• Proceedings of the KIEE Conference
• /
• 1995.07c
• /
• pp.1117-1119
• /
• 1995

Fluoroplastics have been used widely for chemical or electrical facility materials and lubricable engineering structural materials because they have the superior characteristics such as thermal stability, chemical stability, solid lubricity, arc resistance, wearable durability and good sealing property. In this study, PTFE composite materials for the insolation parts of high voltage and current breaker were investigated and estimated.

• Macromolecular Research
• /
• v.16 no.1
• /
• pp.31-35
• /
• 2008

Photoreactive polymers as a color filter resist containing both photoreactive acrylate and cinnamate double bonds were synthesized usin two step reactions. The chemical structures of the synthesized polymers were confirmed by $^1H$-NMR and FT-IR spectroscopy. The photoreactive polymers were quite soluble in most common organic solvents and produced excellent quality thin films by spin-coating. The photocuring kinetics of the acrylate and cinnamate double bonds were examined by FT-IR and UV- Vis spectroscopy, which confirmed the excellent photoreactivity of both the acrylate and cinnamate double bonds in the polymers. Upon UV irradiation, photocuring was almost completed within approximately 5 min, irrespective of the type of the prepolymers. The polymers also exhibited superior thermal stability, showing little change in transmittance in the visible region even after heating to $250^{\circ}C$ for one hour. Photolithographic micropatterns could be obtained with a resolution of a few microns.

• Transactions of the Korean hydrogen and new energy society
• /
• v.30 no.2
• /
• pp.128-135
• /
• 2019

In this study, the mesoporous $SiO_2$ (5, 10, or 15 wt%) was incorporated into the polybenzimidazole matrix in order to improve the proton conduction as well as physiochemical properties of composite membrane. The chemical structure of mesoporous $SiO_2$ and crystallinity of as-prepared membranes were analyzed by Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis, respectively. The thermal stability of the pristine $X_1Y_9$ and composite membranes were evaluated by thermogravimetric analyzer (TGA). On other side, the physical and chemical properties of the pristine $X_1Y_9$ and composite membranes were also determined by acid uptake and oxidative stability tests, respectively. With the incorporation of 15 wt% $SiO_2$, the composite membrane exhibits the higher proton conductivity that may be applicable for non-humidified high temperature fuel cell applications.

• Journal of the Korean Applied Science and Technology
• /
• v.25 no.1
• /
• pp.15-22
• /
• 2008

The effects of fillers on the mechanical and thermal properties of glass/novolac composites have been studied. The matrix polymer and reinforcement were novolac type phenolic resin and milled glass fiber, respectively. Three different fillers, such as calcium carbonate, aluminum oxide, and wood powder were used for glass fiber reinforced plastic(GFRP) manufacture. Gravity, moisture content, tensile and flexural strength were measured to analyze the mechanical properties of GFRP and the final composites was burned in the electronic furnace at $1000^{\circ}C$ to confirm thermal properties GFRP containing aluminium oxide shows the highest thermal stability with 32% of weight loss at $1000^{\circ}C$ for one hour. GFRP containing calcium carbonate shows the maximum flexural strength (146 MPa), but that containing wood powder dose the highest tensile strength (65 MPa). Conclusively, we found that the characteristics of final composites strongly depend on several factors, such as types of materials, contents and chemical affinity of fillers. Therefore, it is very important to set up the combination of fillers for GFRP manufacturing to improve both mechanical and thermal properties at the same time.

• Journal of the Korean Ceramic Society
• /
• v.54 no.6
• /
• pp.484-491
• /
• 2017

Chalcogenide glasses have been investigated in their thermodynamic, structural, and optical properties for application in various opto-electronic devices. In this study, the $Sb_{20}Se_{80-x}Ge_x$ with x = 10, 15, 20, and 25 were selected to investigate the glass stability according to germanium ratios. The thermal, structural, and optical properties of these glasses were measured by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and UV-Vis-IR Spectrophotometry, respectively. The DSC results revealed that $Ge_{20}Sb_{20}Se_{60}$ composition showing the best glass stability theoretically results due to a lower glass transition activation energy of 230 kJ/mol and higher crystallization activation energy of 260 kJ/mol. The structural and optical analyses of annealed thin films were carried out. The XRD analysis reveals obvious results associated with glass stabilities. The values of slope U, derived from optical analysis, offered information on the atomic and electronic configuration in Urbach tails, associated with the glass stability.

