The Crystallization, Orientation Structure And Properties Of PP/carbon Nanotube Via Shear Stress Field

In our work, the interfacial adhesion bwteen carbon nanotube and polypropylene was enhanced by modification of raw MWCNTs through grafting C18 alkyl chains on the backbones of nanotubes. The morphology of polymer/carbon nanotubes composites were controlled via dynamic packing injection molding (DPIM) and extrusion-tensile process. The dispersion of carbon nanotube, oritentation structure, the interfacial adhesion and crystallization behavior of composites under shear stress field were researched. SEM, TGA, FT-IR, Rheological measurements, PLM, DSC and mechanical testing et al were used to characterize the samples obtained.Highly oriented structure with both PP chain and grafted MWCNTs oriented along the shear flow direction has been obtained via dynamic packing injection molding. Not only the Young's modulus and tensile strength can be enhanced, but more importantly, the oriented composites show an order of magnitude ductile than the iPP/PP-g-MMA matrix. This could be understood as due partially to the increased mobility for both PP chain and grafted MWCNTs as they are oriented along tensile deformation direction. On the other hand, we have found the evidence that oriented grafted MWCNTs with large respect ration could also serve as a bridge for crack development, leading to an increased elongation thus a great improvement of toughness.Shear-enhanced crystallization of PP/grafted MWCNTs nanocomposites has been followed by dynamic melt rheometry. Rheological measurements could provide the quantitative estimation on the overall rate of crystallization proceeded upon quiescent and pre-shear conditions. Combined crystallization kinetics analysis obtained via rheometry and morphological observation of crystals growth performed on POM, two different mechanisms of shear-enhanced crystallization for PP/ grafted MWCNTs composites were suggested: (1) at low temperature, strong heterogeneous nucleation plays a dominant role on the. crystallization behavior, which would be saturated at a higher filler content, and the effect of shear-enhanced crystallization was weak; (2) at high temperature, the effect of heterogeneous nucleation was substantially depressed, and the crystallization of the composite was obviously accelerated by pre-shear and the thread-like crystallites were generated earlier than the spherulites.The morphology of composite and the dispersion and oritentation of carbon nanotube were controlled by controlling the tensile ratio in procession of extrusion-tensile. And the crystallization behavior and mechanical properties of composite were controlled.