Structure development during the melt spinning of polyethylene and poly(vinylidene fluoride) fibers by in situ synchrotron small- and wide-angle X-ray scattering techniques

In the present study, the structural and morphological development during m elt spinning of polyethylene and poly(vinylidene fluoride) fibers was studi ed using simultaneous in-situ synchrotron small- and wide-angle X-ray scatt ering (SWAXS) techniques. The spinning apparatus consisted of a single scre w extruder, which was mounted on a horizontal platform that could be transl ated in the vertical direction allowing different spinneret distances to be sampled with the X-ray beam. Effects of take-up speed (10.6-61.0 mpm) and spinneret distance (30-87.5 cm) on crystallinity and morphological paramete rs were investigated. A suggested model of structural development during cr ystallization details the formation of defective shish crystals, followed b y the formation of kebob crystals. The defective shish-kebob structure even tually transforms into a well-defined lamellar structure. This model is con sistent with the qualitative appearance of the two-dimensional SAXS and WAX S patterns, as well as the quantitative analysis of the SAXS/WAXS data usin g position-sensitive wire detectors.