In-situ polymerization of olefins on nanoparticles or fibers by metallocene catalysts

This paper shows the capability and advantage of the in-situ polymerization of olefins as a technique for the preparation of nanocomposites. The nanocomposites base on high molecular weight and highly isotactic polypropylenes and oxidized multi-walled carbon nanotubes (HMWiPP/MWCNT). Since a good interfacial adhesion between the matrix and the filler is crucial for the successful preparation of nanocomposites the polymerizations were performed with MAO anchored covalently to the surface of the nanotubes. Thus, a heterogeneous co-catalyst is formed and the polymerization starts directly on the tube surface. The resulting nanocomposites contain 0.9-25 wt% multi-walled carbon nanotubes and polypropylene with a molecular weight of about 1.4 × 10 ⁶ g/mol. They were investigated with respect to their properties, like crystallization and melting temperature, as well as half-time of crystallization which decreases very strong in dependence on a rising filler content. The morphology analysis shows a homogeneous CNT distribution, a good separation of the individual particles, a very good interfacial adhesion and that every nanotube is covered by a thin polymer layer.