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

Abstract

In the present study, the structural and morphological development during melt spinning of polyethylene and poly(vinylidene fluoride) fibers was studied using simultaneous in-situ synchrotron small-and wide-angle X-ray scattering (SWAXS) techniques. The spinning apparatus consisted of a single screw extruder, which was mounted on a horizontal platform that could be translated 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 parameters were investigated. A suggested model of structural development during crystallization details the formation of defective shish crystals, followed by the formation of kebob crystals. The defective shish-kebob structure eventually transforms into a well-defined lamellar structure. This model is consistent with the qualitative appearance of the two-dimensional SAXS and WAXS patterns, as well as the quantitative analysis of the SAXS/WAXS data using position-sensitive wire detectors.

Online wide‐angle X‐ray diffraction/small‐angle X‐ray scattering measurements for the CO2‐laser‐heated drawing of poly(ethylene terephthalate) fiber

“…Similar equatorial streak development was reported for polyethylene and poly (vinylidene fluoride) fibers by Schultz et al 14,15 . They suggested that the streak corresponds to the development of shish crystal, because it was vanished when the crystal reflection appeared 15 .…”

“…measured both WAXD and small-angle x-ray scattering (SAXS) images simultaneously for the spinning process of polyamide 6, polyethylene, and poly (vinylyden fluoride) 14,15 . For the drawing process, most on-line measurement studies fall into one of two categories; batch drawing under small strain rate [20][21][22][23][24][25][26][27][28][29][30][31][32] , and draw ratio dependence of continuous drawing [33][34][35][36] .…”

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

“…Here, Q s , depends upon the volume fraction of crystallites but may also be affected by the volume of material at the X-ray point. In this case, the decrease in tape volume would decrease Q s , however it is only a scaling factor in the correlation function and other authors [34,38] assume that any reduction is small. Thus generally, an increase in Q s correlates to an increase in scattering from the crystallization in the polymer tape.…”

“…Other groups have also seen similar results when investigating the early stages of the fibre melt spinning process. Samon et al [34][35][36][37][38] have reported on the crystalline development in melt spinning of several polymers (nylon 6, PE, PVDF and poly(oxymethylene) (POM)) again using SAXS/WAXS as a function of distance and take-up speed from the spinneret. Equatorial SAXS scattering was seen to develop before the meridional SAXS patterns, which was interpreted as indicating the initial stages of shish-kebab or microfibril crystallization.…”

“…Previous works have only detailed investigations on high density PE (HDPE) fibres [34,36,37]. Here, in-line SAXS was used to monitor the crystallinity, orientation and structure development of the LDPE tape with respect to varying processing parameters: haul-off speed and distance down the tapeline.…”