Preparation And Mechanical Properties Of The Polyimide/Multi-walled Carbon Nanotubes Hybrid Films

In recent years, people pay more and more attention to polyimide/inorganic nanocomposite.When inorganic nano-particles was used to modify polyimide, it can prove the performances of polyimide and synthesize their characteristics and advantages of the two components. Compared to other nano-inorganic particles, carbon naotubes have many advantages, such as length-diameter ratio, high strength and toughness, small density and so on. It becomes the ideal modification of polymer materials. So in this article multi-walled carbon nanotubes were used as the modification of the polyimide in order to obtain high performance polyimide/multi-walled carbon nanotubes (PI/MWNTs) naocomposites. But the agglomeration is caused easily because of high specific surface area and surface activation energy of carbon nanotubes. In order to improve the dispersion of carbon nanotubes, we choose two functional processing methods to modify multi-walled carbon nanotubes. This paper mainly studies the effect of functionalized modification of carbon nanotubes on the mechanical properties of polyimide.MWNTs were functionalized by acidification treatment and amino processs respectively, and then were dispersed in solvent to prepare polyamic acid via In-Situ polymerization, then the polyamic acid was further imidized into polyimide films by heating process.The change of groups in the surface of MWNTs was characterized by means of Fourier transform infrared spectroscopy. The dispersion of MWNTs in solvent was characterized by means of Scanning Electronic Microscopy (SEM) before and after functionalization. Morphology of the surfaces and the cross section of PI/MWNTs films were investigated by SEM. The mechanical properties of hybrid films were tested too. The results of the study indicate that functionalized modifications of MWNTs make the dispersion of MWNTs in solvent and PI matrix improved. The tensile strength of the hybrid films first increased then decreased with the increase of the content of MWNTs, but the elongation at break decreased. When the doping content of MWNTs was close to 0.92wt%, the tensile strength of the hybrid films that were made by incorporating acid treatment of MWNTs to polyimide (PI/acid-MWNTs) reached a maximum, with its value being 116.83 MPa. It was impoved by 13% than the pure PI films.The elongation at break declined by 64%. When the doping content of MWNTs was close to 0.53wt%, the tensile strength of the hybrid films that were made by incorporating amino treatment of MWNTs to polyimide (PI/amino-MWNTs) reached a maximum, with its value being 107.81MPa. It was impoved by 4.3% than the pure PI films.The elongation at break declined by 60%. The elastic modulus of the PI/acid-MWNTs hybrid films was raised by 54% maximumly. The elastic modulus of the PI/amino-MWNTs hybrid films was raised by 25% at most.