기술을 확립하였으며, 그 결과 직경 5cm의 실리콘 잉고트를 1,5mm/min의 속도로 무접촉 조건에서 연속주조할 수 있었다.

• Polymer(Korea)
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• v.26 no.6
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• pp.737-744
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• 2002

Thermodynamic miscibility of the binary blends composed of semi-crystalline poly (butylene 2,6-naphthalate) (PBN) and amorphous poly (4-vinylphenol) (PVPh) was investigated using differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. DSC scan results showed that there was a single glass transition temperature (T$\_$g/) for each blend. Crystalline melting temperature (T$\_$m/) depression of the PBN in the blends was also observed with the increase of PVPh content. Both results of the single T$\_$g/ and the depression of T$\_$m/ for the PBN/PVPh blends indicate that the blends are thermodynamically miscible at the molecular level. FTIR spectroscopic analysis confirmed that strong intermolecular hydrogen bonding interactions between the ester carbonyl groups of the PBN and the hydroxyl groups of the PVPh are occurred.

• Elastomers and Composites
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• v.42 no.3
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• pp.137-142
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• 2007

In the performance test of polytetrafluoroethylene (PTFE) membrane, melting temperature and crystallinity were $344.1^{\circ}C$ and 42.5%, respectively, according to TGA and DSC analysis. These values were similar to those of commercially available GE Osmonics PTFE membrane. The average of pore size was observed $0.716{\mu}m$ and the average flow rate was 1.570 LMH. These are slightly higher values than those of GE Osmonics sample. The filtering efficiency rate was 30.5%.

• Polymer(Korea)
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• v.36 no.4
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• pp.407-412
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• 2012

The characteristics of nylon6/ionomer semi interpenetrating networks (IPN) as a molded-in-color (MIC) compound had been studied, and comparison was made with nylon6/ionomer blends. Nylon6/ionomer semi IPN shows better homogeneity in phase morphology than nylon6/ionomer blend, and it caused better anti-scratching performance than the blend. This semi IPN structure resulted in lowered crystallization rate, increased melt viscosity and less temperature dependency of viscosity. As a result, we may expect the enhancement of melt processing characteristics in an injection molding process using nylon6/ionomer semi IPN as a MIC compound.