• Textile Coloration and Finishing
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• v.11 no.5
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• pp.44-54
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• 1999

Poly(ethylene 2,6-naphthalate), PEN, is a relatively well-known polymer used for engineering purposes. Naphthalene ring provides rigidity to the polymer backbone, thus, it elevated the glass transition temperature and enhanced mechanical properties. The structure and properties of PEN affect a processing conditions severely, and the high-thermal stability have been had a poor thermal processibility. Hence, the basic mechanism of solvent drawing, is very much the same as that of thermal drawing from glassy state since both involve the inducement of segmental mobility. The former achieves the goal by use of chemical energy, and the latter does so by use of thermal energy. Generally, the sorption of the solvent by the polymer has a plasticizing effect, and leads to a lowering of the glass transition temperature, $T_g$. In this paper, the dynamic viscoelasticity behavior in liquid-drawing process of an unoriented amorphous PEN films were investigated using Rheovibron. The results are as follows ： (1) For the drawing in silicone oil, the drawing below $T_g$. had $\alpha{2}$-dispersion due to an inhomogeneous taut structure. (2) For the drawing in water, the inhomogeneous taut structure reduced by the effect of plasticization even below $T_g$. (3) For the drawing in butanol, the only aliphatic segment in PEN have some molecular mobility but the mobility of the aromatic segment having naphthalene ring is nearly impossible. (4) For the drawing in dioxane/water mixing solvent, the solvent effect is complementary each other and accordingly the entire molecular conformation have stable state. (5) For the drawing in dioxane/butanol mixing solvent, the inhomogeneity of the taut structure and the aromatic segment increase with increasing the temperature and this tendencies correspond with that of the draw ratio.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.7-15
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• 2008

In this paper, the Chip-On-Flex (COF) assembly process using anisotropic conductive films (ACFs) was investigated and the reliability of COF assemblies using ACFs was evaluated. Thermo-mechanical properties of ACFs such as coefficient of thermal expansion (CTE), storage modulus (E'), and glass transition temperature $(T_g)$ were measured to investigate the effects of ACF material properties on the reliability of COF assemblies using ACFs. In addition, the bonding conditions for COF assemblies using ACFs such as time, temperature, and pressure were optimized. After the COF assemblies using ACFs were fabricated with optimized bonding conditions, reliability tests were then carried out. According to the reliability test results, COF assemblies using the ACF which had lower CTE and higher $T_g$ showed better thermal cycling reliability. Consequently, thermo-mechanical properties of ACFs, especially $T_g$, should be improved for high thermal cycling reliability of COF assemblies using ACFs for compact camera module (CCM) applications.

• Korean Journal of Materials Research
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• v.32 no.12
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• pp.515-521
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• 2022

Various types of optical materials and devices used in special environments must satisfy durability and optical properties. In order to improve the durability of zinc sulfide multispectral (MS ZnS) substrates with transmission wavelengths from visible to infrared, Ge-Sb-Se-based chalcogenide glass was used as a sealing material to bond the MS ZnS substrates. Wetting tests of the Ge-Sb-Se-based chalcogenide glass were conducted to analyze flowability as a function of temperature, by considering the glass transition temperature (T_g) and softening temperature (T_s). In the wetting test, the viscous flow of the chalcogenide glass sample was analyzed according to the temperature. After placing the chalcogenide glass disk between MS ZnS substrates (20 × 30 mm), the sealing test was performed at a temperature of 485 ℃ for 60 min. Notably, it was found that the Ge-Sb-Se-based chalcogenide glass sealed the MS ZnS substrates well. After the MS ZnS substrates were sealed with chalcogenide glass, they showed a transmission of 55 % over 3~12 ㎛. The tensile strength of the sealed MS ZnS substrates with Ge-Sb-Se-based chalcogenide glass was analyzed by applying a maximum load of about 240 N, confirming its suitability as a sealing material in the far infrared range.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.134-136
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• 2003

In this work, we have seen the effect of hole-transporting layer in organic light-emitting diodes using N,N'-biphenyl-N,N'-bis-(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine(TPD) and N,N'-biphenyl-N,N'-bis-(1-naphenyl)-[l,l'-biphenyl]-4,4'-diamine(NPB). NPB is regarded as a better hole trans porting material than TPD, since it has a higher glass transition temperature($T_g$). And current-voltage, luminance-voltage and external quantum efficiency of device were measured with the thickness variation of buffer layer using copper phathalocyanine(CuPc) am polytetrafluoroethylene (PTEE) at room temperature. We have obtained an improvement of External quantum efficiency when the CuPc 30[nm] and PTFE 1.0[nm] is used.

