The Effect of Acrylonitrile Content on the Thermo-Oxidative Aging of Nitrile Rubber

Pazur, Richard J.; Cormier, John G.; Korhan-Taymaz, K.

doi:10.5254/rct.13.87937

Cited by 33 publications

(35 citation statements)

References 8 publications

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“…106 kJ/mol for EPDM determined from elongation at break data and 72 kJ/mol for a peroxide‐cured HNBR which was determined from intermittent CSR measurements). However, activation energies strongly depend on the exact material composition as well as the test method . The value for FKM corresponds well with the literature value of 55 kJ/mol for CS data of a Viton FKM …”

Section: Resultssupporting

confidence: 86%

Influence of Ageing on Sealability of Elastomeric O‐Rings

Kömmling

Jaunich

Pourmand

et al. 2017

Macromolecular Symposia

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Summary At BAM, which is the federal institute for materials research and testing in Germany, it is one of our tasks to evaluate the safety of casks designed for transport and/or storage of radioactive material. This includes the assessment of the service lifetime of elastomeric seals that are part of the container lid system with regard to the requirements for long‐term safety (40 years and more) of the containers. Therefore, we started an accelerated ageing programme with selected rubbers often used for seals (HNBR, EPDM and FKM) which are aged at four different temperatures (75 °C, 100 °C, 125 °C and 150 °C) up to 1.5 years. In order to assess sealability, O‐rings are aged in compression by 25% (corresponding to the compression during service) between plates as well as in flanges that allow leakage rate measurements. For comparison, uncompressed O‐rings are aged as well. Further methods characterising seal performance are compression stress relaxation (CSR) reflecting the loss of sealing force of a compressed seal over time, and compression set (CS) which represents the recovery behaviour of a seal after release from compression. Additionally, hardness is measured for information about the change of mechanical properties. The experimental results indicate that while hardness, CSR and CS show considerable degradation effects, the leakage rate stays relatively constant or even decreases until shrinkage combined with the loss of resilience of the aged seal leads to leakage. This demonstrates that static leakage rate, which is the only available direct seal performance criterion, has only limited sensitivity towards the degradation of the seal material. CS data is extrapolated using time‐temperature shifts and Arrhenius graphs. An exemplary CS of 50% would be reached after approx. 1.2, 17 and 29 years at 60 °C for HNBR, EPDM and FKM respectively.

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Section: Resultssupporting

confidence: 86%

Influence of Ageing on Sealability of Elastomeric O‐Rings

Kömmling

Jaunich

Pourmand

et al. 2017

Macromolecular Symposia

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“…However, for the specimens aged in air at 110 °C, crosslinking reactions were dominant at the initial stage, causing the rapid increase in crosslinking density, whereas the chain scission reactions predominated after that and inhibited the increase of crosslinking density. Additionally, the alkyl, alkoxy or peroxy radical could connect with each other to result in occurrence of crosslinking [7,41]. The results of ATR-FTIR measurements before and after exposure to air present that oxidation reactions also occurred during the degradation process, including the formation of oxygenated species like hydroxyl groups, carboxyl groups, and amide groups.…”

Section: Discussionmentioning

confidence: 99%

Synergistic Effects of Multiple Environmental Factors on Degradation of Hydrogenated Nitrile Rubber Seals

et al. 2018

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Degradation tests of hydrogenated nitrile rubber seals, often used as sealing components in hydraulic systems, were conducted under the free and compression state in air and hydraulic oil at three elevated temperatures for several days to investigate the synergistic effects among three factors. The crosslinking and chain scission reactions both occurred simultaneously at higher temperature during the degradation process, and crosslinking predominated for most cases. Additionally, the synergistic effect between compression stress and hydraulic oil further slowed the degradation rate by limiting oxygen access. However, the higher temperature and hydraulic oil both promoted the formation of oxidation products, whereas the compression stress restrained the formation of amide groups. The fracture morphology results show that the defects gradually formed on the fracture surface, especially for the uncompressed specimens. The increase of the compression set aged in air was more than that in hydraulic oil, implying the more serious degradation. Moreover, rubber seals under the synthetic effect of three environmental factors presented the minimum degradation level. The degradation of the compressed and uncompressed specimens exposed to hydraulic oil is more serious than that of specimens exposed to air.

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“…The temperature range was chosen as 60 C to 100 C, in accordance with previous similar works on the thermal aging of HNBR. 11,25 At least three specimens were tested under each aging condition. Aer reaching the prescribed aging time, the specimens were stored in air for more than 16 hours.…”

Section: Methodsmentioning

confidence: 99%

“…The degradation and aging mechanisms of HNBR have attracted a great deal of attention. [9][10][11][12] Since the service lifetime of rubber components can be as long as many years, a reliable accelerated test method is necessary. Much work has been done to study the aging behaviour as well as the aging mechanism of various rubbers at elevated temperature.…”

Section: Introductionmentioning

confidence: 99%