• Elastomers and Composites
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• v.34 no.5
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• pp.383-390
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• 1999

Functionally graded polyurethane elastomers PUEs/grad. Poly(dimethylammoninum ethylacrylate bromide)(PDMAEA) were prepared by the method of electrophoresis. Results of elemental analysis showed that concentration of PDMAEA had gradient across the thickness(2mm) of the base PUEs. The modified PUEs(PUEs/grad. PDMAEA) containing high concentration of PDMAEA displayed low degree of swelling in benzene which was poor solvent for PDMAEA, and high degree of swelling in water which was good solvent. For the each layer of modified PUEs, glass transition temperature, dynamic storage modulus were stooled by DSC, Rheovibron DDV-IIC dynamic viscoelastomer. The chemomechanical properties of modified PUEs was explored by the electric-stimulus.

• The Korean Journal of Rheology
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• v.9 no.3
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• pp.118-123
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• 1997

검화도와 분자량이 상이한 폴리비닐 알코올을 디멜틸 설폭사이드에 녹여 폴리비닐 알코올/디멜틸 설폭사이드 용액을 준비하고 동적 유변학적 특성에 대한 시간과 온도 의존성 을 고찰하였다. 고농도 폴리비닐 알코올 용액의 유변학적 특성은 시간 의존성을 보여주었다. 복합점도와 저장탄성률은 시간에 따라 증가하였다. 또한 저장 탄성률과 손실탄성률의 그래 프에서 저장탄성률은 신간에 따라 증가하였으나 기울기는 시간에 따라 증가하였다. 또한 저 장탄성률과 손실탄성률의 그래프에서 저장탄성률은 시간에따라 증가하였으나 기울기는 시간 에 따라 감소하였다. 유변학적 특성의 시간 의존성은 분자량이 높을수록, 측정온도가 높을수 록 더 두드러지게 나타났다.

• Preventive Nutrition and Food Science
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• v.17 no.3
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• pp.192-196
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• 2012

This study investigated the effects of galacomannans (guar gum, tara gum, and locust bean gum) on the rheological properties of buckwheat starch pastes under steady and dynamic shear conditions. The power law and Casson models were applied to describe the flow behavior of the buckwheat starch and galactomannan mixtures. The values of the apparent viscosity (${\eta}_{a,100}$), consistency index (K), and yield stress (${\sigma}_{oc}$) for buckwheat starch-galactomannan mixtures were significantly greater than those for the control, indicating that there was a high synergism of the starch with galactomannans. The magnitudes of storage modulus (G') and loss modulus (G") for the starch-galactomannan mixtures increased with increasing frequency (${\omega}$). The dynamic moduli (G', G"), and complex viscosity (${\eta}^*$) for the buckwheat starch-galactomannan mixtures were significantly higher than those for the control.

• Journal of KSNVE
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• v.8 no.5
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• pp.900-907
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• 1998

Rubber materials are extensively used in various machine design application, mainly for vibration/shock/noise control devices. Over the years an enormous effort has been put into developing procedures to provide properties of rubber material for design function. However, there are still a lot of difficulties in the understanding of dynamic characteristics of the rubber components in compression. In this paper, the dynamic characteristics of rubber materials for anti-vibration under compression were investigated. Dynamic and static tests for rubber material with 3 different hardness were performed. In dynamic tests, non-resonance method, impedance method, was used to obtain the complex modulus(storage modulus and loss factor) and the effects of static pre-strain on the dynamic characteristics were investigated. Also, a relation equation between linear dynamic and nonlinear static behavior of rubber material was discussed and its usefulness to predict their combined effects was investigated.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.824-829
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• 2007

Mechanical and thermal analysis properties of carbon fiber/epoxy composite for train carbody were evaluated by varying with environmental factors such as ultraviolet, temperature, and moisture. Accelerated environmental aging tester was utilized for this study. Testing temperature was set to $80^{\circ}C$ and ultraviolet was obtained through xenon-arc lamp. To consider moisture, water sprayed on specimen for 18 minutes every 2 hour. All the specimens were made of CF1263/Epoxy composite. Mechanical properties such as tensile, bending, and shear properties were evaluated through a material testing system. Also, thermal analysis properties such as storage shear modulus, loss shear modulus, and tan ${\delta}$ were measured through dynamic mechanical analyzer. Finally surfaces of the composite exposed to environmental factors were examined using a scanning electron microscope. From experimental results, those properties of CF1263/Epoxy composite were shown to be slightly decreased due to environmental factors.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.722-727
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• 2001

The dynamic characteristics of Viscoelastic(VE) damper are experimentally studied. An experimental test was carried out to study the effects of frequency on the damping and stiffness of VE damper. Various cyclic loading tests are conducted. A good agreement was achieved between the experimental results and analytical model proposed by Kasai et al. Also the damping of acrylic rubber is compared with that of PNR material. It was concluded that the damping value of acrylic rubber is higher than that of PNR material.

