Abstract: Polypropylene (PP)-based composites containing multi-wall carbon nanotubes (MWCNTs) with contents of 1.0 wt %~5.0 wt % were prepared by melting extrusion, and their thermal, crystallization, mechanical and electrical properties were investigated. The results indicated that the MWCNTs were dispersed in the matrix in two modes, i.e. existing in grain and distributing along the grain boundaries. These two modes are beneficial to the improvement of mechanical properties, heat distortion temperature and melt flow rate for the composites. As the content of MWCNTs reached 3.0 wt %, the composites exhibited an electrical percolation behavior, with which the composites exhibited excellent conductivity at room temperature. The polarizing microscopy showed that PP grains became smaller due to the addition of MWCNTs, and the grain size tended to decrease with an increase of MWCNTs content. XRD measurement demonstrated that the presence of MWCNTs did not influence the crystal form and crystalline structure of PP. In addition, MWCNTs could act as a nucleating agent to enhance the crystallinity of PP, thus resulting in a shift of α-crystallization peak to a high temperature with an increase of crystallization temperature and improving the thermal stability significantly.

Key words: carbon nanotube, polypropylene, composite, crystalline morphology, melting behavior