Evaluation of the orientation coefficient for the c axis in poly(ethylene terephthalate) fibers

Abstract

SYNOPSISThe literature methods for the determination of the mean of the crystallite orientation distribution for the c axis, that is of the orientation coefficient f,, for poly(ethy1ene terephthalate) (PET), based on the azimuthal scan of the (i05) reflection, are reviewed. These methods appear unsuitable for samples presenting the "tilted orientation"; that is, the molecular chain axis inclined by some degrees with respect to the fiber axis, as frequently occurs for P E T fibers. A new method for the determination of fe for PET, also based on the azimuthal scan of the (i05) reflection (which can be applied also to samples with "tilted orientation"), is proposed. This method implies as a first step the determination of the tilt angle, for which the complete fiber pattern is required. A possible simplifying assumption, which allows use of the sole azimuthal (705) profile and makes the method also applicable to poorly oriented samples (for which the determination of the tilt angle is not easy), is also discussed. 0 1995 John Wiley & Sons, Inc.

Real-time FTIR and WAXS studies of drawing behavior of poly(ethylene terephthalate) films

“…The 1 05 plane normals make an angle of approximately 10°with the crystal c axis. 6 In order to place the diffraction peak of the reflection exactly on the Ewald sphere, it is necessary to incline the specimen at an angle of hkl , the Bragg angle for the reflection. The Bragg angle for the 1 05 reflection is ϳ21°for the wavelength of radiation produced at the Daresbury Synchrotron Radiation Source (SRS), and so the sample must be tilted through this angle if accurate orientation information is to be recorded from this reflection.…”

“…If defining the chain axis direction rather than the plane normal corresponding to the 1 05 reflection is desired, it is necessary to make a further correction, as discussed by Auriemma et al 6 To a very good approximation the angle between the c axis and the draw direction is given by…”

The development of microstructure in oriented polyethylene terephthalate (PET) during annealing

“…Also some authors attempted to model the structure of the PET mesophase. Auriemma et al [14,15] through a series of experimental and modelling studies, concluded that a model of isolated chains could qualitatively account for the observed mesophase pattern with monomer units in random minimum energy conformations. Nicholson et al [16] found that the energy minima for the COeOeCeC dihedral angles in PET are close to 80 .…”

Crystalline structure of poly(ethylene terephthalate) filaments

“…It does not present (hkl) planes normal to the c axis with observable intensity. 15 However, the planes with Miller indices (21 0 5) give a very strong X-ray diffraction intensity and their normal makes an angle of 9.778 with the c axis, calculated with the PET lattice parameters given by Daubney et al 14 The (21 0 5) reflection is used for the evaluation of crystalline orientation factorðf c Þ. Often it does not overlap with other (hkl) reflections.…”

“…Often it does not overlap with other (hkl) reflections. 15 Dumbleton and Bowles 12 used the azimuthal scan of X-ray diffraction intensity distribution from (21 0 5) planes to calculate f c .…”