• 대한토목학회논문집
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• 제28권6A호
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• pp.861-872
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• 2008

콘크리트충전 유리섬유 복합소재 튜브는 좋은 내구성과 심한 부식환경에서 견딜 수 있는 높은 화학적인 저항성으로 인해서 해양구조물에서 종종 사용된다. 이 연구는 원형 콘크리트충전 유리섬유 복합소재 튜브에 대한 다양한 실험을 수행하고 결과를 분석한다. 유리섬유 직포 수적층, 필라멘트 와인딩 적층을 압축을 받는 관의 바깥 튜브로 사용하는 경우에 고려해야 하는 몇 가지 측면을 실험 분석한다. 이 연구의 목적은 다음과 같다: (1) 유리섬유 층의 필라멘트 와인딩 각도의 효율성 검증 (2) GFRP 적층수가 강도 및 최고 변형률에 미치는 영향 평가 (3) 단부 재하조건이 구속효과 및 파괴양상에 미치는 영향 파악, 그리고 (4) 구속 상태에서 콘크리트의 응력-변형률 거동을 모사하는 해석적인 모델 제시이다. 세 가지 서로 다른 종류의 섬유 구성이 사용되었다: 직포층, ${\pm}45^{\circ}$ 필라멘트 와인딩 층, 그리고 ${\pm}85^{\circ}$ 필라멘트 와인딩 층. 각 층은 독립적으로 혹은 복합적으로 함께 사용되었다. 시편의 비 및 지름이 서로 다른 경우도 실험하였다. 총 27개의 GFRP 튜브 시편을 이용해서 인장 실험을 수행하였고, 66개의 콘크리트충전 GFRP튜브 시편을 이용해서 압축 실험을 수행하고 결과를 분석하였다. 구속상태의 콘크리트 응력-변형률 거동을 모사하는 해석적인 모델 및 영향계수를 제시하였다.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.23-36
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• 2008

고분자-점토 나노복합체는 소량의 점토를 사용하여 큰 기계적 물성향상을 나타내 많은 관심을 끌고 있는 분야이다. 층상 구조를 갖고 있는 점토를 고분자 matrix에 분산하는 과정으로 요약할 수 있는 고분자-점토 나노복합체 제조는 친수성 점토 표면을 조절하는 기술, 점토의 물리적 성질을 이용하는 무기재료에 관한 지식, 고분자 합성, 고분자 유변학, 고분자 용액 거동, 기계적 물성이 복합적으로 작용하는 계이다. 이러한 복잡성을 설명하기 위해, 이 총설에서 점토 종류와 그 특성을 설명하였다. 또한 점토 특성과 고분자-점토 나노복합체 제조 방법의 연관성에 대해 설명하고, 제조된 복합체의 구조 분석과 방법에 대해 설명하였다. 그리고 복합체의 특징적인 물성을 분류한 후 그 물성과 복합체의 구조를 연관하여 살펴보았다. 마지막으로 최근의 연구 경향과 향후 연구 경향을 제시하였다.

• 한국유변학회:학술대회논문집
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• 한국유변학회 2002년도 춘계 학술발표회 논문집
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• pp.133-136
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• 2002

• Bulletin of the Korean Chemical Society
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• 제33권3호
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• pp.975-979
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• 2012

Structure and Dynamics of dilute two-dimensional (2D) ring polymer solutions are investigated by using discontinuous molecular dynamics simulations. A ring polymer and solvent molecules are modeled as a tangent-hard disc chain and hard discs, respectively. Some of solvent molecules are confined inside the 2D ring polymer unlike in 2D linear polymer solutions or three-dimensional polymer solutions. The structure and the dynamics of the 2D ring polymers change significantly with the number ($N_{in}$) of such solvent molecules inside the 2D ring polymers. The mean-squared radius of gyration ($R^2$) increases with $N_{in}$ and scales as $R{\sim}N^{\nu}$ with the scaling exponent $\nu$ that depends on $N_{in}$. When $N_{in}$ is large enough, ${\nu}{\approx}1$, which is consistent with experiments. Meanwhile, for a small $N_{in}{\approx}0.66$ and the 2D ring polymers show unexpected structure. The diffusion coefficient (D) and the rotational relaxation time ($\tau_{rot}$) are also sensitive to $N_{in}$: D decreases and $\tau$ increases sharply with $N_{in}$. D of 2D ring polymers shows a strong size-dependency, i.e., D ~ ln(L), where L is the simulation cell dimension. But the rotational diffusion and its relaxation time ($\tau_{rot}$) are not-size dependent. More interestingly, the scaling behavior of $\tau_{rot}$ also changes with $N_{in}$; for a large $N_{in}$ $\tau_{rot}{\sim}N^{2.46}$ but for a small $N_{in}$ $\tau_{rot}{\sim}N^{1.43}$.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.73-73
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• 2006

