Synthesis And Properties Of Polyimide Resin With High Thermal Resistant

Because of the polyimide has high thermal resistance and excellent mechanical properties,so it has been widely used in the aerospace,aviation and other fields.As the phenylethynyl-terminated polyimide resin oligomers in the heat curing,can be cross-linked to form a network structure,resulting in chain growth,grafting,and curing process of non-volatile compounds generated,the cured resin has excellent high temperature resistance and mechanical properties.Therefore,phenylethylene-terminated polyimides have become a central issue.However,the solubility of the first generation PMR-type polyimide(PI)matrix resin and the heat-resistant stability and thermal oxidation stability in the high-temperature environment is poor,which seriously affect the high-temperature performance of the material.In this paper,a series of copolymerization and blending polyimide resins with phenylethynyl and norbornene capping were designed and synthesized,and their thermal and thermal decomposition kinetics were studied in detail.First of all,phenylethynyl and norbornyl capping agents and three kinds of comonomers(6FDE,BTDE,NE)were synthesized by catalytic substitution and acidification.Then,a series of polyacrylates were synthesized by"Two-step Method".The structure and characterization of the synthesized intermediates and final products were characterized by FT-IR and ~1H NMR.Secondly,a series of different proportion blends and copolymerized PI resin molded powders were prepared by blending and copolymerization,and the corresponding PI resin were prepared by hot pressing.Then,the thermal properties of the PI resin were analyzed by thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC)to determine the high temperature performance of each series of PI resin.Finally,the thermal decomposition kinetic behavior of the fully cured series of PI resin were studied.The average thermal decomposition activation energy E and the decomposition reaction number of the fully cured series PI were calculated.The results show that the thermal decomposition performance of the blended PI resin system is better than that of the copolymerized PI resin system,the T5 of the blended PI resin are higher than 510oC,and the T5 of the copolymerized PI resin are between 500 and 510oC,and the former has a higher glass transition temperature than the latter.And the average thermal decomposition activation energy E value of the fully cured PI resin and the calculation result of the decomposition reaction order are approximately 1,which belongs to the first order reaction.