• 한국전기전자재료학회논문지
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• 제34권4호
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• pp.229-241
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• 2021

Since 2010, polymer-based magnetoelectric (ME) composites have been developed with detailed investigations of multiferroic properties such as piezoelectric, magnetostrictive, and magnetoelectric, etc. In particular, as a piezoelectric polymer, poly(vinylidene fluoride) and its co-polymers have been widely used in ME composites for energy harvesting, health monitoring, environment treatment, and bio-medical applications. In this study, main research trend and selected experimental results of polymer-based ME composites are briefly reviewed with respect to composite structure as well as application field. A conclusion was drawn that the polymer-based ME composites would be feasible as flexible devices or functional membranes in the near future.

• 한국산업융합학회 논문집
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• 제27권3호
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• pp.619-627
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• 2024

By analyzing the structure of the currently used Lead Tab tape structure, the outermost layer, low-temperature fusion functionalized olefin, was composed of pp base. To determine whether this could be used as the outermost layer of tab tape, the adhesive strength to metal foils such as copper and aluminum was measured and the adhesive strength was compared with commercially available functionalized olefin. When chlorine was grafted onto PP among the PP used in the composition, the average adhesive strength was similar to that of commercially available LT200T and superior to RE140R and LE320V. The maximum adhesive strength exceeded that of LE200T. When it comes to solvents, xylene has been shown to be better than any other. Physical methods such as substitution of other monomers, switching of additives or let-down hardly changed the adhesion of grafted PP, and the selection of PP is an important factor in preparing functional polymers.

• Macromolecular Research
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• 제8권1호
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• pp.44-52
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• 2000

Styrenic macromonomers with/without a silyloxy-functional group were synthesizedvia chain-end functionalization using 4-vinylbenzyl chloride as a terminating agent insec-butyllithium-initiated polymerization of styrene. The yields were 92 mol% for the silyloxy group and 88 mol% for the styrenic unit. Crystalline polystyrene-g-amorphous polystyrenes were synthesized by (η$^{5}$ -indenyl)-trichlorotitanium ((Ind)TiCl$_3$)-catalyzed copolymerizations of the macromonomers with styrene in the presence of methyl-aluminoxane (MAO) in toluene at 4$0^{\circ}C$. The macromonomer having $\alpha$, $\alpha$'-bis (4-[tert-butyldimethylsilyl-oxy]phenyl) group was also utilized for the preparation of a precursor of hydroxyl-functionalized syndio-tactic polystyrene. The obtained polymers were characterized by a combination of$^1$H, $^{13}$ C NMR spectroscopic, size exclusion chromatographic, and differential scanning calorimetric analysis. The (Ind)TiCl$_3$-catalyzed copolymerization of styrene with the macromonomer carrying the silyloxy functional group was found to be an efficient method to modify syndiotactic polystyrene without a great loss of physica] property by controlling the feud ratio of the macromonomer.

• Fibers and Polymers
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• 제7권4호
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• pp.389-397
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• 2006

The beneficial effects of graduated compression stockings (GCS) in prophylaxis and treatment of venous disorders of human lower extremity have been recognized. However, their pressure functional performances are variable and unstable in practical applications, and the exact mechanisms of action remain controversial. Direct surface pressure measurements and indirect material properties testing are not enough for fully understanding the interaction between stocking and leg. A three dimensional (3D) biomechanical mathematical model for numerically simulating the interaction between leg and GCS in dynamic wear was developed based on the actual geometry of the female leg obtained from 3D reconstruction of MR images and the real size and mechanical properties of the compression stocking prototype. The biomechanical solid leg model consists of bones and soft tissues, and an orthotropic shell model is built for the stocking hose. The dynamic putting-on process is simulated by defining the contact of finite relative sliding between the two objects. The surface pressure magnitude and distribution along the different height levels of the leg and stress profiles of stockings were simulated. As well, their dynamic alterations with time processing were quantitatively analyzed. Through validation, the simulated results showed a reasonable agreement with the experimental measurements, and the simulated pressure gradient distribution from the ankle to the thigh (100:67:30) accorded with the advised criterion by the European committee for standardization. The developed model can be used to predict and visualize the dynamic pressure and stress performances exerted by compression stocking in wear, and to optimize the material mechanical properties in stocking design, thus, helping us understand mechanisms of compression action and improving medical functions of GCS.