We investigate the influence of the confinement on the mesophase formation of diblock copolymer caged in a cylindrical pore in which the surface of the pore preferentially attracts one of the blocks. Using cell dynamics simulation, we construct phase maps as a function of the composition of diblock copolymer (f) and the pore diameter (D) relative to the period at bulk ($L_{o}$). Depending on f and $D/L_{o}$, we observe a variety of confinement-induced mesophases ranging from a simple dartboard-like structure to more complicated structures involving various forms of helices or doughnuts.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.314-314
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• 2006

The FRET property has been extensively studied from the theoretical view points to the practical applications. In case that the donor and acceptor are confined in nanodimension, the FRET effectively occurs, because of their distant dependent characteristic. However, there are no reports concerning FRET with one dimensional (1D) nanomaterial. We have successfully prepared the PMMA nanotubes using vapor deposition polymerization as the platform of FRET. The dye-PMMA composite nanofiber has also been produced without phase separation and any deterioration of properties of the dyes. The PMMA 1D nanocomposite doped two dyes with great spectral overlap between donor and acceptor displayed FRET property.

• Journal of Electrochemical Science and Technology
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• 제9권4호
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• pp.301-307
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• 2018

The current study fabricated magnetic functional reduced graphene oxide (MFRGO) by relying on ${FeCl_4}^-$ magnetic anion confined to cationic 1-methyl imidazolium. Furthermore, for improving the electrochemical performance of conductive polymer, hybrid poly ortho aminophenol (POAP)/ MFRGO films have then been fabricated by POAP electropolymerization in the presence of MFRGO nanorods as active electrodes for electrochemical supercapacitors. Surface and electrochemical analyses have been used for characterization of MFRGO and POAP/ MFRGO composite films. Different electrochemical methods including galvanostatic charge discharge experiments, cyclic voltammetry and electrochemical impedance spectroscopy have been applied to study the system performance. Prepared composite film exhibited a significantly high specific capacity, high rate capability and excellent cycling stability (capacitance retention of ~91% even after 1000 cycles). These results suggest that electrosynthesized composite films are a promising electrode material for energy storage applications in high-performance pseudocapacitors.

• Advances in concrete construction
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• 제6권2호
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• pp.199-220
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• 2018

In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.

• 폴리머
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• 제27권4호
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• pp.293-298
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• 2003

제한공간에서 형성되는 폴리(트리메틸렌 테레프탈레이트) (PTT)의 결정구조를 광학현미경, 소각 광산란 및 X-선 회절로 조사하였다. 인자 $\delta$로 대표할 수 있는 배제 성분의 이동거리는 폴리(에틸렌 테레프탈레이트) (PET/PTT) 블렌드의 형태구조 패턴을 결정하는데 중요한 역할을 하였다. 단계 결정화할 경우, PTT 결정화는 앞서 성장한 PET 결정의 구정 사이 영역에서 시작되었으며, 구정 사이 영역이 채워질 때까지 진행하였다. PET 구정 표면은 PTT 결정화에 매우 효과적인 핵 생성 작용을 유도함으로써 transcrystalline 구조의 PTT 결정을 유도하였다. 그 결과 PTT가 많은 상에서 전형적인 구정 구조와 함께 transcrystalline구조가 혼재하는 독특한 형태구조가 관찰되었다. PET 구정의 라멜라 사이나 피브릴 사이의 영역에서는 공간적 제한으로 인하여 PTT분자들의 형태 자유도가 감소하였으며, 이러한 감소 요인은 PET구정 내ㆍ외부에서의 PTT 결정화와 용융 거동에 차이를 유발하였다.

• Elastomers and Composites
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• 제56권2호
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• pp.72-78
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• 2021

A phase-change material (PCM) is a material that has the ability to delay heat transfer by absorbing heat from its environment or releasing heat to its environment while its phase changes from solid to liquid or liquid to solid at a specific temperature. As it is applied, it can contribute to environmental conservation such as energy savings and carbon dioxide emission reduction. In order for a PCM to store and release heat, the volume change during its phase transition should be large, and thus a phase transition space is required. When a PCM is used as a polymer additive, it is confined within the polymer, and there is no phase transition space; thus, its ability to absorb and release heat is significantly reduced. Therefore, in this study, porous silica was used to provide EVA/PCM compounds with sufficient space for their phase transition, and to improve the compatibility between the EVA and PCM, modified silica is used: surface-modified 5 wt% silica with 3-methacryloxypropyltrimethoxysilane. The compound was prepared and compared with the silica compound. The presence or absence of the modified silica surface modification was confirmed using Fourier-transform infrared spectroscopy and thermogravimetric analysis, the heat capacity of the compound was evaluated based on a differential scanning calorimetry analysis, and its mechanical strength and morphology were determined using scanning electron microscopy.