• Elastomers and Composites
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• v.59 no.1
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• pp.8-16
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• 2024

As regulations on greenhouse gas emission have strengthened globally, the demand for improved fuel efficiency in automobiles continues to rise. In response, the tire industry is actively conducting research to improve fuel efficiency by enhancing tire performance. In this study, silica-filled epoxidized natural rubber (ENR)/butadiene rubber (BR) blend compounds were manufactured according to ENR types and silica contents, and their physical properties and vulcanizate structure were evaluated. ENR-50, which has a higher epoxide content than ENR-25, exhibited stronger filler-rubber interaction, resulting in superior abrasion resistance. In addition, because of its high glass transition temperature (T_g), the wet grip performance of ENR-50 improved, even though the rolling resistance increased. Increasing the amount of silica had little effect on the abrasion resistance due to the increase in filler-rubber interaction and decrease in toughness. In addition, ENR-50 exhibited better wet grip performance; however, the rolling resistance increased. The results indicated that truck bus radial (TBR) tire tread compounds can be designed by applying ENR-50 to improve wear resistance and wet grip performance. In addition, by applying ENR-25 and reducing the silica contents improve fuel efficiency.

• Macromolecular Research
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• v.14 no.3
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• pp.343-347
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• 2006

A novel, blue light-emitting polymer, poly(phenyl-9,9-dioctyl-9',9'dihexanenitrile)fluorene (PPFC6N), containing an alkyl and cyano group in the side chain, was synthesized by Suzuki polymerization and characterized. The polymer structure was confirmed by $^1H-NMR$. The number average molecular weight and the weight average molecular weight of the obtained polymer were 9,725 and 9,943 respectively. The resulting polymer was thermally stable with a glass transition temperature ($T_g$) of $93^{\circ}C$, and was easily soluble in common organic solvents such as THF, toluene, chlorobenzene and chloroform. The HOMO and LUMO energy levels of the polymer were revealed as 5.8 and 2.88 eV by cyclic voltammetry study, respectively. The ITO/PEDOT:PSS (40 nm)/PPFC6N (80 m)/LiF (1 nm)/Al (150 nm) device fabricated from the polymer emitted a PL spectrum at 450 nm and showed a real blue emission for pure PPFC6N in the EL spectrum. When t-butyl PBD was introduced as a hole blocking layer, the device performance was largely improved and the EL spectrum was slightly shifted toward deep blue. The device with PPFC6N containing t-butyl PBD layer showed the maximum luminance of 3,200 $cd/m^2$ at 9.5 V with a turnon voltage of 7 V.

• Composites Research
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• v.27 no.4
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• pp.168-173
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• 2014

The optimum condition of glass fiber/epoxy composites was investigated according to mixing ratio of two epoxy matrices. Novolac type epoxy and isocyanate modified epoxy were used as composites matrix. Based on chemical composition of mixing matrix, optimum mixing ratio of epoxy resins was obtained through various experiments. In order to investigate thermal stability and interface of epoxy resin, glass transition temperature was observed by DSC instrument, and static contact angle was measured by reflecting microscope. Change of IR peak and $T_g$ was conformed according to different epoxy mixing ratio. After fabrication of glass fiber/epoxy composites, tensile, compression, and flexural properties were tested by UTM by room and high temperature. The composites exhibited best mechanical properties when epoxy mixing ratio was 1:1.

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.251-258
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• 2015

In the study, PLLA with 12,000 g/mol ($M_n$) and 14,000 g/mol ($M_w$) was synthesized from L-lactide, and used to synthesize PLLA-Br intermediate. PLLA-block-PMMA with 84,000 g/mol ($M_n$) and 126,000 g/mol ($M_w$) was finally synthesized from PLLA-Br intermediate. The glass transition temperature ($T_g$) and initial pyrolysis temperature of PLLA-block-PMMA are $95.5^{\circ}C$ and $289^{\circ}C$, respectively. The PLA film of $50{\pm}3{\mu}m$ thickness was prepared by blending PLA with 9 phr PLLA-block-PMMA followed by stretching biaxially at 3 times under $95^{\circ}C$, and annealing at $120^{\circ}C$ for 2 min. The light transmittance at 550 nm and tensile strength of the film are 88.5% and 44.5 MPa, respectively. To enhance the tensile strength of PLA film, it was required to keep the film more than 2 min at $120^{\circ}C$ during the annealing step after a biaxially orientation.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.427-431
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• 1999

Copolyester resins for the coil coating process of aluminium and steel strip were synthesized and their thermal properties, molecular weight and solvent solution characteristics were examined. Copolyesters were obtained by two step reactions. The first step was to prepare bishydroxyethyl terephthalate (BHET), bishydroxyneopentyl terephthalate (BHNPT), bishydroxyethyl isophthalate (BHEI), bishydroxyneopentyl sebacate (BHNPS), bishydroxyneopentyl adipicate (BHNPA) and bishydroxyethyl adipicate (BHEA) oligomers by esterification reactions. The second step was the polycondensation reaction utilizing those oligomers to obtain relatively high molecular weight copolyesters (Mw = 30,000~59,000 g/mol) as measured by GPC. These copolyesters were amorphous polymers as shown by DSC without $T_m$ peaks probably due to the kink structure introduced by BHET oligomer and relatively large free volume by bulky BHNPT and BHNPS oligomers. The copolyester samples with half of BHET oligomer substituted by BHNPT while keeping BHEI (0.3 mole) and BHNPS (0.1 mole) ratio constant showed glass transition temperature above $40^{\circ}C$ and good solubility in toluene both at low ($-5^{\circ}C$) temperature and room temperature.

