• Macromolecular Research
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• 제16권8호
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• pp.725-733
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• 2008

Polyimide (PI) multilayer thin films were prepared by spin-coating from a poly(amic acid) (PAA) and poly(amic acid) ammonium salt (PAAS). PI was prepared from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (ODA) PAA. Different compositions of PAAS were prepared by incorporating triethylamine (TEA) into PMDA-ODA PAA in dimethylacetamide. PI multilayer thin films were spin-coated from PMDA-ODA PAA and PAAS. The PAAS comprising cationic and anionic moieties were spherical with a particle size of $20{\sim}40\;nm$. Some particles showed layers with ammonium salts, despite poor ordering. Too much salt obstructed the interaction between the polymer chains and caused phase separation. A small amount of salt did not affect the interactions of the interlayer structure but did interrupt the stacking between chains. Thermogravimetric analysis (TGA) showed that the average decomposition temperature of the thin films was $611^{\circ}C$. All the films showed almost single-step, thermal decomposition behavior. The nanostructure of the multilayer thin films was confirmed by X -ray reflectivity (XRR). The LF 43 film, which was prepared with a 4:3 molar ratio of PMDA and ODA, was comprised of uniformly spherical PAAS particles that influenced the nanostructure of the interlayer by increasing the interaction forces. This result was supported by the atomic force microscopy (AFM) data. It was concluded that the relationship between the uniformity of the PAAS particle shapes and the interaction between the layers affected the optical and thermal properties of PI layered films.

• 한국태양에너지학회 논문집
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• 제33권1호
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• pp.73-78
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• 2013

Hexadecane and exfoliated graphite nanoplate (xGnP)composite was prepared as a shape-stabilized phase change material (SSPCM) in a vacuum to develope thermal energy storage. The Hexadecane as an organic phase change material (PCM) is very stable against phase separation of PCM and has a melting point at $18^{\circ}C$ that is under the thermally comfortable temperature range in buildings. The xGnP is a porous carbon nanotube material with high thermal conductivity. Scanning electron microscope (SEM) and Fourier transformation infrared spectrophotometer (FT-IR)were used to confirm the chemical and physical stability of Hexadecane/xGnP SSPCM. In addition, thermal properties were determined by Deferential scanning calorimeter(DSC) and Thermogravimetric analysis (TGA). The specific heat of Hexadecane/xGnPSSPCM was $10.0J/g{\cdot}K$ at $21.8^{\circ}C$. The melting temperature range of melting and freezing were found to be $16-25^{\circ}C$ and $17-12^{\circ}C$. At this time, the laten heats of melting and freezing were 96.4J/g and 94.8J/g. The Hexadecane was impregnated into xGnP as much about 48.8% of Hexadecane/xGnP SSPCM's mass fraction.

• 멤브레인
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• 제20권4호
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• pp.335-341
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• 2010

본 연구에서는 음이온교환막 개발에 관한 것으로 poly(ethylenimine) (PEI) / poly(vinyl alcohol) (PVA)의 혼합비율에 따라 막을 제조하였다. 제조된 막의 특성화를 평가하기 위하여 함수율, 접촉각, FT-IR, 이온교환용량, 이온전도도, 열 중량분석, 탄성계수 측정을 실시하였다. 이온전도도 측정 결과 PVA/PEI의 함량이 90 : 10으로 제조된 막의 경우 $5.16{\times}10^{-2}S/cm$의 값을 나타내어 우수한 음이온전도도를 나타내었으며 접촉각 측정 결과 PEI의 함량이 증가함에 따라 막표면의 소수성이 $78.3^{\circ}$까지 함께 증가하는 결과를 나타내었다. 또한 열에 대한 안정성은 PVA의 우수한 성질을 변화시키지 않았으며 탄성계수 측정을 통해 고강도 기계적 물성을 확인할 수 있었다.

