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Comparison of The Dimensional Stability of Kel-F 81 and Neoflon CTFE M400H Polychlorotrifluoroethylenes Used in Valve Seat ApplicationThe dimensional stability of polychlorotrifluoroethylene (PCTFE) valve seats used in oxygen regulator applications was determined by thermomechanical analysis (TMA). Two traceable grades of PCTFE were tested; Kel-F 81 and Neoflon CTFE M400H. For these particular resins, the effect of percent crystallinity, zero strength time (ZST) molecular weight, resin grade, process history (compression-molded versus extruded) on the dimensional stability and annealing behavior was determined. In addition to the traceable Kel-F 81 and Neoflon CTFE M400H grades, actual PCI'PH valve seats of differing geometry and design were tested by TMA. The PCTFE valve seats were of unspecified resin grade, although certain inferences about the grade could be drawn based on knowledge of the valve seat fabrication date. Results consistently revealed dimensional instability of varying magnitude at temperatures ranging from 40 to 70 degrees Celsius. Furthermore, some of the pre- 1 995 seats appeared to be more dimensionally stable than those fabricated after 1995. The TMA results are discussed in the context of several proposed ignition mechanisms; namely, particle impact, presence of contaminant oils and fibers, and localized heating by flow friction and/or resonance. The effect of metal constraint on the dimensional stability of PCTFE is also discussed. Finally, the effect of percent crystallinity, ZST molecular weight, resin grade, process history (compression-molded versus extruded) on the AIT, delta Hc and impact sensitivity of various types of Neoflon CTFE M400H was determined using Kel-F 81 as a control. Results show that the AIT, delta Hc and impact sensitivity were essentially independent of Neoflon CTFE process history and structure.
Document ID
20000102416
Document Type
Conference Paper
Authors
Waller, Jess M. (Allied-Signal Technical Services Corp. Las Cruces, NM United States)
Beeson, Harold D. (White Sands Test Facility Las Cruces, NM United States)
Newton, Barry E. (Wendell Hull and Associates Las Cruces, NM United States)
Fries, Joseph
Date Acquired
August 19, 2013
Publication Date
January 1, 2000
Subject Category
Nonmetallic Materials
Meeting Information
9th International Symposium on Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres(Paris,)
Funding Number(s)
CONTRACT_GRANT: NAS9-95682
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.