Determination of the Orientation of Crystallites in PET Fibres

Abstract

A method for the determination of the average angle of orientation of crystallites φ from the azimuthal record of the meridional reflection of the 1 05 diatropic plane for PET fibres is widely used. The 1 05 reflection is the closest to the meridian and the normal to this plane making an angle of approximately 10[ddot] with the c axis. The intensity distribution measured by this method reflects the distribution of the 1 05 plane normals and therefore it comprises: the distribution of the 1 05 plane normals relative to the c crystallographic axis, the distribution of the crystallites relative to the reference fibre axis and the tilted orientation; that is the molecular chain axis inclined by some degrees with respect to the fibre axis. By the studying of the diffraction intensity distribution from the 1 05 diatropic plane this particularly should be taken into account. The sub-meridional (1 05) reflection was scanned in two different geometries: omega and chi scan. Supercritical CO2 fluid as an alternative dyeing medium changes the fibre structure to a certain extent in dependence on the treatment temperature and pressure used. Therefore the changes of crystalline orientation in poly(etbylene terephthalate) (PET) fibres as brought about under the influence of supercritical CO2 fluid were investigated.