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A crystal structure of ultra-dispersed form of polytetrafluoroethylene based on X-ray powder diffraction data

Published online by Cambridge University Press:  06 March 2012

V. M. Bouznik,
S. D. Kirik,
L. A. Solovyov and
A. K. Tsvetnikov
V. M. Bouznik
Affiliation:
Boreskov Institute of Catalysis, Russian Academy of Sciences, Siberian Branch, Novosibirsk 630090, Russia
S. D. Kirik*
Affiliation:
Institute of Chemistry and Chemical Engineering, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660090
L. A. Solovyov
Affiliation:
Institute of Chemistry and Chemical Engineering, Russian Academy of Sciences, Siberian Branch, Krasnoyarsk, 660090
A. K. Tsvetnikov
Affiliation:
Institute of Chemistry, Russian Academy of Sciences, Fareast Branch, Vladivostok, 690022, Russia
*
a)Electronic mail: kirik@icct.ru
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Abstract

An X-Ray powder diffraction study of ultra-dispersed polytetrafluoroethylene was carried out. As well as a regular polytetrafluoroethylene the ultra-dispersed form contents a high proportion of the crystalline phase. The X-ray diffraction pattern could be described with two-dimensional hexagonal unit cell [a=5.685(1) Å, symmetry group p6mm]. Structural modeling with a continuous electron density approach as well as with a discrete disordered atoms distribution was accomplished. The model was refined using the Rietveld method. The structure is characterized by a spiral arrangement of polymers (CF2-)n along the z-axis with complete mutual disordering by rotational displacement around z, as well as a partial molecular translation along the z-axis. Molecular disordering results in a systematic absence of reflections with 1≠0 and as a sequence in two-dimensional unit cell effect. The presence of complete rotational disordering distinguishes the ultra-dispersed form of polytetrafluoroethylene from the standard one (fluoroplast-4), where only partial disordering is observed.

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Type
Technical Articles
Information
Powder Diffraction , Volume 19 , Issue 3 , September 2004, pp. 219 - 224
Copyright
Copyright © Cambridge University Press 2004

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