The influence of catalyst system and polymerization conditions on polypropylene properties

Polypropylenes prepared using the catalyst system MgCl2 . TiCl4 .,diphthalate ester/AlEt(3) . alkoxysilane were evaluated by their xylene-insoluble fraction, intrinsic viscosity, molecular weight and molecular weight distribution (MWD). These properties were dependent on the nature and concentration of the external donor for both slurry and bulk polymerization carried out in the absence and presence of hydrogen, respectively. The catalyst system presented a different response to the hydrogen and external donor type used, producing polymers with different molecular weight or melt flow index at the same hydrogen concentration.