Abstract:In this paper, hyperbranched polyamide grafted modified carbon nanotubes with different branching degrees were prepared, and the microstructure of carbon nanotubes before and after grafting was characterized. The results of FTIR and TGA showed that hyperbranched polyamide was successfully grafted onto the surface of carbon nanotubes; TEM analysis showed that the hyperbranched polyamides with three degrees of branching formed a polymer coating on the surface of carbon nanotubes, and the pipe diameter increased significantly, and the higher the degree of branching, the more the pipe diameter increased. Furthermore, the hyperbranched polyamide modified carbon nanotubes prepared above were added to the epoxy resin system to prepare different modified epoxy resin composites. The results of DMA and mechanical properties analysis showed that the storage modulus, glass transition temperature Tg, and the height of mechanical loss peak is lower than that of unmodified carbon nanotube / epoxy resin composite, and the impact toughness is significantly improved. It is proved that a large number of molecular branches of hyperbranched polyamide contribute to the toughening of epoxy resin, and the higher the degree of branching, the more obvious the toughening effect is; SEM analysis showed that the addition of hyperbranched polyamide significantly improved the dispersion of carbon nanotubes in epoxy resin; The toughening mechanism of the system belongs to the carbon nanotube pull-out mechanism. The pull-out objects of carbon nanotubes are basically pulled out by short convex edges, and most carbon nanotubes are pulled off, indicating that hyperbranched polyamide modified carbon nanotubes form a very firm connection with epoxy resin, which has excellent toughening effect on epoxy resin.