Preparation And Characterization Of Polyamideimide/Poly(Omethoxyaniline)/Carbon Nanotubes Composites

Carbon nanotubes(CNTs)have been widely used for conductive polymer composites(CPCs)due to their excellent properities such as high electrical conductivity and good mechanical property.Unfortunately,CNTs are prone to agglomerate in the polymer matrixes owing to their large specific surface area and high aspect ratio,as well as the strong van der Waals force between the carbon nanotubes.Therefore,much more attention has been paied to improve the dispersion of CNTs in the polymer matrixes.In this thesis,two different strategies(ternary blending and chemical grafting)have been adopted to improve the dispersion of CNTs in the polymer matrix(Polyamideimide,PAI).The crystallinity,themol,mechanical,electrical properties and morphology of PAI conductive composites were respectively investigated by Differential Scanning Calorimeter(DSC),X-ray Diffractometer(XRD),Thermogravimetric Analysis(TGA),Four tubes technology,Universal Tensile Testing Machine and Field Emission Scanning Electron Microscopy(FESEM).In addition,the effects of proportion and preparation methods of conductive fillers on the properties of PAI composites were also discussed.The main conclusions are as follows.The functionalized multi-walled carbon nanotube(FMWCNTs)was incorporated into polyamide-imide/poly(o-methoxyaniline)(PAI/POMA)binary composites to fabricate PAI/POMA/FMWCNTs ternary conductive composites by the simple solution casting method.It is found that the conductive and mechanical properties of the PAI/POMA/FMWCNTs ternary composite films were correspondingly improved with increasing FMWCNTs content.In more detail,when the weight ratio of FMWCNTs reached 20 wt%,the electrical conductivity of the PAI/POMA/FMWCNTs ternary composite film increased to 48.4 S/m,which is much higher than that of PAI/FMWCNTs binary composite film(13.5 S/m).In addition,the tensile strength of the ternary composite film(65.8 MPa)is also higher than that of the binary composite film(52.1 MPa).This is because that there is strong hydrogen bond interaction among the three components of PAI,POMA,and FMWCNTs,which can effectively break the van der Waals forces between FMWCNTs chains to improve the dispersion of FMWCNTs in PAI.Furthermore,the surface roughness of the PAI/POMA/FMWCNTs ternary composite film is much lower than that of the PAI/FMWCNTs binary composite film,and the surface energy of POMA(20.4 m J/m~2)is located between PAI(27.8 m J/m~2)and FMWCNTs(10.9 m J/m~2),which means that POMA worked as an interface compatibilizer to promote the dispersion of carbon nanotubes in the polymer matrix.Poly-o-methoxyaniline grafted functionalized multi-walled carbon nanotubes(FMWCNTs-POMA)was synthesized and used as conductive filler to prepare PAI conductive composites.It is found that the conductive and mechanical perfomances of PAI/FMWCNTs-POMA composites was further enhanced compared to PAI/POMA/FMWCNTs ternary composite.When the content of FMWCNTs-POMA reached 20 wt%,the electrical conductivity and tensile strength was further increased to 79.6 S/m and 74.7 MPa,respectively.This is beause that POMA grafted on the surface of FMWCNTs can further improve the compatibility between FMWCNTs and PAI,and promote the uniform dispersion of FMWCNTs in PAI,and form much more intensive conductive network.