Ziegler-Natta catalyst produced from MgCl_2/organically modified Mt/DI/TiCl_4 for in situ synthesis of polypropylene nanocomposites

摘要

Spherical Ziegler-Natta catalysts containing clay mineral are a more favorable way for the synthesis of nanocomposites and masterbatches of polyolefins. With the application of in situ polymerization technique, it was possible to overcome challenges such as intercalation/exfoliation of clay mineral, avoiding lamellae reaggregation in order to obtain materials with superior properties than the currently available ones, such as gas barrier and thermal resistance. In this study, support precursors and catalysts were prepared by chemical route with sodium clay mineral (Mt, montmorillonite) modified with different amounts of ammonium quaternary salt. The preparation of the catalyst precursor was performed using the mass ratios of MgCl2 to modified sodium Mt of 1:1 and 1:2 and it was possible to observe different thermal decomposition profiles compared to the standard catalytic support precursor (adduct MgCl2.EtOH) prepared as a reference. The catalysts obtained therefrom maintained a spherical morphology and X-ray diffractions (XRD) exhibit peak shift showing an increase of interlayer space of the Mt In order to obtain nanocomposites and masterbatches of polypropylene/modified Mt, the polymerization reaction was conducted in different reaction times. Polypropylene nanocomposites presented the high thermal degradation temperature (459 degrees C) and isotacticity (98%). XRD and transmission electron microscopy (TEM) analyses revealed exfoliated and intercalated morphologies even with high Mt contents in the polypropylene matrix.