Study On Preparation And Performance Of Honeycomb/Polyimide Foams

In this paper,the polyimide precursor powders was prepared successfully by using BTDA,BPDA and MDA as the main raw materials via the method of solution polymerization.Finally,a new honeycomb/polyimide foam materials was obtained by using polyimide precursor powders,aluminum honeycomb and self-made carbon fiber honeycomb via the two-step method.BTDA esterification product,BPDA esterification product and polyimide precursor powders were analyzed by fourier transform infrared spectroscopy(FT-IR),respectively.The form of polyimide precursor powders was microspheres structure by SEM observation.The polyimide precursor powder was synthesized by different molar ratios of BTDA and BPDA was present as microspheres,microspheres particle size was 0.5 ?m-40 ?m.The range of foaming temperature was determined by TGA curve analysis of polyimide precursor powder and the range was 100?~250?.The activation energy(Ea)and pre-exponential factor(A)of three stages of foaming process for polyimide precursor powder were 2.5 KJ/mol,17.0 KJ/mol and 35.3 KJ/mol,15125,2289 and 1203,respectively.The effect of dosage of BTDA and BPDA on performance of polyimide foam was studied.The structure and properties of polyimide foams were characterized by FT-IR,SEM,thermo gravimetric analyzer(TGA),dynamic mechanical property analyzer(DMA),limit oxygen index meter(LOI),microcomputer control electronic universal testing machine and DR-1 thermal conductivity detector.The results had shown that The polyimide foam with BTDA and BPDA molar ratio of 7: 3 had the same cell and smaller size,maximum compressive strength,minimum thermal conductivity and best thermal insulation performance.Thermal decomposition temperature(Td)of polyimide foam with different molar ratio of BTDA and BPDA were more than 400?.Glass transition temperature(Tg)of polyimide foam with different molar ratio of BTDA and BPDA were about 257?.Limiting oxygen index(LOI)of polyimide foam with different molar ratio of BTDA and BPDA were more than 40%.The properties of aluminum honeycomb/polyimide foam materials were characterized by computer-controlled electronic universal testing machine,limit oxygen index meter(LOI)and DR-1 thermal conductivity detector.Compared to the pure polyimide foam,50% compression strength of aluminum honeycomb/polyimide foam materials increased by at least 350%,the smaller of honeycomb grid side,the greater the effect of the reinforced polyimide foam.Aluminum honeycomb/ polyimide foam materials have poor thermal insulation properties.But,there is no change in flame retardancy.Compared to the pure polyimide foam carbon fiber honeycomb/polyimide foam materials are more excellent on compressive strength,thermal insulation and flame retardancy.50% compression strength of carbon fiber honeycomb/polyimide foam materials nearly increased by 300%.