Polypropylene carbon nanotube composites by in situ polymerization

The preparation of isotactic polypropylene nanocomposites filled with crude, purified and oxidized multi-walled carbon nanotubes (MWCNTs) was accomplished by polymerization of propylene with a metallocene/methylaluminoxane (MAO) catalyst and in situ coating. A good interfacial adhesion between the matrix and the filler is crucial for the successful preparation of nanocomposites; therefore, the polymerizations were performed with a new in situ coating process, which is a promising approach for increasing the matrix adhesion. This coating technique is derived from the Polymerization-Filling Technique (PFT) and based on a covalent bonding of the cocatalyst on the surface of oxidized MWCNT.The resulting nanocomposites contained a filler content of 0.1–8 wt% and were investigated with respect to their properties, such as morphology, crystallization and melting temperature, halftime of crystallization which decreases very strongly in dependence on a rising filler content. Since MWCNTs behave as nucleating agents, a detailed discussion on the Avrami analysis (rate constant of crystallization, dimensionality of the crystalline growth) is made.