Study On MWNTs Functionalized And Mechanical Properties Of Modified PI Hybrid Films

In recent years, works of research scholars at home and abroad usednanometer particle modifying polyimide in order to adapt to high performancedemand of polyimide films in more areas. Multi-walled carbon nanotubes,because of its large length to diameter ratio, high surface energy, high thermalconductivity and conduction, were usually used to modifying polymer. So thispaper tried to use MWNTs modifying polyimide films, research thefunctionalization process of MWNTs and the influence of polyimide mechanicalproperties on MWNTs with different length.In this paper, at first the MWNTs are treated by fenton reagent and mixedacid reagent, the effect and the dispersion of functionalized MWNTs areanalyzed by electronic scanning electron microscope (SEM) and infrared (IR)spectrum. Choose mixed acid method to modify MWNTs, PAA/MWNTs hybridsolution were prepared via in-situ polymerization method, then casting on glassesfor heat amine to films. The influence of hybrid films’section morphology,thermal decomposition temperature, dielectric strength and mechanical propertieswith the MWNTs introduction was analysed.The results showed that the surface of MWNTs after Fenton and mix acidtreatment introduced carboxyl and hydroxyl, the dispersion of MWNTs inethanol were improved. When the MWNTs content in hybrid films were lowerthan4wt%, PI hybrid films’thermal decomposition temperature increased but nottoo much with MWNTs contents increasing. The tensile strength of PI hybridfilms first increased and then decreased with the MWNTs content increasing, theelongation at break decreased all the same, and the serious structure defects wereformed within the hybrid films at the doping amount more than2wt%. Whenusing MWNTs with200length to diameter ratio to modify PI films, tensile strength reaches maximum116.76MPa at0.6wt%carbon content, increasednearly6.7%with pure PI films, elongation at break decreased5.45%. Whenusing MWNTs with50length to diameter to modify PI films, tensile strengthreaches maximum119MPa at1.2wt%carbon content, increased nearly8.2%,elongation at break decreased22.9%. L-MWNTs with length diameter ratio200had more contribution to toughness for PI hybrid films, and S-MWNTs withlength diameter ratio50had more contribution to strength for PI hybrid films.