THE INFLUENCE OF CATALYST SYSTEM AND POLYMERIZATION CONDITIONS ON POLYPROPYLENE PROPERTIES

Polypropylenes prepared using the catalyst system MgCl2 . TiCl4 .,diph thalate ester/AlEt(3) . alkoxysilane were evaluated by their xylene-in soluble fraction, intrinsic viscosity, molecular weight and molecular weight distribution (MWD). These properties were dependent on the natu re and concentration of the external donor for both slurry and bulk po lymerization carried out in the absence and presence of hydrogen, resp ectively. The catalyst system presented a different response to the hy drogen and external donor type used, producing polymers with different molecular weight or melt flow index at the same hydrogen concentratio n.