• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.1-8
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• 2013

Coolant rubber hoses for automotive radiators can degrade under thermal and mechanical loadings and thus fail owing to the influences of locally formed electricity. In this study, an advanced test method was developed to simulate the failure of a rubber hose. The aging behavior of carbon-black-filled ethylene-propylene diene monomer (EPDM) rubber used as a radiator hose material under a combination of electrochemical stresses and tensile strain was analyzed. The changing behaviors of the current and the resistance as a function of the aging time were analyzed in consideration of the tensile strain, voltage, and aging temperature. Sectioned specimens clarified the failure mechanisms of the aged skin layer under the combined electrochemical stresses.

• Elastomers and Composites
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• v.47 no.2
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• pp.156-161
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• 2012

Difference in recovery behaviors from the circular deformation of natural rubber (NR) composites aged in air and distilled water, respectively were investigated. Recoveries of the samples aged in air were larger than those of the samples aged in distilled water. Recovery rates of the samples reinforced with filler were faster than those of the unreinforced ones. Recovery rates of the carbon black-filled samples were faster than those of the silica-filled ones. Difference in the recovery behaviors according to the aging media can be explained by the crosslinking density changes and the annealing effect.

• Elastomers and Composites
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• v.33 no.3
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• pp.159-167
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• 1998

Rubber products are aged like human complexion by the attack of oxygen, ultra violet, ozone, etc.. Aging is very important and also very complicated phenomenon to understand. This may explain the rarity of papers on this subject. In this study, we tried to understand the aging behavior of EPDM compared to that of natural rubber. We also compared the sulfur vulcanized system to the peroxide vulcanized one. In our experiment, the peroxide vulcanizates were more advantageous in aging than the sulfur vulcanizates. The authors belived that this study about the high performance EPDM would be applicable to rubber industry.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.46-51
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• 2019

Intermittent CSR testing was used to investigate the degradation of a NBR O-ring, and also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. Degradation of O-rings by thermal aging was observed between $40^{\circ}C$ and $120^{\circ}C$. O-rings showed non-linear degradation behavior under $80^{\circ}C$. At 20% of failure condition, predicted life-times were 32.5 years by Arrhenius plot and 22.6 years by WLF plot.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.1-8
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• 2011

The objective of this paper is to evaluate the performance of low $CO_2$ asphalt binder properties using LEADCAP$^{(R)}$(Low Energy and Carbon Asphalt Pavement) additive as function of various aging methods such as RTFO(Rolling thin film oven), Ultraviolet(UV) lay. In order to simulate the short-term aging of asphalt binder that occurs during the hot-mixing asphalt process, the Rolling Thin Film Oven(RTFO) was used. Asphalt binder using LEADCAP$^{(R)}$ is prepared by addition of a photoinitiator activated by ultraviolet lay. The mechanical and rheological properties of the asphalt binder were estimated using UTM(Universal Testing Machine) and DSR(Dynamic Shear Rheometer). The test results showed that the asphalt binder using LEADCAP$^{(R)}$ additive was improved the rutting resistance at testing temperature ($70^{\circ}C$) and increased tensile strength at low temperature. Also, Thermal analysis shows that the Melting Point(Tm) of asphalt binder using LEADCAP$^{(R)}$ additive was constant although the asphalt binder was aged by Ultraviolet.

• Elastomers and Composites
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• v.35 no.1
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• pp.38-45
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• 2000

Influence of rubber composition on migration of antiozonants to the surface in ternary rubber-based vulcanizates composed of natural rubber (NR) styrene-butadiene rubber (SBR), and butadiene rubber (BR) was studied. Of the three rubbers, contents of two rudders were same and only the other one content was different (variable rubber) IPPD and HPPD were employed as antiozonants. Migration experiments were performed at $60^{\circ}C$ for 21 days and outdoors for 4 months. Migration rates of the antiozonants increase by increasing the content ratio of the variable rubber in the vulcanizares from NR/SBR/BR=1/1/0.2 to 1/1/1 and then decrease with an increase of the content ratio of the variable rudder from 1/1/1 to 1/1/5. Migration behaviors of the antiozonants in the ternary rudder-based vulcanizates depending on the rubber composition were explained by the intermolecular interactions between rubber and antiozonant, by the solubility difference of the antiozonants for the rubbers, and by the interface formed between dissimilar rubbers in the triblends.