• The Korean Journal of Rheology
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• v.10 no.3
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• pp.137-142
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• 1998

유변물성 자료로부터 고분자의 다분산성을 예측하는 방법은 신속한 중합반응 공정 제어를 위해서 중요한 연구분야중 하나이다. 본 연구에서는 다양한 분자량과 분자량 분포를 가진 폴리에틸렌에 대한 Shroff와 macridis 가 제시한 다분산성 매개변수 ER과 ET를 구하 고 겔투과 크로마토그래피에서 얻은 Mw/Mn과의 상관관계를 조상하였다. Mw/Mn과 비례적 인 상관관계를 보여주었으나 ET는 상관성이 없는 것으로 나타났다. ER값에는 분자량 분포 도 외에 LCB의영향도 큰 것으로 나타났다. 또한 분자량 분포중에서 고분자량 부분의 미미 한 변화에도 ER이 크게 변해 GPC보다 다분산성의 변화를 더 민감하게 예측할수 있음을 알 수있었다.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2008.10a
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• pp.107-122
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• 2008

종이의 도공액이 고농도화 됨에 따라 도공액의 유동학적 특성에 대한 연구가 더욱 더 중요시 되고 있다. 기존의 합성 증점제의 경우는 단순히 증점 보수제의 기능을 가지고 있으므로 고농도/고속 도공시 블레이드하에서 점탄성적인 성질 중 팽윤에 의한 탄성의 성질이 더 강하게 남아있게 되어 다양한 도공 트러블의 원인이 될 수 있다. 최근에는 이러한 단점을 개선하기 위한 표면 흡착형 유동성 조절제가 소개되고 있다. 따라서 본 연구에서는 알카리 팽윤형 합성 증점제와 표면 흡착형 유동성 개량제로 업계에 알려진 2종의 유동성 조절제가 고농도 도공액의 점탄성적인 유동특성에 미치는 영향성을 검토하였고, PDA(Penetration Dynamic Analyzer) 모듈을 이용하여 원지에 흡수되는 흡수 거동을 관찰하였다.

• Carbon letters
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• v.11 no.4
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• pp.311-315
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• 2010

In this work, the effect of glycidyl methacrylate grafted multi-walled carbon nanotubes (GMA-MWCNTs) on the viscoelastic behaviors of polypropylene (PP) based nanocomposites was studied. The GMA-MWCNTs/PP was prepared using a bravender at $200^{\circ}C$ by melt mixing as a function of GMA-MWCNT content. The viscoelastic behaviors of GMA-MWCNTs/PP nanocomposites were measured by a rheometer. It was found that the GMA-MWCNTs were homogeneously dispersed in the PP matrix. The GMA-MWCNTs/PP nanocomposites showed higher storage modulus, loss modulus, and shear viscosity compared to pure PP nanocomposites and the maximum value was shown at 2.0 wt% GMA-MWCNTs loading. These results were probably attributed to the strong interfacial interaction between the GMA-MWCNT and the PP matrix.

• Macromolecular Research
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• v.11 no.4
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• pp.224-230
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• 2003

The blends of polypropylene (PP) with glass filled thermotropic liquid crystalline polymer (LCP-g) have been prepared by melt mixing techniques at different blend ratios. The thermal, dynamic mechanical, crystalline and morphological characteristics of these blends were investigated. Higher percent crystallinity was observed for 10% level of LCP-g in the blend in comparison to that of other blend ratios. The thermal stability increased with LCP-g concentration in the blend with PP. The variation of storage modulus, stiffness and loss modulus as a function of blend ratios suggested the phase inversion at the 50% level of LCP-g in the blend. The scanning electron microscopy (SEM) photographs showed the creation of voids and destruction of the fiber structures during the dynamic mechanical measurements. Processing behavior of the blends depended on the fiber forming characteristics of LCP-g, which again varied with the molding temperatures.