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- Study of low catalytic activity systems (Biscyclopentadienyl complexes-aluminoxane) on olefin polymerizationPublication . Justino, Jorge; Marques, M.M.; Correia, S.; Dias, A.R.; Lemos, F.; Ribeiro, F.R.Olefin polymerization using low activity catalyst systems: Cp2WCl2-methylaluminoxane, [Cp2Mo(CH3)2][PF6]-methylaluminoxane and Cp2Mo(CH3)2-methylaluminoxane, is described. All these catalyst systems were studied in ethylene and propylene polymerization; however, they only showed catalytic activity for ethylene. Only one type of methylaluminoxane (MAO) was used, prepared in an Al/H2O ratio of 2. The kinetics of polymerization were examined and the experimental data (either presented here or in previous papers) were fitted to the kinetic models developed previously and now extended to account for the methylaluminoxane effect.
- Polymerization of ethylene using metallocene and aluminoxane systemsPublication . Justino, Jorge; Dias, A.R.; Ascenso, J.; Marques, M.M.; Tait, P.J.T.This paper describes ethylene polymerization using a number of metal-locene and aluminoxane catalyst systems, Cp2MR2 and methylaluminoxane [M = Zr, W, Nb; R = Cl, CH3]. Two types of methylaluminoxane, MAO (1) and MAO (2), were used as cocatalysts. The polymerization activities of the complexes Cp2WCl2 and Cp2NbCl2 were compared with that of Cp2ZrCl2. The Nb and W complexes were found to be less active than the Zr complex. Polyethylene characterization was also carried out by the following methods: gel permeation chromatography (GPC), differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR).