Daniela Bianchini

Polypropylene obtained with in situ supported metallocene catalysts

Propylene homopolymerization was carried out with Me2Si(Ind)2ZrCl2 immobilized on commercial MAO-modified silica by the in situ supporting technique. Adsorption isotherm determination for this metallocene on silica indicated that the saturation level is reached at 2.0 wt.% Zr/SMAO. Catalyst systems were shown to be active in the absence of external MAO, being activated by common alkylaluminum cocatalysts, namely triethylaluminum (TEA), isoprenylaluminum (IPRA) and triisobutylaluminum (TIBA). The effect of the nature and concentration of cocatalyst on catalyst activity and on polypropylene (PP) properties was evaluated. Best catalyst activity was observed in low concentration of IPRA (1.4 kg PP/g cat h). The resulting polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), 13 C nuclear magnetic resonance (NMR) spectroscopy, and scanning electronic microscopy (SEM).

Thermal decomposition studies of the polyhedral oligomeric silsesquioxane, POSSh, and when it is impregnated with the metallocene bis(η5-cyclopentadienyl)zirconium (IV) dichloride or immobilized on silica

Thermal decomposition studies of the free polyhedral oligomeric silsesquioxane, POSSh, and when this compound has been impregnated with Cp2ZrCl2 (Cp = eta5-C5H5) or immobilized on SiO2 were conducted using infrared emission spectroscopy (IES) over a 100-1000 degrees C temperature range and by thermogravimetric analysis (TGA). The organic groups in POSS(h) apparently decompose thermally into Si-CH3, Si-H and other fragments. Upon impregnation with Cp2ZrCl2, however, a different thermal decomposition pathway was followed and new infrared emission bands appeared in the 1000-900 cm(-1) region suggesting the formation of Si-O-Zr moieties. When immobilized on SiO2 and subjected to thermal decomposition, the POSSh compound lost its organic groups and the inorganic structure remaining was incorporated into the SiO2 framework.