• Elastomers and Composites
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• v.54 no.3
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• pp.175-181
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• 2019

The research and development of high-performance polymer materials with excellent gas barrier properties has gained considerable attention from the viewpoint of expanding their applications in various fields, including tire automobile parts and the polymer film industry. Natural rubber (NR) has been widely used as a rubber material in real-life, but its application is limited owing to its poor gas barrier properties. In this paper, we study the gas barrier properties of NR, epoxidized natural rubber (ENR), and their blend compositions by using molecular simulation. The results show that ENR-50 has superior oxygen barrier properties than those of NR. Moreover, the oxygen barrier properties of a blend of NR/ENR-50 improve with increasing volume fraction of ENR-50. The trend of improved oxygen barrier properties of NR, ENR-50, and their blend is in good agreement with experimental observations.

• Journal of the Korean Society of Safety
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• v.6 no.4
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• pp.5-12
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• 1991

The dielectric properties of natural rubbers for electric safety are very important to investigate the molecular structure. The electric safety characteristics of the dielectric absorption in aging vulcanized natural rubber were studied in the range of frequency from 1$\times$10$^3$［Hz］to 3.2$\times$10$^3$［Hz］l at the temperature of 23［$^{\circ}C$］. As the results, it has been confirmed that in the case of aging natural rubber of above 2 phr the specimens exhibit two kinds of dielectric losses due to the dipole polarization by impurities and sulfurs, and of raw rubber exhibit the kind of losses due to the dipole polarization. Rurthermore, dielectric loss maximum tansspectrum in high freguency region for electric safety, which removed to the low freguency according to increasing sulfur, depends greatly on sulfur.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.3
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• pp.112-117
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• 1984

The dielectric propertries of polymers are very important to investigate the molecular structure of polymer. The characteristrics of the dielectric absorption in vulcanized natural rubber were studied in the range of frequency from 10[KHz] to 32[MHz] at the temperature of 25[$^{\circ}C$]. As the results. it has been confirmed that in the case of natural ruber vulcanized between 2 and 4phr the specimens exhibit two kind of dielectric losses due to the dipole polarization by impurites and sulfure, and of above 7phr was only a loss due to the dipole polarization by sulfure and of natural rubber exhibit two kind of losses due to the interfacial and the dipole polarization. Furthermore, dielectric loss maximun tan spectrum, which removed to the low frequency according to increasing sulfure, depends greatly on sulfure. The volume resistivity of $10^{7}$~$10^{11}$[$\Omega\cdot$cm], regardness whether the crosslinking of rubber are tired by sulfure or, was observed.

• Elastomers and Composites
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• v.45 no.2
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• pp.106-111
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• 2010

Magneto-rheological elastomers (MREs) were manufactured by incorporation of magnetic responsible powder (MRP) into natural rubber and silicone rubber. The optimum loading amounts of MRP was 30 vol.% and the natural rubber based MRE (NR-MRE) showed better mechanical property than that of silicone rubber based MRE (S-MRE). However, the modulus shift ratio caused by S-MRE, measured by Self-modified Electromagnet Applied Fast Fourier Transform Analyser (SEFFTA), was higher than that of NR-MRE. The modulus shift ratio caused by NR-MRE was 10%, while the modulus shift ratio caused by S-MRE was 35.7%. The modulus shift ratio could be improved by orienting the magnetic direction of MRP before crosslinking the MRE. The degree of orientation of MRP was analyzed using SEM.

• Elastomers and Composites
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• v.36 no.2
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• pp.121-129
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• 2001

The friction characteristics of natural rubber plates under various conditions including sliding speed, normal force, hardness, lubrication conditions and thickness of plate are analyzed experimentally. The frictional force and normal force are measured by a tester pin and a load ceil with strain gages. Experimental results suggest that the coefficient of friction decreases with increasing the hardness of rubber and decreasing the thickness of plate. The effect of sliding speed is not significant over the speed range employed. The coefficient of friction is found to be about 0.1 under oil lubrication condition and varies from 0.9 to 3.9 under no lubrication condition.

• Elastomers and Composites
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• v.56 no.1
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• pp.20-31
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• 2021

There is an increasing demand for the rolling resistance reduction in truck bus radial (TBR) tires in the tire industry. In TBR tires, natural rubber is used as a base polymer to prevent wear and satisfy required physical properties (cut and chip). A binary filler system (silica and carbon black) is used to balance the durability of the tire and rolling resistance performance. In this study, natural rubber (NR) compounds applied with a binary filler system were manufactured at different cure temperatures for vulcanizate structure analysis. The vulcanizate structures were categorized into carbon black bound rubber, silica silane rubber network, and chemical crosslink density by sulfur. Regardless of the cure temperature, the cross-link density per unit content of carbon black had a greater effect on the properties than silica due to affinity with NR. The relationship analysis between the mechanical, viscoelastic properties with vulcanizate structure could be a guideline for manufacturing practical TBR compounds.

• Elastomers and Composites
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• v.33 no.1
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• pp.17-26
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• 1998

Natural rubber was filled with 8 commercial carbon blacks covering range of rubber-grade products at different levels of filler loadings in order to investigate physical compound and vulcanizate properties. It was found that the curves of rubber property vs filler loading of both uncured compounds and vulcanizates can be superposed to one single master curve by introducing an effective volume fraction which is based on CDBP. The effective volume fraction, $V_{EFF}$ was utilized to explain the variation of the stiffness of all rubber compounds. The surface area-corrected effective volume fraction, V', was utilized to explain the formation of bound rubber, rebound and lambourn wear.

• Elastomers and Composites
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• v.36 no.4
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• pp.262-267
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• 2001

Insulating rubber gloves with antibacterial and withstand voltage properties were prepared by blending the natural rubber latex(NRL), waterborne polyurethane(PU) and 4N-chitosan. Tensile strength of rubber glove increased with increasing amount of PU, and elongation decreased. The property of withstand voltage of rubber gloves improved with increasing leaching time, and the rubber gloves showed insulating capability of 10000V at leaching time of 3 hours. Little bacteria existed after 4N-chitosan was added to rubber gloves.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.855-864
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• 2013

The dynamic characteristics of natural rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear properties. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they inevitably end up facing damage. A main cause of aging like this is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have some effects on shear stiffness, energy absorption, and equivalent damping coefficients of the bearings. Furthermore, a deterioration in the dynamic properties of the natural rubber bearings caused by the thermal aging was applied to an actual bridge and then the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the natural rubber bearings caused by the thermal aging bring only a minor effect on the seismic performance of bridges.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.307-316
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• 2005

This study analyzed the characteristics of four kinds of bridge rubber pads and suggested a method of determining the stiffness and the damping ratio of the pads.The stiffness of rubber pads can be estimated by a direct static test and a dynamic test indirectly.This study used both methods to determine the pad's stiffness.The damping ratio of pads can be obtained using the dynamic test and the damping ratio of polyurethane rubber pads was estimated to aproximate that of natural and chloroprene rubber pads.The polyurethane rubber pads are harder than natural and chloroprene rubber pads and thus carry larger load bearing capacity.In addition, they showed higher stiffness with the same shape factor than the others and thus are more available for bridge bearings.Although natural and chloroprene rubber pads are elongated to large deformation in the horizontal direction due to vertical loads, polyurethane rubber pads almost do not generate horizontal deformation due to vertical loads regardless of the thickness and hardness of the pads.Therefore, they do not need reinforced plate to restrict horizontal deformation.