• Title/Summary/Keyword: Dynamic mechanical analyzer

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Styrenic Polymer/Organoclay Nanocomposite Prepared via in-situ Polymerization with an Azoinitiator Linked to an Epoxy Oligomer

  • Jeong, Han-Mo;Choi, Mi-Yeon;Kim, Min-Seok;An, Jin-Hee;Jung, Jin-Su;Kim, Jae-Hoon;Kim, Byung-Kyu;Cho, Sung-Man
    • Macromolecular Research
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    • v.14 no.6
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    • pp.610-616
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    • 2006
  • An azoinitiator linked to an epoxy oligomer, which could easily diffuse into the organoclay gallery and swell it, was used as an initiator to enhance the delamination of an organoclay, Cloisite 25A, in a matrix of styrenic polymers, poly(styrene-co-acrylonitrile) and polystyrene, during the preparation of a nanocomposite via an in-situ polymerization method. X-ray diffraction results and transmission electron microscopic observation of the morphology showed that the epoxy segment enhanced not only the delamination but also the extrication of ammonium cations from the organoclay gallery into the polymer matrix. The latter phenomenon induced the structural change of the alkyl group of ammonium cations in the gallery from a bilayer to monolayer structure, and also decreased the glass-rubber transition temperature as measured by a differential scanning calorimeter and dynamic mechanical analyzer.

Surface Modification Effect and Mechanical Property of para-Aramid Fiber by Low-temperature Plasma Treatment (저온 플라즈마 처리를 이용한 파라 아라미드 섬유의 표면 개질 효과 및 역학적 특성)

  • Park, Sung-Min;Kwon, Il-Jun;Kim, Myung-Soon;Kim, Sam-Soo;Choi, Jae-Young;Yeum, Jeong-Hyun
    • Textile Coloration and Finishing
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    • v.24 no.2
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    • pp.131-137
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    • 2012
  • para-Aramid fibers were treated by low-temperature plasma to improve the adhesion. The surface of para-aramid fibers were treated with gaseous plasma of several discharge power and treatment time in oxygen gas at 1Torr pressure. The treated fibers at low-temperature plasma were taken oxygen-containing functional groups and micro-crator on the surface. The modified fibers were measured by dynamic contact angle analyzer and XPS(X-ray photoelectron spectroscopy). The Interfacial adhesion properties of aramid fabric and polyurethane resin were determined by T-peel test. The surface of aramid fibers were observed by FE-SEM photographs. It was found that surface modification and chemical component ratio of the aramid fibers were improved wettability and adhesion characterization.

Analysis on a Hip Joint System of New RGO Using Accelerometers (가속도계를 이용한 왕복보행보조기의 고관절 시스템 해석 -인체 진동해석과 FEM 해석을 중심으로-)

  • 김명회;장대진;장영재;박영필
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.882-887
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    • 2003
  • This paper presented a design and control of a new RGO(reciprocating gait orthosis)and its simulation. The new RGO was distinguished from the other one by which had a very light-weight and a new RGO(reciprocating gait orthosis) system. The vibration evaluation of the hip joint system on the new RGO(reciprocating gait orthosis)was used to access by the 3-axis accelerometer with a low frequency vibration of less than 30 ㎐. The gait of the new RGO depended on the constrains of mechanical kinematics and the initial posture. The stability of dynamic walking was investigated by analyzing the ZMP (zero moment point) of the new RGO. It was designed according to the human wear type and was able to accomodate itself to the environments of S.C.I. Patients. The joints of each leg were adopted with a good kinematic characteristics. To analyse joint kinematic properties, we made the hip joint system of FEM and the hip joint system by 1-axis and 3-axis Accelerometers.

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A Study on the Fatigue Property of Magneto-Rheological Elastomers

  • Kim, Tae Woo;Choi, You Jin;Kim, Nam Yoon;Chung, Kyung Ho
    • Elastomers and Composites
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    • v.53 no.3
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    • pp.150-157
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    • 2018
  • Fatigue properties of rubber are one of the most important characteristics in the rubber industry. In this study, the fatigue properties of MREs (magneto-rheological elastomers) based on NR (natural rubber), EPDM (ethylene-propylene diene monomer), and AEM (ethylene/acrylic elastomer) were investigated. For comparison, MREs with a Shore hardness of 60A were prepared. According to the relative results, the fatigue properties of EPDM MRE were the worst. Thus, we investigated methods to improve the fatigue properties of EPDM MRE by varying the carbon black content and curing systems of EPDM as the matrix of the MRE. Dynamic properties were measured using a fatigue tester and an RPA (rubber process analyzer), and the XPS (X-ray photoelectron spectroscopy) was used to analyze the curing system of the EPDM matrix. According to the results, the Payne effect increased and the fatigue resistance decreased as the carbon black content increased. In case of the curing system, the CV (conventional vulcanization) system was superior to the EV (efficient vulcanization) system in terms of the fatigue resistance. This was because the number of flexible bonds in the case of the CV system was higher than that in the case of the EV system. However, the EV system showed excellent mechanical properties because it had many monosulfidic bonds with strong binding energy.

