Control of Molecular Weight Distribution in Propylene Polymerization with Metallocene/Metallocene Catalyst Mixtures

Several polypropylene (PP) reactor blends are synthesized using homogenous binary metallocene catalytic systems composed of rac-Me2Si(2-Me-4-Ph In)2ZrCl2 (I) and (2-Ph In)2ZrCl2 (II). The reactor blends are analyzed using Gel permeation Chromatography (GPC) and Differential Scanning Calorimetry (DSC). All of the blends show bimodal molecular weight distribution and the molecular weights are shifted toward higher values compared with PPs synthesized with each of individual catalysts, showing probable interactions between the two active sites. Upon changing molar ratio of the catalysts in the binary system melting points of produced PPs do not alter significantly while the crystallinities decrease when the amount of II increases