• Korean Chemical Engineering Research
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• 제51권2호
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• pp.285-291
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• 2013

Quartz crystal microbalance (QCM)을 기반으로 기체 흡착센서 시스템을 구성하기 위하여 감지물질, 코팅방법, 희석가스 및 온도의 영향 등이 면밀하게 검토되었다. 특히 주요 대기 오염물질로 알려진 $NO_2$와 $SO_2$를 감지할 수 있도록 polypyrrole과 poly(3,4-ethylenedioxythiophene) 고분자 물질이 코팅된 QCM 센서소자를 구성하였으며, 만들어진 센서소자들은 ppm 수준의 농도에서 두 가스에 대한 높은 선택성과 감도를 보였다. 센서소자의 감지특성과 응답속도는 감지물질의 코팅방법과 코팅량에 크게 의존하였다.

• 폴리머
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• 제24권4호
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• pp.556-563
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• 2000

일반적으로 열가소성 복합재료는 섬유와 기지재료간의 결합력이 약하다는 단점을 가지고 있어 개발의 한계를 가져왔으나 점차적으로 수지의 개발, 공정의 개선, 계면상의 도입으로 지속적인 물성 향상을 이루고 있다. 특히 계면상의 도입은 외부에서 받은 충격을 잘 흡수할 뿐만 아니라 기지재료와 섬유와의 결합력을 높여 준다. 본 연구에서는 탄소섬유의 전기전도성을 이용하여 전착(electrodeposition)에 의해 탄소섬유와 수지 사이에 계면상을 도입하였으며 계면상 물질과 폴리프로필렌 수지와의 약한 결합력을 개선하기 위해 modified polypropylene을 수지에 첨가하였다. 대표적인 열가소성 수지인 폴리프로필렌을 기지재료로 사용하여 복합재료를 제조하여 층간전단강도, 충격강도 등의 기계적 물성을 평가한 결과, 전착을 통한 계면상을 도입하였을 경우가 물성이 우수함을 확인할 수 있었다. 전착 공정에서는 anhydride 또는 free acid group을 가진 반응성 고분자를 사용하여 수용액상에서 전하 운반체 역할을 수행할 수 있게 하였고 고분자의 종류를 달리하여 계면상 물질의 변화에 따른 복합재료의 물성 차이를 평가하였다. 또한 함침 용액의 농도, 전류밀도 및 전착시간을 변화시키면서 탄소섬유에의 전착수율을 평가하였다.

• 한국염색가공학회지
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• 제8권2호
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• pp.1-7
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• 1996

Thermotropic liquid-crystalline polyurethanes were synthesized by the polyaddition reaction of such para-substiuted diisocyanate monomer as 1,4-phenylene diisocyanate(1,4-PDI) and 2,5-tolylene diisocyanate(2,5-TDI), with 4,4'-bis($\omega$-hydroxyalkoxy)biphenyls(BPm: $HOC_{m}OC_{6}H_{4}C_{6}H_{4}OC_{m}H_{2m}OH$; m is the carbon number of the hydroxyalkoxy group). These polyurethanes have mesogenic biphenyl units in the main chain. Properties of polymers were studied by differential scanning calorimetry, wide-angle X-ray scattering, thermogravimetic analysis, polarizing microscopy, and infraed spectroscopy. DSC thermograms for these polymers exhibited two endothermic peaks corresponding to phase transitions of melting and isotropization. Mesomorphic behavior of the polyurethanes were also observed under the polarizing microscope. For example, polyurethane 2,5-YDI/BP5 with [$\theta$]=0.44 prepared from 2,5-TDI and BP5 exhibited a liquid crystalline phase from 194 to 205$^{\circ}C$. Infrared spectrum study indicated that the hydrogen bonding between urethane linkages affected the mesomorphism. The thermostabilities of polyurethanes 2,5-TDI/BP5 and 1,4-PDI/BP5 were measured at a heating rate of 1$0^{\circ}C$/min in air. The temperatures of 5% weight loss for 2,5-TDI/BP5 and 1,4-PDI/BP5 were 297 and 334$^{\circ}C$, respectively.

