Abstract

Studies related to the behavior of different metallocene catalysts for the homopolymerization of 1-octadecene and its copolymerization with ethylene will be presented. The metallocenes: rac-Et(Ind)(2)ZrCl2, rac-Me2Si(Ind)(2)ZrCl2 and Ph2C(Flu)(Cp)ZrCl2 were chosen for the homopolymerization study. They show important differences in catalytic activity at high temperatures (greater than or equal to 70 degrees C), with rac-Et(Ind)(2)ZrCl2 showing the highest activity. At lower temperatures (less than or equal to 30 degrees C) the differences are negligible. For the copolymerization of ethylene with 1-octadecene only the catalysts rac-Et(Ind)(2)ZrCl2 and rac-Me2Si(Ind)(2)ZrCl2 were studied. The results show that their catalytic activity is just like that for the homopolymerization of 1-octadecene, with higher activity for the metallocene with the Et-bridged catalyst. C-13-NMR analysis shows that the composition of the copolymerization products depends on the catalytic systems. Copolymers obtained with rac-Me2Si(Ind)(2)ZrCl2 have greater comonomer incorporation. Thermal analysis shows that poly-1-octadecene synthesized with the catalyst rac-Et(Ind)(2)ZrCl2 is very dependent on the polymerization temperature. The homopolymer obtained at 70 degrees C presents two endothermal peaks at 41 degrees C and 53 degrees C, as compared with the one obtained at 30 degrees C which presents one wider peak with a maximum at 67 degrees C. For the catalyst rac-Me2Si(Ind)(2)ZrCl2 this trend is not observed. The type of metallocene and the reaction time do not significantly change the intrinsic viscosity, but the polymerization temperature changes it drastically, giving higher values at lower temperature. Viscosity measurements on the copolymers show that an increase of comonomer concentration in the feed reduces the molecular weight of the copolymer, and it was also found that for homopolymer, the molecular weight is independent of the catalytic systems.