Effect of thermal aging on the crystal structural characteristics of poly(tetra fluoro ethylene)

Jain, Anjana and Vijayan, Kalyani (2007) Effect of thermal aging on the crystal structural characteristics of poly(tetra fluoro ethylene). Polymer Engineering and Science, 47 (11). pp. 1724-1729.

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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. POLYM. ENG. SCI., 47:1724-1729, 2007. xA9; 2007 Society of Plastics Engineers

Item Type: Article
Additional Information: Copyright for this article belongs to Wiley InterScience
Uncontrolled Keywords: Crystal structure;Cumulative thermal
Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
Depositing User: M/S ICAST NAL
Date Deposited: 22 Feb 2010
Last Modified: 17 Jun 2010 08:15
URI: http://nal-ir.nal.res.in/id/eprint/4880

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