Study of the structure development during the melt spinning of nylon 6 fiber by on-line wide-angle synchrotron X-ray scattering techniques

The melt spinning of nylon 6 has been studied with on-line wide-angle synchrotron X-ray scattering techniques. The apparatus consisted of a single screw extruder and a metering pump mounted on a horizontal platform that could be translated in the vertical direction allowing a range of distances to be sampled with the X-ray beam. The structure development, equatorial crystallinity index, and crystalline orientation were studied as a function of take-up speed and position along the spinline. For low-speed (50 mpm) situations, the nylon chains crystallize into independent hydrogen bonded sheets that start to interact with each other as their concentration starts to increase. For higher speed situations, the nylon chains crystallize directly into the interacting hydrogen-bonded sheet structure. Upon conditioning at room temperature for 24 h, this interacting hydrogen-bonded sheet structure transforms into the well-known three-dimensional alpha and gamma phases of nylon 6, probably existing in a shish-kabob structure. The equatorial crystallinity index increases as distance from the spinneret increases and as take-up speed decreases. The crystalline orientation function is constant along the spinline for a constant take-up speed, and increases as take-up speed is increased. Conditioning further increases both the crystallinity and crystalline orientation of the fibers.