• Transactions on Electrical and Electronic Materials
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• v.13 no.2
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• pp.89-92
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• 2012

The effect of organic impurities on the electrical properties of a neat epoxy resin was studied. 0.05, 0.5 and 1.0 phr of iso-propyl alcohol (IPA) and methylene chloride (MC) mixture (50/50 wt%) were used as impurities. The current density, volume resistance and impedance characteristics of the epoxy/IPA/MC systems were measured with a high voltage source meter and broadband dielectric spectroscopy. Glass transition temperature (Tg) was measured by a differential scanning calorimetry (DSC) and it was found that Tg decreased slightly with increasing IPA/MC content. It was also found that Tg values of the epoxy systems with various IPA/MC contents were closely related to the current density, volume resistance and impedance characteristics.

• Proceedings of the Korean Fiber Society Conference
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• 1996.10a
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• pp.468-472
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• 1996

A series of UV-curable polyurethane acrylate ionomer were synthesized from isophorone diisocyanate(IPDI), poly(tetramethylene ether glycol)(PTMG), 2,2-bis(hydroxymethyl)propionic acid (CMPA), triethylamine(TEA), 2-hydroxy ethyl acrylate (HEA), and dibutyl tin dilaurate (DBT) as a catalyst. 2,2-dimethoxy-2-phenyl acetophenone(DMPAP) was used as a photoinitiator. The films of UV-cured polyurethane acylate ionomer were prepared by casting the formulated materials onto a glass plate at room temperature and cured using a medium pressure mercury lamp (80 W/cm, max = 365nm). Effects of DMPA content, molecular weight of PTMG and degree of neutralization on the properties were invesigated. It is found that the storage modulus increased with increasing DMPA content. The glass transition temperature of sample A shifted to higher temperature as the content of DMPA was increased. Tensile modulus also increased with increasing DMPA content. Modulus and Tg decreased with increasing molecular weight of PTMG form 650 to 2000. With increasing the degree of nutralizaion, ionomers exhibited improved modulu.

• Korean Journal of Materials Research
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• v.12 no.7
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• pp.545-549
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• 2002

Potassium-Calcium-Phosphate glasses in range $XCaO\cdot(50-X)K_2O$ \cdot $50P_2$$O^{5}$were investigated. Glass transition temperature(Tg) of prepared glasses were below $520^{\circ}C$, thermal expansion coefficient from $270.3$\times$10^{7}$ to $604.5$\times$10^{7}$/$^{\circ}C$. The structure of XCaO.(50-X)$K_2$O\cdot$50P_2$$O^{5}$ glasses were examined by FT-IR spectroscopy indirectly. As CaO was increased, Ts, Tg, P-O-P bonding strength and chemical durability were increased. Glass surface change was observed with increasing dissolution time using bulk specimen, weight loss and pH change were measured as function of the dissolution time.

• Macromolecular Research
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• v.13 no.3
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• pp.212-217
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• 2005

The pyrolysis kinetics of polyurethanes synthesized from polycaprolactone diol (PCL) and diisocyanate (HDI, $H_{12}MDI$) using catalysts such as dibutyltin dilaurate (DBTDL) were studied by a thermogravimetric (TG) technique, which involved heating the sample at the rates of 10, 20 and $30^{\circ}C$/min. The effect of the kind of diisocyanate and the hard segment contents on the activation energy and reaction order were examined at conversions ranging from 1 to $100\%$. The activation energies at first increased slowly with increasing conversion. Also, differential scanning calorimetry (DSC) was used to investigate the structural differences in each polyurethane. DSC can reveal the melting behavior, in terms of the glass transition temperature ($T_g$), which is known to vary as a function of the stoichiometry and processing conditions.

• Journal of the Korean Applied Science and Technology
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• v.17 no.4
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• pp.262-266
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• 2000

Acrylic pressure sensitive adhesives of n-butyl acrylate, 2-ethyl acrylate, methyl acrylate, vinyl acetate, acrylic acid, acrylonitrile and 2-hydroxyethyl acrylate were synthesized and basic physical properties of pressure sensitive adhesives with increasing the contents of 2-hydroxyethyl acrylate were investigated. 2-Hydroxyethyl acrylates effects on glass transition temperature, viscosity, hardening time and peel strength. Glass transition temperature(Tg) decreased with increasing the contents of 2-hydroxyethyl acrylate. Viscosity and hardening time were increased with increasing the contents of 2-hydroxyethyl acrylate. On the other hands, peel strength increased with increasing the contents of 2-hydroxyethyl acrylate up to 6 wt% and the decreased at further higher contents of 2-hydroxyethyl acrylate. In peel test, interfacial failure was occured in 8 wt% and 10wt%.

