ABSTRACT:The efficiency of a macromolecular compatibilizer for reactive blending is strongly dependent on its potentiality of producing a grafted or block copolymer during processing. For the preparation of such a compatibilizer, the grafting of two different reactive groups onto the backbones of ethylene/propylene copolymer macromolecules was performed. The ethylene/propylene (70/30) copolymer was then processed in a Brabender mixer at 190°C in the presence of a mixture of maleic anhydride and diethylmaleate with either dicumyl peroxide or di-tert-butyl peroxide as an initiator. The experiments clearly showed that the two functionalities, 2-diethyl succinate and 2-succinic anhydride, could be grafted in one step. The effect of the feed composition demonstrated that the two monomers influenced the reciprocal reactivity and the resulting product. A detailed Fourier transform infrared analysis of the grafted macromolecules was performed, and the respective amounts of ester and anhydride derived groups were detected by deconvolution of the vibrational bands in the carbonyl spectral region. The validity of the process on an industrial scale was tested by the successful performance of the reaction in a twin-screw extruder.
Trialkylsilanols were reported to modify and also to improve the catalytic performance in ethylene polymerization when added to zirconocene/methylaluminoxane (MAO) systems. In order to obtain more information about the chemistry involved, a new stable catalytic precursor was investigated in this work. The precursor bis(h5-cyclopentadienyl)bistriphenylsilanolatozirconium(IV) [ZrCp2(OSiPh3)2] was compared to ZrCp2(CH3)2 and ZrCp4, which can generate ZrCp2(OSiPh3)2 in situ on triphenylsilanol addition. In ethylene polymerization, ZrCp2(OSiPh3)2 exibits a comparable activity and a larger stability than dicyclopentadienylzirconium complexes. On addition of triphenylsilanol to zirconocenes, the productivity increased and the molecular weight sharply decreased, thus suggesting the occurrence of ligand substitution in solution. The reported results are discussed with reference to the proposed mechanism of ethylene polymerization with the conventional ZrCp2Cl2/MAO system.
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