Thermally induced structural changes in Twaron fibres using13; crystallographic date

Anjana, Jain (2005) Thermally induced structural changes in Twaron fibres using13; crystallographic date. In: ISAMPE National Conference on Composites / INCCOM - IV, 9-10 Dec 2005, Coimbatore, India.

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The high strength, high modulus Twaron fibers are made up of poly (p-phenylene terephthalamide) or PPTA. Since these fibres are recommended for high temperature applications, it is essential to study the thermal properties of these fibres to have the optimum utilization in practice. This paper presents the X-ray analysis on the effect of in situ heating on the crystallographic unit cell dimensions of twaron. Variations of basal plane and axial dimension have been studied with temperature. These dimensional changes have been used to estimate the corresponding coefficient of13; thermal expansion along the basal plane and axial direction . Enlargement of the unit cell with the thermal heating is a common behavior but the Twaron fibers behave differently. There is a thermal expansion along basal plane and contraction along the axial dimension. The axial contraction has been correlated to partial changes in molecular conformation and molecular dimensions. In contrast to axial dimension, there is thermal expansion along the basal plane. Expansion is more along a-direction than b-direction, which again is related to crystal structure of Twaron. Along a-direction, adjacent layers stack together via week Van der Watt's interactions. So deformation in any form say thermal or otherwise is expected to influence the week interactions. However, in 13; b-direction, adjacent chains are linked by hydrogen bonds. Variation of volume has also been studied with temperature and it is found to increase with temperature. So, although there is contraction along c-direction and expansion along basal plane, overall there is expansion in the unit cell13; volume.

Item Type: Conference or Workshop Item (Paper)
Additional Information: Theme:High performance composites - materials, design and manufacturing
Uncontrolled Keywords: Twaron fibres;Crystallographic date;P-phenylene terephathalamide
Subjects: CHEMISTRY AND MATERIALS > Composite Materials
Depositing User: Mr. Ravikumar R
Date Deposited: 28 Aug 2006
Last Modified: 24 May 2010 04:18

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