Polypropylene Nanocomposite Employing Sodium Clay as Support for an Isospecific Metallocene Complex

摘要

Propylene polymerization was performed using homogeneous and supported rac-SiMe2(2-Me-Ind)2ZrCl2 catalysts. The supports used were commercial sodic bentonites from different sources. The influence of polymerization time and nature of catalyst support on the nanocomposites syntheses and the consequent properties of obtained composites, were evaluated at two different reaction temperatures and with two cocatalyst systems (MAO and a mixture of MAO/TIBA). The highest catalytic activities were obtained at 60°C with the cocatalyst mixture MAO/TIBA in the reaction medium. Polymeriza-tion rate profiles were obtained as well as melting and crystallization temperatures, crystallinity degree, isotactic index, and number-average molecular weight. The polypropylene produced with the supported catalyst pretreated with TIBA instead of MAO showed higher crystallinity degree, melting and crystallization temperatures, however, it presented lower catalyst activity. Clay exfoliation was verified by the absence of diffraction peak in the range of 29 from 2.5° to 7° of X-ray diffractometry analyses and by transmission electron microscopy. The thermogravimetric analyses showed an increase of PP degradation temperature of above 70°C when synthesized with clay supported catalysts in relation to the PP obtained by means of homogeneous system.