Preparation And Characterization Of Phenylethynyl-Terminated Polyimide And Its Composite Materials

Polyimide and phenylethynyl-terminated polyimide films were synthesized from4,4'-oxydianiline,3,3',4,4'-biphenyl tetracarboxylic dianhydride and capped by4-phenylethynylphthalic anhydride through two-step method.Polyimide/carboxylated multi-walled carbon nanotube,Phenylethynyl-terminated polyimide/carboxylated multi-walled carbon nanotube and Phenylethynyl-terminated polyimide/carbon fiber composite films were prepared by in situ polymerization under sonication.The morphology,T_g and thermal properties were analyzed by Fourier transform infrared,scanning electron microscope,dynamic mechanical analyzer,thermo-gravimetric analysis,at the same time mechanical property and electrical performance were tested by microcomputer control universal testing machine and high resistance meter.The results show that carboxylated multi-walled carbon nanotubes were uniformly dispersed in the phenylethynyl-terminated polyimide matrix.There were overlapping and interpenetrating between the fibers in PETI/CF composite films.Polyimide and phenylethynyl-terminated polyimide films have excellent thermal properties.The T_g and thermal properties of phenylethynyl-terminated polyimide was slightly improved as adding carbon nanotubes.While,the addition of carbon fiber have no influence on T_g and thermal properties.The surface resistivity and volume resistivity of PETI/MWNT-COOH composite films were decreases with the increase of MWNT-COOH content and decreased by one order of magnitude.It shows that composite films in high content of MWNT-COOH have high conductivity.The tensile strength of the PETI/MWNT-COOH composite films was higher than the PI/MWNT-COOH films within the range of 0-0.5wt%MWNT-COOH.With higher MWNT-COOH content,the tensile strength of the PI/MWNT-COOH composites and the PETI/MWNT-COOH composites showed little difference.When the content is 5 wt%,the tensile strength has a little decrease.The tensile strength of PETI/CF increases first,and then decrease with the increase of CF content,and under the premise that PETI/CF composite films containing the same content of CF,the tensile strength of PETI/CF(3 mm)composite films were greater than the one of PETI/CF(2 mm)composite films.