Structure development during the melt spinning of poly(oxymethylene) fiber

The structural and morphological development during the melt spinning of poly(oxymethylene) was investigated via synchrotron small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) techniques. Various distances from the spinneret at selected take-up speeds were examined in situ by mounting a vertically translating extruder in the synchrotron beam. The results indicate that a microfibrillar morphology is present for all cases. It is likely that the fibrils are twisted together into bundles. SAXS and WAXS patterns develop simultaneously, indicating that the fibrils develop by nucleation and growth from the amorphous melt. SAXS analysis appears to show that the long period and lamellar stack length both increase with take-up speed. The magnitude of the lamellar stack length however is grossly underestimated due to a large number of incorporated defects in the lamellar structure. The orientation of the lamellar stacks is similar to the orientation of the crystallites, showing that the macroscopic strain is transferred to the microscopic dimensions efficiently. Only at the largest take-up speed studied (850 mpm) was the influence of strain-induced crystallization seen. This was indicated by an initial decrease of crystallinity index with take-up speed at a given distance from the spinneret, followed by an increase at 850 mpm.