Anjana, Jain and Vijayan, Kalyani (2007) Effect of thermal aging on the crystal structural characteristics of TEFLON. Polymer Engineering and Science, 47 (11). 1724 -1729.
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Abstract
The residual effects of cumulative thermal aging on the crystal structural characteristics of the fluoro carbon poly(tetra fluoro ethylene) (PTFE) have been studied by X-ray diffraction methods. The initial hexagonal arrangement of the PTFE chains in a 157 helical conformation is left unaffected by the exposures to temperatures (T), up to and beyond its melting point, Tm. The unit cell registers a residual anisotropic volume expansion. The anisotropy arises from the enhanced enlargement of the basal plane dimension a compared with the axial dimension c. Conformational changes contributing to the observed increase in the chain length have been examined. Enhancement of residual crystallinity of samples aged at T's lt; Tm suggests that the selective thermal aging could be used as an effective tool to improve the initial crystallinity of commercially available PTFE. The activation energy for 50% enhancement in initial crystallinity has been estimated as 53.9 kJ mol-1. Aging at 400xB0;C, a temperature above Tm, is accompanied by markedly different features viz., deterioration in crystallinity and other structural characteristics. The overall behavior of thermally aged PTFE bears a marked similarity to many polyamides.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | X-ray diffraction;Thermal aging;Polymeric materials |
| Subjects: | AERONAUTICS > Aeronautics (General) CHEMISTRY AND MATERIALS > Chemistry and Materials (General) |
| Depositing User: | Ms. Alphones Mary |
| Date Deposited: | 03 Jun 2009 |
| Last Modified: | 22 Aug 2012 09:13 |
| URI: | http://nal-ir.nal.res.in/id/eprint/5138 |
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