• Journal of Computational Design and Engineering
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• 제3권1호
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• pp.37-52
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• 2016

To injection mould polymers, designing mould is a key task involving several critical decisions with direct implications to yield quality, productivity and frugality. One prominent decision among them is specifying sprue-bush conduit expansion as it significantly influences overall injection moulding; abstruseness anguish in its design criteria deceives direct determination. Intuitively designers decide it wisely and then exasperate by optimising or manipulating processing parameters. To overwhelm that anomaly this research aims at proposing an ideal design criteria holistically for all polymeric materials also tend as a functional assessment metric towards perfection i.e., criteria to specify sprue conduit size before mould development. Accordingly, a priori analytical criterion was deduced quantitatively as expansion ratio from ubiquitous empirical relationships specifically a.k.a an exclusive expansion angle imperatively configured for injectant properties. Its computational intelligence advantage was leveraged to augment functionality of perfectly injecting into an impression gap, while synchronising both injector capacity and desired moulding features. For comprehensiveness, it was continuously sensitised over infinite scale as an explicit factor dependent on in-situ spatio-temporal injectant state perplexity with discrete slope and altitude for each polymeric character. In which congregant ranges of apparent viscosity and shear thinning index were conceived to characteristically assort most thermoplastics. Thereon results accorded aggressive conduit expansion widening for viscous incrust, while a very aggressive narrowing for shear thinning encrust; among them apparent viscosity had relative dominance. This important rationale would certainly form a priori design basis as well diagnose filling issues causing several defects. Like this the proposed generic design criteria, being simple would immensely benefit mould designers besides serve as an inexpensive preventive cliché to moulders. Its adaption ease to practice manifests a hope of injection moulding extremely alluring polymers. Therefore, we concluded that appreciating injectant's polymeric character to design exclusive sprue bush offers a definite a priori advantage.

• KSBB Journal
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• 제20권4호
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• pp.260-265
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• 2005

N-CBZ-L-phenylalanine를 주형분자로 하고 MAA와 4-VPY를 기능성 단량체로 하여 분자각인 고분자를 합성하였다. N-CBZ-L-phenylalanine와 MAA, 4-VPY는 수소결합의 영향을 많이 받고 있으며 이온결합과 소수성결합도 작용하고 있다. 혼합성분을 기능성 단량체로 사용함으로 하여 단량체의 성분들 사이에서 상호작용 효과를 나타냈다. 실험결과에 의하면 혼합 성분인 MAA와 4-VPY를 기능성 단량체로 한 분자각인 고분자에서의 체류인자가 단일성분인 MAA를 사용한 고분자에서의 체류인자보다 컸고 컬럼 효율은 낮았지만 분리도는 높았다. 산성인 MAA와 염기성인 4-VPY를 함께 사용함으로써 거울상 이성질체인 N-CBZ-L-phenylalanine과 N-CBZ-D- phenylalanine의 분리도를 증가시킬 수 있었다. 혼합된 성분의 기능성 단량체로하여 제조된 분자각인 고분자를 키랄 물질의 분리를 비롯한 천연물질의 분리에 더 광범위하게 사용될 수 있을 것이다.

• Bulletin of the Korean Chemical Society
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• 제32권2호
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• pp.613-619
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• 2011

Colloidal silver nanoparticles (AgNPs) have been commercialized as the typically stabilized form via the addition of a variety of surfactants or polymers. Herein, to examine the effects of stabilizing AgNPs in suspension, we modified the surface of bare AgNPs with four type of surfactants (NaDDBS, SDS, TW80, CTAB) and polymers (PVP, PAA, PAH, CMC). The modified AgNPs was applied to compare suspension stability and nanotoxicity test using Escherichia coli (E. coli) as a model organism. Modification of AgNPs surface using chemical stabilizer may be not related with molecular weight, but chemical structure such as ionic state and functional group of stabilizer. In this study, it is noteworthy that AgNPs modified with a cationic stabilizer (CTAB, PAH) were importantly toxic to E. coli, rather than anionic stabilizers (NaDDBS, SDS). Comparing similar anionic stabilizer, i.e., NaDDBS and SDS, the result showed that lipophilicity of chemical structure can affect on E. coli, because NaDDBS, which contains a lipophilic benzene ring, accelerated the cytotoxicity of AgNPs. Interestingly, none of the stabilizers tested, including biocompatible nonionic stabilizers (i.e., TW80 and cellulose) caused a reduction in AgNP toxicity. This showed that toxicity of AgNPs cannot be reduced using stabilizers.