| Polyimide(PI)is a polymer with imide ring or phthalimide ring structure on the molecular chain,with excellent mechanical properties,electrical properties and good chemical resistance,radiation resistance,widely used in aerospace,military chemical,electronic devices,filters and other fields.With the development and progress of science and technology,people put forward higher requirements on the performance of polyimide,especially in the mechanical properties.At present,the main means to enhance the mechanical properties of polyimide is to add reinforcing agents to improve its mechanical properties by adding inorganic reinforcing fillers such as carbon nanotubes(CNTs)and graphene to the polyimide matrix.However,these fillers have poor dispersion and tend to agglomerate in the polyimide,which has limited improvement on the mechanical properties of polyimide,and there is an urgent need to improve the dispersion of carbon materials.Fluorination is one of the most effective methods to improve the dispersion stability as it can disrupt the conjugate structure of the carbon material itself and enhance its dispersion.In view of this,in order to investigate the mechanical enhancement effect of fluorinated carbon materials on polyimide,this thesis prepares terpolymerized polyamido acid precursor solution by copolymerization method,and then blends it with zero-dimensional fluorinated acetylene black(FAB)and one-dimensional fluorinated carbon nanotubes(FCNTs)in different ratios,combining with electrostatic spinning technology and high-temperature thermal imidization,to prepare inorganic nanoparticles with FAB and FCNTs as The electrospun PI/FAB and PI/FCNTs composite nanofiber tapes with FAB and FCNTs as inorganic nano-fillers were prepared.The physicochemical properties and mechanical properties of the composite nanofiber tapes were also discussed and analyzed in detail by characterization means such as field emission scanning electron microscopy,infrared spectroscopy,thermogravimetric analyzer,dynamic mechanical analyzer and tensiometer.The specific studies are as follows:(1)Firstly,PI/FAB composite nanofiber tapes were prepared by blending and electrostatic spinning techniques using zero-dimensional material FAB as filler and polyamide acid prepared by terpolymerization as precursor solution,and the effects of different contents of FAB on the mechanical properties of PI/FAB composite nanofibers were investigated.The results show that the doping of FAB can effectively improve the mechanical properties of PI/FAB composite nanofiber tapes.When the FAB content was 1.0 wt%,the tensile strength and modulus reached the maximum of910 ± 34.11 MPa and 8.75 ± 0.43 GPa,which were 33.8% and 64.5% higher than those of pure PI,respectively.In addition,the incorporation of FAB also brings some improvement and enhancement to the properties of PI nanofibers such as thermal properties and hydrophobicity.(2)Compared with the zero-dimensional FAB particles,the one-dimensional FCNTs have a larger aspect ratio and can further improve the mechanical properties of polyimide.Therefore,in this chapter,PI/FCNTs composite nanofiber tapes with different contents of FCNTs were prepared by replacing FAB with one-dimensional material FCNTs as the reinforcing filler,and the effects of different contents of fluorinated carbon nanotubes on the properties of PI/FCNTs composite nanofibers were investigated.It was found that the doping of fluorinated carbon nanotubes had a more prominent effect on the mechanical property enhancement of PI/FCNTs composite nanofiber tapes.When the content of FCNTs was 0.7 wt%,the tensile strength and modulus were as high as 1045±21.07 MPa and 10.61±0.33 GPa,respectively,which were 54.6% and 101.3% higher than those of pure PI,and 1.15 and 1.21 times higher than those of PI/FAB composite nanofiber tapes.The above results indicate that fluorinated carbon nanotubes have potential applications in the field of mechanical property enhancement of PI composites. |
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