In situ X-ray characterisation of isotactic polypropylene during melt spinning

Abstract

In fibre production, draw induced crystallisation and orientation are the dominant factors that influence the properties of the final end use article. These properties depend on processing conditions; in particular, the rate of temperature change, which affects crystallinity, and the stress applied during the drawing process, which affects orientation and may also facilitate crystallisation. Polymer crystalline regions can be characterised by wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). An X-ray system capable of in situ determination of fibre structure as it develops during processing has been designed and installed at Clemson University, allowing simultaneous measurement in the WAXS and SAXS regions from the extruder exit and down the spinline. Results from the in situ study of isotactic poly(propylene) with determinations of crystallinity and crystalline orientation from WAXS patterns, and lamellar long period from SAXS patterns, diameter, temperature and velocity, at varying distances from the exit of the extruder are presented.