Effect of Electron Donors on Propylene Polymerization with Ziegler-Natta Catalyst

Using electron donors in Ziegler Natta catalyst system in propylene polymerization influences the final properties of polymer's microstructure. This paper is a review which gives an account on the effect of internal and external electron donors on propylene polymerization using Ziegler-Natta catalyst. At first, the mechanism of propylene polymerization is introduced. The internal electron donors are discussed with respect to their interaction with the surface of catalyst support and the resulting polypropylene properties, like molecular weight distribution. Subsequently, the importance of external donors, especially in the third and fourth generations of Ziegler-Natta catalyst is shown. The review further extends the discussion on the effect of alkoxysilanes as external donors in relation to propylene polymerization and activity of catalyst and properties of polypropylene like isospecificity and weight average molecular weight.