• Korean Journal of Materials Research
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• v.33 no.8
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• pp.323-329
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• 2023

There are many types of foam molding methods. The most commonly used methods are the pressure foaming method, in which foam resin is mixed with a foaming agent at high temperature and high pressure, and the normal pressure foaming method, which foams at high temperature without pressure. The polymer resins used for foaming have different viscosities. For foaming under normal pressure, they need to be designed and analyzed for optimal foaming conditions, to obtain resins with low melt-viscosity or a narrow optimal viscosity range. This study investigated how changes in viscosity, molding temperature, and cross-link foaming conditions affected the characteristics of the molded foam, prepared by blending rubber polymer with biodegradable resin. The morphologies of cross sections and the cell structures of the normal pressure foam were investigated by SEM analysis. Properties were also studied according to cross-link/foaming conditions and torque. Also, the correlation between foaming characteristics was studied by analyzing tensile strength and elongation, which are mechanical properties of foaming composites.

• Polymer(Korea)
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• v.31 no.1
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• pp.8-13
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• 2007

To overcome drawbacks of the nylon 6/poly (acrylonitrile-co-butadiene-co-styrene) (ABS) blend, nylon 6 blend with poly (acrylonitrile - co-styrene - co-acrylic rubber) (ASA) which containing poly (butyl acrylate) as a rubber phase in substitute of poly (butadiene) in ABS, was examined. Poly (styrene-co-maleic anhydride) (SMA) containing 25 wt% of maleic anhydride (MA) or poly (styrene- co-acrylo-nitrile-co-maleic anhydride) (SANMA) containing less than 3 wt% MA was used as a compatibilizer to fabricate blends having high impact strength. Changes in the mechanical properties of nylon 6/ASA blend with compatibilizer content were similar with those of nylon 6/ABS blend. Blends haying high impact strength was produced when blends contained more than about 20 wt% rubber. Blends containing SAM or SANMA as a compatibilizer were stayed in a injection molding machine at the molding temperature and afterwards specimens for the examination of the impact strength was prepared. Impact strength of blends containing SMA was decreased with retention time, while that of blends containing SANMA was not changed with retention time.

• Applied Chemistry for Engineering
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• v.16 no.6
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• pp.842-847
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• 2005

Virgin NBR and recycled NBR particles, which were pulverized from NBR scraps by high temperature shear-crushing technique, were blended with different mixing ratio. The effects of the recycled NBR content on the cure characteristics and physical properties of these blends were investigated and resistance properties of these blends to heat and various fluids were also studied. The study of cure characteristics showed that the viscosity increased but the scorch time decreased. The physical properties of rubber blends were improved with the addition of the recycled NBR for heat resistance and various fluid tests.

• Tribology and Lubricants
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• v.22 no.1
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• pp.20-25
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• 2006

The stress behavior analysis of a-rings and packing for a LPG filling unit has been presented using a finite element analysis technique by non-linear MSC/MARC program. The sealing performance and endurance of a-rings and packing are affected by working conditions such as filling pressure, friction coefficient, compression ratio, and material properties. The elastomeric polymers of O-rings and packing are nitrile butadiene rubber (NBR) and polytetrafluoroethylene (PTFE), which are selected as proper materials of a-rings and packing based on the stress analysis results. The calculated FEM results showed that the proper material of O-ring is NBR as a secondary sealing component and the recommended material of packing is PTFE as a primary sealing unit during a LPG filling process.

• Polymer(Korea)
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• v.34 no.5
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• pp.430-433
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• 2010

The gasket materials of for the lithium ion battery requires chemical resistance to electrolyte, electrical insulating, compression set, anti-contamination and low temperature property. To check the special characteristics of fillers which are applied to rubber for gasket, compound of EPDM, NBR and FKM (fluoro elastomer) were made by adjusting weights of carbon black and silica additive. Using these compounds, we had done tests of long-term stability against electrolyte, compression set and low-temperature property with considering operating condition of the lithium ion battery. From this test, we investigated the physical and chemical characteristics of rubber with using of carbon black and silica additive in each.

