Multiwalled Carbon Nanotubes-Based Polypropylene Composites: Influence of Interfacial Interaction on the Crystallization Behavior of Polypropylene

Composites of polypropylene (PP) and multi-walled carbon nanotubes (MWCNTs) were prepared via melt-mixing utilizing Li-salt of 6-amino heaxanoic acid (Li-AHA) modified MWCNTs in the presence of a compatibilizer (polypropylene- g-maleic anhydride; PP-g-MA). Improved interaction between the anhydride group of PP-g-MA and the amine functionality of Li-AHA was confirmed via FTIR and Raman spectroscopic analysis. A higher glass transition temperature (Tg) of the PP phase has been observed in these composites as compared to pristine MWCNTs-based composites. The crystallization temperature (Tc) of the PP phase was increased as a function of pristine MWCNTs concentration in PP/MWCNTs composites indicating heteronucleating action of MWCNTs. However, Tc value was decreased in the presence of Li-AHA modified MWCNTs indicating the adsorbed Li-AHA on the MWCNTs surface. Moreover, Tc value was higher in the presence of Li-AHA modified MWCNTs with PP-g-MA as compared to that of without PP-g-MA, suggesting the desorbed Li-AHA from the MWCNTs surface due to melt-interfacial reaction. Further, MWCNTs were extracted by hot vacuum filtration technique from PP/ MWCNTs composites containing Li-AHA and PP-g-MA. The isothermal crystallization kinetics showed a variation in crystallization behavior of the PP phase in the corresponding composites as compared to the "extracted MWCNTs. (C) 2016 Society of Plastics Engineers