Studies On Grafting Polymer Onto The Surface Of Carbon Nanotubes And Its Application

Since their discovery in 1991, carbon naonotubes have encouraged the development of new nanotechnologies because of their outstanding electronic, mechanical and thermal properties. However, since carbon nanotubes are large molecules with thousands of carbon atoms in an aromatic delocalized system and strong intertube van der Waals attraction, they are practically insoluble in all solvents and, consequently, their applications are limited.In this paper, in order to get MWNT-PBA, atom transfer radical polymerization (ATRP) was used to graft Poly (n-butyl acrylate) (PBA) from the surface of MWNT to establish an organic shell structure. The results of Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) show that we are succeeded in bonding PBA with MWNT and getting a polymer brush from its surface.Polypropylene (PP)/ MWNT-PBA composites were prepared by melting mix process. The results of TEM, scanning electron microscope (SEM), and mechanical properties testing show that MWNT-PBA are more easily dispersed in the matrix than MWNT-COOH. The impact property of PP/ MWNT-PBA composites is apparently improved.The effect of the addition of MWNT-COOH and MWNT-PBA on the crystallization and thermal stability properties of PP were studied by the characteristics of wide-angle X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The results show that the addition of MWNT-COOH and MWNT-PBA did not change the hexagonal system of PP crystal, just decreased the micro-crystal size of the polymer. Moreover, the spherulite size becomes smaller as the addition of fillers while the crystallinity becomes higher, which verified that the fillers of bare MWNT-COOH and MWNT-PBA serve as a nucleating agent for the crystallization resulting in a higher crystallinity. TGA result shows that the resistance of thermal degradation of PP-based nanocomposites is clearly higher than that of PP. The incorporation of inorganic fillers enhanced the thermal stability property of PP. It is obvious that MWNT-PBA play a more important role in the influence on the thermal stability of PP than MWNT-COOH.Polyvinyl chloride (PVC) based nanocomposites were prepared by melting mix process. The results of TEM, SEM, TGA, Vicat softing point (VSP) and mechanical properties testing show that the dispersibility of MWNT-PBA in the PVC is greatly improved, and accordingly the mechanical properties of PVC/ MWNT-PBA are apparently improved. In comparison with MWNT-COOH, MWNT-PBA plays a more important role in the enhancement of the VSP of PVC, however, the thermal stability of PVC nearly does not change as the filling of MWNT-PBA.The theological properties of pure PVC and PVC based composites were studied by the torque theometer. The result shows that MWNT-COOH can reduce the melting time of PVC because of the effect of the abrasion among MWNT which can easily produce much thermo-energy in a short time, but the torque becomes too higher. However, MWNT-PBA may prolong the time of melting process of PVC, but, apparently, the balance torque are much lower.