• 한국수산과학회지
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• 제44권6호
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• pp.591-596
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• 2011

The present study examined the physical properties of biofilms manufactured from yellowfin tuna Thunnus albacares skin gelatin with the aim of developing a biofilm from fisheries by-products to replace mammalian sources. The physical properties of biofilms from yellowfin tuna gelatin were compared with those of biofilms from porcine gelatin. The yellowfin tuna gelatin biofilm exhibited higher tensile strength (69.08 MPa) and greater elongation (14.32%) than did porcine gelatin biofilm (50.50 MPa and 10.21%, respectively). The ${\Delta}E$ and YI (yellowness index) Huntercolor values of yellowfin tuna gelatin biofilm were three-fold and 15-fold higher, respectively, than values for porcine gelatin biofilm. The opacity value of yellowfin tuna gelatin biofilm was higher than that of porcine gelatin biofilm. The stability against water of yellowfin tuna gelatin biofilm was lower than that of porcine gelatin biofilm at pH 3 to pH 11. Thermogravimetric analysis (TGA) indicated that the thermal stability of the biofilms was about $270^{\circ}C$ for porcine gelatin biofilm and about $250^{\circ}C$ for yellowfin tuna gelatin biofilm.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.579-584
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• 2011

Sulfonated poly (ether sulfone)s containing BFBN were prepared from 2,3-bis(4-fluorophenyl)-2-butenedinitrile , 4,4-sulfonyldiphenol and sulfonated 4,4'-difluorodiphenylsulfone sodium salt using potassium carbonate, and followed acidification reaction with 1M $H_2SO_4$. BFBN was prepared from 4-fluorobenzylcyanide, $CCl_4$, NaOH using trimethylbenzylammoniumchloride . Sulfonated poly(ether sulfone)s containing BFBN were studied by FT-IR, $^1H$-NMR spectroscopy, and thermo gravimetric analysis (TGA). The water uptake of synthesized S-PBFBN membranes exhibit 31~62% compared with 28% of Nafion 211. The S-PBFBN membranes exhibit proton conductivities ($80^{\circ}C$, RH 100) of 53.8~117.4 mS/cm compared with 137.4 mS/cm of Nafion 211.

• 한국수소및신에너지학회논문집
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• 제22권5호
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• pp.569-578
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• 2011

The $SiO_2$ membranes for polymer electrolyte membrane fuel cell (PEMFC) are preapared by electrospinning method. It leads to high porosity and surface area of membrane to accommodate the proton conducting materials. The composite membrane was prepared by impregnating of Nafion ionomer into the pores of electrospun $SiO_2$ membranes. The $SiO_2$:heteropolyacid (HPA) nano-particles as a inorganic proton conductor were prepared by microemulsion process and the particles are added to the Nafion ionomer. The characterization of the membranes was confirmed by field emission scanning electron microscope (FE-SEM), thermogravimetry analysis (TGA), and single cell performance test for PEMFC. The Nafion impregnated electrospun $SiO_2$ membrane showed good thermal stability, satisfactory mechanical properties and high proton conductivity. The addition of the $SiO_2$:HPA nano-particle improved proton conductivity of the composite membrane, which allow further extension for operation temperature in low humidity environments. The composite membrane exhibited a promising properties for the application in high temperature PEMFC.

• 한국전기전자재료학회논문지
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• 제31권7호
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• pp.455-461
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• 2018

Boron nitride (BN) nanofibers were fabricated using BN nanoparticles (70 nm) by electrospinning. Morphologies such as the diameter and density of the BN nanofibers are strongly influenced by the viscosity and dispersion state of the precursor solution. In this study, the precursor solution was prepared by ball milling BN nanoparticles and polyvinylpyrrolidone (PVP, Mw~1,300,000) in ethanol, which was electrospun and then calcined to produce BN fibers. High-quality BN nanofibers were well fabricated at a BN concentration of 15 wt% with their diameters in the range of 500 nm to 800 nm; the viscosity of the precursor solution was $400mPa{\cdot}S$. The calcination of the as-electrospun BN fibers seemed to be completed by holding them at $350^{\circ}C$ for 2 h considering the TGA data. The morphologies and phases of the BN fibers were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively; Fourier transform infrared (FT-IR) was also used for structure analysis.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.465-469
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• 2013

