• Advances in nano research
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• 제5권4호
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• pp.337-357
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• 2017

Knowledge of thin films mechanical properties is strongly associated to the reliability and the performances of Nano Electro Mechanical Systems (NEMS). In the literature, there are several methods for micro materials characterization. Bulge test is an established nondestructive technique for studying the mechanical properties of thin films. This study improve the performances of NEMS by investigating the mechanical behavior of Nano rectangular thin film (NRTF) made of new material embedded in Nano Electro Mechanical Systems (NEMS) by developing the bulge test technique. The NRTF built from adhesively-bonded layers of basalt fiber reinforced polymer (BFRP) laminate composite materials in Nano size at room temperature and were used for plane-strain bulging. The NRTF is first pre-stressed to ensure that is no initial deflection before applied the loads on NRTF and then clamped between two plates. A differential pressure is applying to a deformation of the laminated composite NRTF. This makes the plane-strain bulge test idea for studying the mechanical behavior of laminated composite NRTF in both the elastic and plastic regimes. An exact solution of governing equations for symmetric cross-ply BFRP laminated composite NRTF was established with taking in-to account the effect of the residual strength from pre-stressed loading. The stress-strain relationship of the BFRP laminated composite NRTF was determined by hydraulic bulging test. The NRTF thickness gradation in different points of hemisphere formed in bulge test was analysed.

• Bulletin of the Korean Chemical Society
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• 제32권1호
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• pp.71-76
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• 2011

An efficient nucleophilic [$^{18}F$]fluorination has been studied to reduce byproducts and preparation time. Instead of conventional aqueous solution of $K_2CO_3-K_{222}$, several organic solution containing inert organic salts were used to release [$^{18}F$]fluoride ion and anion bases captured in the polymer cartridge, concluding that methanol solution is the best choice. Comparing to azeotropic drying process, one min was sufficient to remove methanol completely, resulting in about 10% radioactivity saving by reducing drying time. The polymer cartridge, Chromafix$^{(R)}$ (PS-$HCO_3$) was pretreated with several anion bases to displace pre-loaded bicarbonate base. Phosphate bases showed better results than carbonate bases in terms of lower basicity. tert-Butanol solvent used as a reaction media played another critical role in nucleophilic [18F]fluorination by suppressing eliminated side product. Consequent [$^{18}F$]fluorination under the present condition afforded fast preparation of reaction solution and high radiochemical yields (98% radio-TLC, 84% RCY) with 94% of precursor remained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.413-413
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• 2007

In recent years, flexible display devices such as liquid crystal display (LCD), organic light emitting diode (OLED), etc. have attracted considerable interest in a wide variety of applications. Polymer substrate is absolutely necessary to realize this kind of flexible display devices. Using the polymer as a substrate, there are lots of advantages including not only mechanical flexibility such as rolling and bending characteristics but also light weights, low cost and so on. In detail, thickness and weights is only one forth and one second of glass substrate, respectively. However, it needs low temperature below $150^{\circ}C$ in the fabrication process comparing to conventional deposition process. The polymer substrate is not thermally stable as much as the glass substrate so that some deformation can be occurred according to variation of temperature. In particular, performance of devices can be easily deteriorated by shrinkage of substrate when heating it. In this paper, pre-annealing and deposition of buffer layer was introduced and studied to solve previously mentioned problems of the shrinkage and followed shear stress.

• 한국전산유체공학회지
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• 제18권3호
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• pp.20-25
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• 2013

In various manufacturing industries, an in-mold decoration (IMD) process for plastic objects is widely utilized because a film forming and an injection molding processes run simultaneously. In the present study, the deformation of polymer film and filling of resin in the IMD process were numerically investigated to evaluate the quality of the plastic object formed by the IMD process, which consists of thermoforming and injection molding processes. To obtain the initial shape of the polymer film during the injection molding process, the deformation of the polymer film in the thermoforming process was pre-formed using the vacuum conditions to attach the film to a cavity. Since the properties and deformation of polymer film are greatly affected by the behavior of polymer resin being injected into a mold cavity, numerical simulations for the injection molding and film forming were performed with one-way coupling method. The results showed that the injected resin could lead to the tearing of the polymer film in local regions near the corners. In order to verify the proposed numerical methodology, the numerical results of the deformation patterns printed on the initial polymer film were compared with the experimental data. The proposed methodology to couple film forming analysis with injection molding analysis can be used to predict the deformation of film in IMD process.