Sulfonated Polystyrene Ionomers Containing 4-Aminobenzoic Acid Studied by a Small-Angle X-Ray Scattering Technique

  • Song, Ju-Myung;Hong, Min-Chul;Kim, Joon-Seop;Jikang Yoo;Yu, Jeong-A;Kim, Whangi
    • Macromolecular Research
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    • v.10 no.6
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    • pp.304-310
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    • 2002
  • In a recent study by the same authors using a DMTA (Dynamic Mechanical Thermal Analyzer), it was found that the 4-aminobenzoic arid (ABA) molecules acted as either a neutralizing agent, or a plasticizer, or a filler, depending on the order of mixing of poly(styrene-co-styrenesulfonic acid) (PSSA), ABA, and NaOH. Subsequent to that study, we here pursued the same topic, i.e., the effect of the addition of CsOH (instead of NaOH) and ABA on the morphology of PSSA, but this time, by using a small-angle X-ray scattering (SAXS) technique. In line with the previous results, the present study with the SAXS technique verified that the order of mixing has a significant effect on the morphology of ionomers. In addition, with the SAXS data and the density values of the ionomers, we attempted to calculate both the number of sulfonate ionic groups per multiplet and the size of the multiplet of the ionomer.

Studies on the Thermomechanical Characteristics of the Blend Film of Chitosan/Gelatin (키토산/젤라틴 블랜드 필름의 열적특성에 관한 연구)

  • Kim, Byung-Ho;Park, Jang-Woo;Hong, Ji-Hyang
    • Korean Journal of Food Science and Technology
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    • v.37 no.4
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    • pp.567-573
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    • 2005
  • Compatability of films made of chitosan, gelatin, and their blends prepared by aqueous solution casting was investigated using a thermogravimetric analyzer(TGA) and a dynamic mechanical analyzer (DMA). TGA showed gelatin is more thermally stable than chitosan, and thermal stability of chitosan in blends was higher than that of pure chitosan due to interaction among functional groups of component polymers in blend. Glass transition temperature $(T_g)$ of blends was dependent on chitosan content of blends. Blend films exhibited good miscibility. Moisture and glycerol contents of blend strongly affected thermal properties of two component polymers.

Energetic Thermoplastic Elastomers from Azidated Polyepichlorohydrin Rubber (Az-PECH)/ Styrene Acrylonitrile Copolymer (SAN) Blends (아지드화 폴리에피클로로히드린 고무/스티렌-아크릴로니트릴 공중합체 블렌드로부터 에너지함유열가소성탄성체 제조)

  • Choi, Myung-Chan;Chang, Young-Wook;Noh, Si-Tae;Kwon, Jung-Ok;Kim, Dong-Kook;Kwon, Soon-Kil
    • Applied Chemistry for Engineering
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    • v.20 no.4
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    • pp.375-380
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    • 2009
  • Polyepichlorohydrin rubber was treated with sodium azide (Na$N_3$) to replace its chlorine by azide ($N_3$). Then, the azidated polyepichlorohydrin rubber (Az-PECH) was blended with thermoplastic styrene-acrylonitrile copolymer with the rubber/plastic ratio of 80/20, 70/30 and 60/40 (wt/wt). The miscibility, mechanical and dynamic mechanical properties as well as elastic recovery properties of the blends were evaluated by DMA (Dynamic Mechanical Analyzer) and tensile tests. When azidation level in azidated PECH was upto 50%, the blends exhibited excellent miscibility, manifested by a single $T_g$, and fairly good elastic recovery. When azidation level was 75%, the blends showed phase separation. The miscible Az-PECH/SAN blends exhibited typical thermoplastic elastomer like properties, ie. melt processibility and high extensibility as well as good elastic recovery rate. It was also observed from combustion test that higher energy is released with the increase in the azidation level of the Az-PECH in the blends.

Measurement of Mechanical and Physical Properties of Pepper for Particle Behavior Analysis

