Polypropylenes (PP) prepared with MgCl2/TiCl4-Et3Al and MgCl2/TiCl4/bis(2-ethylhexyl)phthalate-Et3Al/Ph2Si(OMe)2 catalyst systems were fractionated by the temperature-rising elution fractionation method in the wide temperature range of -65 to 140-degrees-C. The fractionations were proved to take place mainly on the basis of isotacticity from the analyses of key fractions by C-13 nuclear magnetic resonance, gel permeation chromatography, differential scanning calorimetry and X-ray diffraction. PP was shown to have a broad and continuous distribution of tacticity, ranging from nearly atactic to highly isotactic structures in the case of no electron donor system. The addition of electron donor, however, drastically reduced the amount of atactic and low isotactic PP, resulting in a very sharp tacticity distribution.
