Carbon nanotubes morphology and dispersion in nanocomposites

The unique properties of carbon nanotubes (CNTs) offer great opportunities for nanocomposites with applications in many different sectors. Carbon nanotubes can be found in electronic devices, in application related with transportation, as well as energy and biotechnologies. Currently, the most popular use for carbon nanotubes is as reinforcement for polymer nanocomposites both for electrical and structural applications. CNTs are more efficient compared with other traditional fillers, primarily thanks to the large aspect ratio and surface area which increases the stress transfer and promote the formation of percolation network in the matrix. At the same time, the particular structure of the nanotubes also promotes the aggregation of the nanotubes due to strong Van der Waals attraction between the nanotubes, limiting the final properties of the nanocomposites. The ability to tailor electrical and mechanical properties and to totally employ the potential of CNTs widely depends on the ability to obtain a homogeneous dispersion of the fillers in the polymeric matrix. The influence of the morphology of the CNTs on the dispersion and on the rheological, electrical, mechanical and thermal properties of PC/CNTs and HDPE/CNTs were studied. Different synthesis conditions and different catalysts were tested in order to produce CNTs with different morphology. From the TEM analysis of the samples it was clear that particles produced at high temperature are characterized by larger diameters. Rheology measurements were performed on the samples in order to evaluate the level of dispersion of the nanotubes, showing significant differences between samples produced by different catalysts. Various nanocomposites were produced by micro compounding experiments in order to study the electrical properties of the samples and to discriminate the best ones. Finally, a study concerning the electrical and mechanical properties of specimens produced by injection molding was performed.