• Elastomers and Composites
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• v.45 no.3
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• pp.212-216
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• 2010

The materials of the lithium ion battery gasket require chemical resistance to the electrolyte, electrical insulating, compression set, anti-contamination and heat resistance. To estimate suitability for rubber which has better performance to compression set than PFA, each compound were made with various rubbers, such as EPDM, NBR, FKM, FVMQ, VMQ and we checked the characteristics of each compound. Samples from each compound was deposited in Propylene Carbonate and tested for changing of Hardness and Volume during 1,000 hr with $80^{\circ}C$. EPDM and VMQ showed good performance to chemical resistance to the electrolyte, and also we could get the values over $10^{10}{\Omega}cm$ on volume resistance basis in electrical insulating. EPDM and VMQ were judged as the most suitable material.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.82-86
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• 2006

When a domestically manufactured floater is used in a general gasoline or LPG car, or a flowmeter is floated long time in the engine oil under above $150^{\circ}C$, the floater will be swelled or its organization will be slackened because weight and volume will be changed due to the osmosis of fuel. In this study, we conducted a research on a manufacturing technique of a foam-floater with the small changse in weight and volume, oil-resistance, and thermal resistance in the high temperature engine oil. When the prepared floater TROF II-3, where Nitrile Butadiene Rubber (NBR) as basic material of the floater was superseded by Hydrogenated Nitrile Butadiene Rubber (HNBR), was floated for 100 h at the engine oil of high temperature ($150^{\circ}C$), the change rates of the weight and the volume were 2.90%, and 2.56%, respectively. These were less than the NBR (TROF I-3) case, where the change rates of the weight and the volume were 10.81% and 3.08%, respectively, Therefore, TROF II-3 was determined to be suitable as an engine-oil floater in high temperature because the change of weight and volume were small, the appearance, and the specific gravity of floater were maintained uniformly in the high temperature.

• Journal of Adhesion and Interface
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• v.8 no.4
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• pp.14-22
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• 2007

In the present study, the effect of milled glass powder and liquid-type nitrile rubber (NBR) on the thermal stability of phenolic resin and the dynamic mechanical properties of glass braid/phenolic composites has been investigated by means of thermogravimetric analysis and dynamical mechanical analysis. It was found that both milled glass power and NBR filled in the waterborne phenolic resin significantly influenced the thermal stability of phenolic resins and the storage modulus and tan delta of the composites. The presence of glass powder increased the thermal stability of the phenolic resin, whereas the presence of NBR resulted in the weight loss in the specific temperature range. The thermal stability of the phenolic resins without and with the fillers was dependent not only on the cure temperature but also on the cure time. The variation of the storage modulus and tan ${\delta}$ of strip-type glass braid/phenolic composites was also influenced with the introduction of glass powder and NBR to the phenolic matrix as well as by the cure conditions given.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.182-188
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• 2016

A decoy is a weapon system that can protect vessels from an enemy's torpedo. Thus, the decoy should be able to operate in the field without any failure. Because the decoy can be inoperable once its sealing is broken and water permeates inside the system, the hermetic sealing capability considering the operational environment is mandatory. To be hermetically sealed, a rubber-type O-ring is generally used in a decoy system. The sealed performance of rubber-type products, however, tends to age and deteriorate with time. Therefore, the O-ring needs to be maintained or changed periodically. This paper proposes a method to estimate the proper maintenance period using the hardness and elongation percentage, which represents the performance of the O-ring product and test data from Accelerated Life Test (ALT) of the product. The O-ring used in this paper is a NBR type, and the temperature was chosen to be the main accelerating factor as referenced in many studies. The criteria for the failure of the O-ring was set for the product to be 50% degraded compared to the initial performance. In addition, the Korean standard KS M 6518 was adopted and referenced for the preparation of test samples and the calculation of estimates. The O-ring's predicted life was simulated by analyzing the test results from a computer program, and the optimized maintenance period for the product was determined.

• The Journal of Korea Robotics Society
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• v.11 no.2
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• pp.100-107
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• 2016

To realize a robot hand interacting like a human hand, there are many tactile sensors sensing normal force, shear force, torque, shape, roughness and temperature. This sensing signal is essential to manipulate object accurately with robot hand. In particular, slip sensors make manipulation more accurate and breakless to object. Up to now several slip sensors were developed and applied to robot hand. Many of them used complicate algorithm and signal processing with vibration data. In this paper, we developed novel principle slip sensor using separation layer. These two layers are moved from each other when slip occur. Developed sensor can sense slip signal by measuring this relative displacement between two layers. Also our principle makes slip signal decoupled from normal force and shear force without other sensors. The sensor was fabricated using the NBR(acrylo-nitrile butadiene rubber) and the Ecoflex as substrate and a paper as dielectric. To verify our sensor, slip experiment and normal force decoupling test were conducted.