• 접착 및 계면
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• 제3권4호
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• pp.27-36
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• 2002

다양한 가능을 가진 고분자 복합재료인 Core-shell 복합인자를 제조하여 부직포 바인더로 사용하기 위하여 유기/유기계 core-shell 에멀젼 중합을 시도하였다. 유기/유기계 Core-shell 중합으로 메틸메타아크릴레이트(MMA), 스티렌(St)의 core와 shell의 단량체, 개시제는 과황산암모늄(APS) 유화제는 도데실벤젠슬폰나트륨(SDBS)의 농도, 교반속도를 변화시켜 전환율, 분자량, 입자경과 입자형태, 유리전이온도, 인장강도를 측정하여 최적반응조건을 산출하였다. 1) PMMA, PSt core와 shell의 입자중합은 각각 개시제의 농도 $1.58{\times}10^{-3}mol/L$와 $4.0{\times}10^{-4}mol/L$가 최적이다. 2) PMMA/PSt의 PMMA core 중합에서 유화제의 농도는 $1.45{\times}10^{-5}mol/L$, PSt/PMMA의 PSt core 중합은 $2.91{\times}10^{-5}mol/L$가 최적이다. 3) 유화중합에 최적교반속도는 200 rpm이며, 입자안정성은 유화제 첨가량과 비례하여 증가하였다. 4) Core-shell 복합입자는 동일조성의 공중합체에 비하여 유리온도 조절이 용이하고, 인장강도값도 높게 측정되었다.

• Advances in nano research
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• 제4권1호
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• pp.15-29
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• 2016

A low cost environmentally benign surface coating binder is highly desirable in the field of material science. In this report, castor oil based hyperbranched polyester/bitumen modified fly ash nanocomposites were fabricated to achieve the desired performance. The hyperbranched polyester resin was synthesized by a three-step one pot condensation reaction using monoglyceride of castor oil based carboxyl terminated pre-polymer and 2,2-bis (hydroxymethyl) propionic acid. Also, the bulk fly ash of paper industry waste was converted to hydrophilic nano fly ash by ultrasonication followed by transforming it to an organonano fly ash by the modification with bitumen. The synthesized polyester resin and its nanocomposites were characterized by different analytical and spectroscopic tools. The nanocomposite obtained in presence of 20 wt% styrene (with respect to polyester) was found to be more homogeneous and stable compared to nanocomposite without styrene. The performance in terms of tensile strength, impact resistance, scratch hardness, chemical resistance and thermal stability was found to be improved significantly after formation of nanocomposite compared to the pristine system after curing with bisphenol-A based epoxy and poly(amido amine). The overall results of transmission electron microscopic (TEM) analysis and performance showed good exfoliation of the nano fly ash in the polyester matrix. Thus the studied nanocomposites would open up a new avenue on development of low cost high performing surface coating materials.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.35-41
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• 2017

