Kinetics Study on Melt Compounding of Carbon Nanotube/Polypropylene Nanocomposites

The multiwalled carbon nanotubes/polypropylene nanocomposlites (PP/CNTs) were prepared by melt mixing using maleic anhydride grafted polypropylene (mPP) as the compatibilizer. The effect of mPP on dispersion of CNTs was then studied using the tool of rheology, aiming at relating the viscoelastic behaviors to the mesoscopic structure of CNTs. To further explore the kinetics of hybrid formation, a multilayered sample with alternatively superposed neat mPP and binary PP/CNTs microcomposites (without addition of mPP) sheets was prepared and experienced dynamic annealing in the small amplitude oscillatory shear flow. The results show that melt blending CNTs with PP can only yield the composites with microscale dispersion of CNTs, while adding mPP promotes nanoscale dispersion of CNTs as smaller bundles or even as individual nanotubes, reducing percolation threshold as a result. However, the values of apparent diffusivities of the composites are in same order with that of self-diffusion coefficients of the neat PP, indicating that the presence of detached CNTs nearly does not inhibit PP chain motion. Hence, the activation energy of hybrid formation is close to the self-diffusion of PP. This also indicates that although addition of mPP can improve the compatibility between CNTs and PP thermodynamically, those dynamic factors, such as shear flow, however, may be the dominant role on hybrid formation. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym phys 47: 608-618, 2009