Study On Fabrication And Properties Of Polyimide Matrix Composite Foams

Polyimide?PI?foam is a kind of high performance insulation material.The material has excellent electrical properties,mechanical properties,electrochemical properties and high temperature resistance,and is used in the field of aerospace and electronic and electrical fields.The high thermal stability and excellent mechanical properties of polyimide foam,which provide an important guarantee of performance for nano modified materials,have been favored by many researchers in this field.It is an effective method for the preparation of organic-inorganic nanocomposite materials by introducing the inorganic component into polyimide matrix.In this paper,different series of PI matrix composite foams with different filler typies and contents were prepared by choosing three different properties of particles?metal Ag particles,hydroxylated graphite micro-sheets and Fe₃O₄ nano-particles?as fillers.The microstructures,crystal phase transition,thermal stability and electrical properties of the composite foams were characterized.The effects of different fillers and its' contents on microstructure and properties of the composite foams were analysized.Results showed that the Ag particles prepared by the direct ion self metallization method are nano scale.Some slight agglomeration of Ag particles existed in PI composite foam.XRD analysis showed that the obvious four peaks at 38.45°,44.1°,64.55° and 77.6° in patterns were assigned to diffraction from the?111?,?200?,?220?and?311?planes of pure face-centered-cubic?fcc?silver crystals.The diffraction peaks have rather sharp,and shows no miscellaneous peaks,which indicate that the PI foam have good crystalline performance.Thermal analysis results indicated that the introduced nanoparticles have no effect on initial thermal decomposition temperature of the composite films.SEM results showed that the increase in the weight of silver nitrate in the solution increased the content of reduced silver nano-particles in the resulting foams,then resulted the great increase in spatial distribution density of silver nano-particles in PI/Ag foams and the cell size of the foam was decreased.within a set range of silver nitrate content,the content of silver particles?Ag0?was gradual increased and there was a good linear relationship between reflectivity and silver nitrate content.However,as silver nitrate content increased beyond a set amount,the reflectivity of the foam and the silver content was no longer a linear relationship.Using the hydroxyl graphite micro-sheets as fillers,SEM showed that the diameter of prepared graphite sheets is micron level and they dispersed better in PI matrix.XRD spectrum indicated that the introduced of graphite micro-sheets have little effect on the phase change of graphite micro-sheets.According to FT-IR analysis,it is showed that the addition of graphite micro sheet has no effect on the basic structure of PI foam.DSC test results indicating that the composite material has a distinct glass transition,can ensure use of materials under high temperature,has high heat resistance.From the TGA analysis test,we can know that the thermal stability of PI/graphite micro sheet composite foam is improved compared with the pure PI foam,which shows that the graphite micro sheet has a certain value to improve the thermal stability of the polymer material.The microstructure of the material was analyzed by SEM,the results showed that the graphite micro sheet was dispersed evenly and tightly in the PI foam substrate.Mechanical properties test can be seen that the addition of graphite micro sheet to make the foam become hard,and flexibility to reduce.Using Fe₃O₄ particles as fillers,SEM analysis showed that most of the Fe₃O₄ particles prepared by Sol-gel method,both of them dispersed in the PI foam matrix uniformly.By infrared spectrum analysis,the chemical structure of pure PI foam and PI/Fe₃O₄ composite foams with different Fe₃O₄ content were same basically,and the structure of PI foam was not affected by the addition of Fe₃O₄.By the XRD test,found that the crystallization performance of the composite foam with the different Fe₃O₄ magnetic particles addition content is good,and there is no miscellaneous peaks.Through the TG test,was found to the decomposition temperature of PI/Fe₃O₄ composite foam have little difference with the PI foam material,which showed that the Fe₃O₄ magnetic particles had little effect on the thermal stability of polyimide foam.The mechanical properties of PI/Fe₃O₄ composite foams were tested,and the compressive strength increased with the increase of the content of Fe₃O₄ magnetic particles,and the ability of foam material to resist deformation increased.In summary,when the amount of Fe₃O₄ magnetic particles to achieve 6g,can make the PI/Fe₃O₄ composite foam to achieve the best performance index,thereby obtaining both thermal stability and electromagnetic shielding of the PI composite foam.