• Composites Research
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• v.22 no.3
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• pp.35-43
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• 2009

In this study, for a radiator hose made of carbon black filled EPDM(ethylene-propylene diene monomer) rubber, a measuring method of crosslink density was established to analyze the aging behaviors under thermo-oxidative stresses. At $125^{\circ}C$, the crosslink density of the rubber specimens decreased slightly in the initial stage, but increased with increasing the aging time. Such variation in crosslink density was similar to that of tensile strength. This might be due to the formation of sulphoxide crosslinks as well as to additional crosslinks made by the reaction of unvalcunized sulfurs. A high temperature aging of rubber specimens at $180^{\circ}C$ caused a slight increase in crosslink density while it did a large decrease in tensile strength and elongation. With aging at high temperature, the formation of carbonyl groups in EPDM molecule chain and formation of sulphoxide crosslink, rather than the crosslink density variation itself, had a large influence on such changes in mechanical property.

• Elastomers and Composites
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• v.48 no.3
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• pp.181-189
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• 2013

Unfilled, carbon black-filled, and silica-filled natural rubber (NR) composites were aged with a circular deformation at $60-90^{\circ}C$ and the recovery behaviors were investigated. The samples were aged under the altering aging medium systems of air and distilled water every day for 10 days. The order of the recoveries according to the filler systems was unfilled > silica > carbon black. The recoveries of the samples aged in the air to water altering system were greater than those of the samples aged in the water to air altering system. The initial aging medium dominantly influenced the deformation level.

• International Journal of Highway Engineering
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• v.1 no.2
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• pp.121-133
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• 1999

This study was based on the evaluation of 9 asphalts that were produced in five major Korean refineries. The study was concentrated to identify the problems of the current asphalt specification (KS M 2201) and to determine the ranges of visco-elastic asphalt behavior. As a conventional asphalt property. asphalt penetration, ring and ball(R&B) softening point, asphalt viscosity, and flash point of asphalt were measured. Also Dynamic Shear Rheometer (DSR) were used to evaluate visco-elastic properties of asphalts in the $-20^{\circ}C$ through $30^{\circ}C$ temperature range. These properties before and after the short-term (RTFO) and long-term (PAV) aging were compared and analyzed to achieve the research objectives. The conclusion from this study can be summarized by the followings. The low temperature rheological behavior of all the straight asphalt from five major Korean refineries is similar regardless of asphalt grade. In the mean while, the rheological behavior at high and intermediate temperature of Korean straight asphalt varies depending on asphalt grade.

• Elastomers and Composites
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• v.44 no.4
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• pp.442-446
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• 2009

Recovery behaviors of unfilled NR, BR, and SBR vulcanizates after aging with a circular deformation were compared to prevent the influence of reinforcing agent. Samples were aged at room temperature, 50, 70, and $90^{\circ}C$ for 10 days. Recovery increased by increasing the measurement time. Instantaneous recoveries less than 1.0 sec were obtained using the recovery variations with the measurement time. For aging at room temperature, difference in the recoveries of the rubber samples was not significant because the aging time was too short. However, for accelerated thermal aging at 50, 70, and $90^{\circ}C$, difference in the recoveries of the rubber samples was significant. Degree of recovery of BR specimen was higher than those of the others, while that of SBR was lowest. However, for accelerated thermal aging at $90^{\circ}C$, recovery of the NR sample was higher than that of the BR one. The initial recovery decreased by increasing the aging temperature and the decrement of SBR was larger than the others. The experimental results were explained with the resilience properties of rubbers and the crosslink density changes by thermal aging.