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Biaxial stretching of pet films: A molecular description
Author(s) -
Tassin JeanFrançois,
Vigny Murielle,
Veyrat Didier
Publication year - 1999
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.19991470121
Subject(s) - amorphous solid , materials science , crystallite , crystallization , composite material , relaxation (psychology) , orientation (vector space) , diffraction , crystallography , infrared , optics , thermodynamics , geometry , chemistry , physics , psychology , social psychology , mathematics , metallurgy
Biaxially oriented poly(ethylene terephthalate) films were prepared under well defined stretching conditions in order to mimic the three stages of the industrial inverse drawing process. Molecular orientation has been characterized through X‐ray diffraction and infrared dichroism. The main orientation mechanisms in the constant‐speed drawing of an amorphous film as well as in the constant‐force transverse drawing of monodrawn samples are described. It is shown that relaxation phenomena dominate the orientation of an amorphous sample. Reorientation along the second drawing direction involves rotation of crystalline blocks along the draw direction and further crystalline growth. The high‐temperature heating stage leads to an almost four‐fold increase in the size of the crystallites. The orientation of the amorphous phase is controlled by the mechanisms occurring during crystallization (relaxation followed by extension).