Structure and Morphology of Highly Stereoregular Syndiotactic Polypropylene Produced by Homogeneous Catalysts
- Adam Galambos
Adam GalambosHimont Research and Development Center, 800 Greenbank Road, Wilmington, DE 19808More by Adam Galambos
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- Michael Wolkowicz
Michael WolkowiczHimont Research and Development Center, 800 Greenbank Road, Wilmington, DE 19808More by Michael Wolkowicz
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- Robert Zeigler
Robert ZeiglerHimont Research and Development Center, 800 Greenbank Road, Wilmington, DE 19808More by Robert Zeigler
Abstract
A highly stereoregular sample of syndiotactic polypropylene (s-PP) produced via homogeneous catalysis was examined using a variety of analytical techniques to determine how the crystallization properties compared to those of commercial isotactic polypropylene (i-PP) and to investigate the dependence of multiple crystalline forms and morphologies on thermal and mechanical processing conditions. The thermal properties suggested that with comparable thermal history, s-PP had a melting point about 10 °C less than that of i-PP, and had a slower spherulitic growth rate at a given crystallization temperature. Two crystal forms of s-PP were observed by solid-state NMR: An all-trans form promoted by cold drawing and the more typical "figure-8" helical form produced during quiescent crystallization. Multiple melting behavior of the "figure-8" crystalline form was dependent on the thermal processing conditions. Finally, a transition from a spherulitic to an axialitic growth habit of the "figure-8" crystalline form was observed to occur as the isothermal crystallization temperature was increased from 138 to 148 °C.