본 연구는 반탄화된 OPF(oil palm fronds)의 연료로써 이용가능성을 알아보았다. OPF는 200, 250, 300, $350^{\circ}C$에서 각각 1시간과 2시간 동안 반탄화를 진행하였다. 반탄화된 OPF는 온도가 높아짐에 따라 그리고 반탄화 시간이 증가됨에 따라 발열량이 증가하였다. 또한, 반탄화 시간보다는 반탄화 온도가 더 중요한 요소였다. 하지만 반탄화 온도가 높아질수록 반탄의 수득률이 감소함으로 적절한 반탄화 온도가 요구되었다. $250^{\circ}C$에서의 반탄화로는 헤미셀룰로오스의 분해가 상당히 진행되고 $300^{\circ}C$에서는 셀룰로오스의 분해까지도 거의 진행됨을 OPF의 열분해 거동으로부터 알 수 있었다. 또한, 반탄화된 OPF는 바이오매스의 grindability를 향상시킴으로 분쇄에 소모되는 에너지를 감소시킴을 예측할 수 있었다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.182-185
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• 2004

In this work, the effect of chemical treatments on surface properties of SiC was investigated in mechanical interfacial properties of carbon fibers-reinforced composites. The surface properties of the SiC were determined by acid/base values and contact angles. The thermal stabilities of carbon fibers-reinforced composites were investigated by thermogravimetric analysis (TGA). Also, the mechanical interfacial properties of the composites were studied in interlaminar shear strength (ILSS) and critical strain energy release rate mode II $(G_{IIC})$ measurements. As a result, tile acidically treated SiC (A-SiC) had higher acid value than that of untreated SiC (V-SiC) or basically treated SiC (B-SiC). According to the contact angle measurements, it was observed that chemical treatments led to an increase of surface free energy of the SiC surfaces, mainly due to the increase of the specific (polar) component. The mechanical interfacial properties of the composites, including ILSS and $(G_{IIC})$, had been improved in the specimens treated by chemical solutions. These results were explained that good wetting played an important role in improving the degree of adhesion at interfaces between SiC and epoxy resin matrix.

• Elastomers and Composites
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• 제39권2호
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• pp.105-120
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• 2004

본 연구에서는 금속수산화물과 다양한 인계 난연제를 포함한 난연 acrylonitrile-butadiene rubber (NBR) 발포체를 제조하고, 이때 인 함유량에 따른 열적특성. 난연특성, 발포특성 등의 변화 및 이들의 상관관계를 조사하였다. NBR 발포체의 발포특성 및 모폴로지 분석 결과 인/질소계 난연제 10 phr 범위 내에서 대체적으로 인/질소계 난연제를 투입하지 않은 금속수산화물만을 사용한 경우와 유사한 발포특성 및 모폴로지를 가짐을 알 수 있었다. 열 분석에서는 인 함유량이 많은 인/질소계 난연제를 사용할 경우 화염분위기 하에서의 char 형성과 관련한 잔류량이 많아짐으로써 난연성이 향상됨을, LOI 분석에서도 인 함유량이 증가함에 따라 LOI가 증가함을 알 수 있었다. cone-calorimeter 분석 결과 열 및 LOI 분석 결과와 유사한 경향성을, 인 함유량이 증가함에 따라 HRR, THR, EHC 등이 감소하는 반면에 COY는 증가함을, 즉 난연성이 상승함을 확인할 수 있었다. 연기밀도 분석 결과 cone-calorimeter 분석에서의 (A)-COY와 같은 경향성을 보여주었다.