• Applied Chemistry for Engineering
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• v.18 no.2
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• pp.121-125
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• 2007

Siloxane monomer and oligomer were introduced to n-butyl acrylate and methyl methacrylate copolymer for improvement of water resistance and tactile sensation of acryl-type emulsion. Terpolymerimerization of n-butylacrylate, methyl methacrylate and siloxane monomer or oligomer was carried out in aqueous solution. The glass transition temperature (Tg) of terpolymer decreased with increasing siloxane monomer, however, the Tg of terpolymer increased with increasing siloxane oligomer due to the crosslinking of acrylated end group. The adhesion property and surface energy of the obtained terpolymer decreased with introducing siloxane monomer or oligomer in terpolymer. Decrement of tack and surface energy means the enhancement of water resistance and tactile sensation of the emulsion.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.252-255
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• 2003

Recently, there is a growing trend in the United States toward replacing latex additives in polymer-modified cement mortars with redispersible polymer powders. This movement is relatively new in the U.S. but is further advanced in Europe due to the more extensive use of cement and concrete in residential construction. Hitherto, in Korea - there is a very diminutive movement towards this growing trend. Thus, there is limited availability of data on redispersible polymer powders. This study investigates the effectiveness of redispersible polymer powder on improvement of the mechanical properties of modified mortar. It was concluded from the results of the experiments that the size of the dispersed polymer particles, variations in glass transition points (Tg), and variations in minimum film formation temperature (MFT) influenced the strength development of the modified mortars, and optimum strength in modified mortars using redispersible powders can be achieved when the Tg which accounts for the degree of powder flexibility is considered.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.453-467
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• 1998

This study helps to clarify conflicting reports by comparing the physical properties and accuracy of complete denture processed by the pack and press technique, continuous- pressure injection technique(SR-Ivocap system) and Mark press technique. The 6 different specimens have been evaluated using the SEM, Impact test, DSC (Differential Scanning Calorimetry) and DMTA (Dynamic Mechanical Thermal Analysis). Each sample was made of SR-Ivocap resin and QC-20 resin by different processing methods. The results were as follows ; 1. As the result of the observation on the fracture surface of resin by use of SEM, sample SR-Ivocap resin cured by continuous pressure injection method showed the most homogeneous structure. This is why molecules in SR-Ivocap resin have no orientation. 2. As the result of the Impact test in order to measure the deformity, fracture energy and impact resistance of resin, the samples with QC-20 acrylic resin and SR-Ivocap resin cured by continuous pressure injection method were exellent. 3. In consequence of measuring ${\alpha}$-glass transition temperature by use of DSC on the basis of temperature change, the glass transition temperatures of sample QC-20 resin cured by pack and press method and sample SR-Ivocap resin cured by continuous pressure injection method were very similar. Thus volumetric stability could not be evaluated only by glass transition temperature. 4. In comparing volumetric stability data by DMTA, the glass transition temperature(Tg) showed $137.88^{\circ}C$ at sample QC-20 resin cured by pack and press method and $139.78^{\circ}C$ at sample SR-Ivocap resin cured by continuous pressure injection method. Therefore sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in the dimensional stability at high temperature. 5. In comparing storage modulus data by DMTA, the storage modulus of sample SR-Ivocap resin cured by continuous pressure injection method was higher than that of sample QC-20 resin cured by pack and press method. So. sample SR-Ivocap resin cured by continuous pressure injection method seems to be superior to sample QC-20 resin cured by pack and press method in impact strength.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.416-419
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• 2003

There is a growing need for a nonvolatile memory technology with faster speed than existing nonvolatile memories. We studied of phase-change according to temperature and voltage in chalcogenide thin film base on $Ge_2Sb_2Te_5$. Searching for Tg(Glass transition temperature) temperature controlled on hotplate with RT quenching. We measure I-V characteristic through out bottom electrode(ITO) and top electrode(Al) between $Ge_2Sb_2Te_5$. And compared with I-V characteristics after impress the variable stress.

• Journal of the Korean Ceramic Society
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• v.31 no.7
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• pp.695-702
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• 1994

Current study was undertaken to explain the structural evolution and corresponding changes in the properties of calcium aluminate glasses with the variation of SiO2 doping concentration. Calcium aluminate glasses in the compositional ranges of (100-x)(0.6CaO+0.4Al2O3)+xSiO2(where x=0~60) were fabricated. DTA analysis confirmed an anomalous behavior in glass transition temperature (Tg) with the maximum of 887$^{\circ}C$ and minimum of 859$^{\circ}C$ when x=5 and 50, respectively. densities and refractive indices monotonically decreased with increasing SiO2 content and IR transmitting cutoff shifted to shorter wavelength side when the amount of added SiO2 exceeded 5 mole%. IR fundamental vibration absorption peaks showed the change that NBOs were inclined to SiO4 tetrahedron in the low-silica region and NBO per SiO4 tetrahedra changed from 2 to 0 with increasing silica content. Based on the analysis of IR fundamental vibration absorption peaks, the model of the structural change can be proposed in three step: 1) SiO4 scavenged the NBOs located at AlO4-tetrahedra, which resulted in the increased of Tg values, 2) NBOs located in the main network again with a decrease in Tg, and 3) dominated by the decrease in the relative amount of NBOs in the glass system, where Tg re-increased.