Stress-Relaxation Measurements on Rubbers in Compression. Equipment and Methodology

Armah, J. C.; Birley, A. W.; Fernando, Kamal P.; Hepburn, C.; Tahir, Mohammed

doi:10.5254/1.3538232

Cited by 12 publications

(6 citation statements)

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“…where The result given by eq. (5) has been shown to be in excellent agreement with experimental results for several stabilized elastomers, including a nitrile rubber and a neoprene rubber [ 191.…”

Section: Diffusion-limited Oxidation (Dlo) Effectssupporting

confidence: 53%

New method for predicting lifetime of seals from compression-stress relaxation experiments

Gillen¹,

Keenan²,

J³

1998

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Interpretation of compression stress-relaxation (CSR) experiments for elastomers in air is complicated by (1) the presence of both physical and chemical relaxation and (2) anomalous diffusion-limited oxidation (DLO) effects. For a butyl material, we first use shear relaxation data to indicate that physical relaxation effects are negligible during typical high temperature CSR experiments. We then show that experiments on standard CSR samples (-15 mm diameter when compressed) lead to complex non-Arrhenius behavior. By combining reaction kinetics based on the historic basic autoxidation scheme with a diffusion equation appropriate to diskshaped samples, we derive a theoretical DLO model appropriate to CSR experiments. Using oxygen consumption and permeation rate measurements, the theory shows that important DLO effects are responsible for the observed non-Arrhenius behavior. To minimize DLO effects, we introduce a new CSR methodology based on the use of numerous small disk samples strained in parallel. Results from these parallel, minidisk experiments lead to Arrhenius behavior with an activation energy consistent with values commonly observed for elastomers, allowing more confident extrapolated predictions. In addition, excellent correlation is noted between the CSR force decay and the oxygen consumption rate, consistent with the expectation that oxidative scission processes dominate the CSR results.

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Section: Diffusion-limited Oxidation (Dlo) Effectssupporting

confidence: 53%

New method for predicting lifetime of seals from compression-stress relaxation experiments

Gillen¹,

Keenan²,

J³

1998

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“…After completing what were essentially static tests, the o-rings were examined for their dynamic response in a compression stress relaxation device [7][8][9]. The unit used by METSS was fabricated by Akron Rubber Development Labs specifically to handle both fluid environmental exposures and cyclic thermal behavior.…”

Section: Test Proceduresmentioning

confidence: 99%

Hydrocarbon stability of perfluorinated polyether rubbers at elevated temperatures

et al. 2005

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Recently introduced perfluorinated polyether rubbers have been found to be useful materials for use as o-rings in harsh environments. They have a very broad range of thermal utility, -55°C to 200°C, and exhibit strong resistance to harsh chemical environments over the entire temperature range. The data presented here demonstrate the excellent high and low temperature performance of perfluorinated polyether rubbers after extended exposures to jet fuel and synthetic hydraulic fluids. Demonstration of an appreciable degree of retained sealing force by molded o-rings down to -40°C is shown in a compression stress relaxation device. Perfluorinated polyether o-rings are demonstrated to offer significant improvement in performance over current nitrile-based o-ring materials. POLYM. ENG. SCI., 45: 1622-1629, 2005.

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“…For seal materials, the property of paramount interest is the sealing force, and the experimental approach most closely related to this property involves compression stress-relaxation (CSR) measurements [9][10][11]. Stress-relaxation in general results from a combination of socalled physical relaxation processes and chemical effects [12-1 4].…”

Section: Introductionmentioning

confidence: 99%

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

Gillen

Celina

Keenan

2000

Rubber Chemistry and Technology

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We have been working for many years to develop improved methods for predicting the lifetimes of polymers exposed to air environments and have recently turned our attention to seal materials. This paper describes an extensive study on a butyl material using elevated temperature compression stress-relaxation (CSR) techniques in combination with conventional oven aging exposures. The results initially indicated important synergistic effects when mechanical strain is combined with oven aging, as well as complex, non-Arrhenius behavior of the CSR results. By combining modeling and experiments, we show that diffusion-limited oxidation (DLO) anomalies dominate traditional CSR experiments. A new CSR approach allows us to eliminate DLO effects and recover Arrhenius behavior. Furthermore, the resulting CSR activation energy (EJ from 125°C to 70"C is identical to the activation energies for the tensile elongation and for the oxygen consumption rate of unstrained material over similar temperature ranges. This strongly suggests that the same underlying oxidation reactions determine both the unstrained and strained degradation rates. We therefore utilize our ultrasensitive oxygen consumption rate approach down to 23°C to show that the CSR E~likely remains unchanged when extrapolated below 70°C, allowing very confident room temperature lifetime predictions for the butyl seal.

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Stress-Relaxation Measurements on Rubbers in Compression. Equipment and Methodology

Cited by 12 publications

References 0 publications

New method for predicting lifetime of seals from compression-stress relaxation experiments

New method for predicting lifetime of seals from compression-stress relaxation experiments

Hydrocarbon stability of perfluorinated polyether rubbers at elevated temperatures

Methods for Predicting More Confident Lifetimes of Seals in Air Environments

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