Preparations And Properties Of Polyimide Films

Polyimide,a polymer containing lots of imide-ring-structure on the main chain,has been widely used in aerospace,microelectronics,and separation membrane fields due to its features such as outstanding high temperature resistance,dielectric properties,dimensional stability and mechanical properties.Especially as a thin film product,polyimide is widely used in electronics,information products,computers,LED and other fields.However,higher performance,more applications,its performance still needs to be improved accordingly.Therefore,oriented by market,this article explores the development of polyimide film that meets the needs of the enterprises.(1)To meet the demand for high modulus of polyimide film for industrial applications,two attempts were took respectively,improving the rigid on the structure of the PI main chain and filling with inorganic rigid particles.Two rigid monomers,3,3',4,4'-biphenyltetracarboxylic dianhydride(s-BPDA)and p-phenylenediamine(PPD),are used to replace part of the original dianhydride and diamine of PI respectively.and then the effect of their respective substitution amount on the properties of PI films was studied.Inorganic rigid fillers were selected from talc powder to observe the effects of talc content,particle size and surface modification of the coupling agent on the performance of PI films.The results show that:(1)PPD can significantly increase the elastic modulus of the PI film,which is much higher than that of s-BPDA;(2)With the talc powder,the elastic modulus of the PI film can also significantly be increased.The greater the amount of talc powder,the higher the modulus of elasticity of the film.The mechanical properties of the PI can be further improved through the tensile process in the industrial production.Result of different experiment shows that the rigidity of the PI film can be effectively improved by the replacement of the main chain of the rigid structural unit and the filling of the inorganic rigid particles.Industrialized productionshows that the scheme can meet the needs of industrialized production,and other mechanical properties of the PI film products keeps stable.(2)With the rapid development of the LED and OLED industries,it also puts up with higher requirements on high-performance polymer film products.However,traditional aromatic PI usually has drab and crimson,which limits its application in this field.Therefore,this paper then carried out a further study on the transparency of the film.Fluorinated diamine,2,2'-bis [4-(4-aminophenoxybenzene)]hexafluoropropane(6FBAPP),fluorinated dianhydride,2,2'-bis(3,4-Dicarboxylic acid)hexafluoropropanedianhydride(6FDA)and a non-coplanar structure dianhydride-bisphenol A type dietherdianhydride(BPADA)are selected to replace some of the dianhydride and diamine in traditional PI(PMDA/ODA),so as to produce light-colored or colorless transparent PI film,and evaluate the transparency of the film by measuring the light transmittance and haze of the film.The results show that under the same content,the effect of 6FDA on film transmittance is higher than that of BPADA,and the increase of 6FDA content will not cause the increase of film's haze;when 6FBAPP and 6FDA replace all the corresponding diamine(ODA)and dianhydride(PMDA),the transmittance of PI of6FDA/ODA system is about 21.2% higher than that of PMDA/ODA system;while PMDA/6FBAPP system only improves about 12.6%;on the basis of 6FDA replacing PMDA,reuse 6FBAPP to extract ODA in order to improve the transmittance of the film.(3)Engineering plastic products are another major application of PI,but the application is limited because of its poor processability.Traditional PI is difficult to melt and not easy to produce because the PMDA / ODA structure has a rigid main chain,the molecular segment has poor flexibility.Therefore,based on the previous work,this paper introduces a commercial flexible long-chain aromatic diamine monomer—4,4?-bis(3-aminophenoxy)benzophenone(in the PMDA/ODA system).BABP),part of PI films,through the investigation of film mechanical properties,thermal properties and melt processingproperties,etc.,to look for an effective way to produce melt-processable thermoplastic polyimide(TPI)with excellent comprehensive properties.Macroscopic thermal stretching results and dynamic thermomechanical performance characterization results show that BABP can effectively improve the thermoplastic plasticity of PI.When the BABP content is 50%,the film undergoes obvious thermoplastic stretching at 300 ?.DMA results show that its temperature of glass transformation still maintains at a relatively high temperature(290 ?),and its elastic modulus and tensile strength are not decrease significantly than those of pure PI.All results show that the copolymerization method is an effective way to produce TPI with excellent comprehensive performance.