Long-chain branched polyethene polymerized by metallocene catalysts Et[Ind](2)ZrCl2/MAO and Et[IndH(4)](2)ZrCl2/MAO

Ethene homopolymers and ethene copolymers with I-hexene were prepared by Et [Ind](2)ZrCl2/ MAO and Et[IndH(4)](2)ZrCl2/MAO catalyst systems in slurry p olymerizations. The melt behavior of the polymers was studied with small am plitude dynamic rheological measurements. The low-frequency complex viscosi ty of the polymers was higher than expected on the basis of their GPC molec ular weights. Furthermore, the polymers exhibited elevated activation energ y for flow. The polymers catalyzed by Et[Ind](2)ZrCl2/MAO had an Arrhenius- type flow activation energy of 50-60 kJ/mol, and those catalyzed by Et[IndH (4)](2)ZrCl2/MAO a somewhat lower value of 40 kJ/mol. Branching could be de tected by C-13 NMR in homopolyethene samples polymerized by Et[Ind](2)ZrCl2 /MAO, We suggest that these properties are due to long-chain branching that occurs via in situ incorporation of vinyl-terminated polyethene macromonom ers. With Et[Ind](2)ZrCl2/MAO the polymerization parameters affecting the r heological behavior most were ethene partial pressure and comonomer concent ration, whereas with Et[IndH(4)](2)ZrCl2/MAO the major factor was the amoun t of hydrogen.