Preparation, Structure And Property Of Polypropylene/Multi-walled Carbon Nanotubes Nanocomposites

Carbon nanotubes (CNTs) are one-dimension nanostructure materials with special properties, extremely mechanical strength and well electronic properties have extensive applications in polymer. The main purpose of this work is focused on preparing nanocomposites with better performance via blending PP with CNTs modified by polypropyle-graft-maleic anhydride (PP-g-MAH) andβnucleating agent, studying the relationship between the structure and the properties. The major work of this paper is as following:1. PP nanocomposites reinforced by polypropyle-graft-maleic anhydride (PP-g-MAH) modified multi-walled carbon nanotubes (MWNTs) have been prepared through solution mixing. FTIR and TEM results indicated PP-g-MAH molecules were adsorbed on the surfaces of MWNTs. PP-g-MAH-MWNTs dispersed well in the PP matrix and has an improved adhesion with PP compared to untreated-MWNTs. The tensile strength and the conductivity of the PP/PP-g-MAH-MWNT composite were increased, especially the conductivity increasing two orders of magnitude compared to that of PP/untreated-MWNTs composite.2. A new noncovalent modification of MWNTs with P nucleating agent (N,N-dicyclohexyl-2,6-naphthalenedicarboxamide) was raised. P-nucleating agents can not only improve the dispersion of CNTs in PP as a result ofπ-πstacking, but also decrease the crystalline size to obtain homogeneous network structure of MWNTs in the matrix. The results from DSC and XRD showed that the addition ofβ-nucleating agents induced muchβcrystallites and higher crystallinity. PP/β-NA-MWNTs(5wt%) nanocomposite had improved strength and toughness with the electrical conductivity up to 4.0×10-3S/cm, which was 3 orders higher than that of PP/MWNTs. The relationship between the dispersion ofβ-NA-MWNTs, crystalline behavior of matrix and the properties were investigated and corrsponding conductive mechanism was brought forward.3. The conductive percolation was observed at the content of 0.3wt%β-NA-MWNTs which was less than 1.5wt% for PP/MWNTs. The effect of the crystalline size on the electrical conductivity of the nanocomposites was studied. The electrical conductivity of PP/β-NA-MWNTs was increased at first and then decreased with increasing time of isothermal crystallization. And the more MWNTs added, earlier the maxium conductivity of PP/β-NA-MWNTs appeared. At the same content of MWNTs, the isothermal time for the maxium conductivity at 140℃was longer than that at 1308. This was because higher isothermal temperature needed more time to obtain the same crystallinity.