Study of structure development during melt spinning of isotactic polypropylene fibers using Raman spectroscopy and wide angle X-ray diffraction simultaneously

Isotactic polypropylene (iPP) is a commercially important semicrystalline polymer. It is widely used in the manufacturing of fibers, with a variety of applications. Specific end-use applications require specific properties, which are dependent on the polymer morphology produced during processing. Therefore, final properties of a material are dependent on the processing parameters.; iPP fibers are produced mainly by melt spinning, and the important processing parameters in the melt spinning process include the extrusion temperatures, the throughput and shear rates, rate of cooling, and the feed and draw roll take-up velocities. Studying the structure development of iPP fibers during their formation gives valuable information on fiber microstructure or morphology, i.e., the degree of crystallinity and molecular orientation of the crystalline material. An understanding of how the morphology develops along the spinline, and the effect of processing parameters on the morphology is crucial in optimizing the melt spinning process.; The objective of this work was to study the development of structure in the fiber as the polymer was transformed from a molten amorphous state to a semi-crystalline material, and to investigate the effects of throughput rate and take-up velocity on the structure development along the spinline. Raman Spectroscopy and Wide Angle X-ray Diffraction (WAXD) were used simultaneously to characterize the morphology of iPP along the spinline during melt spinning. DSC and birefringence measurements were also collected for the as-spun fibers.; Two throughput rates (0.67 and 0.89 g/min/hole) and two take-up velocities (400 & 800 m/min) were used. The polymer processing temperature was 220°C and the extruder pressure was set to 500 psi. Raman (polarized and unpolarized) and WAXD data were simultaneously collected at six different positions along the spinline (60, 50, 40, 35, 30 and 25 cm from the spinneret).