A synchrotron X-ray study of melting and recrystallization in isotactic polypropylene

Abstract

SAXS/WAXS/d.s.c. at the SRS has been used to follow the melting and recrystallization of isotactic polypropylene (iPP). The time correlation is perfect between the three techniques which show good agreement with respect to crystallinity and kinetics. The degree of crystallinity and the lamellar thickness of iPP have been calculated from SAXS and WAXS patterns, obtained simultaneously during melting and crystallization, by integrated intensity and correlation function techniques. The long spacing was obtained from the peak in the Lorentz-corrected SAXS pattern and was in good agreement with that calculated from the correlation fuction ( γ 1). The degree of crystallinity was obtained from a combination of the SAXS invariant and the integrated WAXS intensity (due to the crystals), and the local crystallinity was obtained from γ 1. The data obtained during melting and recrystallization were interpreted in terms of a polydisperse lamellar model.