  • Nam, Ju-Seok;Byun, Jun-Hee;Kim, Tae-Hyeong;Kim, Myoung-Ho;Kim, Dae-Cheol
    • Journal of Biosystems Engineering
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    • v.43 no.3
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    • pp.173-184
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    • 2018
  • Purpose: This study was conducted to investigate the mechanical and physical properties of a Korean red pepper variety for particle behavior analysis. Methods: Poisson's ratio, modulus of elasticity, shear modulus, density, coefficient of restitution, and coefficient of friction were derived for "AR Legend," which is a domestic pepper variety. The modulus of elasticity and Poisson's ratio were measured through a compression test using a texture analyzer. The shear modulus was calculated from the modulus of elasticity and Poisson's ratio. The density was measured using a water pycnometer method. The coefficient of restitution was measured using a collision test, and the static and dynamic friction coefficients were measured using a inclined plane test. Each test was repeated 3-5 times except for density measurement, and the results were analyzed using mean values. Results: Poisson's ratios for the pepper fruit and pepper stem were 0.295 and 0.291, respectively. Elastic moduli of the pepper fruit and pepper stem were $1.152{\times}10^7Pa$ and $3.295{\times}10^7Pa$, respectively, and the shear moduli of the pepper fruit and pepper stem were $4.624{\times}10^6Pa$ and $1.276{\times}10^7Pa$, respectively. The density of the pepper fruit and the pepper stem were $601.8kg/m^3$ and $980.4kg/m^3$, respectively. The restitution coefficients between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.383, 0.218, 0.277, 0.399, and 0.148, respectively. The coefficients of static friction between pepper fruits, pepper stems, a pepper fruit and a pepper stem, a pepper fruit and plastic, and a pepper stem and plastic were 0.455, 0.332, 0.306, 0.364, and 0.404, respectively. The coefficients of dynamic friction between a pepper fruit and plastic and a pepper stem and plastic were 0.043 and 0.034, respectively.

Flexibility Improvement of InGaZnO Thin Film Transistors Using Organic/inorganic Hybrid Gate Dielectrics

  • Hwang, B.U.;Kim, D.I.;Jeon, H.S.;Lee, H.J.;Lee, N.E.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.341-341
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    • 2012
  • Recently, oxide semi-conductor materials have been investigated as promising candidates replacing a-Si:H and poly-Si semiconductor because they have some advantages of a room-temperature process, low-cost, high performance and various applications in flexible and transparent electronics. Particularly, amorphous indium-gallium-zinc-oxide (a-IGZO) is an interesting semiconductor material for use in flexible thin film transistor (TFT) fabrication due to the high carrier mobility and low deposition temperatures. In this work, we demonstrated improvement of flexibility in IGZO TFTs, which were fabricated on polyimide (PI) substrate. At first, a thin poly-4vinyl phenol (PVP) layer was spin coated on PI substrate for making a smooth surface up to 0.3 nm, which was required to form high quality active layer. Then, Ni gate electrode of 100 nm was deposited on the bare PVP layer by e-beam evaporator using a shadow mask. The PVP and $Al_2O_3$ layers with different thicknesses were used for organic/inorganic multi gate dielectric, which were formed by spin coater and atomic layer deposition (ALD), respectively, at $200^{\circ}C$. 70 nm IGZO semiconductor layer and 70 nm Al source/drain electrodes were respectively deposited by RF magnetron sputter and thermal evaporator using shadow masks. Then, IGZO layer was annealed on a hotplate at $200^{\circ}C$ for 1 hour. Standard electrical characteristics of transistors were measured by a semiconductor parameter analyzer at room temperature in the dark and performance of devices then was also evaluated under static and dynamic mechanical deformation. The IGZO TFTs incorporating hybrid gate dielectrics showed a high flexibility compared to the device with single structural gate dielectrics. The effects of mechanical deformation on the TFT characteristics will be discussed in detail.

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Hybrid complementary circuits based on organic/inorganic flexible thin film transistors with PVP/Al2O3 gate dielectrics

  • Kim, D.I.;Seol, Y.G.;Lee, N.E.;Woo, C.H.;Ahn, C.H.;Ch, H.K.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.02a
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    • pp.479-479
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    • 2011
  • Flexible inverters based on complementary thin-film transistor (CTFTs) are important because they have low power consumption and other advantages over single type TFT inverters. In addition, integrated CTFTs in flexible electronic circuits on low-cost, large area and mechanically flexible substrates have potentials in various applications such as radio-frequency identification tags (RFIDs), sensors, and backplanes for flexible displays. In this work, we introduce flexible complementary inverters using pentacene and amorphous indium gallium zinc oxide (IGZO) for the p-channel and n-channel, respectively. The CTFTs were fabricated on polyimide (PI) substrate. Firstly, a thin poly-4-vinyl phenol (PVP) layer was spin coated on PI substrate to make a smooth surface with rms surface roughness of 0.3 nm, which was required to grow high quality IGZO layers. Then, Ni gate electrode was deposited on the PVP layer by e-beam evaporator. 400-nm-thick PVP and 20-nm-thick ALD Al2O3 dielectric was deposited in sequence as a double gate dielectric layer for high flexibility and low leakage current. Then, IGZO and pentacene semiconductor layers were deposited by rf sputter and thermal evaporator, respectively, using shadow masks. Finally, Al and Au source/drain electrodes of 70 nm were respectively deposited on each semiconductor layer using shadow masks by thermal evaporator. Basic electrical characteristics of individual transistors and the whole CTFTs were measured by a semiconductor parameter analyzer (HP4145B, Agilent Technologies) at room temperature in the dark. Performance of those devices then was measured under static and dynamic mechanical deformation. Effects of cyclic bending were also examined. The voltage transfer characteristics (Vout- Vin) and voltage gain (-dVout/dVin) of flexible inverter circuit were analyzed and the effects of mechanical bending will be discussed in detail.

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