Functionalized CNTs And Its Effects On Mechanical Properties Of Polyimide Films

Since discovered by Iijima in 1991, CNTs had attracted great interests throughout the academic and industrial world due to its extraordinary electrical, mechanical and thermal properties, which makes them possible to possess percolation threshold at low loading in polymer matrix nanocomposites. But CNTs tend to form into aggregates for their high specific area and extremely high surface energy, which lead to heterogeneous dispersion in the polymer matrix and negative effects on the properties of the resulting composites. Therefore, great attentions were focused on the effective functionalize method on CNTs.In this paper, Multi-wall carbon nanotubes (MWNTs) were acid modified by refluxing with the mixture of H2SO4 and HNO3 under ultrasound, then were attended into the synthesis of PI/MWNTs hybrid films via in situ polymerization process. The dispersion situation of MWNTs in the nanofilms was characterized using scanning electronic microscopy (SEM); mechanical and thermal properties of nanoflims were tested, with the results indicating that the acid modified able to facilitate the homogeneous dispersion of MWNTs in the ethanol solvent, remain in fine monodispersity condition after one week; functionalized MWNTs can be dispersed homogeneously in the PI matrix with MWNTs content under 1wt%, the the addition of functionalized MWNTs increase the heat resistance of PI/MWNTs appreciably, slow down its thermal decomposition with the increased MWNTs content; as the MWNTs increased, the mechanical property has not an significantly discipline, tensile strength of nanofilms content reaches 110.05MPa at the MWNTs content of 0.36wt%, while its elongation is 31%, 15% lower than the pure PI films.