Studies On Mechanical Properties Thermal Performance And Electric Performance Of MWNTs/PI Composite Films

Pyromellitic polyimide film is aromatic heterocyclic polymer containing imide groups in the main chain,Because of its unique structure Polyimide film(PI)has excellent mechanical properties,thermal stability and electrical performance which is widely used in many fields.Such as the aerial?the new energy materials?flexible printed circuit board?inverter motor slot insulation and cable wrapping material.However,with the development of science and technology,the polyimide film performance requirements are also increasing,Meanwhile,With the nanotechnology more and more attention and investment,nanomaterials are more and more widely used in various fields.therefore,scholars began working doped nanoparticles modified polyimide film in recent years.Because of its unique structure of carbon nanotubes,and different from other structure of nano-reinforced materials,this experiment using carbon nanotubes modified polyimide film.In this experiment,the monomers pyromellitic dianhydride(PMDA)and 4,4'-diamino diphenyl ether(ODA)as raw material,N,N-dimethylacetamide(DMAc)as solvent,carbon nanotubes by function treated as reinforcement,PAA/MWNTs hybrid adhesive solution was prepared by in-situ polymerization,and simulated industrial tape casting membrane,finally heated the amination,then a series of thin film was prepared.Using a scanning electron microscope observe hybrid films fracture surface.MWNTs surface functional groups to be tested by Fourier transform infrared spectroscopic spectra.And test tensile strength,elastic modulus,elongation at break,dielectric constant,dielectric loss and volume resistivity,breakdown strength,and the thermal decomposition temperature of Hybrid film.The test results showed that: after the carbon nanotubes by mixed acid oxidation and Fenton reagent oxidation process,hydroxy and carboxy were introduced to the surface of carbon nanotubes.The functionalized carbon nanotubes by silane coupling agent KH550 modified can improve the interface interaction between the carbon nanotubes and the polyimide substrate,But the dispersion of MWNTs modified by silane coupling agent KH550 is not improved in composites.Adding KH550 silane coupling agent can improve the mechanical properties of hybrid films,especially treating carbon nanotubes by mixed acid oxidation and then modified by silane coupling agent KH550.When the doping amount of carbon nanotubes was 1wt%,the tensile strength reaches about 129 Mpa.Adding KH550 silane coupling agent also have some influence on the electrical properties of hybrid films.Adding KH550 silane coupling agent can improve the dielectric constant of hybrid films,especially treating carbon nanotubes by Fenton reagent and then modified by silane coupling agent KH550.KH550 added can appropriately reduce dielectric loss of polyimide film hybrid.To some extent,with the increasing of the carbon nanotube content,the volume resistivity of the hybrid film declining can be suppressed,And also slightly enhance the breakdown strength of the hybrid film.KH550 silane coupling agent slightly increase hybrid films thermal decomposition temperature,But did not affect the polyamide acid imide closed-loop process.It did not obviously affect the effect of the mechanical and electrical properties.