Effect of carbon nanotubes on dynamic mechanical properties, TGA, and crystalline structure of polypropylene

摘要

This paper is devoted to the preparation of thermoplastic nanocomposites of polypropylene (PP) and different amounts of single-walled carbon nanotubes (SWNTs) in the range 0.25-2 wt %. The effect of SWNT content on the dynamic mechanical behavior, thermal degradation, crystalline structure, and the kinetic crystallizability of PP were studied. The results obtained from dynamic mechanical thermal analyzer (DMTA) showed that the maximum storage modulus was achieved when 1 wt % SWNT was added into the pristine polymer. Thermal stability of the nanocomposites was measured by thermogravimetric analyzer (TGA). From the TGA results, it was found that the weight fraction of PP which was located at the interface for the nanocomposite containing 0.5% SWNT was about 60%, and this value did not change much with the addition of higher amounts of SWNT. Moreover, the thickness of the interface between PP and SWNT was estimated to be of the order of 10 ~1 nm which is very close to the radii of gyration of PP molecular chains. Wide angle X-ray diffractometer (WAXD) was used to explore the crystalline structure of water and slow-cooled samples. It was found that the crystallization of PP in 040 lattice plane increased for the nanocomposites compared with PP for both cooling rates studied. It was also found that the kinetic crystallizability values were nearly the same for PP and the nanocomposites.