The Investigation Of Carbon Nanotube-Polypropylene Composites

The super high strength, ductility, nanometer scale and large aspect ratio of carbon nanotubes (CNTs) make it an ideal reinforcement additive for composites. Also, the good electrical conductivity, high thermal conductivity, good thermal and chemical stability of carbon nanotubes could make the composites versatile. In this paper, polypropylene(PP) as matrix was modified by CNTs. The mechanical property, electrical conductivity, thermal conductivity and crystallization behavior of the composite were studied after modification. The catalyst was first produced by sol-gel method and the carbon nanotubes were high yield synthesized by the catalytic chemical vapor decomposition method. In order to get rid of the impurity, the as-CNTs were refluxed by nitric acid and muriatic acid. After refluxing, the carbon nanotubes were completely purified, the end and wall of carbon nanotubes were attached with carboxyl and hydroxyl groups. These functional groups could make carbon nanotubes hydrophilic. Then , the CNTs/MAH-g-PP composites were prepared by in situ graft method. The mechanical, electrical and thermal properties of the composite were investigated systematically. The results indicated that the incorporation of carbon nanotubes could enhance the strength, conductivity and thermal stability of composites. The carbon nanotubes enhanced the nucleation of PP crystallization and made the size of the spherulites smaller and even. Very low concentration of carbon nanotubes could greatly enhance the thermal stability of PP in nitrogen at high temperature. Finally, the modification of CNTs with poly(Butyl Methacrylate)(PMBA) by grafting polymerization method were studied to prepare PBMA-g-CNTs/PP composite. The properties of the composite were explored. The results showed that the CNTs encapsulated by PBMA could be dispersed more evenly in the matrix of PP and raised the crystallizing point and increased the nucleation rate of the composite, but the crystalline rate of the composite were reduced. The results also indicated that the introduction of the modified CNTs could cause the α-crytalline form of the composite be transformed to β-crytalline form so as to enhance the mechanical properties of the composite.