• Journal of Adhesion and Interface
• /
• v.5 no.3
• /
• pp.10-17
• /
• 2004

We investigated the effect of stabilization processing parameters on the thermal shrinkage, thermal stability and microstructure of rayon fabrics stabilized under various conditions such as heating rate, stabilization temperature, atmosphere gas, and chemical treatment. The presence and absence of phosphoric acid treatment and the heating rate have most importantly influenced the thermal shrinkage and the weight change of rayon fabrics. Especially, the phosphoric acid treatment decreases the reduction of thickness, length, and weight of the fabrics by about 80%, 20%, and 26%, respectively, in comparison with the untreated counterparts, showing the protective effectiveness of the thermal shrinkage involved. The thermal stability of stabilized rayon fabrics is also affected by all the processing conditions used: stabilization temperature, phosphoric acid treatment, atmosphere gas, and heating rate. In addition, the surface and diameter of the stabilized fiber significantly depend on the treatment of phosphoric acid prior to stabilization process.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07b
• /
• pp.1499-1502
• /
• 2005

Dense $BaMgAl_{10}O_{17}:Eu^{2+}$ phosphor particles with a spherical shape have been synthesized through spray pyrolysis method using basic aluminum nitrate precursor as a spray solution. This $BaMgAl_{10}O_{17}:Eu^{2+}$ particles prepared by the spray pyrolysis have shown the stronger emission intensity compared to the commercially-available $BaMgAl_{10}O_{17}:Eu^{2+}$. However, thermal stability of the BAM:Eu b lue phosphor is very poor due to changing from $Eu^{2+}$ to $Eu^{3+}$ at the thermal process, so brightness of the phosphor decreases. To improve the thermal stability of the dense BAM:Eu phosphor, the spherical BAM:Eu particles were coated with pure $BaMgAl_{10}O_{17}$ layer using the hydrolysis reaction in a solution system. The synthesized powders were characterized by XRD, SEM and PL. On the other hand, the emission properties of the BAM:Eu phosphors coated with $BaMgAl_{10}O_{17}$ layer before and after thermal treatment at $500^{\circ}C$ for 30 min were estimated under VUV excitation. The brightness of the coated phosphor was higher than that of the uncoated phosphor. Also, the coating thickness of BAM layer in the BAM:Eu particles was optimized.

• Korean Chemical Engineering Research
• /
• v.43 no.3
• /
• pp.401-406
• /
• 2005

In this work, the effect of chemical treatment of multiwalled carbon nanotubes (MWNTs) on glass transition temperature (Tg), thermal stability, and dynamic viscoelastic behaviors of MWNTs-reinforced epoxy matrix composites has been studied by differencial scanning calorimeter (DSC), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA) measurements. The MWNTs were chemically treated with 35 wt％ $H_3PO_4$ (A-MWNTs) or 35 wt％ KOH (B-MWNTs) solutions and the changes of surface properties of chemically treated MWNTs were examined by pH, acid and base values, Fourier transfer-infrared spectroscopy (FT-IR), and x-ray photoelectron spectroscopy (XPS) analyses. The chemical treatments based on acid and base reactions led to a significant change of surface characteristics and chemical compositions of the MWNTs, especially A-MWNTs/epoxy composites had higher thermal stability and dynamic viscoelastic properties than those of B-MWNTs and non-treated MWNTs/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.2
• /
• pp.449-452
• /
• 2012

A polyaniline-gold composite was prepared via the polymerization of aniline hydrochloride with or without water-soluble graphite oxide using auric acid as an oxidant. The reaction products were characterized using Xray photoelectron spectroscopy. The thermal stability and embedded crystallinity of the composites were also investigated using thermogravimetric and X-ray diffraction analyses. The electrical properties of the composites were examined using cyclic voltammetric measurements at room temperature and temperature-dependent DC conductivity within 300-500 K. Compared to pure graphene oxide and polyaniline-gold composite, the polyaniline-gold-graphene composite exhibited higher crystallinity and thermal stability, and higher current density response under equivalent conditions.

• Bulletin of the Korean Chemical Society
• /
• v.20 no.12
• /
• pp.1421-1427
• /
• 1999

4-Hydroxy-4'-methoxyazobenzene and 4-hydroxy-4'-cyanoazobenzene were synthesized from phenol with p-anisidine and p-aminobenzonitrile through a diazotization reaction, respectively. They were reacted with 2-chloroethanol, 2-(2-chloroethoxy)ethanol, or 2-[2-(2-chloroethoxy)ethoxy]ethanol to produce six kinds of new mesogenic alcohols having an azobenzene group that is sensitive to the ultraviolet. Twelve kinds of new photoresponsive monomers with two symmetrical mesogens were prepared by the reaction of the mesogenic alcohols with fumaric acid or maleic acid through a Mitsunobu reaction. The resulting monomers have different length of flexible ethyleneoxy spacer tethered to azobenzene group. The length of the spacer affected their thermal stability, solubility, and phase transition temperature. Structures of the monomers were identified by FT-IR and ¹H-NMR spectra. Their phase transition temperatures and thermal stability were also investigated by a differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA). From an optical polarizing microscopy, all the prepared monomers except fumarate-1 and maleate-1 were found to show enantiotropic liquid crystallinity with a smectic texture like focal-conic, fan-shaped, and batonnet textures.