Validation of improved methods for predicting long-term elastomeric seal lifetimes from compression stress-relaxation and oxygen consumption techniques.
Conventional high-temperature compression stress-relaxation (CSR) experiments (e.g., using a Shawbury-Wallace relaxometer) measure the force periodically at room temperature. In this paper, we first describe modifications that allow the force measurements to be made isothermally and show that such measurements lead to more accurate estimates of sealing force decay. We then use conventional Arrhenius analysis and linear extrapolation of the high-temperature (80--110 C) CSR results for two commercial butyl o-ring materials (Butyl-A and Butyl-B) to show that Butyl-B is predicted to have approximately three times longer lifetime at room temperature (23 C). To test the linear extrapolation assumed by the Arrhenius approach, we conducted ultrasensitive oxygen consumption measurements from 110 C to room temperature for the two butyl materials. The results indicated that linear extrapolation of the high temperature CSR results for Butyl-A was reasonable whereas a significant curvature to a lower activation energy was observed for Butyl-B below 80 C. Using the oxygen consumption results to extrapolate the CSR results from 80 C to 23 C resulted in the conclusion that Butyl-B would actually degrade much faster than Butyl-A at 23 C, the opposite of the earlier conclusion based solely on extrapolation of the high-temperature CSR results. Since samples of both materials that had aged in the field for {approx}20 years at 23 C were available, it was possible to check the predictions using compression set measurements made on the field materials. The comparisons were in accord with the extrapolated predictions made using the ultrasensitive oxygen consumption measurements, underscoring the power of this extrapolation approach.
- Research Organization:
- Sandia National Laboratories
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 917488
- Report Number(s):
- SAND2003-0977J
- Journal Information:
- Proposed for publication in Polymer Degradation and Stability., Journal Name: Proposed for publication in Polymer Degradation and Stability.
- Country of Publication:
- United States
- Language:
- English
Similar Records
Evidence that Arrhenius high-temperature aging behavior for an EPDM o-ring does not extrapolate to lower temperatures
New method for predicting lifetime of seals from compression-stress relaxation experiments