In situ study of structure development during continuous hot-drawing of poly(trimethylene terephthalate) fibers by simultaneous synchrotron small- and wide-angle X-ray scattering

Off-line small- and wide-angle X-ray scattering and optical birefringence measurements on partially oriented yarns (POY) of poly(trimethylene terephthalate) prepared at different take-up speeds suggest the formation of a rigid amorphous phase for intermediate take-up speed POY. Simultaneous synchrotron small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques were utilized to perform an in situ study of structure development of these POY during continuous hot-drawing. From SAXS patterns, it is suggested that a lamellar stacking arises at temperature above 100°C during drawing. A model of lateral growth of crystallites with extended chains as nucleation sites is suggested. The microfibril length and long period of the lamellar stacking depend upon the preparation take-up speeds of POY and draw ratio. From WAXD patterns, it is observed that crystallinity developed above 100°C with draw ratio 1:1 is temperature controlled. Both orientation and unit cell dimensions were extracted from WAXD patterns. At 100°C, while orientation increases with draw ratio, the unit cell dimensions, especially the dimension of the c-axis, and the crystallinity depend on both draw ratio and take-up speeds. This dependence can be explained by a transformation process coupled by defect creation/transport and crystallization.