Elastomers and Composites

The Rubber Society of Korea (한국고무학회)
권호 표지
DOI QR코드

DOI QR Code

Study on the Thermal Degradation Behavior of FKM O-rings

  • Lee, Jin Hyok (Department of Polymer Engineering, Pusan National University) ;
  • Bae, Jong Woo (Rubber Research Team, Korea Institute of Footwear & Leather Technology) ;
  • Choi, Myoung Chan (Rubber Research Team, Korea Institute of Footwear & Leather Technology) ;
  • Yoon, Yoo-Mi (Rubber Research Team, Korea Institute of Footwear & Leather Technology) ;
  • Park, Sung Han (Agency for Defense Development) ;
  • Jo, Nam-Ju (Department of Polymer Engineering, Pusan National University)
  • Received : 2018.11.13
  • Accepted : 2018.11.23
  • Published : 2018.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

The degradation mechanism and physical properties of an FKM O-ring were observed with thermal aging in this experiment. From X-ray photoelectron spectroscopy (XPS) analysis, we could observe carbon (285 eV), fluoro (688 eV), and oxygen (531 eV) peaks. Before thermal aging, the concentration of fluoro atoms was 51.23%, which decreased to 8.29% after thermal aging. The concentration of oxygen atoms increased from 3.16% to 20.39%. Under thermal aging, the FKM O-ring exhibited debonding of the fluoro-bond by oxidation. Analysis of the C1s, O1s, and F1s peaks revealed that the degradation reaction usually occurred at the C-F, C-F2, and C-F3 bonds, and generated a carboxyl group (-COOH) by oxidation. Due to the debonding reaction and decreasing mobility, the glass transition temperature of the FKM O-ring increased from $-15.91^{\circ}C$ to $-13.79^{\circ}C$. From the intermittent CSR test, the initial sealing force was 2,149.6 N, which decreased to 1,156.2 N after thermal aging. Thus, under thermal aging, the sealing force decreased to 46.2%, compared with its initial state. This phenomenon was caused by the debonding reaction and decreasing mobility of the FKM O-ring. The S-S curve exhibited a 50% increase in modulus, with break at a low strain and stress state. This was also attributed to the decreasing mobility due to thermal aging degradation.

Keywords

HKGMCJ_2018_v53n4_213_f0001.png 이미지

Scheme 1. Chemical structure of FKM rubber

HKGMCJ_2018_v53n4_213_f0002.png 이미지

Scheme 2. Intermittent CSR jig

HKGMCJ_2018_v53n4_213_f0003.png 이미지

Figure 1. XPS spectra of FKM O-ring; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0004.png 이미지

Figure 2. XPS spectra, C1s level of FKM O-ring; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0005.png 이미지

Figure 3. XPS spectra, O1s level of FKM O-ring; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0006.png 이미지

Figure 4. XPS spectra, F1s level of FKM O-ring; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0007.png 이미지

Figure 5. DSC analysis result of FKM O-rings; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0008.png 이미지

Figure 6. Load vs. displacement of FKM O-ring by intermittent CSR test method; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

HKGMCJ_2018_v53n4_213_f0009.png 이미지

Figure 7. Strain/stress curve of FKM O-ring; (a) non-treated, (b) thermal aging treated (170℃, 24 days).

Table 1. The Formulation of FKM O-ring

HKGMCJ_2018_v53n4_213_t0001.png 이미지

Table 2. Atomic Concentration (%) of the Different Elements Consisting the FKM O-ring According to Thermal Aging at Atmosphere

HKGMCJ_2018_v53n4_213_t0002.png 이미지

References

  1. ISO 11346, "Rubber, vulcanized or thermoplastic - Estimation of life-time and maximum temperature of use" (2004).
  2. K. T. Gillen, Robert Bernstein, and M. Celina, "Non-Arrhenius behavior for oxidative degradation of chlorosulfonated polyethylene materials", Polymer Degradation and Stability, 87, 335 (2005). https://doi.org/10.1016/j.polymdegradstab.2004.09.004
  3. K. T. Gillen, M. Celina, and R. Bernstein, "Validation of improved methods for predicting long-term elastomeric seal lifetimes from compression stress-relaxation", Polymer Degradation and Stability, 82, 25 (2003). https://doi.org/10.1016/S0141-3910(03)00159-9
  4. M. Celina, K. T. Gillen, and R. A. Assink, "Accelerated aging and lifetime prediction: Review of non-Arrhenius behavior due to two competing processes", Polymer Degradation and Stability, 90, 395 (2005). https://doi.org/10.1016/j.polymdegradstab.2005.05.004
  5. J. Wise, K. T. Gillen, and R. L. Clough, "An ultrasensitive technique for testing the Arrhenius extrapolation assumption for thermally aged elastomers", Polymer Degradation and Stability, 49, 403 (1995). https://doi.org/10.1016/0141-3910(95)00137-B
  6. K. T. Gillen and M. Celina, "The wear-out approach for predicting the remaining lifetime of materials", Polymer Degradation and Stability, 71, 15 (2001).
  7. R. Bernstein and K. T. Gillen, "Predicting the lifetime of fluorosilicone O-rings", Polymer Degradation and Stability, 94, 2107 (2009). https://doi.org/10.1016/j.polymdegradstab.2009.10.005
  8. J. H. Lee and J. W. Bae, "Life-time prediction of a Chloroprene Rubber O-ring Using Intermittent CSR and Time-temperature Superposition Principle", Macromolecular Research, 19, 6 (2011).
  9. J. H. Lee and J. W. Bae, "Life-time prediction of a FKM Oring Using Intermittent Compression Stress Relaxation (CSR) and Time-temperature Superposition (TTS) Principle", Elast. Compos., 45, 4 (2010).
  10. ISO 3384, "Rubber, vulcanized or thermoplastic - Determination of stress relaxation in compression at ambient and elevated temperatures" (2005).
  11. R. P. Brown and F. N. B. Bennett, "Compression Stress Relaxation", Polymer Testing, 2, 125 (1981). https://doi.org/10.1016/0142-9418(81)90030-1
  12. P. Tuckner, "Compression, Compression stress relaxation test comparisons and development", SAE Technical report 2000-01-0752 (2001).
  13. P. Tuckner, "Compression stress relaxation testing - comparisons, methods, and correlations", SAE Technical report 2001-01-0742 (2001).
  14. S. Ronan, T. Alshuth, S. Jerrams, and N. Murphy, "Long-term stress relaxation prediction for elastomers using the time-temperature superposition method", Materials and Design, 28, 1513 (2007). https://doi.org/10.1016/j.matdes.2006.03.009
  15. M. Rjeb, A. Labzour, A. Rjeb, and S. Sayourl, "Contribution to the Study by X-ray Photoelectron Spectroscopy of the Natural Aging of the Polypropylene", M. J. Condensed Matter, 5, 168 (2004).