Influence of Chemical Treatment on Sodium Clay for Obtaining Polypropylene Nanocomposites

Maria Marques, Jeferson Rosa and Kamilla Cruz
Universidade Federal do Rio de Janeiro, Instituto de Macromoléculas Professora Eloisa Mano, CP 68525, 21941-590, RJ, Brazil;
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Commercial clay was chemically treated with aluminum alkyl to prepare a Ziegler-Natta pro-catalyst containing MgCl2 and clay (as inert support) for the synthesis of polypropylene nanocomposites by in situ polymerization technique. The performance of this catalyst was compared with a reference one (catalyst prepared without clay), as well as with another one, composition of which presents the same clay content, without prior chemical treatment. Propylene polymerizations were performed varying the amount of external donor in the reaction medium in order to evaluate the response of catalysts toward increase in isospecificity. Properties of the polymeric materials obtained employing those catalysts were also compared. The results showed a marked reduction in activity of both bisupported catalysts in comparison with that of the reference system, and a slight reduction in polypropylene melting temperature. The melt flow index of polymers obtained with the treated clay was notably higher than those synthesized with the untreated clay. Therefore, the treated clay caused the production of PP with a lower molar mass. On the other hand, the clays showed an increase of the d-spacing and irregular stacking of the lamellas in the bisupported catalyst and also in the produced PP/clay nanocomposites, especially when using the chemically treated clay.

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