Polypropene nanocomposites by metallocene/MAO catalysts

Abstract In our experiments, monospheres (balls of silica, diameter 200–250 nm), carbon fibers (diameter 200 nm, length 0.5–3 mm) and carbon nanotubes (diameter 15–25 nm, length 50 μm) were used as fillers. Before polymerization, the fillers were separated by ultrasound and then treated by methylaluminoxane (MAO). The MAO reacts partially with the OH-groups of the silica and the formation of methane. Catalytically active centers are formed after adding the zirconocenes or other transition metal complexes. The thickness of the polyolefins can be controlled by the pressure of ethene or propene and by the polymerization time. By this method, highly filled nanocomposite polypropenes can be obtained with a silica content of up to 60 wt%. Such combined materials are stiff and hard. Every particle is surrounded by a thin film of polyolefin with a thickness of 30 to 100 nm. Carbon fibers and carbon nanotubes can be covered also within isotactic or syndiotactic polypropene. Because of the hydrophobic character of the carbon surface, the polymer is drawing on the fiber. This leads to a reinforced combined polymer with special properties. Keywords: NANOCOMPOSITESPOLYPROPENEMETALLOCENE CATALYSTSSILICA NANOBALLSCARBON NANOTUBES