Preparation And Syudy Of High Performance Polyimide/Carbon Nanotubes Composites Films

Since it discovery by Iijima in 1991, carbon nanotubes (CNTs) is of great scientific interest because of its outstanding structural, chemical, electrical, and thermal properties. It is believed that the incorporation of carbon nanotubes in polymer matrices endow the composites with many enhanced properties. Aromatic polyimides (PIs) are well known as functional materials with high thermal resistance and thermal stability, low dielectric constant, and excellent mechanical strength. So preparing CNTs/PI nanocomposites materials is an effective way to improve the properties of polyimides.However, it is a big challenge to have them homogeneously dispersed in desired polymer matrices, given that the carbon nanotubes are generally insoluble and severely bonded. For this reason, surface modification of CNTs must be performed before fabrication of nanotube-reinforced polymer composites. In this thesis, multi-walled carbon nanotubes were Modificated by organic molecules, then the modificated MWNTs were filled into polyimide composites films through liquid blending and in situ polymerization. The resulting composite films were characterized by FT-IR, UV-vis, XRD, SEM and AFM. The properties of these composite films include mechanical, thermal, conductive and solar absorptance were also tested.The main content of this thesis is list below:1. The hydroxylation of MWNTs (MWNTs-OH) purchased from the Nanotech Port Company were reactived with 3-aminopropyltriethoxysilane (KH550) and 3,3',4,4'-oxy--diphthalic ahydride (ODPA) to get amino-MWNTs (MWNTs-NH2) and anhydride-MW--NTs (MWNTs-COOOC). They were confirmed by elementary analysis, FT-IR and TG. Comparing with MWNTs-OH, the organic compatibility of the modificated MWNTs were improved.2. A new aromatic unsymmetrical ether diamine with trifluoromethyl pendent group, 1,4-(2'-trifluoromethyl-4',4"-diaminodiphenoxy)benzene (PAPB), was successfully synthe-sized in three steps using hydroquinone as starting material.3. MWNTs-g-PI composites films had been prepared using liquid blending with the starting materials of unsymmetrical diamine monomers (PAPB), dianhydride monomers (ODPA) and MWNTS-NH2. The resulting composites films exhibited more excellent mechanical, thermal and conductive properties than neat PI. The tensile strengths and Young's modulus of MWNTs-g-PI composites films increased 25.1 MPa and 0.52 GPa at 0.6 wt% content, respectively. Meanwhile, the volume resistivity and surface resistivity were decreased by six orders of magnitude and seven orders of magnitude, while achieved the level of ESC mitigation.4. MWNTs-s-PI composites films had been prepared using in situ polymerization with the starting materials of unsymmetrical diamine monomers (PAPB), dianhydride monomers (ODPA) and MWNTs-COOOC. The resulting composites films also exhibited more excellent mechanical, thermal and conductive properties than neat PI, and the enhancement is better than MWNTs-g-PI. The tensile strengths and Young's modulus of MWNTs-g-PI composites films increased 30.7 MPa and 0.62 GPa at 0.6 wt% content. The surface resistivity and volume resistivity were smaller than MWNTs-g-PI at the same content of MWNTs.