• Polymer(Korea)
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• v.37 no.1
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• pp.41-46
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• 2013

The glass transition temperature ($T_g$) and conversion (${\alpha}$) were measured for a diglycidyl ether of bisphenol A (DGEBA) epoxy/aromatic amine system incorporated with an organic-inorganic hybrid molecule, polyhedral oligomeric silsesquioxane (POSS). Samples isothermally cured at varying cure temperatures and times were analyzed by differential scanning calorimetry (DSC). $T_g$ vs. ln (time) data at an arbitrary reference were superposed by time-temperature shifts for the kinetically controlled reaction, and the shift factors were used to calculate an Arrhenius activation energy. Influence of POSS was investigated from $T_g$ vs. ${\alpha}$ data, which in turn were fitted with DiBenedetto equation.

• 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.

• Bulletin of the Korean Chemical Society
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• v.30 no.2
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• pp.334-338
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• 2009

Trifunctional epoxy resin triglycidyl paraaminophenol (TGPAP)/$CaCO_3$ nanocomposites were prepared using the melt blending method. The effects of nano-$CaCO_3$ content on the thermal behaviors, such as cure behavior, glass transition temperature ($T_g$), thermal stability, and the coefficient of thermal extension (CTE), were investigated by several techniques. Differential scanning calorimetry (DSC) results indicated that the cure reaction of the TGPAP epoxy resin was accelerated with the addition of nano-$CaCO_3$. When the nano-$CaCO_3$ content was increased, the $T_g$ of the TGPAP/$CaCO_3$ nanocomposites did not obviously change, whereas the crosslinking density was linearly increased. The nanocomposites showed a higher thermal stability than that of the neat epoxy resin. This result could be attributed to the increased surface contact area between the nano-$CaCO_3$ particles and the epoxy matrix, as well as the high crosslinking density in the TGPAP/$CaCO_3$ nanocomposites. The CTE of the nanocomposites in the rubbery region was significantly decreased as the nano-$CaCO_3$ content was increased.

• Textile Coloration and Finishing
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• v.3 no.3
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• pp.23-28
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• 1991

Poly(1, 4-cyclohexanedimethylene/ethylene terephthalate), PCET was prepared by condensing 1, 4-cyclohexanedimethanol(CHDM) and ethylene glycol with dimethylterephthalate(DMT), and some thermal properties of PCET were studied by DSC at a heating rate $20^{\circ}C$min. On increasing the CHDM content in PCET up to 20 mole%/DMT, the glass transition temperature(Tg) decreased a little and the crystallizability reduced sharply, and from 20 to 50 mole %/DMT the $T_g$ did not changed and the crystallization temperature was not detected. But on increasing the CHDM content above 70 mole %/DMT the TEX>$T_g$/ and the melting temperature increased.

• Progress in Superconductivity and Cryogenics
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• v.17 no.4
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• pp.30-33
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• 2015

We report the synthesis of Ni-doped $BaFe_2Se_3$ single crystals by using a flux method. X-ray diffraction (XRD) of $Ba(Fe_{1-x}Ni_x)_2Se_3$ shows a gradual peak shift with an increase in the nominal Ni-doping rate, x = 0, 0.05, and 0.10, due to a decrease in unit-cell volume. All samples show a spin glass transition, and temperature dependence of magnetic susceptibility shows a negligible change in the spin-glass transition temperature ($T_g$) with Ni concentration x. The temperature dependence of electrical resistivity for $BaFe_2Se_3$ shows an insulating behavior, and the resistivity value at 295 K and the activation energy ($E_a$) obtained from the Arrhenius plot decrease with increasing x. These results suggest that the Ni doping can be effectively worked as a dopant for electron charge carriers, but is less efficient in controlling the magnetic property, such as spin glass transition, in the $BaFe_2Se_3$ compound.

• Journal of Adhesion and Interface
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• v.23 no.4
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• pp.137-143
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• 2022

In this study, the polyurethane acrylates (PUA) resin with good adhesive and flexibility for adhesive for shoes and clothing were synthesized using that poly(tetramethylene adiphate glycol) (PTAd), poly(tetramethylene ether glycol) (PTMG) as polyester polyol and polyether polyol respectively, including 4,4'-methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), 1,4-butandiol (1,4-BD), 2-hydroxyethyl methacrylate (2-HEMA) and dibutyl amine (DBA). The effect of polyol blend in the polyurethane acrylate on thermal and mechanical properties, adhesion strength and flexural strength were studied. The glass transition temperature (T_g) of PUA was confirmed in range of -70~-40 ℃. In addition, the glass transition temperature (T_g), decomposition temperature (T_d), tensile strength adhesion strength and heat resistance were increased as increasing of PTAd amount while the elongation, water resistance and flexural properties were decreased. The synthesized polyurethane acrylate with 5:5 ratio of PTAd and PTMG indicated the highest adhesion strength and flexural properties.