The use of engineering plastics in automotive components is increasing with the trend towards improving the car strength and reducing weight. Among the different choices of materials, engineering plastic emerged as the necessary material for achieving lower costs, reduced weight and improved production efficiency. To produce the automotive parts, it is important to predict defect and validation of injection molding prior to design. Injection molding analysis and structural analysis are widely applied as a part of the design process when developing automotive parts. Injection molding analysis, in particular, involves a highly complicated mechanism that requires deep knowledge of polymer properties as well as an analytic approach different from that used for a general isotropic material when the molded material is used as a structural material. This is because the parts made of polymer have pre-stress factors such as intrinsic deformation and residual stress. The most important factors for injection molded plastic products are injection molding condition and cavity design, taking into account ease of molding, mass production and application. Despite optimal injection molding conditions and cavity design, however, glass fiber orientation is critically linked to strength reduction. The application of injection molding and structural coupled analysis provides a low-cost solution for product molding and structural validation, all prior to the actual molding. The purpose of this study involves the validation, pre-study, and solution of defect in injection-molded polymer automotive parts using the simulation software for injection molding and structural coupled analysis. Finally, this thesis provides validation of an injection molding and structural coupled analytic mechanism that can demonstrate the effect of glass fiber orientation on mechanical strength. Design improvement ideas for the injection molded product of PPS (Poly Phenylene Sulfide)+40% glass fiber are also suggested.

• 폴리머
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• 제26권2호
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• pp.153-159
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• 2002

본 연구에서는 지하수 중의 NO$_{3}^{-}$ 이온을 선택적으로 흡착 제거시키기 위하여 E-beam 전조사법에 의해 GMA 단량체를 폴리프로필렌 섬유 기재에 그라프트 반응시켜 PP-g-GMA 공중합체를 제조한 후 아민화 반응을 통하여 강염기성 APP-g-GMA 음이온교환수지를 합성하였다. 공중합체의 그라프트율 및 TMA에 의한 아민화율은 반응온도가 증가할수록 증가하였으며, $60^{\circ}C$일 때 각각 133%, 88% 최대치를 나타내었고, 이때의 팽윤율과 이온교환용량은 각각 86%, 2.5 meq/g으로 IMAC HP555, Amberlite IRA 400와 같은 상용 이온교환수지 보다 높게 나타났다. $NO_3;^-$ 이온흡착의 최적 조건은 pH 5~6이었으며, trimethylammonium 기를 갖는 -Cl형의 APP-g-GMA 이온교환체가 가장 높은 선택 흡착성을 나타냈다.

• 폴리머
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• 제25권4호
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• pp.451-459
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• 2001

스티렌 단량체를 E-beam 전조사법에 의해 폴리프로필렌 섬유에 그라프트 반응시켜 PP-g-styrene 공중합체를 제조한 후 클로로메틸화 반응과 아민화 반응을 통하여 아민형 이온교환수지를 합성하였다. 공중합체의 그라프트율은 스티렌 단량체의 농도가 증가할수록 증가하였으며, 스티렌 단량체의 농도가 80% 일때 118%로 최대치를 나타내었다. Mohr's salt와 황산의 최적 농도는 1.0 ${\times}\;10^{-3}$ M 과 0.1M 로 나타났다. 아민화율은 그라프트율이 증가할수록 증가하였다. 합성한 아민형 이온교환체의 팽윤율은 기재보다 높게 나타났으며 이온교환용량은 6.7 meq/g으로 상용 이온교환수지에 비하여 3배 정도의 수치를 나타내었다. 붕소이온흡착의 최적 조건은 pH 4에서 나타났으며, 붕소이온 흡착량은 아민화율이 증가할수록 증가하였다.

• 폴리머
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• 제35권6호
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• pp.610-614
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• 2011

본 연구에서는 방사선 전조사법으로 ETFE(polyethylene-co-tetrafluoroethylene) 불소고분자 필름에 VBC(vinylbenzyl chloride) 단량체를 그래프트할 경우 사용되는 용매의 영향을 평가하였다. ETFE 필름을 전자선을 조사하여 필름에 라디칼을 형성시킨 후 톨루엔, 햅탄, 이소프로판올 등 다양한 용매로 희석된 VBC 단량체 혼합물에 넣어 그래프트 반응을 진행시켜 그래프트율을 측정하였다. VBC-g-ETFE 필름은 FTIR 기기를 사용하여 성공적으로 그래프트 되었음을 확인하였다. 여러 용매에서 제조된 필름의 기계적 강도와 필름 단면에 그래프트된 VBC 고분자의 분포도를 측정하여 용매의 영향을 평가하였다.