Research On Preparation And Properties Of Polyimide Matrix Two-dimensional Nano-silver Composite Films

Polyimide based two-dimensional(2-D)nanomaterials are widely studied in recent years.2-D nano-silverpossess many excellent properties,which include outstanding mechanical,thermal and electrical properties,and so on.Besides,their rigidity can effectively avoid the deformation and wrinkling in the polymer matrix.Polyimide(PI)composites doped by silver nanosheets(PI/Ag)were prepared by in-situ polymerization.The micro-structrue,electrical properties,thermal properties and mechanic property of the PI/Ag composites were investigated.Effect of thermal imidization process on the PI/Ag composites were researched,one best process of preparation of PI/Ag composites was confirmed.SEM was used to observe the distributions of the silver nanosheets in the films.The structural characteristics of thecomposites were characterized by FTIR and XRD.SAXS was used to investigate the interface and the fractal characterisitcs of the composites.Dielectricspectrum,AC conductivity,dielectric loss,corona resistance and breakdown strength were carried out to study the electrical properties of the composites.The thermal stability,glass transition and the melting enthalpy of the composites were performed by TGA and DSC.Tensile strength,elongation at break and elasticity modulus ofcomposites were tested by universal tensile testing machine.The results show that composites with a thermal imidization at 320 C for 30 min with good imidization.At the doping concentration of 0-10%,no obvious micro-structure change was found,when the content was above 10%,the matrix were dense and compacte sharply,also,the interface layer between the matrix and nanosheetwas formed obviously at the content of 10%,the thickness of interface layerincreased gradually by increasing the dopant.A maximum dielectric constant of PI/Ag composites was observed at the content of 10%,conductivities and loss tangent of composites didn't increase much;breakdown strength and corona resistant performance reduced generally with increasing the Ag content.With a content of Ag(0-0.75%),thermal decomposition temperature of the composites was increased than that of neat PI,with Ag component(>2%),thermal decomposition temperature of composites decreased comparing to neat PI,the decomposition rate of composites was higher than that of neat PI,because of the introduction of Ag nanosheets,the melting range of the films became shorter,the molecular weight distribution became smaller and the melting enthalpy increased.With an Ag dopant(0-0.75%),tensile strength and elastic modulus of the composites increased,while the elongation decreased,making the film rigid,with a larger Ag dopant(>2%),elongation of the composites increased obviously,making the film flexibler.