• Polymer(Korea)
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• v.25 no.3
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• pp.327-333
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• 2001

Acetylene substituted fluorenes such as 2-ethynylfluorene and 2,7-diethynyl-fluorene were synthesized and thin films were prepared by the vacuum deposition. Curing of these fluorene derivatives could be achieved by heat treatment and UV irradiation. The curing temperature of 2-ethynylfluorene and 2,7-diethynylfluorene were found to be 231 and $198^{\circ}C$, respectively. The cured poly(2-ethynylfluorene) and poly(2,7-diethynylfluorene) started to decompose at 280 and $ 385^{\circ}C$, respectively. Fluorescent characteristics of the cured films were similar to those of monomers, but fluorescent efficiency of the film was decreased about 3 to 10 fold.

• Polymer(Korea)
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• v.24 no.5
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• pp.690-700
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• 2000

In this study, an elastomer-assistered compression molding process was investigated by experiments as well as modeling for the long-fiber reinforced thermoset composites. The consolidation pressure generated by fixed-volume and variable-volume conditions was thermodynamically derived for both elastomer and curing prepregs, and was compared with the pressure measured during curing of epoxy matrix. Exhibiting non-linear viscoelastic characteristics in the compressive stress-strain tests, the measured stress was well compared with a modifed KWW (Kohlrausch-Williame-Watts) equation, which is based on the Maxwell viscoelastic model. Using the developed model equations, the consolidation pressure generated by the elastomer was successfully predicted for the compression molding process of thermoset composite materials in tile closed mold system.

• Polymer(Korea)
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• v.35 no.2
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• pp.141-145
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• 2011

The electron beam (EB) induced curing of a typical resin designed for the hard coating layer of in-mold decoration foils was investigated. The samples were irradiated with different doses of EB and the curing reaction was monitored by Fourier transform infrared (FTIR) spectroscopy. The change in coating properties such as surface hardness and anti-abrasion property was studied as a function of increasing dose. The effect of the addition of nano-particles on the improvement of coating properties was also examined. It was expected that the experimental results could be used for the commercial exploitation of the EB curing system comparable to the ultraviolet (UV) curing system.

• Journal of the Korea Institute of Building Construction
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• v.22 no.6
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• pp.543-551
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• 2022

The mechanical performance and vibration damping ratio performance of a specimen according to the polymer mixing rate were evaluated for polymer modified mortar. As a polymer, Styrene Butadiene Rubber(SBR) liquid polymer with a solid content of about 49~51% was used, and the polymer content was increased by liquid 5%. The specimen was 40*40*160(mm), and after curing, compressive strength, flexural strength, and vibration damping ratio were measured using the ultrasonic pulse method. As a result, it was found that the compressive strength decreased as the polymer was mixed, but the flexural strength was increased. The vibration damping ratio increased by 11% at 5% polymer, 28% at 10% polymer, 33% at 15% polymer, and 72 at 20% polymer. I was found that the incorporation of the polymer was very effective to reduce the vibration of the mortar. In addition, through SEM and SEM-EDS analysis, it is determined that the cause of vibration reduction due to polymer mixing is that the polymer film formed in the transition zone of aggregate and internal voids buffered the vibration of the mortar inside. Taken together, in the scope of this study, the appropriate polymer mixing ratio for reducing the vibration of mortar is judged to be about 7.5%.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.492-497
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• 2005

In this study, we propose an advanced nanoindentaion test, Nano Pillar Compression Test (NPCT) to measure a stress-strain relation for micro scale polymer structures. Firstly, FEM analysis is performed to research behavior of micro polymer pillars in several specimen aspect ratios and different friction conditions between specimen and tip. Based on the FEM results, micro scale UV-curable polymer pillars are fabricated on a substrate by Nano Stereo Lithography (NSL). To measure their mechanical properties, uniaxial compression test is performed using nanoindentation apparatus with flat-ended diamond tip. In addition, the dependency of compression properties on loading condition and specimen size are discussed.

• Polymer(Korea)
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• v.24 no.6
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• pp.837-844
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• 2000

The cure behavior of commercial epoxy molding compounds (EMC) commonly used for IC package was studied at constant cure temperatures as well as at constant heating rates using differential scanning calorimetry (DSC), rheometer, and dielectric analyzer (DEA). The cure kinetics were obtained using autocatalytic reaction model according to the Ryan Dutta method after assuming m+n equal to 2. The prediction of reaction rates by the model equation corresponded well to experimental data at all temperatures except for 10$0^{\circ}C$. The phase transitions such as gelation and vitrification occurred during network formation. At each isothermal cure temperature, $T_{g}$ was measured in accordance with cure time, and the vitrification point was attained when $T_{g}$ was equal to $T_{cure}$. The temperature dependence of gel points and vitrification points showed good agreement with Arrhenius relation. DEA using parallel plate electrode was effective for the monitoring of EMC cure. we knew that if the resin systems are materials of comparable quality, $_{gel}$$T_{g}$ is constant regardless of accelerator concentration in TTT (Time-Temperature-Transformation) diagram.

• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.491-496
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• 1998

The composition of isocyanates and polyols influence prepolymeric properties of adhesive and calking sealant based on polyurethanes (PU). One component moisture curing prepolymers, which reacted with surface humidity of substrate, were synthesized in several kinds of composition. Reactivity, structural change and properties of the prepolymers were studied as a preliminary step to manufacture PU based adhesive and sealant. To study the effects of mole ratio ([NCO]/[OH]), we used toluene diisocyanate (TDI), 4, 4'-diphenylmethane diisocyanate (MDI), and ether-polyols such as PTMG and PPG which have good resistance to hydrolysis and excellent low-temperature properties. The each prepolymers could be prepared in different molecular weight without any significant structural change. The mole ratio 1.78 of [NCO] to [OH] showed the fastest reactivity. It was confirmed that effect of polyols was larger than that of isocyanates on the prepolymer in reactivity. Several kinds of compounds were manufactured with each prepolymer, and tensile and properties were tested. And the optimum quantity of curing accelerator for the PU was 0.05~0.1%. In the tensile test, TDI based PU was superior to MDI based PU, and also PTMG based PU was superior PPG based PU.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.63.1-63.1
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• 2011

현재 상용 중인 터치패널의 전도성 필름으로는 ITO가 주로 사용된다. 하지만, 디스플레이 기기의 수요 증가와 Indium의 고갈로 인한 ITO의 수요 공급 불균형으로 인한 원가 문제가 대두되고 있다. 이 때문에, Carbon nanotube (CNT), Graphene 등의 대체 투명 전도성 물질들이 연구 중에 있지만 투과율 및 저항 문제 등이 문제가 되고 있다. 본 연구에서는 투명 전도성 필름의 광 투과도 향상을 위하여, 자외선 경화 레진을 이용하여, 전도성 필름 상에 모스 아이 레진 패턴을 형성하는 실험을 진행하였다. 패턴이 형성된 이후에는 Scanning Electro Microscope를 통하여 패턴의 형성 유무를 관찰하였고, UV-vis와 4-point probe를 이용하여 투과도 및 저항을 측정하였다. 실험 결과 모스아이패턴을 필름에 패터닝 함으로써, 전체적으로 투과도가 증가된다는 것을 확인 할 수 있었으며, 투과도의 증가폭은 단면 패터닝보다는 양면 패터닝을 한 경우가 높았다. 그리고 저항 변화에 있어서는 패턴이 있는 부분의 경우 표면 잔여층으로 인하여 급격하게 증가하였지만, 전도면 반대편에 패터닝을 진행한 경우 거의 변화하지 않았다는 것을 확인할 수 있었다. 결과적으로, 본 연구를 통해 나노 임프린트 리소그래피를 통해 전도성 폴리머 필름 상부에 모스아이나노 구조물을 제작하였고, 이를 통해 기존의 전도성 폴리머 필름의 낮은 투과율을 향상시킬 수 있었다.

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.190-198
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• 2002

In this research the physical properties of polymer modified mortar containing pulverized FRP(Fiber-Reinforced Plastics) wastes fine powder as a part of fine aggregate were investigated. Styrene-butadiene rubber(SBR) latex, polyacrylic ester(PAE) emulsion and ethylene-vinyl acetate(EVA) emulsion were used as Polymer modifier. Polymer modified mortars containing FRP wastes fine powder were prepared with various FRP wastes fine powder replacement(5∼30 wt％) for fine aggregate and polymer-cement ratios(5∼20 wt％). The water-cement ratio, water absorption rates and hot water immersion test, compressive and flexural strengths of polymer modified mortars were tested and the results compared to those of ordinary portland cement mortar. As the results, compressive and flexural strengths of polymer modified mortar containing FRP wastes fine powder depend on the contents of FRP wastes fine powder, type and additional amounts of polymer modifier. Some of them showed higher compressive and flexural strengths than those of ordinary portland cement mortar. Especially, SBR-modified mortar showed the highest strengths properties among three types of polymer modifier. Also water absorption rates, compressive and flexural strengths of SBR-modified mortar were more superior than those of PAE or EVA-modified mortar. The optimum mix proportions of SBR-modified mortar was 20 wt％ of polymer-cement ratio and 20 wt％ of FRP wastes fine powder replacement. Otherwise heat cured polymer modified mortar accelerated the improvement of early compressive and flexural strengths.

• Elastomers and Composites
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• v.33 no.4
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• pp.267-273
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• 1998

Isocyante terminated urethane prepolymers were synthesized by the reaction of 4,4'-dimethyl phenyldiisocyanate(MDI) and ester type polyols such as ethylene glycol/ butanediol adipate(EBA), neopentylglycol/butanediol adipate (NBA) and hexanediol adipate (HA) . All of the NCO-terminated urethane prepolymers are solid at room temperature, but they become mobile enough to be disposed onto a substrate upon heating about $80^{\circ}C$. Subsequently, they are solidified and cured through the reaction with moisture. Tensile behavior of the ore-thane hotmelt exhibits characteristic features depending on the type of polyol. The adhesive strength determined by single lap shear joint is higher in order of HA, NBA and EBA based ore thane hotmelt, which can be correlated with the magnitude of breaking energy of the cured films. The failure mode are cohesive for all cases and the adhesive strength increases as the test is performed faster. This indicates that the strength of the adhesive joint is primarily dependent upon the bulk properties of the adhesives.