In Situ X-Ray Characterization of Isotactic Polypropylene: Dependence of the Crystalline Properties on the Draw Down Ratio

Polymer crystalline regions can be characterized by wide-angle X-ray scattering (WAXS) and small-angle X-ray scattering (SAXS). The in-situ study of isotactic polypropylene with measurement of wide angle and small angle X-ray scattering (WAXS and SAXS), at varying distances from the exit of the extruder have been successfully completed using an X-ray system with a standard X-ray source. The processing conditions, used were: 50, 100, 200 and 400m.min-1 for the take up speed, 0.3, 0.6, and 1.2 cm3min-1hole-1 for the melt flow rates, and a spinning temperature of 220°C. These experimental conditions produced draw down ratios ranging from 33 up to 1058. The X-ray characterization was carried in-situ at 15, 30, 45 and 60 cm from the exit of the spinneret and also ex-situ. The results obtained show the crystallinity index and the crystalline orientation to increase for the higher draw down rates, as expected under draw induced crystallization conditions, and a logarithmic relationship was observed within the experimental conditions used in this work. This communication reports the relationship between the crystallinity, crystalline orientation and lamellar long period and draw down ratio along the spin line.