REGIME TRANSITIONS IN FRACTIONS OF ISOTACTIC POLYPROPYLENE

Crystal growth rates of spherulites or axialites of low molecular mass (MW = 15 000) and high molecular mass (MW = 300 000) isotactic polypropylene (i-PP) fractions crystallized from the melt have been investigated in an extensive supercooling range (20-70 K). On the basis of the regime theory, a transition between regimes I and II is found at AT s 37 K for the low molecular mass fraction and a transition between regimes II and III is at AT ~ 48 K for both low and high molecular mass fractions of i-PP. Accordingly, the morphological changes observed by a polarized optical microscope at the supercooling range in the vicinity of regime transitions have been examined. The morphological change in this supercooling range does not correlate to the regime transitions. © 1990, American Chemical Society. All rights reserved.