• Bulletin of the Korean Chemical Society
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• v.33 no.7
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• pp.2193-2199
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• 2012

A series of novel polytriazoleimides were prepared from various aromatic dianhydrides and a new kind of 1,2,3-triazole-containing aromatic diamine synthesized by the Cu (I)-catalyzed 1,3-dipolar cycloaddition reaction in DMAc, and characterized by FT-IR, $^1H$-NMR, XRD, DSC and TGA techniques. The results show the polytriazoleimides are soluble in most of strong polar solvents and have inherent viscosity values of 0.51-0.62 dL/g(DMAc). The polytriazoleimide films exhibit a tensile strength of 62.3-104.5 MPa and an elongation at breakage of 4.0-8.1%, a glass transition temperature ($T_g$) of $257-275^{\circ}C$, a decomposition temperature (at 5% weight loss) of $350-401^{\circ}C$ in $N_2$ atmosphere, and a dielectric constant of 2.47-3.01 at 10 MHz, which depend on the structure of the polymers. The polytriazoleimides perform good resistance to acid and alkali solution.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.711-717
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• 1999

A multilayer-structure material containing ductile and brittle layer simultaneously was examined and compared with a single layer material using fracture mechanical properties. We found that impact strength of multilayer structure material was considerably higher than single layer's and toughness was enhanced by about two times or higher in similar glass transition temperature($T_g$) region and the same dimension. The superposition principle of impact pulse was used for interpretation of kinetic stress wave as a high-velocity crack proceeds in the plastic. It was understood that the optimum condition of ductile/brittle thickness ratio could be designed in the final toughness enhancement of multilayer.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.133-136
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• 2008

In order to decrease carbon dioxide, one of the green house gas, poly(styrene carbonate) has been synthesized from carbon dioxide and styrene oxide with zinc glutarate as a catalyst. The polymer has been identified as an alternating copolymer by spectroscopic analysis, FT-IR, $^1H$-NMR, and $^{13}C$-NMR. The number average molecular weight ($M_n$) of the polymer is $5.0{\times}10^4g/mol$ and the glass transition temperature ($T_g$) is $88^{\circ}C$ and its melting point ($T_m$) is $240^{\circ}C$. The cyclic carbonate, styrene carbonate, has been obtained by thermal degradation of the polymer via the unzipping mechanism.

• Macromolecular Research
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• v.11 no.6
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• pp.431-436
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• 2003

A new photoconducting polymer, diphenyl hydrazone-substituted polysiloxane, was successfully synthesized by the hydrosilylation method and characterized by FT-IR, $^1$H-NMR, and $^{29}$ Si-NMR spectroscopy. The glass transition temperature (T$_{g}$) of the polysiloxane having pendant diphenyl hydrazone was ca. 62 $^{\circ}C$, which enabled a component of a low-T$_{g}$ photorefractive material to be prepared without the addition of any plasticizers. This polysiloxane, with 1 wt% of $C_{60}$ dopant, showed a high photoconductivity (2.8 ${\times}$ 10$^{-12}$ S/cm at 70 V/${\mu}{\textrm}{m}$) at 633 nm, which is necessary for fast build-up of the space-charge field. A photorefractive composite was prepared by adding a nonlinear optical chromophore, 2-{3-[2-(dibutylamino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenylidene} malononitrile, into the photoconducting polysiloxane together with $C_{60}$ . This composite shows a large orientation birefringence ($\Delta$n = 2.6 ${\times}$ 10$^{-3}$ at 50 V/${\mu}{\textrm}{m}$) and a high diffraction efficiency of 81 % at an electric field of 40 V /${\mu}{\textrm}{m}$.textrm}{m}$.EX>.

• Journal of the Korean Applied Science and Technology
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• v.24 no.2
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• pp.149-159
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• 2007

In order to prepare high-solid coatings, acrylic resins, HSCs [poly (EA/EMA/2-HEMA/CLA)] that contain 90% solid, were synthesized by copolymerization of ethyl acrylate (EA), ethyl methacrylate (EMA), 2-hydroxyethyl methacrylate (2-HEMA) and caprolactone acrylate (CLA). The high-solid coatings named as CHSCs (HSCs/HDI-trimer) were prepared by the curing reaction between the acrylic resins containing 90% solid contents and the isocyanates (HDI-trimer) curing agent room temperature. The curing behavior and various properties were examined on the film coated with the both high-solid coatings. The glass transition temperatures $(T_g)$ of CHSCs increased proportionally with increasing the predicted $T_g$ value by Fox equation, and had nothing to do with the solid contents. The prepared film showed good properties for $60^{\circ}$ specular gloss, impact resistance, cross-hatch adhesion and heat resistance, and bad properties for pencil hardness, drying time, and pot-life. Among the film properties, the heat resistance was very excellent and could be explained by the introduction of functional monomers of CLA.