Influence of thermal treatments on the polymorphism in stereoirregular isotactic polypropylene: Effect of stereo-defect distribution

Frank P.T.J. Van der Burgt, Sanjay Rastogi, John C. Chadwick, Bernhard Rieger

Research output: Chapter in Book/Report/Conference proceedingConference contribution

26 Scopus citations

Abstract

The influence of cooling rate from the melt on the polymorphism and crystallinity is investigated as a function of isotacticity and stereo-defect distribution in polypropylenes. Detailed analysis of wide angle x-ray diffraction patterns shows that crystallinity in the materials used is nearly independent of the experimental cooling rates (0.5-40 °C/min). At high cooling rates, the materials exist mainly in the α-phase, whereas the amount of the γ-phase increases at the lower cooling rates. With an increasing amount of stereo-defects, this cooling-rate dependence of the polymorphism is enhanced. The effect of different stereo-defect distributions, as observed in metallocene(random) and Ziegler-Natta (blocklike) derived isotactic polypropylenes, was investigated. The formation of the γ-phase is more prevalent in materials with a random defect distribution compared to the materials in which the stereo-defects have a blocklike distribution. The crystallinity decreases more rapidly as a function of the tacticity in the random defect-distributed materials.
Original languageEnglish (US)
Title of host publicationJournal of Macromolecular Science - Physics
Pages1091-1104
Number of pages14
DOIs
StatePublished - Jul 1 2002
Externally publishedYes

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