Effects of the catalyst system on the crystallization of polypropylene

In search of a better understanding of catalyst effects on final product qu alities of polypropylene, an attempt was made to establish a correlation be tween catalyst type, polymer chain structure of homopolymers, crystallizati on behavior, as well as final morphology and mechanical properties. Convent ional Ziegler-Natta catalyst systems as well as novel metallocene catalysts were investigated, and influences of molar mass distribution and chain reg ularity were investigated as separate factors. Metallocene-based isotactic polypropylene shows some special effects regarding the nucleation density a nd the correlation between stereoregularity and mechanics that do not fit i nto the general picture for Ziegler-Natta catalyst based products. (C) 1999 John Wiley & Sons, Inc.