POLYMERIZATION AND CHARACTERIZATION OF ETHYLENE PROPYLENE AND ETHYLENE/1-OCTENE COPOLYMERS PRODUCED WITH BRIDGED ZR-BASED AND HF-BASED METALLOCENES/

Ethylene/propylene (E/P) and ethylene/1-octene (E/O) copolymers were p olymerized with two bridged metallocene catalyst systems, Et(Ind)(2)Zr Cl2/MAO and Et(Ind)(2)HfCl2/MAO, respectively. The copolymers produced and some commercial reference copolymers were characterized by DSC, S EC, DMA and C-13 NMR. The Hf-catalysed E/P polymerizations showed much lower activities than the corresponding Zr-catalysed polymerizations but gave polymers with high molar mass. The Hf-based copolymers also s howed two melting peaks which may be indicative of several active site s of the catalyst. A comparison of E/P copolymers, containing about 20 mol-% propylene and produced with Zr, Hf and homogeneous V-catalysts, respectively, indicated that the Hf and V-catalysts gave material mor e similar to each other. The E/O copolymers produced with Zr-catalysts gave very low molar masses and the reactivity ratios, calculated from the NMR data, indicated that the Hf-catalyst has a slightly higher re activity for 1-octene and the Zr-catalyst some better reactivity for e thylene. Segregation fractionation studies by DSC indicated that a low er 1-octene feed gives more heterogeneous copolymers and the DMA measu rements reveal the existence of a linear correlation between the 1-oct ene content and the intensity of the tan delta(max) peak.