Characterization of Polyamide 66 Obturator Materials by Differential Scanning Calorimetry and Size-Exclusion Chromatography

Report No. ARL-TR-3689
Authors: Frederick L. Beyer, Eugene Napadensky, and Christopher R. Ziegler
Date/Pages: December 2005; 24 pages
Abstract: Samples of two polyamide 6/6 materials used to make obturators were characterized by differential scanning calorimetry (DSC) and by size-exclusion chromatography (SEC). The two materials, commercially available DuPont Zytel 42A and Zytel 101, have been used in obturators, but an increase in undesired part failures occurred when Zytel 101 was replaced with the newer Zytel 42A. DSC analysis of these materials revealed very little variation in the nature of the semicrystalline domains, consistent with a previous analysis using x-ray diffraction. Molecular weight characterization by SEC, however, revealed that the Zytel 101 samples as processed have molecular weights ~10% greater than that of the Zytel 42A samples. The change in molecular weight is reproducible, but contradicts previously collected SEC data from similar samples also from obturator specimens. One factor that is thought to be contributing to the change in molecular weight is the change in the annealing medium from mineral oil to dry nitrogen gas. The apparent variability and significant difference in molecular weight is concluded to be the likely cause of the change in mechanical properties leading to the increased failure rate.
Distribution: Approved for public release
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Last Update / Reviewed: December 1, 2005